The Weather and Circulation of February 1959

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FEBRUARY1959 MONTHLY WEATHER REVIEW

THEWEATHER AND CIRCULATION OF FEBRUARY 1959

J. F. O'CONNOR Extended Forecast Section. U.S. Weather Bureau, Washington. D.C.

1. HIGHLIGHTS 2. CONTRASTWITH PREVIOUS MONTHS February 1959 was amonth of markedvariability February 1959 contrasted sharply with its predecessor, in weather across the United States, asmanifested partly *January, as well as with February of 1958. In the east- by weekly alternations of above and below normal tern- ern half of the country, except New England, a genera1 peratures and of record maximum and minimum tempera- warming, relative to normal, occurred from the cold that tures (for the date) atsome stations in the East (table1). 11ad prevailed duringJanuary, and marked cooling in This month was feat,ured by the highest daily sea level theWest ended the extreme warmththat had existed pressures (up to 1053 mb.) on record at some stations in therein January. Fewextremes of temperature de- the upperMississippi Valley at, the beginning of the veloped, however. month. It was also highlighted by adisastrous storm This month \\-as also a welcome contrast in the eastern on the 9th and 10t,h, accompanied by tornadoes, one of Ihited States,, particularly in Florida, to February of which took the lives of 21 persons in St. Louis, &Io., early the preceding year, which had been the coldest February on the morning of the loth, with hundreds injured and on record in the southeastern quarter of the country [e]. millions of dollars in property damage. In addition to *is might be expected, the axis of maximum westerly tornadoes, this storm included a wide variety of severe winds at 700 nib. wasconsiderably farthernorth over weather, such as blowing dust, glaze, high winds, floods, the Western Hemisphere this February than a year ago, snow, andthunderstorms. It broughta repeat, of flood when the great index cycle of 1968 was in its most de- conditions requiring evacuation to sections of Indiana pressed state with the westerlies at 32" N. or 6' south and Ohio, whereonly 20 days before similardisaster of normal [2]. ThisFebruary the westerly wind axis struck onJanuary 21 [ 11. remained persistently near 43" X., or about 5' north of On a monthly basis few records were broken, although near-record snowfalloccurred at some stations, such as Misoula, Mont., Rochester, Minn., GreenBay and La Crosse, Wis., and also at the higherelevations in the West, such as BlueCanyon and Mt. Shasta, Calif.,Sexton Summit, Oreg., and Ely, Nev. The month was cold and snowy in parts of the Northeast, such as Rochester, N.Y., and Burlington, Vt., but, by way of contrast,, Bingham- ton, N.Y. had its lightest snowfall in 40 years. This was the coldest February in over 20 years in many parts of the northern border States from Montana to Michigan (and the coldest winter season as well). It was a very cloudy and rainy month in the Gulf States with Browns- ville, Tex., reporting rain on 22 days and Lake Chilrles, La., reporting only one clearday during the month.

TABLE1.-Some reversals of daily record temperatures (OF.)during February 1959

I Maximum I Date 11 Minimum I Date FIGURE1.-Mean 700-mb. isotachs for February 1959 in meters Per second.Solid arrows are axes of maximum speed (jets). Dashed lines are jet axes in February 1958. Important feature is confluence of jets in the Xortheast.

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FIGURE 2.-Mean 700-mb. height contours (solid) and departures from normal (dotted) (both in tens of feet) for February 1959. Large negative anomalies in polar regions were accompanied by an almost circumpolar ring of positive anomalies at middle.laMttrBeB in the Western Hemisphere, resulting in contracted circumpolar westerlies-an almost complete reversal from February 1958.

normal, with no significantfluctuations in speed through- 3. MONTHLYMEAN CIRCULATION AND WEATHER out the month. This is somewhat surprising, considering the intra-monthly variability of the weather and circuln- Figure 2 shows the characterist'ics of this month's mean tion over Unitedthe Statesto discussed be belovr. Fig-Lrre The waves were generally close to their normalpositions, with the Asiatic coastal trough 1 shows the distribution of 700-mb. mean winds for tbis much weaker than normal and the Kamchatka center of February,with axes of maximum speed delineated. The action about normal in The gradient of height 'ped for February 1958 are give'' departuresfrom normal in the northern part of the North to the marked this Year Pacific shows t,hat thewesterlies in this areawere stronger Over most Of the hemisphere in ComPariNn With Pal' than normal. This may have contributed to thefact thaf ago. In the western States the axis was farther south the troughin the Maritime Provinces of Canada wa: this year, reflecting cooler conditions inthis areain slightly east of its normal position. Above normal north. contrast to the extreme warmth of February a year ago. westerly flow over Canada was associated with a deepel

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FIGUEE3.-700-mb. heightcontours (solid)and departures from normal (dotted)for February 1958. Noteexpanded circumpolar westerlies due to positive anomalies in polar regions with negative anomalies to south.

