THE WEATHER and CIRCULATION of JUNE 1962 a Generally Cool Month

41 4 SEPTEMBER1962

THE WEATHER AND CIRCULATION OF JUNE 1962 A Generally Cool Month

RAYMOND A. GREEN

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

1. INTRODUCTION 3. MID-MONTH CIRCULATION TRANSITION June 1962 becamethe third consecutivc nlonth that While blocking in Canada was present in t,he monthly large-scale blockingin t'he Pacific was theoutstanding average circul:ltion, it' was solelya charac,teristic of the feature of themean circulation of theKorthcrn He~ni- circulation during t'he first half of the month in which a sphere.Significant blocking also appe:Lred inCanada ridge tlnd weak westerliesextended from southeastern for the first t'inle since hlarch. Its presence was associated IJrlitcd States to north-central Canltda(fig. 2-4). A strong with a soutl~ward push of cool air into the Midwestern positiveheight a,nornal_v cent'erwas located north of United Stat'es where a heat wave had prevailed in 3Itay. Hudson Bay, whereheight, anomrtlics had increased as In someareas the resulting temperature changc w.as rnucl~as 250 ft. fro111the previous half-month (not shown). sufficient' to reverse thenormal upward trend for this At the sanle time, IL largc area of zonally oriented positive time of year, with a nunher of stationsreporti;lg the llcigl~tdepartures dolnintLtd the Pacific. rare occurrence of cooler ttvert1gt.s Ior June thtrn for Ala>-. In late June (fig. 2R), while only a smallremnant of At thesame time precipitation exceeded uormal ill the carlicrpositive height ano1n:tlies appearedin Canada, Gulf Cowst andSouth Atlantic States where drought heights had riscrl sharply in t,he Bering Sea and had fallen conditionswere observed in April and hlay. inthe wcst,crn and mst>ern Pacific (fig. 2C).Thus the circulation alnplificd and blocking increased in the Pacific 2. MEAN CIRCULATION and dinlinishcd ovzr North -4meric:t during the month. Xot only was the ridge over tllc eastern Aleutians (fig. These chnrlges brought, about R lorn1 of retrogression in the 1) the strongest observed for this area in m~>-fJ~me in the p1anet:lry wave pattern, witht'lle est~t~tblishmentof a trough records of the Extended Forec,nst Brtmch (sitlce 1933), the in the Gulf of ;llwsk:L and virtual elirnination of t'lle early $400-€t. anonlaly in the ridge equaled thc strongest 011 June trough ovcr western Unit'edStates. Downstream, record (June 1939) over theNorthern Hemisphere. Tlw he westerlies increased oversouthern Canada and the largest 700-mb. height' anorrlalics of the he1nisphcre have United States with it corresponding warmer trend in the been associatedwith 111eu11 ridgesin t1lE Pacific for the half-nlonthtetllperature rtnornalies over most of the pastthree months. This blocking ridge TWS associated Unit,ed States. with t'he familiar split in the westerly flow pattcrn that resulted in a higher-latitude ridge and a deep low-latitude 4. TEMPERATURE trough. The blocking was reflected at sea level 1))- IIW:~ pressures as much as 10 nib.above rlorlllal in the ridge nnd 3 mb. below in the trough. Circulationfeatures downst'rearn, 1no111decl to n great extent by thePacific ridge, were also much different fro111 normal. In western Canada, where ridge conditions nor- nlally prevail in June[l], cyclonic flow and llegativc height anomalies were therule. Tl1c blockingridge ovcr the Great Lakes was nlucll wcaker, but exllibitcd ch:mwtc\ris- tics sirniltrr t'o blocking in the Pacific. From the Ihritinle Provinces of Canada t~ rather uniform band of xvestrdiw prevailed across the Sort'h Atlantic and northern Europe tonorth-cent,ml Asia. Vigorous mean troughs were located in eastern Europe and off the cast coast of Asia, the lat'ter being ideally suit'ed in both position and arnplitudc to support the strong ridge in the eastern Aleutians.

Unauthenticated | Downloaded 09/28/21 05:00 AM UTC FIGURE1.-Mean 700-mb. contours (solid) and height departures from normal (dotted), both in tens of feet, for June 1962. In response to blocking over Canada, westerlies were slower than normal over the United St,ates east of the Rocky Mountains.

May was considerable (sec "270 ft'., fig. 4A). Frotti the area of maximumchange northernin Canada a posit'ive l."Stations reporlirLg temperature for June than belt extendedacrosswesternt'he Urlit'ed States t'o Baja for May 1962 California,while anarea of negative change extended Temperature (OF.) from t~ center over Greenland to another over Tennessee. Station There was good agreement between this pattern andpattern this agreementbetween good was There May 1 June __ -- changesin temperature anomaly (fig. 4B). Coolingwas 77. 1 76.7 especially pronounced in the south-central Plains, where a 71.1 70.9 72.7 72.5 strentheningnortherly component is implied by the height 75.4 75. 1 75.3 75.2 changefield. It wasin thatarea and eastward t'hat 76.5 76.4 76.2 75.0 temperatureswere cooler than in May, asindicated by

