February 1964 Julian W. Posey 85

THE WEATHER AND CIRCULATION OF

A Warm Month With Drought-Breaking Rains in the East

JULIAN W. POSEY

Extended Forecast Branch, US. Weather Bureau, Washington, D.C.

1. HIGHLIGHTS ridge with a smdl positivc anomaly southwest of Lake Persistence of the warm temperature regime from Baild, a wcaker than usual trough over the h'Icclitcr- October [I] to November was the outstanding fcature of rancan Sell, and R strong ridge over extreme eastern tlie montli. Only 4 of 100 nearly evenly spaced stations Siberia and the Bering Sea. across tlie Nation cxpericncccl temperature cliiinge ol In contrast to thc pattern over the Atlniitic occan and more thrtn 1 class (out of 4 possible), and tlicsc 4 reported Eurasia, 700-mb. heights were above normal ovcr most of onlj- a 2-class change. Tn general, the changes that oc- thc Pacific Occaxi. Thc only negntivc height anomaly in curred wcre in the direction of moderating the extreme thc Pacific area was situated in the Gulf of Alaska with an wwmth. As ill October, tlie oiily sections with bclow intensitj- of 340 feet. The Low center associated with normiil tcmpertiturcs were in California and the extreme this lnrgc aiiomdy is ordinarily over the Bering Sea, Southcast. Thc precipitation pattern was not so per- where this November a strong ridge was observed. sistent, as heavy rains fell in lttrge scctions of eastern Figure 3 illustrates that the mnin core of westerlies at Uriitcd States in November where cirought conditions 700 mb. was very close to its usud liltitudc over most of lind prevtdccl during October. the Pacific, eastern United Statcs, and the wcstern Atlnn- tic. How~ver,across the eastern Atlantic, Europe, and 2. MEAN CIRCULATION tlic western piirt of North America, the jet core was south The mid-tropospheric circulation for November (fig. 1) of its normal position. This reduced iimplitude of the fciitured a ridge vcry near the normal position along the mid-latitude jet stream favored repeated incursions of Rocky Mouiitttins [2], but tlic amplitudc of this ridge was mild Pacific air masses into tlic Uriited Stntes, as is implicd was attenuated tis seen by the negative 700-mb. height anom- by the zonal index which slightly nbove normal in alies (fig. 2) over wcstern Cnriadn nnd northwestern November. At higher latitudes, the upper-levcl flow United Statcs. A decp trough, east of its normtil position, showed quite a differen t cliiLracter, cspccidly ovcr and prcvniled along tlic Atlantic Coast of the United States ncar North America. Strong blocking ridges mentioned and cstcnclcd northwestward to Hudson Bay. The ertrlicr over both tlic Davis Strait and the Bering Sea Ciinridian portion of this trough was weak and its negative rcsultcd in large-amplitude fiow and n much bclow normal tilt wtis :issociated with ti strong blocking ridge over thc polar westerly index for most of the month ovcr the Davis Strait, where a deep Low is usuiilly found. western part of the liemisphcrc (fig. 4). Over the Atltintic 700-mb. heights were mostly bclow normal. An intense trough csterided from a low cctitcr 3. AVERAGE MONTHLY WEATHER south of' Iceland to the Canary Islands off the coast of TEMPERATURE North Africa, while ii riclgc over mid-occan was quitc weak. 'I'hc lnrgest negative licight anomaly in tlic Monthly mean temperatures averaged above 1lOI'Jild Atlantic (4SO ft.) was west of Ircland. over most of the United Sttites during November (fig. 5) The Polar rcgion was dominated by a deep Low near except in much of California and a small part of Florida, Novaya Zemlya which was more than 300 It. below normiil Georgia, and Alabania where departures were slightly and located about 30° of longitude west of tlie expcctccl below normal. The November warmth \vas not as great Novcmbcr position. Below normal 700-mb. heights over as the warnitli of October; maximum tenipernture de- most of Eurasia. wcre associated with a trough extending partures were about 4' E'. less. Yet, a comparison of soutliwtird to the Caspian Sea from this Arctic Low, a the temperature anoiiialies in figure 5 with those for Octo- dcepcr tfittn riormnl trough along the emtern coast of ber (fig. 1 of [I]) reveals tt strong similiirity in both pattern Asia, and the decp eastern Atlantic trough. The excep- and intensity. None of the station climatologicd re- tions to this pcittcrn of negative height anomaly wcre :I ports examined indicated inonthly temperature records

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FIGUREI.-WIeati $00-mb. contours (in tens of feet) for November 1963.

