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 U. S. DEPARTMENT OF AGRICULTURE, 
 
 WEATHER BUREAU. 
 
 ON THE 
 
 NORTH PACIFIC SLOPE 
 
 BY 
 
 B. S. PAGUE, Local Forecast Official, 
 
 AND 
 
 S. M. BLANDFORD, Observer. 
 
 Published by permission of PROP. WILLIS L. MOORE, Chief of Weather Bureau. 
 
 PORTLAND, ORE. 
 
 Weather Bureau Print. 
 
 1897. 
 
U. S. DEPARTMENT OF AGRICULTURE, 
 
 WEATHER BUREAU. 
 
 ON THE 
 
 NORTH PACIFIC SLOPE 
 
 BY 
 
 B. S. PAGUE, Local Forecast Official, 
 
 AND 
 
 S. M. BLANDFORD, Observer. 
 
 Published by permission of PROF. WILLIS L. MOORE, Chief of Weather Bureau. 
 
 PORTLAND, ORE. 
 
 Weather Bureau Print. 
 
 1897. 
 

 PKEFACE. 
 
 FOR the purpose of placing in a comprehensive form 
 the subject of storm development and movement, and the 
 methods of forecasting the weather on the Pacific Coast, 
 this little pamphlet is published. It is believed that the 
 method of presenting to the mind of the layman the sub- ' 
 ject by means of charts is the best. There are many false- 
 theories prevalent in the mind of the public concerning 
 storms in general. A lucid explanation of **cepted theory 
 concerning the Pacific Coast weather is contained herein. ^ 
 Especial attention is invited to the explanation of "Chi- 
 nook" winds on page 10. 
 
 Weather Forecasting in all portions of the globe is a 
 difficult problem, but in no place is it more difficult than 
 on the North Pacific Slope. Storm movements are, in 
 some instances, regular, and again erratic ; the regular 
 movements only are here given. 
 
 The matter contained herein was prepared by Mr. 
 B. S. PAGUE, Local Forecast Official, Weather Bureau, 
 Portland, Oregon, who is the official Weather Forecaster 
 for the Pacific Northwest ; and by Mr. S. M. BLANDFORD, 
 Observer, Weather Bureau, who for five years has been 
 an assistant at Portland, Oregon. 
 
 PORTLAND, OREGON, August 15, 1897. 
 
J/ 
 
 o/* 
 
 WEATHER FORECASTING. 
 
 By B. S. PAGTJE. 
 
 When it is considered that more interests are directly affected by weather 
 changes than by any other factor or condition, it appears strange that more 
 attention is not paid by the people to the study of the weather. 
 
 Forecasts have been made by the unscientific and by the scientific, yet 
 none that are made reach that degree of perfection that is desirable. 
 That they are daily of more value and that their accuracy is steadily 
 increasing, will not be denied, yet much study and investigation is necessary 
 to make the improvements, both as to accuracy and length of time of the 
 forecast that is desired. The old-time almanac contained forecasts of the 
 weather which were relied upon by many, yet those forecasts were often- 
 times based on less data than mere general averages. 
 
 ^ Then there is the so-called "weather forecast" issued by various people, 
 who claim them to be based on the position of various planets. These fore- 
 casts are manifestly inaccurate, vague, and misleading, and should one of 
 the "planet" forecasts be verified, a great victory is claimed for the fore- 
 caster. These forecasts may have their value, but they have certainly not 
 shown it. It is not the purpose of this paper to discuss the forecasts of 
 people who, at the best, and under the most charitable construction, can be 
 designated by the word "charlatan," yet the scientific investigations of the 
 U. S. Weather Bureau and its forecasts issued are so at variance with those 
 of the faker, that this touching of the subject was necessary. 
 
 It should be understood that the weather predictions of the government 
 and other scientific bureaus, made for a day or two in advance, are simple in 
 principle, depending upon well-recognized physical deductions, and partly 
 upon analogical conclusions. There is no mystery either in the theory or 
 practice of such predictions, and the more numerous the observing stations, 
 and the longer the work is continued, the more accurate will become the 
 predictions. 
 
 There are also methods of making predictions for a long time in advance 
 which are scientifically justifiable, and upon which considerable reliance may 
 be placed. When the climatic conditions of a place have been carefully 
 recorded, let us say, for every month for a long time, it becomes possible 
 to predict, with great probability of accuracy, that certain conditions will 
 prevail in any subsequent month; that there will be so much rain, or snow, 
 or so many windy days. Such predicting is merely asserting that the aver- 
 age will prevail. Again, from collateral observations extending over a 
 sufficiently long time, certain ill-defined cycles sometimes appear in weather 
 changes, and by making use of these a general prediction may be made for 
 
\\KATIIKR FORECASTING, 
 
 any future time. While such long-range predictions as these are perfectly 
 legitimate, the data are yet insufficient to make them of much importance. 
 
 There are other weather prophets who pretend to predict for the future, 
 for weeks and even months ahead, and profess to do so by specially, often 
 personally discovered laws, or by methods not known, at least not appre- 
 ciated, by scientific bureaus. This kind of prophecy is generally as baseless 
 as the rain-making claim, and should be entitled to no more consideration. 
 Any one who claims to have discovered definite laws in the changes of the 
 weather is mistaken. Any one who claims to have discovered cycles in the 
 weather changes from a few observations of any sort, is also mistaken. 
 The whole class of long-range weather predictions professedly b-^ed upon 
 the conjunction or opposition of planets, upon the eclipses of the sun, moon, 
 or other celestial bodies, or upon the observed action of animal nature, are 
 unworthy of attention. In general, it may be said that all weather pre- 
 dictions not based upon long, systematic, and extended observations of the 
 weather, are unworthy of consideration, and when any one is found making 
 predictions without such data, he is simply guessing. 
 
 The Weather Bureau issues general forecasts from Washington City, 
 Chicago, 111., San Francisco, Cal., and Portland, Oregon. The forecasts 
 issued from the centers are for a distinct and well-defined territory, and for 
 a stated and stipulated period of time ranging from 24 to 36 hours. Under 
 well-defined conditions, forecasts are issued for a greater period, sometimes 
 for as much as three and four days. Such forecasts are exceptional and are 
 only issued under well-defined conditions. The word "forecast," as used by 
 the Weather Bureau, means that the conditions are such as to indicate that 
 the weather will be as is stated. The forecast is in no sense a prophecy, as 
 that word is usually and technically understood. The Bureau issues fore- 
 casts based on the current weather conditions. By study, observation, and 
 experience, the forecast official knows that usually certain conditions pro- 
 duce certain results. The deductions the forecaster prepares in plain, terse 
 language, and they are then issued to the public. 
 
 Weather observations are made at 5 A. M. and 5 P. M., 120th meridian, 
 or Pacific Coast time; as soon as made, these observations are prepared 
 in cipher, for economy and accuracy, and are at once telegraphed to certain 
 centers, all, however, going direct to the central office of the Bureau in 
 Washington City. As soon as received at the various forecast offices, the 
 reports are translated and charted, and the forecasts are deduced. The 
 Weather Bureau forecasts are verified from 85 to 90 per centum a degree 
 of accuracy very commendable. 
 
 There is no section of the North American continent that is more interesting 
 to study and that will be more fruitful for results than the North Pacific Coast 
 region, extending to and including Alaska. A thorough understanding of 
 the meteorological conditions of this region will tend to explain, to a great 
 extent, the weather changes which affect the climatic conditions of the 
 United States. It has been the privilege and pleasure of the writer to study 
 the weather of the Pacific Slope for the past ten years, and the most marked 
 characteristics, as understood by him, are here given for the benefit of those 
 who may be interested. 
 
NORTH PACIFIC SLOPE. O 
 
 There are but two well-defined or marked types of the weather on the 
 Pacific Slope, which for convenience it has pleased the writer to term as 
 Winter and Summer types. These two parent types have some sixteen mod- 
 ifications, yet there are distinct family resemblances in each. It is acknowl- 
 edged that the food of a storm is heat and moisture without them the 
 storm loses energy and is dissipated. The storm, like an animal, seeks its 
 focd, to enable it to retain life or energy and to grow, where it may find it 
 with as little trouble as possible. A storm, again like an animal, can con- 
 tain only so much food; hence, when it has enough it moves; when the 
 supply is too great it also moves. It has been found taat storm areas center 
 during the winter months along the Washington or Vancouver Island Coasts; 
 with the advance of Summer and the increasing heat, they retreat to the 
 North. The rotation of the earth gives all areas of high or low pressure an 
 easterly movement; hence the storm area retreating from an over-supply 
 of focd passes during the Summer season eastward about the latitude of 
 Sitka, Alaska; from thence it moves towards the Great Lakes, where it may 
 obtain more food. This movement, in high latitudes, is called the Summer 
 movement of areas of low pressure. With the passage of the summer season 
 and the increasing cold of winter, the storm areas move southward again, 
 seeking their food supply and obtaining it about the 50th degree north lati- 
 tude, and 125th degree west longitude, or about Vancouver Island. Here it 
 fattens, as it were, i. e., gains energy, and moves eastward, about the 50th 
 degree north latitude, crossing the Rocky Mountains and passing into 
 Alberta or Saskatchewan, thence to the Mississippi Valley. This is the 
 Winter movement of the storm area, and is what is termed the Winter type 
 of weather conditions on the Pacific Slope. These Winter conditions are 
 shown in several forms, in Charts Nos. 1, 2, and 3, on the following pages. 
 
