JUNE,1922. MONTHLY WEATHER REVIEW. 295 Kbppen in Bsrtholomew's Atlas, which in turn were are dated as to month, though not as to year. Koppen's eralized from Meldrum, long director of the Mauritius tracks are dated only as to season, November and Decem- Kservahry. "he wider lines indicate that three or ber, January to March, and April to May. more stony followed approximate1 that course in a This chart and foregoing data lend little support to the 35-year penod. The numeral at tie end of the line oft-repeated genera.lization that tro ical cyclones origi- indicates the number of storms along that track in that nate in a few restricted areas on t e western sides of eriod. Koppen's charts have been combined and modi- oceans at, the time when the doldrumsR are farthest from led to aid in legibility and have been supplemented by the Equator. Many o ther widely accepted ueneralizations several notable tracks shown in Ein Atlas fiir den In& as to tropical cyclones a pear unsafe in tze light of the &en Ozean, Deutsche Seeciurte, 1891. The latter tracks fuller data being gathereT; . TROPICAL CYCLONES IN THE NORTHEAST PACIFIC, BETWEEN HAWAII AND MEXICO. By STEPHEN S. VIBHER.

\Indiana University, Bloomingtan, Ind.)

Reaeld, in his paper on cyclones of the Pacific, forming List 0~ tropical mjclonic stoma in the northenst PaciJc (west of MeTicoaad a psrt of Co-odore Perry's Narrative of &.pQditioll to , ('ealrul dnuricaa)&deast of the longitude of the Hawaiian Islanda-Con. Japan, devotes six pages to the northeast Pacific,' and presents a chart showmg the approximate tracks of 13 cyclones most1 in the region just west of Mexico, but Year. Month. - Source of Information. partly near Jawaii. In the Segelhardbuch -fGr den North West Stillen Oze.anz there is a list of 45 storms occurring in that mgitude. region between 1832 and 1893, no mention being made - however. of those described bv Redfield. lS5.5 ...... June ...... 20 105 Redfleld. No mention of tropical cyclones occurrinu in this 1s...... Aug.S-6 ...... 1s 1W n. S. H. region between and has conie to ligyit except 1S:S ...... Aua. S-9 ...... 15 I 117 Bedfleld. 1892 1915 1% ...... Bept. I ...... 20 I 1'22 Hedfleld. that the courses of Six are traced by HurdSJ IS57 ...... JuneW ...... 11 110 D. S. H. 1s;...... Sept. ti ...... 19 121 D. 8. H. Severe storms occurring in September, 1915 and Sep- 1SS...... -4ug. 17...... 13 11.5 D. S. H. lSi.5...... Nov. 21...... "1 174 D. 8. H. tember, 1918, are described in the MONTHLYWEATHER lsis ...... dey t ...... 10 16 w D. 8. H. lyii ...... Ju v25 ...... 10 109 D. s. H. lS70 ...... June 17 ...... 16 1% D. 8. H. Since August, 1921, brief mention of four tropical lii0...... Sept. 21-24...... 17 141 D. d. H. 1,571 ...... July3 ...... 16 117 D. 9. H. cyclones haa been made in the same journal? lg74 ...... Nov. I9 ...... lti 161 D. P. H. The followin list includes the 70 storms mentioned in ls77 ...... Nov. 5 ...... 14 1'& D. 8. H. l!W ...... July6 ...... zu rm D. Y. E. these sources of information: 1.W...... , Ozt. 13 ...... I 18 111 D. e. H. I&...... July 3L...... 13 118 D. 8. H. List o tropical yclonic stornis in the northe(i8t Pari c (west of 3iurii.o nwl IS* ...... 1 Repl. 7 ...... 