68 MONTHLY REVIEW. FEBRUARY,1907 This was the first taste of real . Lamp wan lighted in will be of interest to determine the intensity and the proba- the house for the first time this evening.’ This was needed bility of rainfall for each month. on account of the cloudiness and the fact that the sun diaap- As a description of rainfall is incomplete without mention pears behind the mountains in the west and north on Aimter- of its special features, attention ail1 also be given to the dam Island. Snowfall at 6 p. m. measured .15 inch. frequency and intensity of excessive monthly and daily - dugitsf ?S.-Light during the preceding night followed falls, and (since it is not of sufficient importance at this station by cloudy with brisk northeast wind. Light snow flurries at to be considered separately) some information concerning intervals from 10 a. m. to 2 p. m. Temperature below freezing the snowfall will be given. all day. -1n~ual arid sensoiial rai)?fnll. Artgust ,?.9.-Cloudy, cold weather with brisk northeast wind The average annual rainfall at Tacoma is 45.36 inches, the in the forenoon, becoming light in the afternoon. Traces of greatest amount recorded in any one year being 54.67 inches, rain and snow at intervals until 2 1). m., the rain freezing as it fell. the least amount 35.58 inches. Of the average annual amount Heavy snow flurry, 3:30 p. m. to 3:45 p. in., followed by occa- 34.15 inches, or 75.3 per cent., falls from October 1 to Bpril 1, sional lighter ones. Wind became light and ahifted to west SO that the wet may be said to cover the six months about 230 p. in. Snow on ground at G p. m., 1 inch. beginning with October and ending with March, the other six A rrgtrst ZO.--Uloudy with occasional snow flurries. Light being the clrp season. The average monthly amounts for the westerly wind. ranee from Y.:jO inches in October and H.91 inches A //gust .J’I.--Snow cont,inued a11 night with teiiiperature in March to S.%7 inches in Novemlier and ‘7.0s inches in De- below freezing. Snow 4 inches deep at 7 a. m. Snow flurries cember; for the clrp season the range is from .64 inch in July at intervals all clay with fresh westerly wind. Snowfdl for aud .59 inch in August to 2.!)1 inches in April and 2.52 inches prececling twenty-four hours at 6 p. m., ci inches; cleptli on in Septeiiilier. These figures show that the rainfall in No- ground, 5 inches. reniber and Deceniber is cupions and that July and August are almost rainless. The expedition departed froin Danes Island on September il’d mid dry Iwriotls. 4,1906, leaving the instruments in charge of nh. Felix Riesen- berg, mho mill continue the meteorological observations tliru- Defining n rainy clay as one on which .01 inch or more of out the year. The meteorograph, however, was brought bnck rain falls, we inay expect annually 162 rainy days. As a rule, to Paris and left with Richard for repairs. there will be 9 or 10 consecutive rainy clays iu each month from Novemlw to Felxuary, inclusive. The longest rainy ~~ A CLIMATIC SKETCH OF TACOMA, WASH. period on record for the rainy seasnn is 23 clays; the longest By E 8. QITTINI.~,jr , AIsiqtaot I,bst~\ei Ilateol T‘t*o)ii~d, \\ra>li , rclvrw.i) 27, Illlli. period without rain in nieasurable amounts is 15 clays. Dur- ing the there will, as a rule, he only 2 consecutive The object of this sketch is to present in popular form as rainy clays in July and August ancl 4 consecutive rainy clays complete a description of the of this station as is pos- in each of the other four ruonthH. The longest rainy period sible without the introduction of extensive tabular compila- recorded for the dry season is 9 clays; the longest period tions of data. To the ordinary reader nothing cau be less without rain is 39 clays. interesting than column after coluiiin of figures. It is true that these figures are very necessary to the complete under- It1 t~iis if!