The Effect of Lake Erie on the Local Distribution of Precipitation in Winter (II)* LT. JOHN T. REMICK 620 East Ave., Lockport, N. Y.

MAPS OF PRECIPITATION AND SNOWFALL DEPTHS FROM INDIVIDUAL STORMS These maps were difficult to compile. precipitation pattern. Newspaper re- First the dates of possible local storms ports and the author's first hand had to be found. They were obtained knowledge of certain storms were also principally from two sources, the sum- used in the attempt to get the true maries of weather conditions by precipitation pattern. months as they appear by states in JANUARY, 1940 the "Climatological Data" of the The frontal and local precipitation Weather Bureau, and newspaper re- maps (figs. 5 and 6) were drawn by ports—chiefly the New York Times. carefully separating the precipitation When a possible date was found the at all reporting stations into the two situation was looked up on the daily types—frontal and local. The daily weather maps to be sure that frontal precipitation at each station was activity would not explain the storm. listed and then after studying the If there were any type of a front in daily maps the precipitation on all the vicinity it had to, (1) be weak, days on which it possibly could have (2) cause little or no precipitation, and been caused by frontal activity was (3) interfere little, if any, with the added up. These amounts were plotted relatively smooth air flow. The on fig. 5. The local precipitation amounts of precipitation as reported amounts (fig. 6) were arrived at by in the "Climatological Data" were deducting the frontal amounts from then scanned and if they or the news- the total amounts. It is admittedly paper reports showed amounts of pre- sometimes difficult to be sure just cipitation amounting to 0.7" or more when the precipitation is local or the data were plotted on one of the frontal but when in doubtt the frontal base maps and isohyets were drawn at precipitation was given the benefit. convenient intervals. While only 10 Figures 7-9 show three individual storms were found to meet the above situations which contributed toward specifications in the last 15 years it is the total local precipitation during likely that some have been overlooked. January 1940 and are drawn in the The vectors (arrows) drawn on same manner as the other individual some of the individual charts indicate situations. the mean direction and roughly by By January the lake temperature their length the intensity of the geo- has reached the freezing point and strophic wind. They are placed on the considerable ice is present, the amount maps to show the relation of pressure varying from year to year. One gradient to location and intensity of would, therefore, expect the lake ef- local precipitation. fect to become less pronounced and Charts of all 10 storms are repro- precipitation patterns would be more duced (figs. 5-23) but only two will be affected by orographic influences. Jan- discussed in detail. In drawing the iso- uary 1940 was a very cold month, the hyets no station was neglected, but average temperature being about 8° they were smoothed out to some ex- below normal over the region. Figure tent to give a clearer picture of the 5, showing the total frontal precipita- tion for January 1940, should be com- •Concluded from the January BULLETIN, pp. pared with figure 6, showing the total 1-4.

Unauthenticated | Downloaded 10/02/21 03:40 AM UTC local precipitation. The pattern for the Jamestown, New York, area and, the frontal precipitation is very if real, is probably due to some local spotty and is difficult to explain. The peculiarities. Figures 7-9 show 3 maximum occurs in the mountains in- different periods of local precipitation dicating some orographic effect. The which go into making up the totals. pattern for the local precipitation is The period January 1-4 was one of much different, showing a distinct strong Pc flow from the northwest. band of maximum precipitation on January 16-19 was one of moderately the lee side of the lake but about 25 strong Pc flows* and January 26-31 miles inland. The fact that the band was a period of very light winds. Note of maximum precipitation occurs some how the amount of precipitation is distance inland shows that although associated with the strength of the there were many days of cold Pc flows wind. Although January 1940 was an from the west and northwest not unusual month in the amount of cold much moisture was picked up over the P'c air flows the condition occurs lake due to low water temperature enough on the average to show an and short trajectory over water and effect on the normal. The normal pre- therefore some uplifting by the land cipitation pattern shows the maximum was necessary to produce the local to occur some distance inland where snows. Because the condition lasted the orographic effect becomes impor- many days the total local precipita- tant. Also note the similarity of the tion was heavy on the windward side distribution of the local precipitation of the hills. for January 1940 with the distribution Again there seems to be two points of the January normal precipitation. of maximum precipitation: one in the Jefferson, Ohio, region, the other in *Cf. BULL., V. 21, pp. 159-160, 1940.—ED.

