THE WEATHER and CIRCULATION of MARCH 1959 Record Cold in Alaska but Mild Temperatures in the Remainder of the United States

MARCH 1959 MONTHLY WEATHER REVIEW 111 il

THE WEATHER AND CIRCULATION OF MARCH 1959 Record Cold in Alaska But Mild Temperatures in the Remainder of the United States

CARLOS R. DUNN

Extended Forecust Sectlon. U.S. Weather Bureau, Washington, D.C.

1. INTRODUCTION l'ositions (indicated by arrowheads on heavy dashed lines in fig. 2). The departures from normal of circu1:holl and leu- ' In Eurasia the mean winds were generally weak. Re- perature for March 1059 were rather small over most of sidual blocking over Europe, which was associated with the cont,iguous United States. Westerly flow, silnilar to n split jet stream, produceda large area of subnormal the normal [6], prevailedin the mid-troposphere, and wind over central Europe but supernormal wind to the maritime polar airmasses, with their moderating, spring- nort,h and south. One jet stream axis was depressed and time effects, dominated the weather.However, thepre- flowed across northern Africa ; the other was displaced cipitation was more abnormal. There were periodically north of the normal position, producing wind speeds up heavy rain and snow falls as vigorous Lows developed in to 9 m.p.s. above normal between Scandinavia and Spitz- the Southwest and moved across eastern United States. bergen. There were no organizedjet streams at the Some regions received 200-300 percent of their normal 700-mb. level over Asia. precipitation. Returning to the30-day mean circulationover the oceans In sharp contrast to the nlild weather ill the contiguous (fig. 1),we note that the troughs as well as the primary States was the bitter cold throughout the Stateof Alwka. wind maxima were displaced eastward from their normal Long-period Alaskanrecords were broken, andthe positions. This eastwardshift of the Asiatic coastal reported mean temperatures were more typical of micl- trough resulted in above normal heights and abnormally minter than earlyspring. For example, the monthly anticyclonic conditions over Japan and eastern Siberia. mean temperature at Barrow was a frigid 27" below F. The cyclonic areas were also displaced eastward, produc- zero. ing significant negative anomalies in the central Pacific Meanwhile, the Hawaiian Islantls hadunnsually war~n? Ocean and Alaska. n record dry weather.Honolulu, for example, reported The largest anomalies were in northern latitudes,where high mean temperatureand lit,tle precipitation. There the 700-mb. heights were far enough above normal to re- were just 6 days with measurable rai~lf:rll, and tlle total sult in a High over Kamchatka, the approximatelocation for was the month only 7 percent of normal. of the normal Low, and also far enough below normal to produce a trough over Alaska, near the position of the 2. THIRTY-DAY MEAN CIRCULATION normalridge. This anomaloussituation affected the The monthly mean circulation at 700 mb. for Marc11 downstream pattern, so that the trough normally found 1959 consisted of a large-amplitude, three-wave pattern over eastern Canada was displaced approximately 25" of in high latitudes and n smaller-amplitude, four-wave pat- longitudeeastward to southernGreenland, reducing tern in middle latitudes (fig. 1). These two vave trains heights in that areato 510 feet below normal, the largest were approximately 180" out of phase. Only the trough anomaly in the Northern Hemisphere. in Eurasia extended continuously across all latitudes, and In retrospect, it appears that theblock over Europe and even it had a marked slope from northeast to southwest. the unusually strong trough in western Siberia, through Associated with these truncated, out-of-phase troughs and tlle flux of vorticity, molded the well-marked wave train ridges were several confluence zones with accon~panying downstream. In addition, the eastward displacement of strong winds. The most prominent ones were in the At- waves was favoredbystronger-than-normal polar lantic andeastern Pacific, where theheight anon~alies westerlies. (fig. 1) indicatestronger-than-norlrlal westerly geo- In the United States 700-mb. height departures from strophic winds. In fact, wind speed maxima were located normal were snlall (fig. 1). Over the western States posi- in bot,h of these regions, and mean spwls ~1-emore tIm11 tive anomalies were associated with the flat ridge along 8 m.p.s. above normal (fig. 2). The ce~rterin the Atlantic the coast. In the eastern States therewere weak negative was a primary wind maximum, but the one in the eastern anomalies over a broad band, typicalof a flatmean trough. Pacific was essentially justan eastward extension of a The latter feature suggests that cyclonic activity during larger primary wind maximum located in mid-ocean. All March was uniformly distributed over the eastern two- of these wind speed maxima were dl east, of their normal thirds of t,he United States.