/ nil rl 1ii,ohaliilr f y c!f m i )! fdl. standing of a climate in all its varied phases. Still it is be- If we divide the average amount of rainfali in inches during lieved that by presenting and briefly describing the mod im- :tnj iiionth by the average number of rainy clays iu the month, portant features to be found in the tables it is possible to we obtain what is known as the :tverage intensity of rainfall convey to most people a much better general kiiowledge of in inches for a day in that month. In the wet season the the climate of a place than they woulcl be able to gain for intensity varies from .25 in October and .24 in March to .35 themselves, even if they were patient enough to delve into the in December and .4l in November. In the dry season the figures. range is from .1G in July and .15 in August to .a2 in April The records on which this paper is based are those of the and .25 in September, the cleciiual representing the fraction Weather Bureau from May 1, lSY7 (on which (late this sta t’1on of an inch in each case. was established) to January 31, 1907, so that while the period By clivicling the number of rainy day^ in any month by the covered lacks three months of a full ten years, yet it includes number of clays in the month we obtain the proliability of ten Januarys and ten Julys. The subject will be treated under rainfall for that month. In the wet season the probability the following heads: Rainfall, temperature, and miscellaneous esprest in Ibercentage ranges from 42 per cent in October and conditions (including sunshine, cloudiness, etc.). 52 per cent in March to 65 per cent in December and 70 per cent in Noveiiiber; in the dry season the range is from 13 per RAINFALL.‘ cent in July and August to 33 per cent in September and 43 As the rainfall is perhaps the most interesting phase of the per cent in April. climate of this section it will be treated first. Ainong the im- portant things to know about rainfall are the total aniount that falls annually and the distribution of the annual amount anlong When 10 inches or more of rain falls in a month the rainfall the clifferent , the latter especially when the di\tribu- for that month is considered escessive; for 24 hoiirs a fall of tion is very unequal, so that there are a wet season and a dry 2.50 inches or illore is escemire; and for a single hour a fall season, as is the case at this station. Next, considering each of 1 inch or more is excessive. season separately, we wish to know, in addition to the sea- During the past ten years there have been seven months sonal distribution of the total annual rainfall, the following when the rainfall was excessire, five Novenibers and two particulars: The period of time over which each season ex- Pecembers, the greatest monthly fall on record being 14.48 tends, and the greatest number of consecutive rainy clays and inches in December, 1897. There have also been five excessive of days without rain that usually occur in each. Subdividing daily rainfalls, the heaviest 24 hour fall IJeing 3.79 inches in the seasons into months ancl considering these separately, it November, 1904. d fall of 1 inch in a single hour has never - ~ ~ been re corde(1. * See footnote under dune 21. . Sti I i uJfall. Thruout this article whenever the writer uhes the evpressiou raiu- fall ”, he evidently includes the amuunt of melted siinw, if any. The average annual snowfall at Tacoiiia is 15 inches. As a

Unauthenticated | Downloaded 10/02/21 05:35 AM UTC FEBRUARY,1907. MONTHLY WEATHER REVIEW. 69 rule, most of the snow melts as it falls. No snow has ever humidity is due to the prevailing northerly winds becoming been recorded from May to October, inclusive, and only three charged with moisture from the surface of Puget Sound, times in April and five times in November. The average which extends northward from this station. number of days annually on which snow falls is eight, the The freedom of the from long-continued cold spells greatest number in any one year being thirteen, the least, and from extremely low temperatures is much more noticeable two. The month of maximum snowfall is January, with an than is the lack of hot weather in . In fact it is average of 6.6 inches. The heaviest fall recorded in twenty- chiefly to tlie inilclness of the winter season that the equabil- four hours was 8 inches, in January, 1899. The average ity of temperature at this station is clue. The average num- maximum depth to which snow accumulates on the ground is ber of days annually on which the minimum temperature falls 5.9 inches. The greatest depth it ever attained was 16 inches, below the freezing point is 29, these days usually occurring in ,January, 1899. The greatest number of consecutive days between November 1 and April 1; and in October about three with snowfall in appreciable amount was 4. times in five years, in April a1)out once in thee years. The Gr)zc~*nlrmarks o)i rni)fnll. greatest number of successive days ever recorded with rnininia below freezing