had been established, although reports such as “4th over the United States coinputed from Klein’s [3] statis- warnmest” were common. Severd stations reported that tical equations, which specify the surface temperatures the maximum temperature was higher than experienced from the 700-mb. height pattern, were very similar to before on t,he particular day. International Falls, Minn., those indicated in figure 5 for the same stations. Thus, for example, reported unprecedented high temperatures in general, the observed surface temperature was well on November 4, 5, S, 9, lS, and 20, and Green Bay, Wis., relat’ed to the upper-level flow pattern over the United reported a daily record maximum of 59’ F. on the 22d. States. The only temperatures derived from Klein’s Although most reports indicated that much of the United specification equations that differed significantly from the States had quite \varni weather, similar arm Novembers observed November values were slightly below normal have been observed before. temperatures computed for Big Springs, Dallas, and Temperatures for 39 stations fairly evenly distributed Houston, Tex.

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FIGURE2.-Mean 700-mb. height departure from normal (in tens FIGURE3.-Mean 700-mb. isotachs in meters per second for of feet) for November 1963. November 1963. The heavy solid arrows indicate observed axes of maximum wind speed, while dashed lines show the normal axes for November. PRECIPITATION The inean trough observed along the east coast was 1111. reflected in the abrupt change from the drought conditions of October in most eastern states. Rains on November 1 ended the longest recorded period of consecutive days without measurable rainfall at Columbus, Ohio (48), Washington, D.C. (32), linoxville, Tenn. (32), and Albany, N.Y. (23). Details of the storms which brought this much-needed rain will be discussed in the next section. Several stations which had little or no rainfall in October, received record amounts in November, such as 8.58 in. at New Haven, Conn., 7.98 in. at Daytonti Beach, Fla., 7.74 in. at Ctiribou, Maine. Washington, D.C., and New York, N.Y. received the heaviest November rainfall since 1577 and 1889 respectively. In Washington, this followed the first rainless (no measurable amount) month of record. Stronger than normal Southwesterly flow and below normal heights (figs. 1, 2) contributed to continued heavy rains in the Far West (fig. 6). At the same time the anomalous southwesterly flow over the Rocky Mountains from Wyoming northward intensified the “rain shadow” giving less than half the normal rainfall for most of Montana and Wyoming. Precipitation also continued 4. INTRA-MONTHLY VARIATIONS generally deficient in most of the area from the Great IN WEATHER AND CIRCULATION Plains to the Appalachians as northwesterly flow aloft persisted. ,Heavy precipitation in Texas was associated NOVEMBER 1-1 5 with confluence of the flow from the low-latitude trough Rather sudden and important changes occurred in the in the Southwest and the main westerlies to the north. upper-level circulation tit the very beginning of November. Variation of the precipitation pattern elsewhere can best A deep trough with ltuge negative height anomalies de- be explained by examining the half-month circulation veloped along the east cotist of the United States. This patterns under the nest section. deep trough then persisted for the first half of the nionth

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FIGURE5.-Departure of the average surface temperature from normal for November 1963 (from [6]!.

FIGURE6.-Percentage of normal precipitation for November 1963 (from [SI). with the 15-day mean, 700-nib. contours (fig. 7A) looking very much like the first 5-day mean pattern of Norember over the United States. Three major surfitce storms, spaced 4 to 7 days apart, developed in this trough. Cool air surges following these storms resulted in n lnrgc area of below normal temperature in the East (fig. 7B) during the first half of the month. Each storm released large amounts of precipitation (fig. 7C) thnt produced record %hour amounts for November at some stations. Other elements besides precipitation indicated the intensity and persistence of the storminess in eastern United States FIGURE7.-(A) 700-mb. height and departure from normal (both during the first half of the month. Hartford, Conn, and in tens of fcet), (B) surface temperature departure from normal Concord, N.H., for example, reported the lowest Norember (above normal hatched), and (C) total precipitation (less than atmospheric pressure of record, while Allentown, Pa., 0.5 in. unshaded, 0.5 to 2 in. hatched, more than 2 in. crosshatched) registered the lowest pressure for any month. Milton, all for Novembcr 1-15, 1963. Mass., had the least sunshine of record for Noveinbcr, and examination of the diiily sunshine amounts rcvealed that flow gave heavy precipitation along much of the west the shortage occurred during the first half of the month. coast. Abnornially persistent cloudiness seems to have Under and inimediately to the east of the mean ridge been the major factor in the small area of below normal (fig. 7A) over western North America, precipitation was temperature in northern California. Red Bluff, Calif., light and temperatures were above normal. Offshore reported completely overcast skies for 9 days in the first storniiness connected with the deep J1ow in the Gulf of half of the niontli and 2 more days with an average Alaska and the resulting strong southwesterly upper-level cloudiness of 9/10,