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FIGURE1.-Mean 700-mb. contours (solid) and height departures from nornlal (dotted), bothin tens of feet, for Mmvh 1959. Mean ridge in the western and trough in the eastern United States were assoc.iatetl with stormy \\.rather vast of the western niassif. Abnormally deep trough brought cold weather to Alaska.

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FIGURE3.-Difference between monthly mean 700-mb. height anomaly for February and March 1959 (March minus February) in tens of feet.Largest falls were over Great Britain. Changes inmany areas have striking resemblance to 700-mb. height anomalies for March (fig. 1).

700-mb. 5-day mean troughs and ridges (fig. 4) and by their relationship to the 30-day mean chart (fig. 1). The bands of high frequency of troughs and ridges were nar- row, indicating a small variation inthe longitudinal psi- tion of thetroughs and ridges.One except,ion is the eastern United States, where the 5-day mean troughswere rather uniformly distributed from the Mississippi Valley to the AtlanticCoast. It is particularly noteworthy that the positions of the 5-day mean troughsand ridges clusteredaround their respective 30-day mean troughs and ridges. This means that the 30-day mean accurately portrayed the predominant circulation regime of March and was not merely the average of several heterogeneous, short-lived circulations. The 30-day mean flow of small amplitude across North America was accompanied by zonaltrajectories of the FIGURE2.-(A) Mean 700-mb. isotachsand (B) departuresfrom Highs for March (Chart IX in [4] ) . The continental monthly normalwind speeds, both in meters per second, for polar a.nticyclones, whichformed in western Canada, March 1959. Solidarrows in (A) indicateprincipal axes of maximum winds, and dashed arrows their normal March posi- glanced east-southeastward and remained almost entirely tions. Regionswith wind speeds greater than 15 1n.p.s. and in Canada. They affected only the northeastern United anomalies greaterthan 5 m.p.s. are stippled.Principal wind States where the monthly me'an thickness (fig. 5) and maxima werelocated over the Oceans east of theirnormal surface temperatures (fig. 7)averaged below normal. The positions. remainder of the United States was dominated by maritime Pacific air masses, which also moved eastward across 4. RECURRENT CIRCULATIONAND WEATHER the country. A few anticyclonic centers had trajectories The 5-day mean flow patterns during March resembled from the Pacific through the Northwest, but many of the each other andwere quite similar to the30-day mean flow. Highs first appeared over the Plains and Central States This isillustrated by thegeographical frequencies of nnd subsequently moved eastward into the AtlanticOcean.

Unauthenticated | Downloaded 09/25/21 05:26 PM UTC FIGURE5,"Departure from monthly normal of the mean thickness (700-1000 mb.)for March 1959 intens of feet. Isoline intervalis 50 feet. Below normalvalues are stippled. Pattern over the United States bears a striking resemblance to the sur- facetemperature anomalies (fig. 7). Extremenegative departures over Alaska were associated with record cold weather.