14 105 D. 8. H. Cf,itral Amerira and cast oj'the lottgitide <$the aicniiati Islatwis.) IW...... _I Yept. 21-33...... 3u lo5 D. 8. H. Q ASS*...... 01%.3...... 23 108 D. P. H. ISM...... I Xep1.W ...... 17 107 D. 8. H. IS*...... ! Oct. '33...... 24 107 D. P. H. Place of origin, or 1sIi5 ...... July31...... au 130 D. S. H. I 6rst record. 1s...... Sept. 12 ...... I m D. s. H. Month. --- Sourre of information. 1s: ...... Oct. 5-6 ...... ?A 108 D. 8. H. Pear. IW...... Oct. 25 ...... 1uB D. 9. H. North West 1W...... Se t 18 ...... 2 95 D. 8. H. 1 I latitude. longitude lSi ...... Ju& 3u 114 D. H. I ...... S. 1x37 ...... I Out. M ...... li 1Ui D. 8. H. 15 Ell D. S. H. l&%...... Aug. V3-14...... i 1" 1% D. a. H. 1832...... December...... 13 1s D. S. H. 1YW ...... Sept. 10-11 ...... 17 106 D. S. H. 1- ...... Nov. 1 ...... 23 106 D. S. H. IW...... Bept. W ...... 23 107 D. 8. IE. 1840...... do...... "2 105 D. S. H. 1,SgQ...... dllg. >3*...... 14 122 D. 8. H. iM2 ...... October ...... 15 93 D. S. H. 1m...... lug. 18-19...... 16 l2.I D. 8. H. 1e4a ...... sept.23 ...... 13 13Y Redfield. 1S1 ...... Aug. 2 ...... 1G 11s D. 5. H. 1S47...... Oct. 24 ...... 17 Redfleld. 1w1 ...... Aug.7 ...... 11 10i D. 6. H. 1W...... JuneZ1-22 ...... 1 16 110 Redfield. WXZ ...... July 19 ...... zu 1 li D. R. IT. 1850...... Redfield. 1902 ...... Dec. 234011.2..... 21 15s Hurd. 18jg ...... June% ...... 16 10i Redfield. 1904 ...... Nov. SDm.4 .... 18 161 Hurd. 1850...... Aug. 5...... 11 b 117 Redfleld. iw ...... DW.23-30 ...... 15 1.56 Hurd. 1850...... Sept. 9-11 ...... 15 IW Redfleld. 1W...... May 3-10...... I2 151 Hurd. 1850...... hut. Z...... 26 123 Redfleld. 1w16 ...... Oet. w ...... 1s 154 Hurd. 1850 ...... I oct. 14...... I 18 Redfleld. 1- ...... Nov. 8-13...... 20 157 Hurd. 1850...... I oct.3...... I 14 c117 Redfield. 1915...... Sept. 4 ...... 15 110 M. w. R.,a;*. 1850...... October ...... 17 105 D. S. H. 1918...... Sept. l%lti..-. .... 18 105 MWR 46'-568 1851 ...... 15 1'10 D. S. H. 1921...... Sept. 24-30 ...... % 105 M' W' R" 491-518: 1851 ...... 21 107 D. S. H. lWl.-...... Ort. 4...... 22 158 M: W: RY ,49;-579. 1851...... Redfleld. 1921...... Oct. 9...... 17 102 MWR 49:-581. lsSa ...... July 16-19 ...... E :::: D. Y. H. 1Y2...... Feb. 1 ...... I-...... M: W: R:: so;*. 854 ...... I Oei.5 ...... I 28 135 D. S. H. I I a NNE. b N.-W.4. I NE.-NN W.-WN W.-Y W. Fm # SE. c 8W.-BE.-E.-N.-W.-S W. b W E. Hurd: Article Cyclonic storms and typhoons north PsriEc. 8. d BE.-NE. Of the u. eRODlN. Weader Bureau, Januarj. March, and April, 1913. 1 Willlam C RedBeld: Vol. I1 1858 Ben. Doc. 79, pp. 354-359. D&he 8warle ' 189i p. 309. The monthly distribution of these storms is shown in a Wlllis E. Hurd: byclmlc st&mn hnd t hoona of the north Paciflr artirle on the reverse of MetWtOlo 1 Chartd oj the Wrt~Pnrffrc,U. 9. Weather E&eau, January, Table 1. All but two have occurred in the six-month IU8rcl1 mdA ~1 l!!? period June to November, inclusive. September with 'J. f.Kim& A Pw1P.c hurrleane of Saptember 1915' Mo. WEATHERREV., vol. 43, p. 4$& and F. Q. Tingley: Tropical cyclone of Beit. 1&17,1918, Just west of Mexico; 3s per cent is the stormiest month, but October with YO. WEATHeS REV Y' Ml3. * F. Q. Tlngley, MS. WEATEEB REV., 4% 518,579,581; and I; 99. 25 per cent is only slightly behind.