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February 1964 Julian W. Posey 89

portion of the United States was subject to anomalous flow with southerly components at 700 nib. resulting in above normal temperatures for tlie eastern two-thirds of the country and most of the Northwest (fig. 8s). Most of the cool weather in the Southwest wiis associnted with below normal 700-nib. heights and easterly nnomalous flow. Confluence to the enst of the sheared low-latitude trough over Baja California was accompnnied by heavy riiinfdl (fig. 8C) during the last half of the month in parts of Texas and neighboring States. The meiin trough from Olcla- homa northeastward across Wisconsin was responsible for the heavy rain in eastern Iow:i, northern , southern Wisconsin, and parts of Michigan. Large rainfall amounts shown in figure SC for East Coast States occurred liite in the nionth tis the long-wave trough tigain moved enstward, associated with a deep surface storm that wiis located in the Northetist on the last day of the month. Retro- gression of the eastern Pacific trough during tlie last half of November reduced the cimount and extent of west coast precipitation. Relntive dryness persisted over most of the Northern Plains and Rocky Mountains in connec- tion with the nienn ridge northward from the Nevadti- area. One very interesting dry area wliicli is rather difficult to explain was observed during the hitter part ol November in Ohio. Reference to figurcs 7C and SC shows that this dryness persisted all month with soiiie larger amounts of precipitation occurring on all sides, especially so during the last half of November. Perhaps the key is Pound in such reports as the 15.4 in. annual precipitation clcficit at Clevcland, Ohio. O’Connor [4] referred to S months of drought at Cleveland in discussing the August weather. Remnrks in the monthly report from Columbus, Ohio, stated “Rainfall frcquency cqual to long term averngc.” but added “Total precipitation September, October, November 20% of normal. Drought continued.” All of these reports from Ohio lend credibility to tlie feed-back mechanisms so often stressed by Namias [SI. REFERENCES 1. R. A. Green, “The Weather and Circulation of October 1063- Abnormal Warmth and Sevcre Ilrought in the United States and TWOUnusual Hurricanes Offshore,” Monthly Weather Revzew, vol. 92, No. I, Jan. 1964, pp 37-42. 2. U.S. Weather Bureau, “Normal Weather Charts for tlie Northern Heniisphcre,” Technical Paper No. 21, Washington, D.C., 1952, FIGURF:8.-(A) 700-mb. height and departure from normal; (B) surface temperature departure from normal (above normal 74 PP. 3. W. H. Klein, “Specification of Monthly Mean Surface Tempera- hatched), and (C) total precipitation (less than 0.5 in. unshaded, tures from 700-mb. Heights,” Journal of ilpplzed &Jeteorolog?j, 0.5 to 2 in. hatched, more than 2 inches crosshatched) all for vol. I, No. 2, Junc 1962, pp. 154-156. November 16-.30. 1963. 4. J. F. O’Connor, “The Weather and Circulation of July, August, and -Dry and Cool in the East,” IkJonthly Weather Revzew, vol. 91, Nos. 10-12, Oct.-Dec. 1063, pp 737-748. NOVEMBER I630 5. J. Namias, “Influence of Abnormal Heat Sources on Atmospheric During the last half of November (fig. SA) the mean Behavior,” Proceedinqs of the Internatzonal Symposaz~m on Nncnzerzcal Weather Predaction, , Nov. 7-1 3, 1960, Metc- trough over the United States was in the central part of orological Society of Japan, Mar. 1962, pp. 615-627. the country and had much less amplitude than did the 6. U.S. Weathcr Bureau, Weekly Weather and Crop Bulletin Natzonat trough dong tlie east coast earlier in the month. A major Summary, vol. L, Nos. 4s and 50, Dec. 2 and 16, 1963.

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Publications by Weather Bureau Authors