 The movements of the low or storm areas having been briefly described, 
 according to the idea of the writer, the movements of the areas of high 
 pressure will now be briefly outlined: Off the Southwestern Coast of Cali- 
 fornia is an area of perpetual high pressure; apparently from this immense 
 area of high pressure move smaller areas of high pressure in a northeasterly 
 direction, to the California Coast, about Cape Mendocino, from whence they 
 move in winter slightly to the north of east to Southern Idaho, where they 
 become central, sometimes move, but usually dissipate. In summer these 
 areas of high pressure move northward along the coast to about Vancouver 
 Island, whence they move easterly, following closely the path of the 
 winter lows, crossing the Rocky Mountains thence towards the Mississippi 
 Valley. This latter is termed the Summer type of the weather conditions, 
 and is shown in charts Nos. 4 and 5, on the following pages. There is 
 another movement of high pressures, almost exclusively confined to the 
 winter season. These winter highs move from the north of Alberta in a 
 southerly direction, sometimes having a westerly overflow to the Pacific 
 Slope, but more often moving toward the Mississippi Valley. 
 
 These highs from the North occasionally, in winter, join with the highs 
 from the Pacific, in Northern Utah or Southern Idaho. Areas of low 
 pressure rarely move south of the Central Oregon Coast; when they do, 
 they usually develop into very severe storms when crossing Arizona and 
 
6 WKATHEB FORECASTING. 
 
 New Mexico, coming into the influence of the moist air from the Gulf of 
 Mexico. On December 20, 1895, the writer prepared a short sketch of the 
 weather conditions of 1895, which was published in the Monthly Weather 
 Review, the official publication of the U. S. Weather Bureau, in the Novem- 
 ber, 1895, issue. It is very appropriate to reproduce the sketch as it appeared 
 in that publication. 
 
 WEATHER TYPES OF THE NORTH PACIFIC SLOPE. 
 
 There are two distinct, well-defined types of weather on the North 
 Pacific Slope, viz., the Summer type and the Winter type. These are illus- 
 trated by the following sketch of the meteorology of 1895: 
 
 Cn April 20th, the first type of summer weather conditions appeared 
 over the North Pacific Slope, viz., an area of high barometric pressure mov- 
 ing northward along the Coast to Northwestern Washington, and thence 
 eastward over the State of Washington. In the synopsis of April 20th it 
 was officially announced at Portland that the conditions which would prevail 
 until the first appearance of a Winter type of weather would be more in 
 favor of fair weather than of rain, for it had been observed that after the 
 first appearance of a pure type of summer conditions there is seldom a 
 recurrence of the Winter type until the autumn. 
 
 The spring, summer and autumn were unusually dry. This was especially 
 true of the period from September 15 to November 1, which was the driest 
 recorded in the history of this portion of the country during the past fifty 
 years. Experience had shown that no general or continued rain would 
 occur until the first appearance of the winter type of storms, and this 
 knowledge was used in the daily forecasts issuing regularly from the 
 Weather Bureau Office at Portland, Oregon. This winter type finally 
 appeared on the morning of Tuesday, November 12. 
 
 On Monday morning, November 11, 1895, there was no appearance of any 
 storm disturbance, but by noon of that day the rapid fall in the barometer 
 indicated the approach of a well-defined disturbance, and from the evening 
 reports of this date the approaching storm was forecast. The morning 
 reports of November 12 showed that the storm area was central over North- 
 western Washington and that the trough of the depression extended north- 
 eastward toward British Columbia, thereby indicating the probable path of 
 the storm. Warnings of aproaching rains and high winds had been issued 
 on the evening of November 11, or from twelve to twenty hours before 
 the storm arrived. The morning reports of November 12 showed that an 
 area of high barometer was approaching from the southwest toward Cali- 
 fornia. General precipitation occurred over Washington, Oregon, and Idaho 
 on the 12th and 13th, and heavy gales from the south and east prevailed 
 along the coast of Northern Oregon and Washington. 
 
 The morning reports of November 13 showed that the low was now 
 central north of Eastern Montana, and that the high pressure was moving 
 inland over Southern Oregon and Northern California. The morning reports 
 of November 14 showed the low area in about the same position, but more 
 distinctly defined, and the high area central near the region where Oregon, 
 
NORTH PACIFIC SLOPE. 7 
 
 Idaho, Nevada, and Utah come nearest together. The morning reports of 
 the 15th showed the high over Oregon and Northern Nevada, and the low 
 slightly east of its position of the previous day. 
 
 The feature to which attention is especially called is the passage of the 
 low eastward over Washington and the formation of the area of high pres- 
 sure. This movement of the low and formation of the high was the first 
 of the kind to occur in the autumn of 1895, and indicated that the wet or 
 winter season had set in over the North Pacific Slope. 
 
 The conditions under which areas of high pressure form and move are 
 those under which Chinook winds are formed over the Northwestern portion 
 of the United States. As the low pressure passes to the north and the 
 movement of the wind is from the high on the south and southwest to the 
 low on the northeast side of the mountains, therefore the air flowing down 
 the mountain sides is dynamically heated. 
 
 That the high pressure produced the rise in the temperature and the 
 wind called Chinook in the present case is shown by the following: 
 
 On the morning of November 12, the barometer at Portland was 29.86, 
 the temperature 36; on the morning of the 15th the barometer was 30.62, 
 and the temperature 56, a rise in pressure of 0.76 of an inch and a rise of 
 20 in the temperature. At Roseburg the rise in the barometer was 0.72 
 of an inch, and the temperature rose 16; at Seattle the barometer rose 0.72 
 of an inch, and the temperature 16; at Baker City the barometer rise 0.66 
 of an inch, and the temperature 12; at Spokane the barometer rose 0.42 
 of an inch, and the temperature rose 26; at Helena the barometer rose 0.20 
 of an inch, and the temperature 30. Chinook winds occurred in Montana 
 on November 16 and 17. 
 
 The following, from the November report of the Montana State Weather 
 Service, may, in this connection, be of interest: 
 
 A cold wave signal having been ordered for that date (November 17), 
 and the weather at the time of receipt of order being very warm and 
 pleasant, the observer (Mr. R. M. Crawford, at Helena) decided to pay more 
 than ordinary attention to the expected change. About 3:30 P. M., the 
 wind, which had been blowing gently from the north, veering at times to 
 the northeast, with a velocity of about 9 miles an hour, stiffened quickly 
 and came directly from the north, lowering the temperature 6 in less than 
 five minutes. 
 
 The indications were that the temperature would fall much lower, but 
 suddenly dark, vaporous-looking clouds appeared in the extreme southwest; 
 with them simultaneously a strong gale from the same quarter, blowing 
 at the rate of at least 40 miles an hour. The gale seemed to meet the 
 wind coming in from the north, and drove it in a whirl directly toward the 
 northeast, across the prairie, in a funnel-shaped cone, plainly perceptible for 
 a long distance by the dust gathered. The temperature quickly rose to 58, 
 the maximum recorded for this date, and the Chinook had mastered the cold 
 wave. 
 
 Under some circumstances, a rise from 0.25 to 0.75 inch in pressure will 
 produce colder weather, but under other conditions, such as those that 
 prevailed on this occasion, a rise in pressure will produce a rise in temper- 
 
s 
 
 WEATHER FORECASTING. 
 
 ature, or Chinook winds, over the northwest portions of the United States. 
 The rise in temperature in the latter case, accompanying a rise in pressure, 
 can only be ascribed to dynamic heating. 
 
 The following table, showing pressure and temperature at 8 A. M., 75th 
 meridian time, from November 8 to 18, inclusive, at the regular Weather 
 Bureau Stations, in the region now under consideration, illustrates the con- 
 ditions prevailing during the first Chinook in the autumn of 1895: 
 
 1 
 
 Portland. 
 
 Roseburg. 
 
 Seattle. 
 
 Baker City. 
 
 Spokane. 
 
 Helena. 
 
 ' 
 
 5 
 
 
 
 g 
 
 3 
 
 g 
 
 9 
 
 g 
 
 9 
 
 cd 
 
 S 
 
 g 
 
 3 
 
 i 
 
 
 5 
 
 
 o 
 
 
 3 
 
 t 
 
 3 
 
 P 
 
 3 
 
 -j 
 
 
 
 PI 
 
 1 
 
 r 
 
 j 
 
 ': 
 
 i 
 
 o 
 
 j 
 
 F 
 
 i 
 
 *? 
 
 i 
 
 tJ 
 
 8. 
 9. 
 10. 
 
 30.36 
 30.16 
 30.12 
 
 34 
 34 
 
 48 
 
 30.34 
 30.18 
 31.14 
 
 26 
 32 
 46 
 
 30.36 
 30.10 
 30.02 
 
 46 
 42 
 48 
 
 30.32 
 30.26 
 30.04 
 
 30 
 26 
 34 
 
 30.42 
 30.26 
 30.04 
 
 32 
 32 
 36 
 
 30.30 
 30.30 
 30.22 
 
 34 
 28 
 26 
 
 11. 
 