! than normal center of action near Bafin Island. The mast prominent abnormalities of the monthly circulat,ion were .the extremely deep polar vortex, 550 feet below normal, and the intense and persistent blockingHigh over western Europe, averaging 580 feet above normal for the month. Between the European block and the polarLow an anom- of alous southwesterly gradient almost 1,000 feet existed, " - on the average, between the eastern coast of Greenland 8.4 c.7 P'II.I".R *1-2hc I- and the British Isles. This was expressed as a remark- FIGURE4.-(A) Departure of averagesurface temperature ('I?.) ably strong southwesterly jet in the North Atlanticacross from normal for February 1959. (B) Percentage of normal precipitation for February 1959. (From Weekly Weather and Crop Iceland (fig. 1). Bulletin., National Summary, vol. XLVI, No. 9, March 2, 1959. The subtropical westerlies at 700 mb. were weaker than and So. 10, March 9, 1959). normal during the month throughout the Western Hemi- sphere, especially in the Pacific where they were 6 to 8 The similar contrast of this month with its counterpart meters per second below normal. At sea level the sub- in 1988 may be seen by comparing figures 2 and 3, and, tropical easterlies were st,rongert,han normal, bringing in part.icular, the height departures from normal. It is heavy precipitationto windward locations inHawaii. of interest, in this connection, that February of 1958 was HiIo, a windward station which normally has a prevailingquite similar throughout the hemisphereto January 1959, southwest wind due to local peculiarities, this month re- except that the below normal heights and temperatures in ported a prevailing wind directionof east-northeast, aver- the East andSout,heast were less intense in January 1959. aging about 3 miles per hour above normal, with a result- Figure 4 summarizes the monthly departuresof temper- ing rainfall of 3.61 inches more than normal. ature and precipitation from normal. The northwesterly In contrast to the marked persistence of the large-scale flow along the northern border States, togetherwith snow circulation from December 1958 to January 1959 [ 11, the cover, kept this area well below normal.Montana was circulation this month showed a dramatic reversal from the coldest region, relative to normal, over the whole of the earlier state, particularly as portrayedby the monthly Sorth A4merica, with some sections of Quebec Province mean 700-mb. height anomalies. The extensiveband of running a close second. Nitchequon and Seven Islands, positive anomaly from the Bering Sea to the Denmark Quebec, averaged 10" below normal due to strong north- Strait in January gave way to equally largenegative erly flow associated with the much deeper than normal 'values this month, withheight anomalies decreasing trough in Davis Strait. The warmest section of the con- almost1,100 feet over southernGreenland. Negative tinent,relative to normal, was Aklavik, N.W.T. which height departures of January were also reversed this averaged 12" above normal under the influence of faster month in the eastern Pacific, eastern United States, and than norqal southwesterly flow. in Scandinavia where a strong block became entrenched A$ weak ridge kept the eastern sections of the United early in the month. To conlplete the reversal, above nor- States, from the Ohio Valley southward, relatively warm mal heights in the southwestern United States gave way for this time of year, with Florida the warmest section to negative departures this month. of the country on both a relative and absolute basis. Fort

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FIGURE5.-(A) 5-day mean 700-mb. contours(solid) and height FIGURE6.-(A) 5-day mean 700-mb. contours (solid) and height de departuresfrom normal (dotted) (both in tens of feet)for purtures from normal (dotted) (both in tens of feet) for Feb- February 3-7, 1959. (B) Departure of averagesurface temper- ruary 10-14, 1959. (B) Departure of averagesurface temperature from normal ( OF.),and (C) total precipitation (inches) ature from normal (OF.), and (C) totalprecipitation (inches) for the week ending February 8, 1959. (From Tl-eekZy Tl.eatllC/' for the week ending February 15, 1959. (From Weekly Weather and Crop Bulletin, National Summary, vol. XLVI, No. 6, Feb. 9, and Crop Bzclletin, Natioqzal SzcnzmarZ/, vol. XLVI, No. 7, Feb. 16, 1959.) 1959.)