normal for the northern areas of the United States. This was particularly true for Montana and the Dakotas,where in March continental polarair masses are requiredto produce subnormal thickness, However, the same maritime Pacific air masses produced below normal thickness in the southernStates (fig. 5). The same was generallytrue for the accompanyingsur- face temperatures (fig. 7),but this month an exception existed in the Far Northwest where subnormal surface temperatures were associated with above normal 30-day mean t,hicknesses. The coolest weather here occurred during the second and fourth weeks [7],when there was a strong flow of abnormally cold air from the Arctic and Alaska (fig. 5) into the Northwest. These air masses had a short and rapid trajectory0~7er the ocean, thus minimiz- ing the diabatic heating,so that the airwas still cool when it reached the northwestern United States. During the fourth week t'he cooling vas further enhanced by cyclonic flow aloft. Along the California coast the weather was unusually FIGURE4.-Percent of the time that (A) troughsand (B) ridges warm. Both San Francisco and San Diego, which have on 5-day mean 700-mb. charts were located within 10" longitude long periods of reaord, reported new high mean tempera- intervals at latitudes from20" N. to 70" N. for March 1959. The tures for March. Furthermore,temperatures averaged datawere adjusted to an equivalent basis with 10" at GO" X. asthe unit. Isoline interval is 20 percent.Areas with fre- above normal every day of the month at San Diego and quency greaterthan 20 percentare stippled; zero areas are were belov normal only one day out of the month at Sa11 hatched.Note high frequency of troughsand ridges 1le:Ir the Francisco.Previously, se.veral authors [l, 31 of this locations of the30-day mean troughs and ridges, respectively series of articles have related the persistently above nor- (fig. 1). maltemperatures in recent years along the California These maritime air masses had a thickness or mean tem- coast to abnormalities of the circulation andof sea-surface perature of the layer from700 to 1000 mb. that mas xbore temperatnre.This Mamh therecord high temperatures

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BIQUEE B.-Tracks of selected major cyclones which produced intense storms over the United States during March. Circles are the 1200 BMT locations of cyclone on date indicated by number abore position. Number below is central pressure of Low in tens and unitsof millibars. Each week at least one severe storm moved out of the Southwest producing heavy snow and rain ever large areaseast of the Continental Divide. follow directly from theabove nornml heights at 700 mb., which reached strong storm intensityas they moved north- and inaddition, from the greater than normalnorth- eastward (fig. 6B). The first storm, 11th to 13th, moved easterlyflow at 700 mb. and sea level, produciqg foehn erratically from the lower Mississippi Valley to a posi- winds for the area south of San Francisco (fig. 1, and tion just off the north Atlantic coast and finally turned Chart XI in [4] ) . northward across eastern Maine. This storm produced The cyclones, with two exceptions, wllicll had tracks heavy rains in the South and heavy snows in the North- over the United States also had origins there (Chart X east, ashigh winds raked the entire east coast. More in [4]). Several Lows formed in the Atlantic Seaboard heavy rains in the South and a band of heavy drifting States, but the storms which originated in the Southwest snow from Nebraska to Michigan resulted from thesecond contribute'd most to the weather over the United States. storm of that week (14th to 16th) which moved from the Each week at least one major cyclone formed over the lower Great Plains across the Great Lakes. During the southern Rocky MountainStates and produced severe third week the incidence of Southwest storms continued, weather along its eastward track through the central and but the cyclone which formedover Utah on the 19thmoved eastern UnitedStates. A detailed descripition of the in an east-southeasterly direction with its path traversing effects lof these storms is given in [7]. the Gulf Coast States (fig. 6C). In addition, a cyclone During the first week of March a major storm marked formed over Lake Ontario and slowly traced an erratic by heavy rains, damaging winds, blowing dust; and drift- track across the Maritime Provincesof Canada (fig. SC), ing snow moved from Colorado northeastward across the creating stormy conditions in New England on March 21. Great Lakes into Canada (fig. 6A). The weather during The mild, sunny weather east of the Rocky Mountains the second weekwas influenced mainly by two disturbances during the first part of the fourth weekof March was

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FIGURE?‘.-Departure of average surface temperature from normal

(O F.) for March 1959. Largest anomalies were in the northern Plains and Rocky Mountain States, but the positive anomalies alongthe California coast were associated with rerord ten)- peratures (from [ 71 ).