 30.36 
 
 36 
 
 30.30 
 
 36 
 
 30.32 
 
 40 
 
 30.22 
 
 32 
 
 30.32 
 
 30 
 
 30.28 
 
 28 
 
 12. 
 
 29.86 
 
 36 
 
 29.90 
 
 38 
 
 29.98 
 
 40 
 
 29.96 
 
 20 
 
 30.02 
 
 24 
 
 30.10 
 
 24 
 
 13. 
 
 30.34 
 
 44 
 
 30.40 
 
 36 
 
 30.26 
 
 40 
 
 30.34 
 
 20 
 
 30.30 
 
 32 
 
 30.12 
 
 34 
 
 14. 
 
 30.40 
 
 50 
 
 30.48 
 
 46 
 
 30.28 
 
 54 
 
 30.38 
 
 32 
 
 30.32 
 
 42 
 
 30.32 
 
 42 
 
 15. 
 
 30.62 
 
 56 
 
 30.62 
 
 52 
 
 30.50 
 
 56 
 
 30.62 
 
 32 
 
 30.44 
 
 50 
 
 30.30 
 
 54 
 
 16. 
 
 30.58 
 
 46 
 
 30.52 
 
 48 
 
 30.56 
 
 48 
 
 30.60 
 
 28 
 
 30.50 
 
 42 
 
 30.32 
 
 50 
 
 17. 
 
 30.32 
 
 44 
 
 30.30 
 
 42 
 
 30.26 
 
 48 
 
 30.38 
 
 32 
 
 30.18 
 
 40 
 
 30.08 
 
 44 
 
 18. 
 
 30.36 
 
 44 
 
 30.30 
 
 42 
 
 30.36 
 
 50 
 
 30.32 
 
 30 
 
 30.26 
 
 38 
 
 30.00 
 
 50 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 In the same issue of the Monthly Weather Review appeared the following: 
 
 LONG-RANGE FORECASTS IN OREGON. 
 
 The following extract from the weather synopsis and general forecast by 
 Mr. B. S. Pague, Local Forecast Official at Portland, Or., was published on his 
 morning weather map for November 12, 1895: 
 
 "The first storm of the season is shown on the map this morning. The 
 conditions, as shown, are those peculiar to the winter season and represent 
 the passage of the dry season and the appearance of the wet season. On 
 April 20th last, the first type of summer, dry conditions, appeared. 
 
 "It was then stated that from this date, April 20th, the rain would be light 
 and of a local, more than a general, nature. The conditions from April 20th 
 to date show how well the remarks then made were verified. The phenomenal 
 dry season, which has prevailed over the Pacific Northwest for the past six 
 weeks, was due to the storm areas passing from the north, east of the Rocky 
 Mountains, to the southeast, toward the Great Lakes; usually, the storm 
 areas have this movement during the months from June to the middle of 
 September, when they assume their winter course, and move southward 
 along the coast line, striking land about Vancouver Island, then moving 
 eastward, or at times move in other directions. The period of dry weather 
 is now over; it is probable that short periods of fair weather may prevail, 
 but it is not probable that any extended period of fair weather will again 
 prevail until next spring. Since April 20th last, the conditions were more 
 in favor of dry weather than of wet weather; from now on the reverse of 
 this will be true. 
 
 "The precipitation over the Pacific Northwest, since January 1, has been 
 about 30 per cent deficient, and it is reasonable to assume that for the remain- 
 der of the year there will be an excess.' 
 
NORTH PACIFIC SLOPE. 9 
 
 (Note By Editor of Monthly Weather Review). The importance of long- 
 range predictions, especially when based upon a broad study of atmos- 
 pheric conditions over the whole globe, cannot be overestimated. The 
 changes in the course of storm tracks may be spoken of as either the cause 
 or the concomitant of changes in the weather and climate. In a narrow 
 sense they are the cause, but in a broader sense they may often be con- 
 sidered as simply accompanying or correlated phenomena. The weather on 
 the immediate coast of Oregon and Washington depends so largely upon 
 What is called the general circulation of the atmosphere over the North ana 
 South Pacific Oceans that it may be reasonably hoped that the study of 
 this latter subject will elucidate the matter and render these seasonal 
 forecasts highly accurate and satisfactory.) 
 
 Long-range weather forecasts are only possible if made on the lines sug- 
 gested by the Editor, Prof. Cleveland Abbe, of the Monthly Weather Review. 
 It appears to the writer that no section of the country affords a more 
 fruitful field for investigation than the Pacific Northwest to determine the 
 laws governing storms, their development and movements. The investigation 
 so far enables an accurate forecast to be made of winter and summer 
 conditions, as has been shown on the preceding pages. With the extension 
 of telegraphic communication to Alaska, and meteorological reports there- 
 from, a great advance will be made in the accuracy of all forecasts, and the 
 length of time the forecast is for. A more thorough study may make it 
 possible to determine in at least a general way the probable weather during 
 the prevalence of the Winter and Summer types. These are results that are 
 hoped for. and the writer expects to see realized. 
 
 The change from Summer, or dry, to Winter, or wet, conditions is heralded 
 by a gradual weaker movement of the high areas to the 50th or 52d degree 
 north latitude, and a more distinct southern deflection of the storm areas 
 to those latitudes, until finally the energy of the highs becomes so reduced 
 that they move northward and then eastward about the 40th degree north 
 latitude, and the low area, moves southward to about the 50th degree north 
 latitude. The information can then be issued that the rainy season has 
 commenced. A long period, i. e., three or more days, of rain is improbable 
 until these conditions first appear, and then when the movements are 
 reversed, the. lows retreating to the north, and the highs moving northward 
 to the 50th degree north latitude, then any rainy period in excess of three 
 days is again improbable. These facts have been established and can be 
 recorded as the first rules toward long-range forecasts. 
 
 In the Winter conditions, as has been before noted, areas of high pressure 
 appear over Alberta and move southeastward to the Dakotas, thence toward 
 the Great Lakes. In its southward movement it overflows the mountains 
 to the west, when there is an area of low pressure central about the 
 mouth of the Columbia River. Under these conditions cold weather and 
 snow, changing to fair, cold weather over Washington, Oregon and Idaho, 
 prevails, and then the low or storm area will sometimes move southeastward 
 over California, and become a storm of great energy before it has spent 
 its force. Chart No. 1, on the following pages, shows conditions mentioned 
 above. An examination of Chart No. 1 will show what the writer terms the 
 
10 WEATHER FORECASTING. 
 
 "California dip" in the isobars 29.5 to 30.2, i. e., stretching to the southeast 
 of the low, the isobars "dip" toward California and Nevada, and such a 
 formation precedes general rain in California, and usually indicates the 
 movement of the entire storm in the direction of the "dip." While Chart 
 No. 1 shows typical rain conditions, yet it is not the common type of move- 
 ments of winter low or storm areas which prevail. Conditions shown in 
 Chart No. 1 produce temperatures much below the normal over Oregon and 
 Washington. Charts NOR. 2 and 3 are the more common types of winter 
 storms. Chart No. 2 is given so as to illustrate the conditions in which 
 Chinook winds have their origin. The following description of Chinook 
 winds, prepared by the writer, is here published, for the first time, by 
 permission of the Chief of the Weather Bureau. The Chinook wind is 
 known to all residents of the northwest portion of the United States, and 
 few agree on the causes and origin of the wind. The writer feels that his 
 explanation will stand the test of the most careful investigation, and that 
 the ideas advanced will be accepted as the true explanation of this ever- 
 welcome wind. 
 
 CHINOOK WINDS. 
 (Study Chart No. 2 in this connection.) 
 
 The term "Chinook wind" had its origin from the tribe of Chinook 
 Indians (now almost extinct, but which was very strong and powerful some 
 sixty to seventy-five years ago), that had its home in the southwestern 
 portion of Washington, on the Columbia River. Local historians relate how 
 the northwest wind in the winter season, being the harbinger of fair weather, 
 was called by the trappers at Astoria "the wind from over Chinook camp." 
 
 As the trappers scattered to the east of the Cascades, they occasionally 
 encountered a warm southerly wind which gradually assumed the name of 
 Chinook wind. It was so named from its mildness, resembling to an extent 
 the mild, balmy wind from over Chinook camp. As the trappers spread 
 over the northwestern portion of the United States, the warm southerly 
 wind of winter continued to be called by them "Chinook wind," until the 
 term became common, and was finally accepted by meteorologists. 
 
 The term was first used, so far as research among the files of the Monthly 
 Weather Review, published by the U. S. Meteorological Service, 'Washington, 
 D. C., in connection with the warm, south, southwest, west, northwest and 
 sometimes north, winds in Montana. 
 
 To the earlier extension of the military telegraph lines in Montana than 
 in Washington and Oregon, is due the fact that the term Chinook was first 
 applied to the warm winds of Montana. The operators or observers employed 
 on these telegraph lines vsed the local common name applied to the wind 
 by the stockmen in their reports. The name was thus first applied to the 
 wind in Montana, and yet to a large extent some njeteorologists are of the 
 opinion that the Chinook winds are only east of the Rocky Mountains, and 
 the name is erroneously applied to warm southerly winds in winter to the 
 west of the Rocky Mountains. 
 