Unauthenticated | Downloaded 09/28/21 05:25 PM UTC 296 MONTHLY WEATHER REVIEW. JUNE,1929 TABLEl.-Monthly distribcctwn of the foregoing stomur between Hawaii Table 2 indicates the approximate area of origin or of and Central Anwrku. htreport of these storms. This table is a revision of the one by Schiicke While he studies only the 45 storms listed in the Segelhaiidbu.ch, here GS storms are considered, c) ~ two of the 70 storms given in the foregoing list not being Numbei..... readily located from information at hand. Per rent of total ...... 0 1.6 0 0 0 Figure 1 shows the approsimate courses of about 60 I tropical storms in the region under consideration. These TABLE2.-% ical yebikes of the nmtheuat Poci +Region of origin tracks were obtained from the several sources (l), the or first reeorJof storm for 18$+19Jp, elassijJacoorc+ing to iiioiiths chart by Reclfield,' (2) a chart in the Segolh~dbu,chfiir aid 50 squarcs. den. Stitlen Ozean.8 (3) A large number of the tracks were copied from the official German atlas of the Pacific.g (4) Several tracks are traced on Monthly Meteorological lo .... Chart,s and Pilot Chsrts l1 for the North Pacific. (5) ..... Several recent triroks are from the MONTHLYWEATHER REVIEW, especially those for 1915, 1918, and 1921. June..... 10-15 ...... 1 15-20 ...... 2 .... 3 Table 2 and especially the chart of tracks indicate that most of the recorded storms occur in longitudes 100' Total.. to 130° W. and latitudes lao to 27' N. However it is July...... not improbable that the entire area here shown is occa- ...... sionally crossed by tropical c clones. Certain it is that ...... S even in the midst of the large t lank area between Hawaii Aug ..... and California gales are not lacking, although some such gales are due to steep barometric gradients on the side Tolal.. of the Pacific high-pressure area rather than to local sept ..... storms. However, most unusually steep gradients of .... this sort are closely related to cyclonic stom near by. Total...... As to the courses followed by the storms: The chart Oct ...... 10-15 1 j...... 1 ...... 2 indicates that most of them travel northwest or north ...... 2 a ...... 9 ....I:.. ... in this re ion. However, a number have recurved and 3-25...~ ...... 5 1 ...... 1...... 7 25-30..:_-_-__ -_____1 ...... -_ 1 progressef varying distances toward the northeast. One, Total...... 1 I._. 2 8 1 ...... 1 ...... 2 1 ...... 1; at least, has crossed to the Gulf of bfesico, and over it to ======-==----===I 1 I- Nov ..... 10-15 ..-I...... I .... 1 ...... I...... 1 Florida. Others such as the storni of September, 1921, ... have been traced as Iar as Newfoundland. Still other storms move due westward and some even west-south- Total.. westward. How far such westward nioving storms may Dee...... 6 A. Schiick Zur Iienntnis dfr IWl~rlsturnlein Britragfr :fir iUtrrtakandr, p. 81, Hamburg!.1906. 7 Red6Gld: loc. rit. 8 Lnc. eit.. Tafel IV. u Aths fur dm Stillcn Oxan. Dfutsehf Srewark, Hamburg, 1906. 10 U. S. Weather Bureau. 1813. 11 U. S. Hydrographic Office, 1Y21.

Fra. l.-Approximate tracks of about Bo tropical storms in the Pacific Ocean between ,hfex&o and Hawali. So11d lines, June to October, inclusive; dashed lines, November to May, inclusive.

Unauthenticated | Downloaded 09/28/21 05:25 PM UTC JUNE,192%. MONTHLY WEATHER REVIEW. 297 sometimes go before recurving is unknown, but Kimball so severe perhaps as the average typhoon, or West su gests that some may cross the Pacific to Japan.I2 Indian hurricane, and many are not destructive to 1s to velocity of movement, RedfieldlJ reports that shipping, just as many typhoons and West Indian some move slower than any he knew of in the Atlantic, hurricanes are not destructive to shipping. But on the but not slower thansomein the Bay of Benegal. On the other hand the records indicate that scores of boats have other hand, some of the recent storms, for which the been wrecked by storms in the northeast Pacific, and it information is rather full, as for. example the severe does no good to try to i nore these stornzs or to say that stonn of September, 1918, moved nearly 300 miles in 34 they afford no appreciaB le danger. hours. As to frequency, the list given above suggests that two As to severity: Tro ical cyclones in this region, as in or more tropics\ cyclones occur on the average each all others, vary greatP y in intensity. Unusually severe year off the west coast of Mexico. Twenty-six are re- storms are uncommon. The avera e storm is not corded in 11 years, 1849-1859, and 24 in 13 ears, 1880- 1893. In one year, 1855, seven were recorJd. 19 5. H. Klmball, lor. cit. RedEcld. loc. cit. A METHOD FOR THE CALCULATION OF NORMAL FROST DATES FROM SHORT TEMPERATURE RECORDS. Ry W. B. VAN ARSDEL.