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FIQURE7.-( A) 5-day mean 700-mb. contours (solid) and height de- FIGURE8.- (A) 5-day mean 700-mb. contours (solid) and heightde parturesfrom normal (dotted) (both in tens of feet) for parturesfrom normal (dotted) (both in tens of feet) for February 17-21, 1959. Heavysolid arrow is thetrack of the February 24-28, 1969. (B) Departure of average surface temper- eastern Pacific anticyclonefrom the beginning of themonth. aturefrom normal (OF.), and (C) totalprecipitation (inches) (B) Departure of areragesurface temperature from normal forthe week endingMarch 1, 1959. (From WeeklyWeather (OF.),and (C) total precipitation (inches) for the week ending and Crop Btdkfi,l, National Summary, vol. XLVI, No. 9, March February 22, 1959. (From Weekly Weather and Crop Bzcllctin, 2, 3959.) National Sumnzary, TOL XLVI, 8'0.8, Feb. 23, 1969.)

Unauthenticated | Downloaded 09/27/21 07:58 AM UTC 86 MONTHLYWEATHERREVIEW FEBBUARY1959 Myers reported the second warmest February on record. Another important featureof the mean circulation dur- Strong trough conditions in the West during the middle ing the month was t,he gradual migration of the center two weeks kept theextreme Southwestcooler than normal, of action innorthern Siberia toward the North Pole. except along the immediate coast of cent.ra1 and southern This was brought about in part by the persistent ridging Californiawhere t.he major cit'ies continued toreport tendency over theLake Baikal area due to persistent above normal conditions. Los Angeles airport appeared southerly flow out of the deep trough in the Caspian Sea. to be the warmest point on the coast,, reporting an average The latter was maintained in great strength throughout temperature 3.2" above normal, in contrast to downtown t,he month byflow emanating from the blocking High Los Angeles where the temperature averaged. 0.1" below over western Europe. The tendency toward a polar vor- normal. Asomewhat similar condition existed atSan tex eventually resulted in fast westerlies around the en- Francisco, where temperat~uresat theairport averaged tire hemisphere with spring-like weather over almost all 2.4" above normal and at the downtown office only 0.5" the United States at theend of the month. The week-to- above normal. Seasurface temperature anomalies at week erolntion is summarized briefly as follows: Santa Monica and Avila Beach. averaged about 3.0" above During the first week, retrogression of the mean High normal. This was consistent withthe air temperature in t.he northeastern Pacific favored the development of anomalies on the immediate coast, except at Santa Maria a new trough near the west coast (fig. 5A), m' a manner where surprisingly,the air temperatures averaged 1.2" that has been observed previously [31. below normal. During the second week, the development of the west Heavy precipitation amounts along the Gulf coast and coast trough, which resulted in heavy precipitation along in southeastern United Stateswere produced by persistent the coast, produceda majorreadjustment over North southwesterly winds which lifted moist Gulf air over the America. The trough which had dominated the midsec- polarfront. Somewhat similar conditions prevailed in tion was forced eastmud to the Davis Strait. As a result Montana, where the Arctic front was overrun by moist strong warming occurred in the eastern United States, Pacific air. Above-normalprecipitation in the middle and heavy precipitation spread in the confluent flow from Mississippi and Ohio Valleys was associated with recur- the lower Mississippi Valley to New England (fig. 6). rent confluence and the related trackof migratory cyclones During the third week, a sharp recurvature in its tra- in this area. Heavy precipitation in the West was due to jectory carried the Gulf of Alaska High eastward into persistent storminess during themiddle two weeks associ- western Canada (fig. 7A). The TAW in the Pacific North- ated with the very deep mean trough along the Pacific west remainedcut off andstationary, with heavy pre- coast.. cipitationcontinuing along the west coast. The advent Dry conditionsprevailed inthe central Plains and of the block into western Canada produced a relaxation southern Rockies, primarilydue to downslope effects, of the temperate westerlies over North America, a con- while the relatively dry area from the footof the Appala- dition favorable for retrogression of the trough from the chians northeastward to New England was a manifesta- western Atlantic. to the east coast of the United States. tion of post-trough desiccation. Below normal amounts In addition, flow from the stronger than normal ridge in the upperMississippi Valley were largely the resultof in western Canada helped transport cold Canadian air dry northerly flow prevailing throughout the month. southwardinto the retrograding trough near the east coast. This resulted in areversal of thetemperature 4. WEEK-TO-WEEK VARIABILITY regime in the eastern United States from the warmth of The variability of the weather and circulation within the second week. With northerly wind components over themonth is perhaps best illustrated by the observed much of thecountry, precipitation was mostly light weekly temperature and precipitationanomalies and 5-day except alongthe west coast (fig. 7 B andC). mean 700-mb. contours and heightanomalies centerednear In the fourth week, the center of action in the Siberian the middle day of each week (figs. 5-8). The month was Arctic crossed the Pole and, together with the collapse marked by a migratory anticyclone in theGulf of Alaska of the ridge in western Canada, produced a strong zonal and western Canada, while persistent blocking dominated wind regime. Thisfavored progressive waves inthe western Europe.Retrogression in the first part of the WesternHemisphere, with warm and dry air flooding month resulted in new trough formation, and progression much of the United States, except near the Gulf coast was the rule toward the endof the monthwhen the wester- which was wet and cool (fig. 8). lies speeded up to their maximum of 13 m.p.s., averaged over the Western Hemisphere at temperate latitudes. 5. CYCLONEAND ANTICYCLONE TRACKS An important aspect of the mean circulation in the first This month there were two preferred tracks of anti- part of the month was retrogression of the eastern Pacific cyclones from northwestern Canada, in close agreement anticyclone, which subsequently recurved eastward along with the normal tracks [4], one just north of the Great the southern coast of Alaska, thence southeastward into Lakes and across New England, and the other south of British Columbia by the 3d week, as shown by the trajec- the Lakes and across the Virginia Capes. In all, 10 Highs tory in figure 7A. crossed the east coast during the month, evenly divided