 As the term had its oiigin west of the Rocky Mountains, really to the 
 west of the Cascades, the writer maintains that the term "Chinook wind" 
 
NORTH PACIFIC SLOPE. 11 
 
 can be and is properly applied to the warm southerly winds of winter west 
 of the Rocky and Cascade Mountains. The Chinook is more readily observed 
 in Montana and to the north thereof, due to the preceding low temperature 
 and the rapid and marked rise produced by the Chinook, though marked 
 rises in temperature west of the Rocky and west of the Cascade Mountains 
 are frequently observed. In the American Meteorological Journal, Vol. 3, 
 p. 469, is to be found the following definition of a Chinook: "Warm, dry, 
 westerly, or northerly winds, occurring on the eastern slopes of the mountains 
 of the Northwest, beginning at any hour of the day, and continuing from 
 a few hours to several days." This definition is perfectly correct so far as 
 it goes; but the writer's idea of the definition of a Chinook is: A warm, 
 dry, or moist wind from the southeast, south, or southwest, west of the 
 Rocky Mountains, and from the southwest, west, or northwest, to the east 
 of the Rocky Mountains, beginning at any hour of the day or night, and 
 continuing from a few hours to several days. Such definition is more in 
 accord with the causes which produce these warm winds and agrees with 
 the original application of the term as understood by those who originated 
 or created it. 
 
 Chinook winds, according to the writer's definition of the term, only 
 occur under one kind of atmospheric condition, and without this condition 
 Chinooks are impossible. 
 
 Preceding a Chinook, by from two to six days, an area of low barometric 
 pressure is along tho Washington or Oregon Coast, and an area of high 
 barometric pressure overlies Montana and the British provinces to the 
 north. This area of high pressure has low temperatures, from 10 to 20 
 below zero. The position of these two opposite atmospheric conditions 
 produces north to east winds over Idaho, Washington, and Oregon, and the 
 temperature decreases and snow falls to the east of the Cascades, extending 
 over Idaho and Montana, and sometimes to the west of the Cascades. At 
 the end of about three days the high pressure moves southeastward to the 
 Northern Mississippi Valley, thence to the Great Lakes and on eastward. 
 When the high pressure begins to move, the low pressure along the coast 
 advances northward to about the 50th degree north latitude; thence along 
 that parallel, or near to it, across British Columbia and Saskatchewan; 
 thence towards the Great Lakes. Coincident with the northward movement 
 of the low pressure along the coast, there appears along the Central Cali- 
 fornia Coast an area of high pressure which rapidly increases in density 
 and moves east and northeastward to Northeastern Nevada, Northern Utah, 
 and Southern Idaho, where it becomes central by the time the low pressure 
 is moving eastward over British Columbia. The low on the north and its 
 passage eastward causes the air to move from the high, central about Salt 
 Lake, to the low. Those are the conditions from which a Chinook results. 
 
 Now, the elevation of the land where the high is central is much greater 
 than that of the land where the low is crossing; secondly, the high baromet- 
 ric pressure indicates a greater mass of air extending upward from the 
 earth to a much greater elevation than the air where the low pressure is 
 located. Hence, in the movement of the air from the high to the low there 
 is a great decline, and in making this descent the air is gradually compressed, 
 
12 WEATHER FORECASTING. 
 
 and with the compression warmth is generated, in this way dynamically 
 heating the air as it reaches the lower levels, giving the first warming effects 
 of the Chinook. The meeting of the warmer air with the moist air of the 
 low pressure causes condensation, and rain is the result. The passage of the 
 area of low pressure eastward produces general precipitation, and, meeting 
 the mountains, th moisture which the air contains is more rapidly con- 
 densed, and the greater portion or all of its moisture lost on the windward 
 side of the mountains, the winds to the east of the mountains being warm 
 and dry, and, due to the cyclonic movement of the air, are westerly and 
 northerly. Moist air expands during its rise up the side of the mountain, 
 and is then again compressed in its descent without having any heat 
 added or withdrawn. Furthermore, if the expansion and subsequent com- 
 pression takes place without the precipitation of moisture, the air will reach 
 the same level on the leeward side of the mountain at the same temperature 
 it had at the corresponding level on the windward side. When precipitation 
 has occurred the air v/ill reach the summit of the mountain at a higher 
 temperature than the theoretical rate of decrease which elevation would 
 assign to it, and in this changed condition the initial temperature will be 
 reached at a pressure much lower than the initial pressure. Continuing in 
 its descent, the original level will be reached with a higher temperature 
 than at the starting point, and the air will be much drier, and these con- 
 ditions will be more marked in proportion as the original mass of air is 
 warm and moist or cold and dry. It will be thus seen that the definition 
 of the Chinook as quoted is correct so far as it relates to the eastern side 
 of the Rocky Mountains, but it is not at all applicable to the Chinook to the 
 west of the Rocky Mountains. 
 
 Many persons, residents of the country affected by Chinook winds, are 
 of the opinion that they come from the warmth of the Japan Gulf currents, 
 but such is not the case. Chinooks are not warm winds from the ocean, but 
 are formed, according to the writer's idea, in the manner outlined above. 
 
 In the November, 1895, Monthly Weather Review, p. 148, the following 
 by the writer hereof appeared, which in this connection may be of inter- 
 est and value, for a new thought is advanced relative to the comparative 
 mildness of the winter temperatures over Washington and Oregon: 
 
 "It is not, as I understand, admitted by all that Chinook winds occur 
 west of the Cascades. From my knowledge of conditions over the Pacific 
 Northwest, I maintain that perfect forms of Chinooks occur west of the 
 Cascades and Rocky Mountains. The degree of moisture in the Chinook 
 winds varies with the conditions and the country over which they blow (at 
 Walla Walla, Wash., for example, sometimes the very dry Chinook occurs, 
 which causes the snow to disappear without leaving any water behind it) ; 
 again, under another Chinook the snow is melted and little evaporation takes 
 place. The explanation of this is as follows: In the first case, there is 
 little or no movement of the upper currents from off the ocean, hence 
 the expansion and heating of the air will allow dry air to be brought into 
 contact with the snow which evaporates as it melts. In the second case, 
 there is a decided movement of air from the ocean inland, and the dryness 
 of the Chinook is overcome by the vastness of the supply of moist air. The 
 Rocky Mountains bar the moist air, and, therefore, to the east of the Rockies 
 the dry Chinook usually prevails. 
 
NORTH PACIFIC SLOPE. 13 
 
 "From November to March the mean temperature over Washington and 
 Oregon is materially higher than it is to the east of the Rocky Mountains 
 over the country having the same latitude. This mild winter temperature 
 is generally ascribed to the proximity of the ocean, and to the Japan current. 
 White the ocean does modify the otherwise low temperature, yet the mean 
 temperature is as much or more influenced by the dynamic heating of the 
 air of Chinook winds. If, during the winter season, the low is off the Cali- 
 fornia Coast, the cold air on the northeast flows southwestward and gives 
 the low temperatures over Washington and Oregon; if the low is passing 
 eastward over British Columbia, and a high is central about Salt Lake City, 
 then the dynamic heating, or Chinook wind, prevails, and high temperature 
 occurs. 
 
 "In these two instances the oceanic influence is only indirect. Compara- 
 tively high temperatures also occur in connection with lows moving from 
 off the California Coast northward along the Oregon and Washington Coasts, 
 gradually extending inland; in this latter case the oceanic influence on the 
 mean temperature is of direct effect. 
 
 "Low mean temperatures occur from November to March, when the lows 
 are fiequent and move southward along the Coast to the Columbia River 
 cr farther south (they seldom move much to the south of the Columbia). 
 Mean temperatures above the normal occur when the lows pass eastward at 
 a high latitude, about British Columbia. In the latter case the Chinook or 
 dynamic heating prevails." 
 
 WINTER CONDITIONS. 
 
 Chart No. 3 is a typical one of the conditions which prevail in winter. 
 It is a beautiful illustration of the successive movements of storm areas, 
 while the high pressure remains central over Northern Utah and evidently 
 fed from the permanent high off the Southwest California Coast. 
 
 THUNDER STORMS. 
 
 Chart No. 4 is an illustration of the conditions as they prevail when 
 thunder storms occur over Oregon, Washington, and Idaho, or over portions 
 of these States. Conditions which produce thunder storms, as a rule, orig- 
 inate in the heated valleys of California, whence the storms move northeast- 
 ward to Southeastern Oregon, where their energy is fully developed and 
 thunder storms result. Under these conditions high pressures are present 
 over Northwestern Washington and thunder storms are more usual on the 
 west and northwest side of the areas of low pressure than upon any other 
 side of the lows. 
 
 SUMMER CONDITIONS. 
 
 Chart No. 5 is an excellent illustration of the summer conditions over the 
 Pacific Northwest. The area of low pressure is shown to be central over 
 Manitoba, and evidently moved from the ocean eastward about the 57th 
 degree north latitude, and southeastward over Alberta to its present position; 
 it is now a dry low, but may develop moisture when coming within the 
 influence of the humid atmosphere from the Great Lakes. 
 