Fruus~10.-Nuinber Of days inMarch 1959 withfronts of any type within unit squares (with sides approximately 500 miles). All frontal positiolls are taken from UrriZyl Weather Uup, 1:oO p.m. EST. Arras with le> or more days with fronts are stippled, Active fronts \vew frrqlwntly loc2:ited in Florida, Central Plains, and the Nortlnvrst.

interrnpted by sternly ~veather:IS still anotller Texas dis- hrbance rnovetl northe:~stward on the 25th to 27t)h from the Southwest. across New Jersey (fig. 6D). The severity of the weather associated with these “Southwest, IIows” isattested by thesummary ofthe monthly weather at Dnbuque, Iowa, which felt t,he f~dl brunt of several of these storms. It wasreported that the precipitation for March was the heaviest since the FIGURE8.-Total precipitation(inches) for March 1959. Record beginning of records in 1851. The snowstorm of the 4th amounts fell in Florida (from171 ) . and 5thbrought the greatest amount of snow ever recorded in one 24-hourperiod for any month. The 6.50 inches of moisture for the month exceeds by 1.48 inches the previous wettest March recorded in 1852. The total monthly snowfall of30.2 inches is the greatest for any March and the greatest for any month of the year since January 1929. Similar reportsof record-breaking weather came from stations in Nebraska and Wisconsin. The hulk of the precipitation over the United States tl1wing March (figs. 8, 9)was produced by the major storms whose tracks are shown in figure 6. However, additional rainfall did occur in the Southeast, associated wit,ll fronts which were prevalent over Florida and the Gulf of Mexico (fig. 10). Some of the precipitation was cold-frontal in nature,but) the majority was produced by inc,ipient,cyclone waves alld over-running of the cold air by tropical air masses. Tampa reported the wettest FIGURE9,”Percentage of normalprecipitation for March 1959. Marchon record; ot’her Floridastat,ions broke various March was abnormallywet in the southeastern, northeastern, precipitation records. central, and northwestern States but unusually dry in the north- ernPlains, northern Rocky illountnins,and the Sol1thwPst In the Northwest above normal precipitat,ion occorured (from [71). with f:~ste~~-tha~~-normn.l~z.est,-so~lth\~esterly flowacross