Unauthenticated | Downloaded 10/02/21 03:40 AM UTC RELIABILITY OF DATA going on all day showed 0.07" which he justified by measuring on a wind Horton4 gives the following as the swept box a 1" snow depth which had errors that may occur in the measure- been melting most of the day. The ment of precipitation: 1) observa- precipitation record of 0.07" certainly tional errors, personal equation and was considerably deficient. No doubt mistakes, 2) instrument operation there are times when the conditions error, 3) errors due to evaporation, 4) are reversed and an excessive amount errors due to inclination of gage fun- is recorded. nel, 5) wind or exposure error, 6) The lack of uniformity as to the location error. These errors may not time of taking precipitation observa- be of much importance when precipi- tions is believed to be of considerable tation falls as rain but when it occurs importance, especially when the local as light wind driven snow there must storm occurs just preceding or just be considerable error. after frontal precipitation. At all first After a typical light local snow order Weather Bureau stations such this winter I had demonstrated to me as Cleveland and Buffalo the amount by one of the Weather Bureau's co- recorded is from midnight to midnight operative observers5 the exact tech- while most cooperative observers make nique used in measuring the pre- their observations at sun down. A cipitation. The snow had occurred considerable number of observers, es- during the night with considerable pecially in Ohio, make their observa- wind and a bright warm sun shone all tions in the morning so there is at a day. His measurement taken at 6 at minimum a 12-hour spread in report- night after evaporation had been ing 24-hour amounts of precipitation. When the storm occurs over one day and is not directly preceded or fol- 4Horton, Measurement of Rain and Snow, lowed by frontal precipitation the time Mo. Wea. Rev., vol. 47, 1919, pp. 294-296. difference will not cause any trouble. 5R. N. Clark, Lockport, New York.

Unauthenticated | Downloaded 10/02/21 03:40 AM UTC INDIVIDUAL LOCAL STORMS

OCTOBER 18-19, 1930* chard Park region about 15 miles As an example the extremely heavy south of Buffalo. Needless to say the local snow storm of October 18-19, damage done was tremendous. So 1930 will be discussed. This storm was early in the winter did the storm the best illustration of the lake effect occur that the leaves had hardly be- that could be found. gun to fall. On October 14th an Alberta low One of the remarkable features of developed to moderate intensity and the storm was the very sharp line moved sluggishly eastward along the marking the snow area. In the north Canadian border bringing in much part of Buffalo no snow at all was colder air behind it. This low became reported. In south Buffalo 6 inches stationary over the lower Hudson Bay fell. At Lockport the sun shone region and deepened considerably to brightly both days but the band of less than 29.4 inches. The result of thick dark stratocumulus clouds were this in combination with a strong clearly visible to the south. Polar high to the west and south was Because the heaviest amounts of to set up a strong west-east gradient precipitation occurred just inside the over Lake Erie. The wind at Buffalo lake shore little of it can be blamed was force 5 and 6 from the west and on the upslope of the land. Only one west southwest all during the 18th inch of snow fell at Jamestown—a and 19th. By the 20th the gradient place which seems to get a maximum weakened, the winds died down, and of orographic effect. The shape of the the lake temperature was 5F° lower. precipitation is almost exactly what The temperature of Lake Erie on one would expect with a west and west the 18th and 19th was 59°F. All Lake southwest wind. Had the flow of air Erie temperatures are those recorded been a little more from the southwest by the Buffalo Water Department at it seems logical to suppose that the its intake point some distance into the maximum amount of snow would have lake. The temperature of the air was fallen on Buffalo causing much great- 30°-32°F. The cold Pc air, unstable er damage. as it characteristically is at that time The location and distribution of the of year, was made extremely unstable precipitation occurring from this by the warm lake, thus favoring storm is practically the same as the strong convective action. Conditions, location and distribution of the normal therefore, were ideal for heavy local lake effect precipitation as indicated snows on the lee side of the lake. by the area of heaviest precipitation Figs. 10a and 10b show the precipita- on the October normal map, Figure 4. tion that actually occurred. Fig. 10b DECEMBER 8-10, 1937 was made in the same manner as the As a second severe example the other maps and is included mainly so storm of December 8-10, 1937 will be that a comparison can be made with discussed. Besides being very severe the other storms. Fig. 10b was the storm was unusual in that the made from a special report of the maximum amount of precipitation oc- snow that fell at a great many more curred in the city of Buffalo instead places than usually report and there- of well south as is so often the case. fore gives a more detailed precipita- A wave developed off the Virginia tion pattern. The heaviest fall of capes on December 6. It took an un- snow—48 inches—occurred in the Or- usual path by moving directly over Boston and curving to the northwest. *Cf. BULL., V. 11, p. 181-182, 1930.—ED.