 The high pressure moved northward along the California and Oregon 
 Coasts; when it was central off the Northern California Coast, cloudy and 
 foggy weather prevailed o^er the western portion of Oregon and Washington, 
 with slightly lower temperatures and scattered showers. When the high 
 
14 WEATHER FORECASTING, 
 
 became central over Northwestern Washington, then the clouds and fog 
 were dissipated, and clear, balmy, ideal weather prevailed; with the move- 
 ment of the high eastward the temperatures increased, and when it was cen- 
 tral to the north and northeast of Northeastern Washington, very warm 
 weather prevailed. The hot, dry winds which occasionally damage the grain 
 crop of Eastern Washington and Eastern Oregon occur when the high is in 
 the position last mentioned. The high crosses the Rocky Mountains, and 
 another high appears off the California Coast. It requires from five to 
 seven days for the high to appear, make its north and then eastward move- 
 ment, and to cross the Rocky Mountains. These facts being known, the 
 writer has been very successful in making forecasts covering periods of 
 about one week. Such forecasts were made for Washington, Oregon, and 
 Idaho during the 3ummer season of 1895 and 1896, and the result warrants 
 further efforts in this line. 
 
 THE WEATHER MAPS. 
 
 The Weather Maps issued from the U. S. Weather Bureau Station in 
 Portland, Or., present an outline map of the United States from the Great 
 Lakes westward, and of the British Possessions to the north of the western 
 portion of the United States, showing the stations where weather observa- 
 tions are taken daily at 8 A. M. and 8 P. M., seventy-fifth meridian time (5 A. 
 M. and 5 P. M., 120th meridian time, and telegraphed to Washington, 
 Portland, Seattle, and other cities. These observations consist of read- 
 ings of the barometer, thermometer (wet and dry), direction and velocity 
 of wind, state of sky (whether cloudy or otherwise), and amount of rain 
 or snow. Solid 'lines, called isobars, are drawn through points having the 
 same pressure; a separate line being drawn for each difference of one-tenth 
 of an inch in the height of the barometer. Dotted lines, called isotherms, 
 connecting places having the same temperature, are drawn for each ten 
 degrees of the thermometer. Heavy dotted lines, inclosing areas where a 
 great change in temperature has occurred within the last twenty-four hours, 
 are sometimes added. The direction of the wind is indicated by an arrow 
 flying with the wind, or opposite to the ordinary vane. Shaded areas show 
 where rain or snow has been falling since the last observation. 
 
 The general movement of storms is from west to east, with the trend 
 of the atmosphere, which moves in a series of atmospheric waves, the crests 
 of which are designated on the maps "highs" and the troughs or depressions 
 "lows." The storms affecting the weather on the North Pacific Coast, as 
 a rule, come from the north. The winds blow spirally inward into a storm 
 and spirally outward fiom an area of high pressure; hence, when the storm 
 area is in the north, the winds come from the south, and as the storm area 
 moves eastward the winds veer to the westward. 
 
 There are two distinct types of weather on the North Pacific Coast, for 
 convenience called the Summer and Winter types. As the heat of summer 
 increases, the storm areas retreat to the north, and are carried eastward 
 about the latitude of Sitka, Alaska; once east of the chain of mountains, 
 they do not again materially affect the weather to the west, but move 
 
NORTH PACIFIC SLOPE. 15 
 
 southeastward toward the Great Lakes, and thence across New England or 
 down the St. Lawrence Valley into the Atlantic Ocean. As these storm 
 areas retreat to the northward, the rains over the Pacific Northwest decrease, 
 until finally, during midsummer, almost absolute dryness prevails. Occa- 
 sional showers prevail in summer, sometimes from the influence of the 
 lows passing to the eastward of the Rocky Mountains, their influence extend- 
 ing to the westward; more frequently, however, the occasional summer 
 showers occur from thunder storms. These storms are quite rare on the 
 Pacific Northwest, and when they occur are, as a rule, produced from a 
 low passing to the northeast from the Central California Valleys toward 
 Northern Idaho. The thunder storms usually occur on the west, northwest, 
 and north of these lows. As the heat of summer decreases, the path of the 
 lows gradually moves southerly until, by the 1st of November, it follows 
 the course of the Japan current to Vancouver Island, whence the storms 
 pass eastward, following quite closely the international boundary line, until 
 the eastern side of the Rocky Mountains is reached, when their course is 
 southeastward toward the Great Lakes. With the southern deflection of 
 the storm movements, che rains increase in amount and frequency. The 
 greater portion of the rains is deposited on the western side of the Coast 
 Range of mountains; and about two-thirds as much is deposited between 
 the Coast and Cascade Ranges. In the passage of the storm area over the 
 Cascade Range, the air is forced to such a height, and so much of its moisture 
 is lost by this action, that but a small percentage remains to be deposited on 
 the eastern side of the Cascade Mountains. 
 
 The Summer type of weather consists of areas of high pressure moving 
 northward along the Coast line from Cape Mendocino to Vancouver Island; 
 thence they move eastward, following closely the path of the low pressures 
 in winter. With the approach of high pressures the temperature decreases, 
 the cloudiness over Washington and Oregon increases, and occasionally rain 
 falls west of the Cascades; fog results west of the Cascades when the 
 center of high pressure is about the mouth of the -Columbia River. The 
 cloudiness decreases when the center of the high is over Puget Sound, and 
 when the center crosses the Cascade Mountains the weather becomes clear 
 and the temperature rises. The highest temperatures occur when the center 
 of the high has passed and is to the northeast of Spokane. When the high 
 pressure first appears off Cape Mendocino, cooler weather may be expected 
 for two days, then one day of stationary temperature, then two or . three 
 days of warmer weather. 
 
 In the winter season these highs pass eastward over Southern Oregon 
 and become central about the Great Salt Lake; due to their influence, higher 
 temperatures prevail to the north, northwest, and northeast, especially dur- 
 ing, or after, the passage eastward of a storm area in the path above men- 
 tioned. 
 
 Areas of high pressure also move southerly from the Arctic Region to 
 the north of Montana. During the winter season these high-pressure areas 
 frequently retard the eastern movement of the storm areas from Vancouver 
 Island or the Washington Coast, and then result several days of rain west 
 of the Cascades, and sometimes snow to the east of them. When the high 
 
16 WEATHER FORECASTING. 
 
 pressure area is sufficiently large and dense, and the temperatures low, the 
 storm areas are forced south of the Columbia River; the cold air flows 
 from the northeast, and then results heavy snow to east of the Cascades, 
 and occasionally to the west of them. During the winter season the lows 
 follow each other in quick succession; gales prevail along the coast, and 
 general rain results. In the spring, after the first movement of high pressure 
 from off the California Coast northward to Vancouver Island, thence east- 
 ward, the winter season or type of storm is at an end. In the autumn, after 
 the first winter type of storm appears, the summer types cease. 
 
 SENSIBLE TEMPERATURES. 
 
 EFFECT OF HEAT ON THE BODY IN OREGON. 
 By B. S. PAOUE. 
 
 Much has been said and written of the climate of Oregon, of its lack of 
 sunshine, its rainfall, its temperature and of all phases of the weather, but 
 seldom is anything said of the physiological effect of the heat in Oregon. It 
 is well known that on account of its long sea coast, its mountain ranges and 
 its great plateau region, that within the boundaries of the State may be 
 found any climate that may be desired, save that of the semi-tropical or 
 tropical type. The snow-capped mountains and higher mountain regions 
 -have temperatures equal to the Arctic region, the plateau the climate of Min- 
 nesota and Canada, the valleys that delightful climate peculiar to Virginia 
 or France. The greater portion of the State has a pleasant mean tempera- 
 ture, while the immediate coast has a climate free from heat and free from 
 cold. 
 
 Throughout the great valley of the Columbia, over the greater portion of 
 the plateau region and in the Rogue River Valley, maximum temperatures of 
 from 100 to 108 are recorded during the heat of summer. These high tem- 
 peratures would be sufficient to produce heat prostration and sunstroke, were 
 it not for the safeguards which nature has provided. Temperatures of from 
 85 to 95 are recorded every summer in the great Willamette Valley, and in 
 the Umpqua Valley these two valleys, together with the Rogue River 
 Valley, comprise what is called Western Oregon, excluding the coast region. 
 Facetious remarks are often made that "it rains 13 mouths in the year in 
 Oregon." The name applied to Oregonians is "Webfeet." The section of the 
 United States having the greatest cloudiness is the northwestern portion of 
 the United States, decreasing over Western Oregon, while over Eastern 
 Washington and more especially over Eastern Oregon the cloudiness is not 
 so great as over the thickly settled portion of the country surrounding the 
 Great Lakes, the Atlantic and Gulf Coast States. These data are here 
 inserted to enable an explanation to be made concerning the rainfall and 
 cloudiness before going into the main subject of- this paper. The sunshine at 
 Portland, which is less than that which prevails over the great valleys 
 between the Coast and Cascade Ranges, averages 35 per centum of the possi- 
 ble. In summer the actual sunshine ranges as high as 65 per cent, of the pos- 
 sible, while in winter it decreases to as low as 15 per cent, of the possi- 
 ble. This is less sunshine than that which prevails over the greater portion 
 
NORTH PACIFIC SLOPE. 17 
 
 of the United States. As vegetation has naturally but little growth during 
 the winter months, the absence of sunshine is practically no detriment, while 
 in the spring, summer and autumn, during the growing and ripening season, 
 the sunshine is fully sufficient for all needs, whether for growtli, physical 
 comfort or pleasure. The rainfall is not excessive in the great valleys, for it 
 is less than 50 inches annually. Along the immediate coast, excessive pre- 
 cipitation, i. e., 65 inches or more, occurs almost annually. The rainy period 
 might be so called from October 15 to March 15. From March 15 to June 15, 
 and from September 15 to October 15, showers prevail. From June 15 to Sep- 
 tember 15, the real summer or dry season, showers are rare. Hence it is seen 
 that the facetious remark and the sobriquet are both in error. From Octo- 
 ber 15 to March 15, a period of 150 days, rain falls on an average on from 90 
 to 100 days; so that, even during the mid-rainy season, the number of days 
 on which rain falls is not markedly excessive. However, sufficient in this 
 connection to state that the death rate in Oregon is the smallest of any 
 State in the Union, crops always mature and are very prolific, hen^e the 
 climate cannot certainly be said to be injurious, but rather it is on the whole 
 one of the most pleasant and delightful that can be found anywhere in the 
 whole country, and, considering all things, few climates in the world equal 
 it for its many pleasant and advantageous features. With this digression, 
 the real subject of this paper can now be more intelligently discussed. 
 