Unauthenticated | Downloaded 09/25/21 05:26 PM UTC MARCH 1'359 REVIEW WEATHER MONTHLY 117 the mountain ranges (fig. 1), which intensified orographic lifting.Also favorable were thefrequent invasions of maritime Pacific fronts (fig. 10) and cyclonic flow aloft. (See DaiZy Weather Map [51 .) That precipitation which fell east of the Rocky Moun- tainsoccurred under cyclonicallycurved 700-mb. mean flow and weak easterlyanomalous flow in the Kansas- Missouri-Illinois area ; both types of flow have been related empirically to verticalmotion and precipita.tion. However, the explanation for the precipitation whichoc- curred in the easterlyflow north of the daily Lows, along the eastern slopes of the Rocky Mountains in Colorado and Wyoming, is not easily extracted from the monthly mean circulation at the 700-mb. level. The vertical motion and precipitation in these central Rocky Mountain States were enhanced by orographic effects not reflected FIGURE11.40-day mean vertical motion at the 600-mb. level in millimeters persecond for March 1959. Map was obtained by in the upper-levelcirculation. Also, the precipitation averaging the 60 available twicedaily values computed from occurred during a few shortperiods which were not typi- baroclinic model and observed data. Isoline interval is 2 milli- cal of the predominant pattern of the region and conse- meters per second. Absolute values greater than 2 are stippled. quently would not Ibe reflected in the 30-day mean Descending motion (negative) and ascending motion (positive) circulation. tend to be located east of the 30-day ridges and troughs, respectively. 5. RELATION OF PRECIPITATION TO VERTICAL MOTION Of coursa, subjective evaluation of the monthly mean flow in terms of the average vertical motion or precipitation is rather crude, but until recently, it has not been practiaal to objectively estimatethe verticalmotion. Now, the availability of operational b'aroclinic models and elec- tronic computers enables us to compute, objectively, the vertical motion for a midtropospheric level. The National Meteorological Center of the U.S. WeatherBureau at Suitland, Md., using a two-level baroclinic model, esti- mates twice daily the concurrent vertical motion at 600 mb. from initid (observed) data. The 30-day mean of these values for March 1959 (fig. 11) is a logical pattern roughly consistent with the con- comitant mean 700-mb. circulation. In general in figure FIGURE12.-30-day mean of only the ascending (positive) daily 11, descending motion (negative values) is found west of vertical motion for March referred to in legend of figure 11. Isoline interval is 2 millimeters persecond. Values greater the troughs in the northwesterly flow and ascending mo- than 4 are stippled. Pattern resembles the total monthly pre- tion (positive values) east of the troughs in thesoutherly cipitation (fig. s). flow. Exceptions are thenegative values justoff the northeastern coast of the United States, under and east of the Los Angeles, Calif., reported record dryness for March. mean trough (fig. 1, 11). This, at least at first thought, Helena, Mont., hadthe driest March since 1881. The does not fit the accepted relationship between horizontal ascending motion over the Far Northwest and the States circulation patternand associatedvertical motion, but bordering the Gulfof Mexico fit the precipitation pattern further inspection of figure 1 reveals that subnormal 700- quite well. However, pronounced discrepanciesexisted in mb. heights and marked anomalous, northerly flow ex- theNebraska-Kansas-Iowa and Northeast areas where tended from eastern Canada to New England, suggesting sizable amounts of preclipitation occurred in regions of that cold subsiding air masses frequently invaded the area little or no meanascending motion. This could result in question, off the northeasterncoast of the United States. from the averagingprocess where largeascending motions Portions of the 30-day mean vertical motion were cor- during shortperiods of storminess would be counteracted related with the total monthly precipitation (fig. 8). The by long periods of subsidence. Therefore, the mean of descending motion over the extreme Southwest and the only the positive values (ascending motion) was obtained northern Plains States was relatedto the driest areas this (fig. 12). As expected, there was considerable ascending March. Prescott, Ariz., which had no precipitation, and motionin these wet regions. Apparently, west of the

Unauthenticated | Downloaded 09/25/21 05:26 PM UTC 118 REVIEW WEATHER MONTHLY MARCH1959 mean troughs, on the western fringe of the precipitation an anomaly of f3.7" F., almost 3 stmdard deviations areas, there were periods of both ascendingand descending above normal. motion associated with the lifting and precipitation north This warmth was associated wit,h a deficit of precipita- and east of the daily storms and the sub'sidence in the t,ion at both stations. Honolulu reported only 0.17 inch, cool air behind these same stormsas theymoved eastward. 2.13 inches below normal, and Lihue had 1.37 inches, 2.70 The availability of moisture, which is an additional re- inches less t)han normal. quirement for precipitation, has notbeen considered in this TARLE1.-Alaskan and Hawaiian surfacetemperatures (" P.) for brief investigation, and should be inchded inany further March 1.959 study. Station I M;;gly I Normal 1 Anomaly deviation lbtmdard 1 recordsYear 6. ALASKAN COLDAND HAWAIIAN WARMTH start Most of Alaska experienced a record-breaking cold Alaska /Illi March(table 1). Blarrow, Fairbanks,and Nome, well distributed stations with long periods of record, had the coldest March on record and Anchorage thesecond coldest. Departures from normal of the monthly mean temper- I€au,aiian Islalkds Honolulu ...... ~~~..~...~~~..~~~..~+2.5