Unauthenticated | Downloaded 10/02/21 03:40 AM UTC It finally became practically station- similar to that of the 8th. ary over the lower Hudson Bay re- The direct relation between the ve- gion as an extremely intense cyclone. locity of the wind and the amount of This deep low in conjunction with a precipitation, other things being the Polar high to the west caused a strong same, is well borne out by this storm. flow of Pc air over the lakes with The wind vector on the 8th indicates strong west and southwest winds over that the air flow was greatest on that Lake Erie. At Buffalo the wind was day and the map shows that the force 8 and 9 from the west southwest amount of precipitation was also and southwest for 48 hours, with a greatest on that day. On the 9th and maximum velocity of over 60 mph. 10th the wind vectors are somewhat On December 7 the lake temperature shorter and the precipitation was cor- was 41 °F and the air temperature respondingly less heavy. from the 8th to 10th ranged from 10° By coming from the west southwest to 20 °F. By December 11 the lake and southwest the air had the maxi- temperature had dropped 7F° and the mum possible trajectory over the winds had decreased to moderate water. The reason Buffalo itself is velocities. not hit by more heavy local snows is The heaviest snowfall was 38 inches that a strong flow of cold Pc air usu- and occurred in the north part of Buf- ally comes with a west or northwest falo. Due to the high winds tremen- wind in which case the area south of dous drifts were formed and even the Buffalo receives the precipitation. But main roads became completely blocked because of the increased trajectory of to traffic. Stores were closed and food the air over water the relatively rare supplies practically stopped entering cold strong southwest wind is likely to the city. Conditions became so bad produce heavier precipitation than the that the Red Cross sent aid to feed usual west or northwest wind. and help the storm-stricken people. It is interesting to note that the re- The land over which the precipita- gion at the eastern end of Lake On- tion occurred is very flat and would tario also received heavy snow during cause no forced ascent of the air. All this same period. the precipitation can therefore, be at- tributed to the convergent influence of In this storm as well as the one of the lake shore. October 18-19, 1930 the Weather Bu- reau's forecast was typical of those Figs. 11, 12, 14 show the precipita- issued most of the winter, that is, tion that fell on each day and fig. 13 "probably snow flurries" which indi- shows the total precipitation during cates a very light fall if any. the storm. The effect of the direction of air flow (as indicated by the ar- Although the effect of the lake rows) on the precipitation pattern is snows on the normal is not as clearly very clearly shown. On the 8th the shown by the December normals, Fig- flow was from the west southwest and ure 6, as by the normals of the Fall the isohyets were centered around months for reasons already mentioned, north Buffalo. On the 9th the flow it is evident that the isohyets due to was from the southwest and the iso- this storm are considerably north of hyets are correspondingly shifted to the area which apparently in the nor- the north with an area fifteen miles mal is affected most by the local lake north of Buffalo getting the heaviest snows. The reason, as already stated, amount. On the 10th the air flow was is that the cold Pc air usually comes again from the west southwest and the with west or northwest winds instead isohyets for that day show a pattern of southwest as occurred in this case.