 The temperatures noted are those from the United States Weather Bureau 
 records, and show the temperature of the air, the thermometer being in the 
 shade, exposed in a standard thermometer shelter. The reason that there 
 are fewer injurious effects from the high temperature is that, while the 
 degree of heat noted is that which is actually recorded, due to causes which 
 will be explained, the temperature affecting animal and vegetable life may 
 be less. 
 
 The temperature cf living bodies is influenced by temperature of air, its 
 moisture and its rate of movement; living bodies differing, as a rule, from 
 inorganic masses, in that the former exude constantly a more or less variable 
 amount of moisture to be evaporated, and thereby introduce a factor in ccol- 
 ing not found normally in the latter class of bodies, i. e., evaporation. 
 
 By sensible temperature is meant that which is felt at the surface of the 
 skin. The body, when in a healthy state, is constantly furnishing moisture 
 to the skin, which stands in drops, or, as they are called, "beads of perspira- 
 tion." This moisture is evaporated by the air. The cooling effect of the 
 evaporation is the safeguard against injurious effects by extreme heat. When 
 water is changed from the liquid to the vapor condition, a certain quantity 
 of heat is utilized, which during the evaporation is changed into latent heat, 
 and is no longer sensible. A feeling of coldness therefore results from the 
 change, and as long as evaporation continues, the surface where it takes 
 place is cooler than the general temperature of the surrounding air. When 
 one is heated, a fan is used to give relief and make one more comfortable. 
 The motion of the fan causes a more rapid movement of the air; this air 
 moved by the fan against the face has the same temperature as that which 
 is not disturbed. The cooling effect comes from the more rapid evaporation 
 of moisture from the face and exposed portions of the body, and from the 
 
18 
 
 WEATHER FORECASTING. 
 
 increased convectional loss of heat caused by the more rapid movement of 
 the air. This lower temperature, felt by the face under the influence of the 
 fanning, is the sensible temperature. 
 
 Inasmuch as the temperature of the wet bulb thermometer is that of an 
 evaporating surface, influenced by the prevalent meteorological conditions, in 
 some instances, especially when the atmospheric temperature is very high 
 and the effusion of perspiration consequently great, the sensible temperature 
 will in all probability be less than that of the air, and greater than that of 
 the wet bulb thermometer. Perhaps midway between would be as fair an 
 approximation as could be made in the present state of our climatologic 
 knowledge. For that reason it will perhaps assist our appreciation of cli- 
 matic features of every region to consider the temperature of the wet bulb 
 thermometer in connection with that of the air thermometer. The following 
 statement of average air and wet bulb thermometer readings is given for 
 Portland, Oregon, for the months of June to September inclusive, from 
 readings made during the greatest heat of the day. The data are based on 
 10 years' records: 
 
 
 1 
 
 W. 
 
 1* 
 
 91. 
 
 18 
 
 92. 
 
 18 
 
 93. 
 
 18 
 
 M. 
 
 18 
 
 J5. 
 
 18 
 
 96. 
 
 Months. 
 
 > 
 *T 
 
 Wei Ther- 
 mometer. 
 
 > 
 f? 
 
 Wet Ther- 
 mometer-. 
 
 > 
 n 
 
 Wet Ther- 
 mometer. 
 
 > 
 
 *r 
 
 Wet Ther- 
 mometer. 
 
 > 
 i 
 
 Wet Ther- 
 mometer. 
 
 > 
 n 
 
 Wei Ther- 
 mometer. 
 
 > 
 i" 
 
 j 
 
 Wet Ther- 
 mometer. 
 
 June . . . 
 
 69 
 
 59 
 
 66 
 
 56 
 
 70 
 
 57 
 
 63 
 
 54 
 
 63 
 
 55 
 
 70 
 
 57 
 
 n 
 
 56 
 
 July 
 
 75 
 
 61 
 
 78 
 
 63 
 
 73 
 
 59 
 
 74 
 
 60 
 
 77 
 
 6fl 
 
 74 
 
 59 
 
 80 
 
 63 
 
 August 
 
 76 
 
 6? 
 
 SO 
 
 65 
 
 77 
 
 6? 
 
 76 
 
 61 
 
 79 
 
 64 
 
 75 
 
 60 
 
 73 
 
 62 
 
 September 
 
 7? 
 
 59 
 
 67 
 
 5S 
 
 70 
 
 60 
 
 6? 
 
 56 
 
 66 
 
 56 
 
 6? 
 
 5? 
 
 69 
 
 57 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 In this table it is seen that the wet thermometer temperature is on an 
 average about 14" lower than the air temperature; while on the day of 
 extreme high temperature mentioned the difference was 33, and this differ- 
 ence is dependent upon the amount of moisture in the air. If the air were 
 as moist as that found in the region of the Great Lakes, and along the Atlan- 
 tic seaboard, and the temperature as high as it now is at times, the effect of 
 the heat might be injurious. 
 
 Sunstrokes are produced by heat. The normal temperature of a healthy 
 person is 98.4; if it rises above 99.5 or sinks below 97.3, some form of dis- 
 ease in indicated. If a person is shown to have a temperature of 106, the 
 prognosis is unfavorable, and 110 is almost certain to be fatal. Hence it 
 can be seen that evaporation is absolutely necessary to cool the body during 
 periods of very high temperature, else the blood becomes heated and death 
 ensues. The physiological and social conditions favorable to sunstroke are, 
 anxiety, worry, overwork, irregularities in food, overcrowding and bad ven- 
 tilation, and, to a marked degree, intemperance. One using beer, whiskey, 
 or other blood-heating drinks, is much more predisposed to sunstroke than 
 one using pure water. Personal uncleanliness, which, among other things, 
 
NORTH PACIFIC SLOPE. 19 
 
 prevents the healthy action of the skin; tight garments, which impede the 
 functions alike of the heart and lungs, and living in overcrowded and unsani- 
 tary dwellings, have an equally hurtful tendency. To overcome the unpleas- 
 ant and debilitating effects of heat, as much as possible, it is necessary to 
 keep a clean, healthy skin, to avoid alcoholic drinks, and to have pure food 
 and pure air. To obtain the beneficial effects of the reduction of temperature 
 by evaporation, the shade must be sought, and the direct rays of the sun 
 avoided. Beneficial effects may be obtained by a natural or artificial breeze 
 or wind, and for parts of the body covered by clothing they may be obtained 
 by adapting the clothes to the free passage of air and moisture. For hot 
 weather and in the shade, the color of the clothing is of less consequence 
 than the texture, together with sufficient looseness to permit of the free 
 access of air. 
 
WEATHER TYPES. 
 
 By S. M. BLANDFORD. 
 
 One of the duties of the U. S. Weather Bureau is the charting of meteor- 
 ological conditions, and the issuing of forecasts. On the Pacific Coast there 
 are two places where general forecasts are made. Portland and San Fran- 
 cisco. The territory covered by the forecasts of the Portland office embraces 
 Oregon, Washington, and Idaho. Twice each day forecasts are made. In 
 case severe winds on the coast and Sound are liable to occur, forecasts are 
 sometimes specially made. A daily chart is issued each day, for the benefit 
 of the public, showing the weather conditions, position of the storm, etc. It 
 is for the benefit of those who desire to study the daily weather charts that 
 five distinct types of the weather have been selected for publication. In 
 the Eastern States, to a large extent, and on the Pacific Coast quite gen- 
 erally, the people aie making many valuable uses of the information fur- 
 nished in the daily weather map. 
 
 While many in Oregon are making a practical use of this information 
 to the advancement of their business, there are many who are ignorant of 
 the purpose for which they are issued. It is to enable this class to make a 
 money value through increased knowledge of the daily actual and probable 
 weather changes that these charts are offered. This information is of 
 especial utility to the farmer, as well as to the commercial classes in the city. 
 
 In the study of these charts it must be remembered that the arrows fly 
 with the wind. The first four figures to the right of a station denote the 
 reading of the barometer; the figures above the barometer figures denote 
 temperature; the wind velocity and precipitation figures are below the barom- 
 eter. The letter "S" at a station denotes snow, and the letter "R" denotes 
 rain; a cross denotes cloudy; one mark indicates fair, and the absence 
 of characters or marks means clear weather. The lines in the chart connect 
 places of equal barometric pressure, and are drawn to each tenth of an inch. 
 