C. B. Carney and A. V. Hardy (with C. H. M. van Bavel) , Meteorological Society, vol. 44, No. 12, Dec. 1963 “Weather and Climate in North CarolinaJJJBulletin pp. 791-793. 396, revised, North Carolina State Agricultural E. A. Richardson (with G. L. Ashcroft and L. M. Cox), Experiment Station, University of North Carolina, “The Air Mass in Action,”Utah Farm Home Science, Raleigh, Sept. 1963. vol. 24, No. 4, Dec. 1963, pp. 92-95. R. B. Carson, “On Tropical Meteorology,” [Letter to E. A. Richardson (with G. L. Ashcroft and L. M. Cox), Editor], Bulletin of the American Meteorological “Our Enigmatic Weather,” Utah Farm Home Science, Society, vol. 44, No. 11, Nov. 1963, p. 700. vol. 24, No. 3, Sept. 1963, pp. 60-63, 77. W. M. Culkowski, “Deposition and Washout Computa- H. E. Rosendd, “Mexican West Coast Tropical Cyclones, tions Based on the Generalized Gaussian Plume 1947-1961,” Weatherwise, vol. 16, No. 5, Oct. 1963, Model,” US. Atomic Energy Commission, Div. of pp. 226-229. Technical Tnformation, 0R0-599, Oak Ridge, Sept. H. K. Saylor, “An Analysis of the 500-mb. and Surface 30, 1963, 26 pp. Prognoses Issued by the National Meteorological W. W. Dickey and R. N. Wing, “The Unusual: Arctic Center During the March Storm of 1962,” Journal Air into the Pacific Northwest,” Weatherwise, vol. 16, of Applied Meteorology, vol. 2. No. 5, Oct. 1963, No. 6, Dec. 1963, pp. 259-263, 306. pp. 619-628. R. A. Dightnian, “- 70’F. in Montana,” Weatherwise, G. T. Severynse, “Removal of Aerosol Particles from the vol. 16, No. 6, Dec. 1963, pp. 272-273. Atmosphere by Growing Cloud Droplets, ” Geojsica S. Fritz, “The Diurnal Variation of Ground Teniperature Pura e Applicata, vol. 55, (11) May-, as Measured from TIROS 11,” Journal of Applied pp. 151-163. Meteorology, vol. 2, No. 5, Oct. 1963, pp. 645-648. A. .K. Showalter, “Review of ‘The Errors of the Meteoro- K. C. Giles and J. K. Angell, “A Southern Hemisphere logical Office Radiosonde, iMark 2B,’ Scientijic Paper Horizontal Sounding System-A Preliminary Study,” No. 15, by D. N. Harrison, British Meteorological Bulletin of the American Meteorological Society, vol. 44, Office, 1962, 40 pp.,” Bulletin ofthe American Meteoro- NO. 11, NOV.1963, pp. 687-696. logical Society, vol. 44, No. 9, Sept. 1963, pp. 583-584. D. K. Lilly (with J. S. Turner), “The Carbonated-Water R. H. Simpson, “Comments on ‘Condensed Water in the Tornado Vortex,” Journal of the Atmospheric Sciences, Free Atmosphere in Air Colder than -40’ C.,’” vol. 20, No. 5, Sept. 1963, pp. 468471. [Letter to Editor], Journal of Applied Meteorology, J. Namias, “Large-Scale Air-Sea Interactions over the VO~.2, NO.5, Oct. 1963, pp. 684-685. North Pacific from Summer 1962 Through the Sub- R. H. Simpson (with J. S. Malkus), “An Experiment in sequent Winter, ” Journal of Geophysical Research, Hurricane Modification: Preliminary Results,’’ VO~.68, NO. 22, NOT. 15, 1963, pp. 6171-6186. Science, vol. 142, No. 3591, Oct. 25, 1963, p. 498. F. Nesh, “Method for Vacuum Evaporation of Silicon N. A. Stepanova, “The World’s Lowest Temperature Record,” Oxide Films, ” Review of Scientijic Instruments, 1701. Weatherwise, vol. 16, No. 6, Dec. 1963, pp. 268-269. 34, No. 2, Dec. 1963, p. 1437. S. Twomey, “Measurenients of Natural Cloud Nuclei,” C. W. Newton (with E. Palnih), “Kinematic and Thermal Journal de Recherches Atmosphiriques, vol. 1, No. 3, Properties of a Large-Amplitude Wave in the Wester- Juillet-Septembre 1963, pp. 101-105. lies,,’ Tellus, vol. 15, No. 2, , pp. 99-119. S. Twomey and G. T. Severynse, “iMeasurements of Size J. F. O’Connor, ‘lExtended and Long Range Weather Distributions of Natural Aerosols,” Journal of the Forecasting,” Journal of the American Water Works Atmospheric Sciences, vol. 20, No. 5, Sept. 1963, pp. Association, v01, 55. No. 8, Aug. 1963, pp. 1006-1018. 392-396. P. N. Putnins, ‘(Review of Grosswetterkunde und Witter- R. 0. Weedfall, “Variation of Soil Teiiiperatures in Ogoto- ungsvorhersage by F. Baur, Akademische Verlags- ruk Valley, Alaska,” Arctic, vol. 16, No. 3, Sept. 1963, gesellschaft, 1963, 91 pp.,” Bulletin of the American pp. 181-194.

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