Unauthenticated | Downloaded 09/28/21 05:00 AM UTC FIGVRE2,-hIw11 TOO-mh. contours (solid) and height departures fro111 normal (dot,trd), both in tcbrls of feet, for (A) Jrmc 1-15 mtl (B) Jme 16-30, 1962. (c)depicts thra hc~ightcharrgv from (A) to (B) in trm of feet. I3locking irlcrrastd in the I'acific anddiminished in Canada from the first half to the last half of the mouth.

therepresentative list of cities show1.u intable 1. Sash- ville, Term., :tnd Cairo,Ill., reported this the firstsuch occurrencesince records began in 1871 ~1tl1872, respectively. 5. PRECIPITATION Added to t'he direct, influenceof circulation on telnprrn- turein the South was the coolingeffect of increased cloudirless andprecipitation, particularly in the Gulf Coastand South Atlantic States. Drought relief began there wit'll showers late in May 121 arld rainfnll amounts exceeded normal over most' of that area in ?June (fig. 5).

Unauthenticated | Downloaded 09/28/21 05:00 AM UTC (OF.) forJune 1962. Kotethe absence of largedepartures Drought was broken in the South. (From [3].) (From [:I].)

FIGI-RE6.-"\'unl)cr of days with fronts in equal-area(66,000 n. mi 2, quadrilateralsfor June 1!)62. Precipitation generallyexceeded normal along and southof the axis of maximum frontal frequency from 'l'irginia to Colorado.Overrunning accounted for much precipitation in the Central Plains.

'I't1el.e were some dry regions also, the most extensive of which was allnost all the areA west of the Continental Divide, wllere the Pacific: coast' trough was weaker t'han normal (fig. 1). Subst:~rlt~iallpless thannormal precipi- tRtiorl fell-over most of the upper 3lississippi Valley and it1 tlle Ohio V:tlley where Dayton, Ohio and Parkersburg, FIGURE4.-(A) Change in mean 700-rnb. heightdepartures from IT. Vn., reported their driest June of record dating back normal(tens of feet),and (B) change of surfacetenlper:iture to 1883 and 1889 respectively. C'ombined deficits of May departure from normal (OF.), from May to June 1962. In gcncral and Junebrought' on droughtconditions in portions of there was good correspondence of the change fields in the Unitcd tlle Kortheast',with tlle driest area centered in nort'h- States. eastern Pennsylvania, southeastern New York, and northern Xew Jersey. At, Albanyand Syracuse, N.Y., t'he began at Amarillo, 'I'ex. (1892), Wilnlington, N.C. (1871), Mayv-Junetotals were 38 percent and 35 percent of and at Spartanhurg, S.C., :md the wettest since 1893 at nornd, rcbspect'ively, and thecorresponding figure at Charleston, S.C. Scrnnton, Pa., was only 32 percent.

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6. SEVERESTORMS intensit’y. Ext’ensive bail and wind darnage were reported in Montana, Kebraska, Minnesota, atld Tesas, and de- Tornadoact’ivity was slight in the Korth Central structive winds in Missouri and Iowa. Excessive ra.infal1 Stat’eswhere these violentstornls are normall\- nlost Iron1 a coastalstortll lute in the tnonth caused major frequentin June. In thiscase the circulation (fig. 1) crop darnage in Sorth (’arolina. Wir~dsalong the coast wasnot favorable for suchdeveloprnent. The mean \wre not destructive, however, and there TVRS little tidal trough was too far west’, the anomalous flow was easterly dalnage t’o the Outer Banks. inst’ead of sout>herly in the Midwest’, and the rrlid-tropo- spheric jet was displacednorthward into sout,llernClanatla. REFERENCES Thusthe ternperat’ure pattern (fig. 3) lackedthe con- 1. U.S. \Teather I%urt~au,“Sormal !Teather Charts for the Sorthern trastbet’ween cool Pacific: andtropical GulC airmasses IIemisphrre,” Tech,nicalPaper Yo. 21, ITashi~lgton,D.C., necessary for development of the vigorous wave c-clones 1952. withwhich tornadoes are most oft’enassociated. Pos- 2. ,J. F. O’Co~lnor,“The M-wther and Circulation of May 1962- sibly because of t’he prosin1it.v of a mean trough in early Record Heat inthe Mid-West,” Jlonthly Il-eather Review, VO~.90, SO.8, August 1962, pp. 365-370. were Wyo- June (fig. ZA), several tornadoes observed in 3. U.8. Wrather Rurtlau, 12’eekly Weather and Crop Bulletin, ming, where Lander reported tllc first on record. IVational Surnnzary, ~ol.XLIS, Kos. 27 :md 28, June 2 and There were many severelocal storms of less violent 9. 1962.

CORRECTION

Vol. 90, So. 7, July 1962: P. 274: In figure 5 the plottecl numbers show dt’itude (X 100 ft.) instcad of azimuth. PP. 303 and 305: The maps shown in figures 7 tmtl 9 are not the ones intended. The correct cuts for April 1962 are sllomn below-.

FIGURE7.-Departnre of average temperature from normal (OF.) FIGT-RES.-Total precipitationin inches for April 1962. Largest for April 1962. Except for a small region from thesouthern nrnountsaccumulated in the Southeast and the Pacific North- GreatLakes eastward, temperatures averaged warn1 for the west. Driest regions occurred in the Southwest and thc northern western and cool for the eastern half of the country. Plains. (From [4].)

U S GOVERNMENT PRlNTlNG OFFiCE.1962

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