atures were as large as two or three standard.deviations, ~ Lihue-.-..- ....-...... ----.--~.-i :%:1 %:6"1 +3.7 1 i:: 1 %5" a rather rareevent. Fairbanks, with 16" F. below normal, ___ *Record for March. had the most extreme anomaly, but Barrow, witha frigid mean temperature of 27" F. below zero, suffered the coldest The dry and ext,remely warmweather occurred with weather in the absolute sense. At the lattercity the maxi- a stronger than normal subtropical ridge in the eastern mum daily temperature did not exceed -5" F., and the and central Pacific. Over the Hawaiian Islands 700-mb. minimum was always colder than -21" F. mean heights (fig. I), 1,000-700-mb. mean thicknesses, This cold over Alaska was produced by stronger than and sea level mean pressures were all above normal dur- normal flow between the mean ridge over eastern Siberia ing March. and the trough over Alaska (fig. l), which continually REFERENCES advected cold air masses fromthe Arctic Basin into 1. 14:. M. I!allenzw~ig, "The Weather and Circulation of Sep,tenlber Alaska. This was a very persistent pattern, as illustrated 3958", Monthly Weather Review, vol. 86, No. 9, Sept. 1958, by the 5-day mean trough and ridge frequencies (fig. 4) JQ,. :359-x7. 2. .T. IC. O'Connor, "TheWeather and Circulation of February and produced overAlaska the coldestmean thickness 1959", Montl~l~Weather Review, vol. 8'7, No. 2, Feb. 1959, anomaly for the Northern Hemisphere (fig. 5). PI). 81-90. While the Alaskans were shivering in record-breaking 3. J. F. O'Connor, "The Weather and Circulation of June 1956 cold weather, the Hawaiians basked in record-smashing Record Cold in Northeast and Warmthin Northwest," Monthl,! warmth (table 1). At Honolulu, the daily maxima nver- Weather Review, vol. 86, No. 6, June 1958, pp. 229-236. aged 79" F. and the minima71" F. for themonthof Marcll. 4. lJ.S. Weather Bureau, Clirnatologicnl Uata, Nutional Xunmary, vol. 10, No. 3, March 1959. Of more significance was the monthly mean temperatllre 5. I7.S. WeatherBureau, Jlnily Weather Mal), Washington, U.C., of 74.7" F., the absolute highest since records began in hlureh 1959. 1905. This month'smean temperaturerepresents s de- ti. 17.8. Weather Bureau, "Normal Weather Charts for the North. parture of f2.5" F., which is large for this subtropical ern Hemisphere," Technical Paper No. 21, Washington, D.C., Oct. 1952, 72 pp. station that has la standard deviation of only 1.0" 17. 7. 1T.S. WeatherBureau, Weelcly Weather and Crop Rvlletiq Similar weather was experienced at Lihue, Kauai, where Xntionnl runm mar^, vol. XT4VI, Nos. 10-14, March 9, lc;, 23, 30, a record monthly mean temperature of 74.3" F. proclucetl ant1 April 6, 1959.

CORRESPONDENCE (C'ontinued f~om21. 106) We were not aware of a similar modulated technique in 4-foot pan. Theseobservations have not caused us to use by the Weather Bureau. alt,er our point of view on the disadvantage of pans, gen- We are aware that saturation thresholds are somewhat erally. Frost is a serious limitation to the use of atmom- difficult to work with, but forconditions of level plot land, eters. (In this connection we have been experimenting we assume that a saturation point exists and that any with an instrument which withstands 7 degrees of frost.) precipitation in excess of this value is runoff and hence Our co-workers in Canada have noticed time trends in lost as far as cropuse is concerned. Bellani plate atmometers only when air enters the cup or During the past year we have had the opportunity to when the surface color or porosity changes because of compare: atmometers with the Class A pan, and the bnried dirt or acc1unnlat)edsalt,s.

U S GOVERNMENT PRINTING OFFICE:1959

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