Unauthenticated | Downloaded 10/02/21 03:40 AM UTC WIND AND TEMPERATURE CONDIT NS OF THE OTHER LOCAL STORMS OCTOBER 24, 1937 (FIG. 15) 5 from the west southwest. Note that The water temperature was about the precipitation pattern does not 55 °F and the air temperature about show two points of maximum precipi- 32°F. At Buffalo the wind was force tation as occurred in the previous 4 and 5 from the west. three storms. This may be due to Nov. 29, 1935 (FIG. 16) insufficient data or to the shift in the The water temperature was about wind from west to west southwest. 46 °F and the air temperature about Nov. 21-22, 1929 (FIG. 19) 30 °F and the wind at Buffalo was The water temperature was about force 5 from the west. Note the simi- 48 °F and the air temperature about larity of the precipitation pattern 24°F. The wind at Buffalo was force with that of the Oct. 24, 1937 storm. 5 from the west. Here again there Nov. 27, 1930 (FIG. 17) apparently is only one point of maxi- The water temperature was about mum precipitation, even though the 47 °F and the air temperature about surface conditions are similar to those 18°F. The wind at Buffalo was force of the November 29, 1930 storm. 5 from the west. DEC. 20, 1928; DEC. 18, 1927; DEC. 16, DEC. 3-4, 1929 (FIG. 18) The water temperature was about 1926 (FIGS. 20-22) 43 °F and the air temperature about No wind and temperature data were 20°F. At Buffalo the wind was force available for these storms. They are

Unauthenticated | Downloaded 10/02/21 03:40 AM UTC incuded for purposes of comparison of Hazen, Climate of Chicago, U. S. W. B. Bull., 1893. the precipitation patterns. R. A. Mordoff, Climate of New York State, Since all the storms with two pre- Bull. 444, Agricultural Experiment Station, Cornell University, Ithaca, N. Y. cipitation maxima are the more recent R. M. Dole, Snowsqualls in the Lake Region, ones, when more data was available, it Monthly Weather Review, v. 56, 1928, p. 512-513. is possible that the others would show H. T. Harrison, Terminal Weather Conditions two maxima if more data had been on the Newark-Chicago Airway, United Air Lines Publication. available. The reason for the two J. J. George, On the Distortion of Stream maxima may be some local effect of Fields by Small Heat Sources, Monthly Weather Review, v. 68, 1940, p. 63. the shore line. C. F. Brooks, The Snowfall of Eastern United States, Monthly Weather Review, v. 43, 1915, REFERENCES p. 2. J. B. Kincer, Seasonal Distribution of Rain in Odell, Influences of Lake Michigan on East the U. S., Monthly Weather Review, v. 47, and West Shore, Monthly Weather Review, 1919, p. 624-631. v. 59, 1931, p. 405. C. L. Mitchell, Snow Flurries Along Eastern C. A. Donnel, The Snowstorm of December 10, Shore of Lake Michigan, Monthly Weather 1934, at Chicago, Illinois. Bull. Am. Met'l. Review, v. 49, 1921, p. 502. Soc., v. 16, pp. 111-112, 1935.

On A Hypothesis Regarding Normal Development and Decay of Tropical Hurricanes (II)* W. F. MCDONALD U. S. Weather Bureau, Washington, D. C.

THE SECOND PHASE: DEEPENING

HE SECOND PHASE follows imme- upon this second phase. It is certainly diately on the inception of vorti- under way when a closed isobar of 3 T cal action and lasts until that mb below its tropical surroundings, vortex reaches maximum intensity, and a wind force of Beaufort 8 or which is indicated by the time of the higher is observed. Tingley10 has lowest pressure that develops. Cer- described in detail this second, or tain characteristics can be said to deepening phase in case of a tropical mark quite definitely the entrance 10F. G. Tingley: The genesis of a tropical cyclone. Monthly Weather Review, Vol. 39, •Concluded from Feb. BULLETIN, pp. 73-78. pp. 340-347.

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