is 13. A few general remarks concerning the rainfall may serve to make this description more c*oniplete. The statement that in the winter months periods of ten clays' rainh are to be espectetl The average date of the first killing frost in is No- does not mean that the rainfall during these clays is incessant. reiiiber 19, the earliest ever recorded occurring October 18. The fact is that very much of the rainfdl is intermittent; The averaxe date of t,he last killing frost in is April 1, periods of several hours at a time when it does not rain are the latest ever recorded occurring April 8. quite frequent even during the wettest periocls of the rainy Do il!y ru~ge nntl iwinbility. season. Sometimes there is sunshine for an hour or so The mean daily range of temperature varies quite uniformly between showers. The somewhat prevalent notion that the from 19.9' in ,July to 9.4' in December and January. rainy season here is one of an unending downpoi~ris quite The mean variability, or the change in temperature from erroneous. Another point wortlig of notice is that exceed- one clay to the nest, ranges from 2.6' in August and Septem- ingly heavy showers, such as those that accompany thunder- ber to 3.5" in December, showing that great changes from day and , are almost unkiiown here ; the fact to d:ty are remarkably infrequent at all seasons of the year. that an hourly fall of 1 inch Bas never been recorded bears SUNHHINE, C'IAIUDINESS, AND MIIRCELLANECJUS CONDITIONS. out this stateiiient. The average annual sunshine nt Tacoma amounts to 40 per TEMPER 4TURE. cent of the possi1)le. The sunniest year on record wus 1Y9H, In considering the temperature conditions we sliall fiiicl that with 51 per cent; the year of least sunshine was 1903, with 28 there are no well-defined periods separating the s~ascinsfroill per cent. The sunshine is very unequally clistributed thruout one another; in fact the traiisition froill suninier to winter the year, this distribution following closely the dry and the and from winter to siimmer is so gradual that it is scarcely rainy seasons. The month of maximum sunshine in July, with more noticeable than is the seasonal change from the long an average of 63 per cent; that of minimum sunshine, Decem- clays of simmer to the short ones of winter. ber, with an arernge of 11 per cent. The sunniest month on The mean annual temperizture is 50.9'. The mean monthly record was July, 1906. with a percentage of R4; the month temperatures have a range of 23.7' from G3.3" for July to with the least sunshine was November, 1904, with a percentage 39.6' for January. The extreme monthly range (tlint is, the of 2. difference between the warmest month and the coldest month These figures show tlint in the clry season sunshine is quite on record) is 34.4' from 68.0' for July, 1W6, to 33.6' for Jnn- plentiful, 1)ut in winter tlie sky is usually overcast. During uary, 1907. Tlie means of the extreme nionthly temperatures the five successive nioiiths from October to February the aver- are as follows for the months given: July, masiinuiii SX.C;", age percentage of sunshine for the entire period falls to 23. minimum 47.9"; January, maximuill 55.2", miniiuuiu 91.7 '. The average annual cloudiness is G5 per cent, ranging from The means of the daily maxima ant1 the daily iiiiniina are: for 42 per cent in July to SG per cent in Deceniber. For the year July, maxima 73.2", minima 53.3" ; for January, maxima 44.2", there are 52 clear, 101 partly cloucly, and 192 cloudy days; minima 34.9'. The first group (means of estreines) indicates for July, 15 clear, 10 partly cloudy, and 6 cloudy clap; for that at least once in July a inaxiiiiiim of nbout 88.6" and a December, 2 clear, 4 partly cloudy, and 85 cloudy days. minimum of about 47.9" will usually occur; in Jitn~iarja There is an annual average of 39 foggy days, 5 of which maxiiuuni of about -55 2' am1 a niinimum of about 21.7' may occur during the clry season and 3-1 during the rainy season. lie expected. The extreme ninsiuum on record was 9H.O" in There has been only one dense in *July during the ten July, the extreme iuiniiiimn 9.0" in January, giving n total years covered by the records, while there are, as a rule, 8 range of 89.0'. The second group (ineans of niasima and of foggy days in Deceiiiber. niinima) shows the means of the daily mnsima and of the A light smoke from forest fires usually sets in about the 1st daily minima for tlie respective