1 Erown Co., Berlln, N. H., July S, 1922.1 A few months ago the writer had occasion to examine The smuothecl curve of normal daily minimum teni- the records of five or six cooperative Weather Bureau periiture cun not, of course, be deterniined very accu- stations in a certain small area with a view to estimating rstely froin only 4 or 5 years record. A more precise frost risk in that area. It chanced that some of these iiidiod which IS usually possible consists in utilizing stations had only a short record, and, accordingly, the tho iiiont,lily 1iist.ograni giving the normal daily mini- direct averaging of frost dates, etc., was out of the ques- mum of n near-bv station of 20 years’ or longer record, tion as a method of any trustworthiness, especially since nveragiw the diflerences in monthly means at t,he two some of those few years had passed without any recorded stations Buring t.he 4 or 5 years of simult.sneous record frost. Under these circumstances it was necessar to use at h0t.h shtions, n plying the differences so found to an indirect method of computation, based on t ie tem- the long record, an (P smoothing the correct,ed his togram perature record. The occurrence of a minimum tem- to a cont.inuous curve. erature of 32O or below was taken as the equivalent of a The dispersion of actual niinimn about, the mean is filling frost.’ Then from the available data the smoothed determined directly in ogee form, recording as “prob- curve of “normal” daily minimum temperature was ability that the t,empera.turewill be lower than n degrees drawn, and the dispersion of actual minima about the shove or below the mean.” Table 1 suniniarizes the mean minimum determined. With this material it was dispersion of August and September minima about the possible to calculate the frost data usually re uired, mean determined from Figure 1. The da.ta are taken namely, probable dates of first and last frost, andY eiigth from the records of t,he cooperative observer at. , of growing season in four out of five years. A search of N. H., 33 years observations being avnilablo from which the literature on the mathematkal treatment of frost t.0 draw7 the mem curve. data has failed to reveal any reference to previous use of the method in question. TABLE1. The fundamental idea on which the method is based is -- that the “average” date of, sa , the fist killing frost in Kegat.ivr. I Pusitive. the fall is the mean abscissa o7 a curve whose ordinates ! represent the joint probability that frost will occur and Deviation horn mean...... , that it shall not previously have occurred (since spring) ; in other words, the probability that the Jimt frost will Nlllnber of CLSCS...... occur, plotted against date, is the same curve as the Number of c3scs with lower tern rraiure frequency distribution of first frost over, say, a 100- ear than given &vhtinn Probability that tcm- enod, and will correspond to the same average iate. erature will be ft should be noted that given two stations with identical Power than given number of degrees normal daily minimum temperature curves, frost will from themeau 0.9612 1.001 1.00 occur fist at the station where actual temperatures dis- __fI.920 I erse most widely about the mean; the calculation could {e very greatly simplified if this dispersion could be The ogee curve is drawn though plotted points assumed to be Gaussian, but in fact it is found to be so -15, 0.025: -10, 0.107; -5, 0.360; 0, 0.461; +5, 0.715, asymmetrical that the Gaussian formulas are useless, etc. (Ser fie. 2.) and graphical treatment is preferable in this case to the The probahlity of frost occurrence can now be plotted use of either Pearson’s or Tolley’s skew formulas. a ainst date b determining at, say, five-day intorvals, t %e distance os the mean minipiurn ten1 erature curvc 1 The use of a temperature criterion of frost occurrence while suffering from the grave from tho 33’ line and reading from tR e ogee curve drawback that damage to vegetation Is not a dire$ funthon of temperature alone, still possesses several Important adyanta (See f?mstance ‘‘IWin frost and lengthof (fig. 3) the probability of occurrence of such a deviation season m various section of%ktuc& Fereind J. W%z MO WEATEE~ froni the mean. Figure 3 was drawn in that way from E?%,366 1917 snd “Weather forecasting the Umted States” f.B ‘No.q,, 178.) Mr. William’ 0. Reed comments in a private communicitian as follows: the given data. neral, we have found that temperature methods of determining frost dates are more It is now necessar to determine the probability that reanite’ and probably more accurate than reports of killing host. * * Kllling frost Is ball not a meteorological phehomenon at all but it ifi so tied u .wlth various on an given date rost shall not previously have oc- questions oTplant y+ology that the term mems dinerent things at %Rerent times P and difierent ph. curre8 the vdues of Figure 3, subtracted horn unity, 4sa9--2-2----2

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