 A WINTER STORM. 
 
 Chart No. 1 shows a typical winter storm, though there are some extreme 
 features. The terms "low" and "high," which are used in the description 
 of weather types, are used to describe the condition of the atmospheric 
 pressure as reading low or high. In Chart No. 1 the "low" is off the Wash- 
 ington Coast, and the "high" is over the British Possessions. They rep- 
 resent areas of low and high atmospheric pressure. The "low," representing 
 an area of low atmospheric pressure, is necessarily the center of the storm. 
 The "high," representing the territory where the barometric pressure is 
 great, is generally an indication of fair weather influence. 
 
NORTH PACIFIC SLOPE. 
 
 21 
 
 As regards the wind circulation about the areas of low and high pressure, 
 in the Northern Hemisphere they blow spirally inward and around the 
 "low," opposite to the movement of the hands of a watch, and they blow 
 outward from the "high." The first is a cyclonic and the latter an anti- 
 cyclonic movement. 
 
 Chart No. 1 shows that this law is being obeyed, except where interven- 
 tion of the mountains makes a change. 
 
 (Chart No. 1.) 
 
 During the winter, storms seek a low latitude. The well-beaten track of 
 the winter stoim is between latitude 45 and 50, where they strike the 
 Pacific Coast. From the Pacific Coast they usually move somewhat to the 
 northeastward for about a thousand miles, and then southeastward toward 
 the Great Lakes. 
 
 This type of storm is frequent on the Pacific Coast. Its presence means 
 continued stormy weather, with rain and snow to the west of the Cascades 
 in Washington and Oregon, while in the mountains and elevated districts of 
 Oregon, Washington, and Idaho, snow invariably follows. The presence 
 of the "high" over the British Northwest means that the "low" or storm 
 which is located on the coast will receive its supply of cold air from that 
 source. The tendency of the "high" is toward checking the eastern progress 
 of the "low." Since all storms move from a westerly to an easterly point, 
 
22 \\ ' MA Til KB TYl'KS. 
 
 the "high" in Chart No 1, preceding the storm, acts as a barrier, causing 
 the "low" to remain nearly stationary on the coast. One of the character- 
 istics of a winter "low" whose progress is checked by a "high" is to develop 
 energy. With the disappearance of a "high" to the east, the general course 
 of the "low" is to follow. In the present case, the "low" of February 19 
 moved south into California, thence east. Such a movement, owing to its 
 infrequency, is erratic, "Highs" that continue permanent in the British 
 Northwest have the tendency to force the "lows" southward. The reading 
 of the barometer vas abnormally high over the British Northwest for 
 several days, which resulted in the storm being gradually forced south. 
 
 The most marked feature of the weather that follows the movement of 
 all storms from the North Pacific Coast States southward is the cold 
 northerly winds. While the storm or "low" remains central on the coast, 
 the "high" acts as a feeder; the cold air from the "high" rushing into the 
 field of moisture surrounding the "low" causes snow. With the disappear- 
 ance of the "low" southward through the influence of the "high," the tem- 
 rerature equalizes and the snow ceases. The relative weight or energy of 
 areas of low and high barometric pressure is taken into consideration in 
 determining their probable course. It is in this way that forecasts are 
 made, and, though the layman, who makes a study of the charts, may not 
 possess the skill of an expert, yet he is able, by conscientious study of the 
 weather charts, to make satisfactory forecasts. 
 
 CHINOOK CONDITIONS. 
 
 Chart No. 2 represents conditions most favorable to Chinook winds. 
 It is generally considered by the people living in the States of Oregon, 
 Washington, and Idaho that the word "Chinook," applied to wind, means 
 any warm southerly wind, whether it be dry or moist. It is thought by 
 many that the direct influence which produces the wind comes from the 
 ocean. This is a grave mistake. Chart No. 2 shows the controlling influence 
 to be an area of high barometric pressure over Nevada, Utah, Colorado, 
 Wyoming, Idaho, and the portions of Washington and Oregon lying east 
 of the Cascades. The center of this great field of high pressure is over 
 Northern Nevada, Southern Idaho, and Northern Utah. From the center the 
 greatest influence will be exerted. Chart No. 2 shows the temperature on 
 the morning of January 9, 1894, as follows: Roseburg, 34; Portland, 34; 
 Fort Canby, 38; Seattle, 32; Walla Walla, 28; Spokane, 14; Helena, 10; 
 Miles City, 6; Havre, 20; and Bismarck, 22. Twenty-four hours later 
 the records at Portland showed the temperature to be as follows: Rose- 
 burg, 44; Portland, 42; Fort Canby, 42; Seattle, 40; Walla Walla, 46; 
 Spokane, 34; Helena, 38; Miles City, 40; Havre, 32; and Bismarck, 32. 
 
 It will be observed that the rise in temperature in twenty-four hours was 
 as follows: Roseburg, 10; Portland, 8; Fort Canby, 4; Seattle 8; 
 Walla Walla, 18; Spokane, 20; Helena, 28; Miles City, 46; Havre, 12; 
 and Bismarck, 54. In this case, as in all other cases when Chinook winds 
 are produced, the area of high pressure is located as stated above, while a 
 low area or storm is passing over the British Northwest. The greater the 
 
NORTH PACIFIC SLOPE. 2O 
 
 rapidity of the storm, the higher the wind velocity and the temperature 
 become. 
 
 The principle involved is simple. The storm in passing over the north 
 causes an indraught of the air from the "high" toward the "low." In the 
 Columbia and Walla Walla Valleys, and the passes of the Blue Mountains, 
 Chinook winds are usually of a pronounced type, while under the same 
 conditions they are moderate in the valleys of Western Oregon and West- 
 ern Washington. Though moderate and moist, they are nevertheless 
 Chinook winds. 
 
 (Chart No. 2.) 
 
 Were it possible to trace the course and measure the temperature of a 
 cubic foot of air that drifts from the "high" in Northern Nevada toward 
 a "low" in British Columbia, we would notice a rise in temperature of 1.6 
 for every 300 feet of descent (called dynamic heating) from the high plains 
 of Nevada to nearly sea level, where it would reach the Willamette Valley, 
 for this would be its course. 
 
 When reaching the Willamette Valley, where the local atmosphere would 
 be cool and moist, condensation would take place, since the dynamically 
 heated air would be warmer. During the time the process of condensation 
 is going on in the western portions of Oregon, the storm would be passing 
 over the British Northwest, and its center would have changed to Alberta, 
 
24 WEATHER TYPES, 
 
 in which case there would be a rush of air through the gorges of the 
 Columbia River, and over the Cascades toward the storm center. This 
 cubic foot of air would undergo another change; ip. passing over the Cas- 
 cades, most of its moisture would be lost in condensation, by the meeting 
 of the cooler currents on the higher elevation. By the time this air would 
 have fallen to the plains &nd valleys of Eastern Washington and Idaho it 
 would not only be warmed through its descent but dry through condensa- 
 tion of its moisture. It is in thjs way that the great flow of air from 
 the "high" to the "low" produces the balmy but moist Chinook wind in 
 the valleys of Western Oregon and Western Washington, and the warm 
 and dry Chinook to the east of the Cascades. The farther the wind pro- 
 gresses to the east, the warmer and drier it becomes, the principles of 
 dynamic heating of the air being most perfect as the air flows over the 
 Bitter Root Mountains into Montana. In Montana and the Dakntas the 
 Chinook is a westerly \vind, and its dryness and ability to absorb snow 
 or other moisture is compared with the Foehn wind of the Alps. In explana- 
 tion of the conditions represented in the chart the area of high pressure was 
 formed through the conjunction of two areas of high pressure, one moving 
 south from the British Northwest, and the other moving east from the 
 California Coast. This movement is shown by the records of the U. S. 
 Weather Bureau on January 8th, 1894, the movements being especially 
 rapidly. The "low" first made its appearance during the afternoon and night 
 of the 8th, and arrived at its position, as shown by the chart, by the 
 morning of the 9th. The "low" continued moving rapidly toward the Great 
 Lakes, and the effects of the Chinook continued in Oregon and Washington 
 for twenty-four hours. Without the presence of the "high," the "low" would 
 probably have moved south and resulted in freezing temperatures instead of 
 the balmy Chinook.- 
 
 FIRST WINTER STORM. 
 
 The first "Winter low" of the fall season. By this is meant the first 
 storm in the fall season which appears on the coast and follows the track 
 usually followed by storms in the winter season. 
 
 The difference between an early and a late fall is in the date on which a 
 storm of such a chaiacter first makes its appearance on the coast. In the 
 summer season storms of the character of the North Pacific Coast winter 
 storms move eastward at a latitude too far north to influence the weather 
 of the Pacific Coast of the United States; with the approach of the fall 
 season these storms seek a lower latitude in search of heat, one of the 
 essential attributes of a storm. As the conditions which cause one storm to 
 seek a lower latitude are still present, other storms are influenced in the 
 same direction, resulting in a succession of storms. 
 
 Chart No. 3 shows three "lows," or stages of practically one storm, in 
 progress around an area of high atmospheric pressure. This is a type of 
 weather common to the fall and winter seasons. It is not unusual that 
 three "lows" appear on a single daily weather chart, covering 1,500 miles to 
 the east of the Pacific Coast line. 
 