niontlis and it is of more of August, and generally it continues alniost unabated, corn- importance from a climatological standpoint, as it shows more pletely o1)scuring the horizon, until the middle of September nearly what are the usual conditions. or the 1st of October, when the first general serve to There usually occurs one clay each year with a temperature estiuguish the fires. This smoke occasionally becomes so of 90" or over, and with the exception of one period of three dense as to obscure the SUR as edectually as would thick alto- successive days, more than one day at a time with a mminiuu stratus . of 90" or over has not been recortlecl. From and violent winds Tacoma is remark- In comparing these mnsinium temperatures with those of ably free. As a rule. there are about three thunderstorms in continental, or dry and mountainous regions, it must be a >ear, and most of those that occur are hardly noticeable, it remembered that a high degree of temperature 111 this climate usually being impossible to observe any of the that will be found very much more oppressive than will the same accompanies them. The highed winds occur during the win- degree in those regions. This is explained by the fact that the ter. Most of them are of less intensity than and do not relative humidity at this station is rather high even in sum- do any great clamage. The only damaging winds are those mer. so that the so-called sensible tenipepature, or that actually froni the northerly cluarters, which cause considerable trouble felt by the liunian body, is also quite high. The high suiiimer tn tlie shipping in the harbor; these northerly blows are very

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TABLEI.-Mon.thly rainfall, in inch, at Tawma, Waah. infrequent, however. By far the greater number of high winds come from the southerly directions. The number of gales (winds of 40 miles or over per hour that continue for periods of at least five minutes) is usually about two in three years. 1897...... 1.46 1.54 0.87 0.58 1.41 1.63 12.31 14.4R ...... The highest wind velocity ever recorded at this station was 46 1898.. . 3.01 8.68 2. 26 1.12 2.41 0.26 0.38 4.24 1.60 5.93 4.73 35.58 miles per hour from the southwest. 1899. .. 9.17 4.50 4.58 2.75 1.27 0.21 2.26 1.93 3.23 10.11 7.05 50.88 1900... 4.97 4.66 1. 17 4.62 3.22 0.33 0.84 1.57 I 6.13 5.23 7.97 46.82 TABLES. 1901.. . 6.48 6.66 5.93 2.26 1 1.46 10.60 10.32 12.42 12.60 9.62 4.63 45.75 1902 ... 6.21 7.78 2.96 1.83 1.87 1.91 0.26 2.75 2.88 10.u 10.44 54.6i For the benefit of those who desire more detailed infornia- 1903.. . 8.23 1.35 3.05 1.691.04 12.591.56 10.800.94 10.750.07 13.590.40 I 1.272.72 10.00 4.51 45.11 1904... 6.39 7.57 3.84 11.88 5.07 45.91 tion than that given above, the preceding tables, showing the 1905 ... 4.93 P 51 0.71 4.15 3.23 0.34 0.39 2.79 6.50 36.60 1906.. . 5.85 3.95 1 1.09 290 2.75 0.21 0.08 4.11 5.46 42.10 monthly rainfall, temperature, cloudiness, and the average 1907.. . 3.92 ._...... I...... hourly velocity ancl prevailing direction of the wind for the Av'ge. Illil5.91 6.28 3.91 2.91 2.38 2. 17 0.64 same period have been compiled. Averages in black figures are from 9 )ears record. *Sum of uontbl) aveiages SNOW ROLLERS AT CANTON, N. Y. TABLE2. - Mean tetnpericture, ti degreea F., at Taconta. Wmh. li) XI I,. ~ILICH. Uhserver. 1Iatt.d Cantvii, N T.,hlanh 10, 1907. - ~ ~~ -.- I send a few notes rehtive to the formation of snow rollers Date. k --h - -7 c, i' in the iillage of C'anton on February 19,1907. 1- ~ ~ - ____ ~~~ - The conditions attending the formation of the rollers were ...... 61.4 66.2 56.0 so. 0 42.51 41. 7 ..... 44. Y $9.0 4Y. 2 56.4 60. 3 63 8 65.6 59.6 50.6 43.4 38.2 51. 0 as follows : Upon a dry and evenly distributed snow covering 1899.. . 40.4 ?.Y, 0 42. s 47.2 50.6 56. Y 64. IJ 59.6 60.0 50.7 5o.Y $2. I 5u. 3 of 4 inches depth there fell late in the forenoon of the 19th a 1900.. . 42.2 41. 7 49.0 50.4 55. 2 61.4 64. 0 61. 3 57. 2 50. 0 42.6 44.2 51. G 1931 ... 39.3 41.6 44.6 46.4 5:;. 4 56. 1 60. 8 61. 2 56. 0 51;. 0 47, 6 40. X 511. 6 half inch or more of fine, dry snow. After 1 p. m. the falling 1902.. . 33.4 45. 2 43. R 4s. 2 55.5 59. 1 62. 3 62. 9 57.0 53.0 44.4 4U. 6 50. 9 snowflakes were of greater size, becoming large, moist, and 1903 ... 41.5 38. 7 41.6 46.4 53.3 60.8 6U. 8 64.3 56. 7 si. 2 45. 3 4I.U 50.0 1904 ... 41.0 ?X.1 41.G 51.3 53.6 58.0 63. 