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FIGURE 9.-Daily tracks of migratory cyclones (solid) and anticyclones (dashed) at sea level by weeks. Each trackbegins at approximate location of center at beginning of week, or at location of formation, and ends at approximate position at end of week, or at locationof disappearance.Tracks may becompared with mean flow in figures 5A-SA. between the two tracks. The most frequent interval be- the east coast near 40" N., well to thesouth of the normal tween Highs crossing the coast was 2 days but with in- February track. tervals in the second half of the month quite variable ; A comparison of weekly tracks in figure 9 withthe e.g., a 6-day interval in the3d week. This was the coldest, corresponding meek's meancirculation in figures 5A- period of the month in the eastern and central United 8A shows that generally the cyclones followed the mean States as a cold High from the Yukon, moving steadily flow northward on the eastside of the mean troughs southward, took abouta week toarrive at the North towardthe centers of action,while the Highs glanced Carolina coast, producing some record minimum tempera- off toward the subtropical Highs. tures en route, such as -30" at Huron, s. Dak. on the A brief inspection of the weekly tracks shows that in 19th and 13" at Richmond, Va., on the 21st. the first week, with a strong hwover Hudson Bay and Cyclonic systems originated over a wide range of lati- depressed westerlies along the east coast, the Highs fol- tudes in the western part of North America,with the lowed the southern track. In the second week, with trough majority converging toward the Great Lakes region and development along thewest coast accompanied by ridging thence moving across southern New England, in general over the Southeast and strong confluence over most of agreement withthe prevailing confluent flowof the North America (fig. 6A), the Canadian Highs glanced monthly circulation (fig. 2). The principal track crossed off eastward north of the Great Lakes, with the principal

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FIQURE10.-Sea level weather map for 0100 EST February 10, 1959. Storm ceuter in Missouri spawned St. Louis tornado about 2 hours after map time. h'ote theextreme warmth (near 70" F.) andmoisture (den- lwints about 6.5" I?.)in warm sector.Precipitation area north of front consisted largely of freezing rain. (From Daily li'erctller Mal), U.S. \Yeather Flurean, Feb. 70, 1959.)