NORTH PACIFIC SLOPE. 
 
 25 
 
 The chart represents an area of high barometric pressure prevailng over 
 California, Nevada, Utah, Southern Idaho, and Southern Montana. Anti- 
 cyclonic winds are blowing out from the area of high pressure toward the 
 "lows" or storms. A brisk to high southeasterly wind is blowing in Oregon 
 and Washington, while a severe southwesterly gale is raging at the mouth 
 of the Columbia River and along the Washington Coast. 
 
 (Chart No. 3.) 
 
 Heavy rain is falling in all portions of Western Washington, while light 
 rain is falling in Eastern Washington and Western Oregon. The "low" 
 or storm, which is represented as central about Tatoosh Island, Washington, 
 is the immediate cause of the weather prevailing in Oregon and Washington. 
 Each of the "lows" represented on the chart as preceding the one which is 
 central on Tatoosh Island had its center at or about Tatoosh Island, twenty- 
 four and forty-eight hours before, respectively. The only one of the 
 storms which is instrumental in influencing the weather on the coast is 
 the Tatoosh Island "low"; the others have passed to the east, where there is 
 little moisture or heat to continue the development and activity peculiar to 
 the position on the coast. 
 
 Since the field of supply of air necessary to continue the storm in activity 
 is to the south and southeast, it is essential in order to continue the perfect 
 and regular storm progression that the "high" or base of air supply should 
 
26 WKATHKR TYI'KS. 
 
 not become exhausted. With the exhaustion of the high-pressure area on 
 the south and southeast, the regular storm progression as shown on the 
 chart disappears the winds on the coast and interior abate their fury, 
 the precipitation assumes a different character, and the temperature becomes 
 much colder. 
 
 Storm No. 3 first made its appearance on the coast in the afternoon and 
 evening of October 28th, and was noted in the morning daily weather chart 
 at Portland as typical of the first appearance of a winter storm. It was 
 attended by gales on the coast, ranging from 40 to 60 miles an hour, and 
 having heavy rain in the western portions of Washington and the north- 
 western portions of Oregon. From the conditions represented by Chart 
 No. 3, storms continued to appear over Northwestern Washington at reg- 
 ular intervals of twenty-four hours until the 2d of November, when an 
 area of high barometric pressure of exceptional dimensions appeared on 
 the California Coast, and, moving northward, caused the storms on the 
 north to seek a higher latitude. 
 
 Since eight to twelve hours of temporary clearing weather follow a 
 storm after it has taken an easterly course, study of the above conditions 
 would tend to explain why apparently good local signs of fair weather are 
 so soon followed by stormy weather. 
 
 THUNDER STORM. 
 
 Chart No. 4 was made from conditions which prevailed on the morning 
 of June 3, 1894, at 5 A. M., local time, and is selected to represent typi- 
 cal thunder-storm conditions. Frequent and severe thunder storms occurred 
 on the 2d, 3d and 4th of June, 1894, in many portions of Washington, Ore- 
 gon and Idaho. The above map also represents the conditions preceding 
 the occurrence of a tornado of unusual severity at 11 o'clock on the morning 
 of June 3, at Long Creek, Grant County, Oregon, the only tornado occur- 
 ring in the State of which there is an official record. In the Northwest Pacific 
 Coast territory, embracing the States of Oregon, Washington, and Idaho, thun- 
 der storms attend the advancement of areas of low barometric pressure which 
 have their origin, as a rule, in the northern interior portions of California. 
 These areas of low pressure are the result of excessive heat in Northern and 
 Central California, the temperature frequently rising to 104 to 108 and 
 remaining warm for many consecutive days. Two or three days of excessive 
 warm weather usually suffices to produce a local barometric depression. 
 These areas of low pressure advance northward into Southern Oregon, thence 
 easterly into Eastern Oregon and Southern Idaho, or northeasterly inio East- 
 ern Oregon, Eastern Washington, and Northern Idaho. With the advancement 
 of the areas of low pressure the area covered by them increases. While the 
 conditions most productive of thunder storms have their origin more fre- 
 quently in California, the rule is not unvarying. On June 2 and 3, 1894, 
 through the agency of excessive heat throughout Oregon, portions of Nevada 
 and Washington, an area of low barometric pressure was formed over Oregon 
 which caused general thunder storms and furnished the data for the chart 
 presented herewith. 
 
NORTH PACIFIC SLOPE. 
 
 27 
 
 Thunder storms are frequent in Eastern and Southern Oregon, Eastern 
 Washington, and in Idaho. They rarely occur in the western portions of 
 Washington, and Northwestern Oregon. The rarity of thunder storms is 
 so marked in sections of Western Washington and Northwestern Oregon that 
 season after season passes without so much as a distant peal of thunder being 
 heard. 
 
 (Chart No. 4.) 
 
 Thunder storms arc more frequent during the months of June and July 
 than at any other time, and are almost invariably attended by severe hail 
 of a character to damage crops, and at times imperil the lives of grazing 
 animals. Owing to the small area covered by a thunder storm, several have 
 been known to be raging at the same moment within a single barometric 
 depression; for this reason thunder storm forecasting is unsatisfactory work. 
 That a thunder storm will occur somewhere within an area of low pressure 
 within a specified time can be forecasted with great accuracy, but the exact 
 position of the storm within the area of low pressure is a more difficult prob- 
 lem, and one which requires the light of more frequent telegraphic reports 
 at a greater number of reporting stations. 
 
28 
 
 WEATHER TYPES, 
 
 SUMMER WEATHER CONDITIONS. 
 
 Chart No. 5 represents the appearance of the first summer "high" on the 
 Pacific Coast during the season of 1896. Study of Pacific Coast weather types 
 has determined that there is a well-defined area of high barometric pressure 
 which appears on the North California or Oregon Coast sometimes in the 
 spring or early summer, which, by a characteristic northerly movement, is 
 indicative of a decided change about to commence in the general character 
 of the weather for the remainder of the season. It is important for the 
 
 7 ~*?\ -C. & Dqartmeirt of Agricnllore WaUberJUp. I , 
 
 (Chart No. 
 
 student of the weather or one whose business is affected by weather changes, 
 to know that such a distinguishing feature of the weather develops each 
 spring, and by access to the Daily Weather Maps furnished by the United 
 States Weather Bureau its appearance can be ascertained. It is important 
 for him to know that there is a type of weather which develops each spring 
 and which marks the time between winter and summer. 
 
 It is to be understood that when the "summer high" appears a change 
 in the weather of a summer-like character is about to commence; this is 
 quite certain, whether the high appears in March or in June. It is not to 
 
NORTH PACIFIC SLOPE. 29 
 
 be understood that with the appearance of the "high" the rains will cease, 
 but that the rains will be more showery and less frequent. Increase in the 
 amount of sunshine, higher temperatures, and more frequent periods of fair 
 weather should follow the first appearance of a "summer high." With the 
 appearance of the "summer high" general and prolonged spells of rainfall 
 should cease and temperatures normal or above should follow. 
 
 Chart No. 5 was made from conditions which existed on the morning of 
 June 13, 1896. The "high" is represented as prevailing over Western Wash- 
 ington, extending westward along latitude 48 north. This "high," which 
 is considered typical of summer, moved from the southwest, showing first on 
 the California Coast. It continued moving north along the coast in British 
 Columbia, thence easterly; which is the movement typical of the "summer 
 high" which distinguishes it from the "highs" of the winter season that 
 appear on the California Coast, move northward to about latitude 45, thence 
 east to the North American plateau, where their progress is frequently 
 checked. 
 
 In the spring of 1895, the "summer high" appeared on April 20th; the 
 character of the weather then changed and farming operations progressed 
 with only slight interruptions from the weather. In the spring of 1896 the 
 "summer high" not having appeared until June 13th, the season was consid- 
 ered six weeks late, farming operations were impeded by rain, and seed 
 decayed in the ground, owing to the cool weather. 
 
 Knowledge concerning this feature of Pacific Coast weather is of incal- 
 culable value, since it may be regarded as the initial sign of spring. 
 
INDEX. 
 
 Abbe, Prof. Cleveland 9 
 
 Blandford, S. M 2, 20 
 
 Chart No. i (A Winter Storm) 21 
 
 Chart No. 2 (Chinook Conditions) 23 
 
 Chart No. 3 ( First Winter Storm) 25 
 
 Chart No. 4 ( Thunderstorm) 27 
 
 Chart No. 5 ( Summer Weather Conditions) 28 
 
 Chinook, Definition of Term -*z 10 
 
 Chinook Conditions 22 
 
 Chinook Winds 7, 10, 22 
 
 Forecasts, Long-Range 8 
 
 Forecasting Weather 3 
 
 Moore, Prof. Willis L i 
 
 Pague, B. S 2, 3, 8, 16 
 
 Preface 2 
 
 Sensible Temperatures 16 
 
 Summer Conditions 13, 28 
 
 Thunderstorm 13, 26 
 
 Weather Forecasting 3 
 
 Weather Maps 14 
 
 Weather Types 6, 20 
 
 Winter Conditions 13 
 
 Winter Storm 20 
 
 Winter Storm, First 24 
 
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