2 tX.9 60.2 53.6 48.7 4'2.7 51.2 feathery after 325 p. in. and continuing to 4:25, by which time 1905. .. 39.3 42.2 4s 6 51.3 51.1 5:i.n 64. 8 69.6 59.4 47.4 43.8 -10.7 51.1 1906.. . 41.4 .12. 7 44. 2 52.0 54.2 5i. 8 68.0 64. 1 53.6 53.0 44.2 41.3 51.8 a total of about 6ne inch had fallen. Light snow, with about 1907.. . 33.6 ...... one-tenth inch of dry sleet, occurred from 4:95 to 655 p. m. .4r'ge. 33. 6 41 4 44.2 49. a 54.2 58. s 63.:: li3. 2 58. 1 51.6 45. 4 41.5 60. 9 The teiiiperature, from 10" I?. at the S a. ni. observation, -~. ~ ~~~~ ~~~ ~~ ~ . ~~ ~~ ~ ~ increased to 17" by 3:15 p. m., then rose suddenly to 31' at Averages in black figures art: f'miu 9 yeah record. :<::?(I, and slowly to 3-1" by shortly after G p. m., froin which TABLE3.-Average C~OU~LWR,percentage, ut Tacoma, 1Vtcsh. nmsimum it fell to 17' by 7:15 p. m. .~ ~~ ~~ ~~ ~ - This abrupt rise of temperature and brief thaw accompanied r 0 ca a a a southwest wind nith a velocity of 30 to 40 miles per hour that - z Y * ___ -I--\- ~~ ~ - ~ burst suddenly upon this locality at 3% p. ni., displacing the 1897...... 54 74 27 58 65 90 8; ..... northeasterly winds of 4 to 13 miles of the morning and mid- 1898.. . a0 80 56 58 45 50 43 SI 60 Yl I 74 .iY 1899.. . 90 81 67 71 76 57 6Y 4.3 74 8i 90 70 day, which had continued practically up to that hour. 19ou ... 19 80 71 65 70 63 58 60 75 75 38 09 Tho the formation of the rollers was not witnessed, so far 1901... ,a 6(J 71 61 6:: 70 37 52 69 s3 R6 65 1902.. . 78 83 77 713 76 56 ::7 53 i9 94 94 71 as ascertninecl, it is known to hare occurred in the late after- 19~,., 95 6H 7:< 74 75 74 1;7 71 6" !I I 83 74 IIx)4.. , 85 Sn 66 60 GO 49 I2 Sl; 's! 66 noon or early evening, probably between 5 ancl G p. m. Small 1YU5.. . 70 54 69 52 M 7.5 69 72 89 65 rollers were found nest morning in a variety of locations. The 1906... 94 76 71 6.5 42 59 6s 83 hl 6i 1907... 67 ...... I ...... largest had been developed 011 a sloping lawn where the strong Av'ge. 82 76 69 4s 5i 69 S4 SS 67 wind, striking the esposecl side of a large cottage, had swept

~~ ~~ - -~__ downward and away, rolling the snow downhill. Here the A\rrnges iu black lignrcs are fiom 9 years re,ord. largest attained diameters and lengths of 10 to 13 inches. In TABLE4.--A.~iwilnig wind directions and average hourly velocitieH [if structure they closely resembletl rolls of cotton batting, but Tmv.mlcc, Wuh. the centers were almost invariably shorter than the outer layers. The layers were plainly iuarked and varied somewhat in tliickuess, averaging probably three-fourths of an inch or inore arid being usually thinner near the axis. In occa- 1897...... I..... I ...... ~ .... * * SW. I6.n s\v. 6.4 1898.. .. sw. 5. n ::: ~~~~isn.siv. 17.2'11,~8.3~sw. ~S.41 5.4 sw. 6.5 11. ~6.615.6 11. ,~ 5.4S.7 sioiial instances the centers mere very short or almost wanting; SW. i&5I;sy. 1899.. .. 7. 1 and the rolls, altlio firm enough nest morning to be handled, 19oo... . si,.. 5. 4 sw. sw, 55 11. 5.6 S\\'. 5. 9 11. 1901.... R. 6.2 s. 7.8 st!. 6.9 11. 6.6 sw. 5.4 .-\*'. 6.7 11. 1 z:: were iuuch lighter than snowballs of the same size when rolled 1902.... s. 5.2 1903 _.. si,.. 6. 7 by hand, thm indicating but slight packing of the snow in the 1904.... *w. 7. 1 wind rollers. 1w5 .... sw. 4. 9 1906.... sw. 6.2 From the conditions observed in this instance it would 1907. _.. SK. 7.4 appear that the flakes of a light, fluffy layer of surface snow 6. 2 are made adhesive by a sudden rise in air temperature while

~~ the under snow still remains cold and dry, and the particles of damp surface snow are enabled to adhere to each other but not to the dry under snow. A strong wind inay then push 1897...... over little prominences or projections of the surface snow and 1898 ...... 18Y9...... start them rolling, when of course they will continue to travel 1m...... ancl 1901...... 11. 14.4 I 11. 15.1 I sw. 14.4 I SW. I 5.8 I s~.16.~ i I 5.9 grow until tlie resistances overcome the propelling power 193"...... of the wind. 19w...... 1904...... The accompanying photographs [see figs. 1 and 21 of the 1905...... 19M...... Canton rollers were taken by Mr. Ford &loran,of the class in 1907...... I ...... l .....,...... ~ ...... at St. Lawrence University. Another meniber of the class in cliiuatology, Miss Ione A. ~-___ Jillson, subsequently reportetl having once witnessed the for- Averages in 1 mation of snow rollers, and at the suggestion of the writer

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