storm track from out of the Great Basin. In the third veloped in the central partof the United States andcrossed week, due to new trough development near the east coast, the Carolina coast at the weekend. the tracks exhibited the influence of both east and west By the beginning of the second week there were abun- coast troughs, with some additional transitory influences dant, signs of an impendingchange inthe large-scale in evidence. The fourth week's tracks were more zonal. regime. For example, the \Test coast ridgealoft and the eastern Pacific High cell had retrograded about 15' 6. DAILY WEATHERSYSTEMS of longitude from their positions a week earlier to about Earlyin the first week a, Canadian antic,yclone de- 150" W., permitting cyclonic vorticity maxima to plunge veloped to a record intensity of about 1053 mb. as it moved southward along the west coast. This was manifested by southeastward across the upper Mississippi Valley, pro- a surface disturbance of the "A" type [5] in the western ducingrecord minimum temperatures at some stations Great Basin. With 700-mb. heights increasing and tem- such as Flint, Mich. ( - 18" F. and -22" F. on Feb. 1 peratures warming towell above normal in the East as ZL and 2) and Nantucket, Mass. (8" F. nlinimum on the 2d). result of trongh development in theWest, an Arctic anti- During midweek, cyclonic activity swept Southeastward cyclone in Slberta glanced off eastward along the track from Alberta toward the lower Great Lakes, then north- north of the Great Lakes as didit,s successors in the same eastward in the mean flow (fig. 5A), producing mostly week (fig. 9). Bythe 9th the Great Basin disturbance moderate precipitationin the East. However heavy had deepened to a storm in southwestern Colorado. With amounts fell in the Southeast due to wave activity on the another deepening "A"-type system approaching the Ore- po1a.r front.Late in the week another ant.icyclone de- gon coast, the Colorado storm accelerated eastward across

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FEBBUARY 1959 MONTHLY WEATHER REVIEW 89 the midsection of the country toward the Ohio Valley. southeastwardfrom Alaska, lashing the Pacific North- This storm and its associated fronts produced the most west, andproducing heavy snows at higher elevations. severe weather of the month. Hourly wind speeds in many Record 24-hr. amounts of .22.6 inches were reported at places along its path were \\-ell over 50 knots. For ex- Sexton Summit, Oreg.on the 13th and14th, and 28 inches ample, Roswell, N. Mex.on the9th reported 68 knots, at Jlt. Shasta, Calif. This system was forced inland on St. Louis, Mo., 66 knots, and Dayton, Ohio, 51- knots, 011 a track across Canada toward Hudson Bay on the 15th, the 10th. In t,he dry, unstable, maritime polar air behind in contrast to the prevailing storm track of the second the first cold front dust storms developed in parts of the week across the midsection of the United States. southern Plains such as Amarillo and Dallas, Tex. North On the16th and 17tha secondary disturbancewas form- of the sharp stationary front alongwhich the storm raced ing over the southern Plains, accompanied by a record toward Ohio, a widespread area of freezing rain occurred nla.xilnum temperature for the date of 8'7" F. at Dallas, as extremely warm and moist tropical air in t,he warm Tex. -4t the same timethe coldest anticyclone of the sector overranthe Arctic air north of the front. Rfod- month dereloped in western Canada clue to the recurva- erate to heavy glazing on the 9th and 10th mas reported ture of theupper anticyclone inthe Gulf of Alaska, at such stations as Topeka, Kans., St. Joseph, Mo., Rock- andstarted to inch southward toward the northern ford, Ill., Williamsport, Pa., Albany, N.Y., and Provi- Rockies andGreat Plains. Over-running of theArctic dence, R,.I. front by Pacific air producedabout a foot of snow in Figure 10, a reproduction of the published Dui7y parts of Montana such as GreatFalls and Helena on the 16thand 17th. The disturbance whichoriginated Weather Nap, for 0100 mi- February 10, shows conditions in the southern Plains started to develop strongly near at the surface about 2 hours before a devastating tornado the Carolina coast on the lSth, and became the center of hit St. Louis, Mo. This map shows the storm center just action nearLabrador in the mean circulation of the northwest of Springfield, Mo., where a tornado was also third week, thus effecting retrogression of the mean trough reported one hour earlier about 25 miles northv-est of the to the east coast. This development was in part a E- city. The conditions depicted011 this mapclosely resenlble sponse tothe st,rong buildup of pressurein western those for typical tornadocases [6] which show a confluence Canada that followed development of a major storm off of extremely moist tropical air, dry maritime polar air, the Oregon coast three days earlier. The Yukon ridge de- and continental polar air into a deep storm center (about ployed Arctic air sout,heastward over the United States, 992 mb'. minimum pressure W~Srecorded at St. Louis) with producing record minimum temperatures at such places a cyclonic speed maximum at upper levels (not, shown). as Sort11 Platte, Nebr., with -19" F. on the 20th, and Flood conditions revisited Indiana and Ohio as a result Birmingllam, Ala., with 18" F. on the 21st, and it also of heavy rains falling on frozen ground on t,he 9th and permitted shorter wave spacing from coast to coast due loth, after less than amonth's respite from floods in to red~~ctionof the westerlies. The storm that dominat,ed January. Some places experienced the worst flood condi- the easternPacific off the Oregon coast during the 3d tions since1913. Hard hit areas were the Wabash and \\-eel

L Ohio, reported variousdegrees of flooding \Tit11 evacuation ing High recurving eastward farther north kept it cut and heavy damage in some areas. off. This storm produced the mean Low off the Pacific ' This storm passed rapidly off the middle atlantic coast Korthwest coast in figure 78. on. the loth,setting maximum temperature records at During the lastweek a ridge replaced the Pacific coastal Washington, D.C., Augusta, Ga., Norfolk, and Richmond, trough, ending the abundant precipitation regime of the Va. The anticyclone which followed in its wake brought middle tm-o weeksof themonth in the West. At the , a record minimum of - 4" F. to Schenectady, N.Y. on the same time the polar vortex became entrenched near the 12th. Canadian archipelago, st'rengthening thewesterlies across During this period another disturbance was traversing Korth A4nlerica and favoring progression of the large- the Great Basin from the 10th to the 13th. This storm scale upper waves. Earlyin the week thelast Great produced heavy snows in the West,over a footat Olympia, Basindisturbance emerged on the 22d, deepening and *' Wash., almost 3 feet at BlueCanyon, Calif., 22 inches crossing the Great Lakesregion as it headed for the New 1 at Reno, Nev., and a record 7.7 inches at Ely, Nev. This England coast. This storm produced about 1/2 to 1 inch system, incontrast to its predecessor, remained weak of rain with some flooding reported in Rockford, Ill., and .. while crossing the middle of the United States, but deep- heavy snow in the Northeast. It was followed by a Pa- ened markedly on t,he 14th as it passed off the New Eng- cific anticyclone andlittle weather of any significance land coast. Late in this week a third deep storm plunged dwing the remainder of the month.

Unauthenticated | Downloaded 09/27/21 07:58 AM UTC y,. ‘ -’ ’ -90 MONTHLY WE14THER REVIEW FEBWJABY1959 REFERENCES and Temperature Rerersal over the United States,” Molzthlg Weather Review, vol. 85, 30. 2, Feb. 1957, pp. 5341. 1. L. P. Stark, “The Weather and Circulation of January 1959- 4. W. H. Klein,“Principal Tracks and Mean Frequencies of Cy- A Month of ExceptionalPersistence from the Preceding clones axid Anticyclones in theNorthern Hemisphere,” U.S. December,” Month@Weather Review, vol. 87, No. 1, Jan. Weather Bureau, ResearchPaper KO. 40, Washington, D.C., 1958, pp. 33-39. 1957. 2. W. H. Klein,“The Weather and Circulation of €?ebruary 5. R. D. Elliot, “Weather Types of Xorth America,” Weatherwise, 19&& Monthwith an ExpandedCircumpolar Vortex of vol. 2, Nos. 1-6, Feb.-Dee. 1949. RecordIntensity,” HonthEy Weather Review, vol. 86, Xo. 2, 6. Staff Members,Severe Local StormsForecast Center, Kansas Feb. 1958, pp. 60-70. City, Mo., “ForecastingTornadoes and Severe Thunder- 5. C. M. Woffinden, “TheWeather and Circulation of February storms,” U.S. WeatherBureau, Forecasting Guide No. 1, 1957-Another Februarywith a PronouncedIndex Cycle Washington, D.C., Sept. 1936. (See pp. 22-24.)

11.8. GOVERNMENTPRINTING OFFICE: 1959

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