368

THE WEATHER AND CIRCULATION OF JUNE 1961

A Hot, Dry Month in the West L. P. STARK Extended Forecast Branch, US.Weather Bureau, Washington, D.C.

1. RECENTMONTHLY TRENDS tion in nlid-Pacific, contributed to the anomdous posit'ion ol the Aleutiun Low inthe Gulf of Alaska.Deepening From thru June 1961 there was a not'iceable of the trough in the Gulf ol Alaska wits probably assisted t'rend in, the monthly weather anomalies and circulation by local haroclinic processes, suggested by the dist'rihut,ion over the United St,:Lt#es. Temperatures in the east.crn 11df of t~lonthlyItleitIl 1000-700-rnb. thickness (fig. as well of the Unit,ed Stat,est'entled t'o becomc progressivel- cooler Z), as by hrotropic transport ol vort'icitp from upstream. than normal while tenrperat'ures in thc western hallof the Growth of the ridge in the central Pacific WRS a great countrycontinued a warming trend. ,4t' thesame tilrle, change from ;\lay (see fig. 1 of [2]) when atrough was there was a gradualshift in t'he area of heavierthan locatedin this area. Heigl~t~s at 700 mb. increasedas normal precipitation from nort'hern and eastern portions Inut-h its 400 ft'. from I\I:LJ.to June in the western Aleutians to the Southern States and a noticcable tendency towrrd as the trough mt~sreplaced bv n st'rong ridge in June. drought c,orditiorrs in parts of the West. Over North Rnwrica the ('nnitdian portion of the ridge A corresponding t'rend was apparent in the circul.'l t,'1011 in the West8was sotnewllat~fnrther wst and generally 100 in the mid-troposphere. Comparison of successive month- fcct or nlore stronger than nornull. Its companion trough ly mean 700-rrlb. chart's for hltrrch t'hrough June sl~ows downstream was west of its normal posit,ion and A litt,le t'he gradual displacenlent westward of a long-wave t'rough tlccper thannortnd. 'This shortening of thehall wave- from the western Atlant'ic at the beginning of the period length between t'he ridge :md the t'roughresulted in a to t,heOhio Valley by June. There were ot'her areas in vigorous nort,herly conaponent of the height, anomaly field which apparent retrogrademotion of major syst'enls fro111 northeastern C':rnad:~ to Mexico. occurred, but,in none was it'so pronourlced or so irllport'anrt 11I here were pronounced clrangcs in the ckdation at to t'he weather in the . 700 mb. from the first hall of Junc (fig.3A) to tlle last 2. MONTHLYMEAN CIRCULATION half of the month (fig. 3B). Elements of the circulation over ant1 near North Anlerica for -15 included a The planetary wave pattern at' 700 rnb. in June 1961 colltinerltul ridge :dtwo major troughs, one in the Gulf (fig. I) consisted of well-defined trough ttnd ridge systellls of A1ask:L md the otllcr in eastern (hnada, oriented in a from the western Pacific eastward t'o Eurasia. Whilc this nlotlifietl omega pattern.Flow over theUnited States is shown by t'he height contours done,it is better irdicbatetl was quitmeweak except dong the northern border. Tllcse by theheight departures frolrl norrm~l(dot't'ed linesin features are shown clc:dy by the cont'ours of Ilcight~nnd fig. 1). height anomaly in figure L4. In theAtlantic the circulation was charact~erisctlby From the first hall to tlle last hall of the month the westerlies t'hat averaged considerably faster than norllld circulation was chrwterized 1)y retrogression and gcncrtll in a jet maximum t'hat extended from Kewl'ountllantl to flattening of the pattern at higher latitudes over North t'he United Kingdom. The st'rong westerlies resulted from Alncrica (fig. 3). This was associwt'ed with weakening of the rnoderat'clp deep Icelandic Low in phase with a strollg the TAowin tlrc. Gull of Alaska. At the same t'irnc heights ridgein t'he Atlantic. Tho prinaar.v Icclttntlio Low w:ts incrensctl inwestern L'nitcd States :IS n1uc.h as ZOO Ut. 310 feet deeper than normal and was displaced considcr- over tltc Great Basin. r\lcnnwMe, the trough in enstern ablyczstward t'o theSorwegian Seafrom itsnormal Sorth Anleric:~ retrogrndcd to theOhio Yalley md joined posit'ion near Baffin Island [I]. with tlte trough that,moved c:lst'w:trd from Ritjn ('alifornia. The Aleutian Low was similarly displaced. Its Ilortlld In sut111n:wy, CTune wtts $1 rllorlth of relatively low index positmionin June [I] is in the Bering Sea, and it, is usu:rlly circulation ovcr the ITnited States.This was associated accompanied by II broadcyclonic flow inthe cmltrtd not with blocking as mas %Ia.v, but with a. strong mcridion- Pacific north of 30' N. The observed flow (fig. 1) sl~ows nl flow that was responsible for unseasonable extremes of that the deepening t'rough in enstern Asia and alnphfica- tcrnperature in mun? parts of the country.

Unauthenticated | Downloaded 09/26/21 06:48 AM UTC SEPTEMBER1961 369

FIGURE1.-Mean 700-mb. contours (solid) in tens of fet.t, and tkpart~lrt~sfrom normal (dotted) in 50-ft. int'ervals, for June 1961. The rrleridional rlature of the height arromaly field was indicative of thv low index condition over North America and the Pacific.

Unauthenticated | Downloaded 09/26/21 06:48 AM UTC FIGURE2.-Mean thickness (1000-700 mb.) departure from rlorrnal (isopleth interval50 ft.) forJune 1961. Cool airlnassw dominated the East and subsiding air warmed the West.

bypassed t'he Great Lakes, a very atypical occurrence in June [4]. Theaverage thickness from 700 to 1000 mb. (fig. 2) wasbelow normalalong an axisfrom 1,abratlor t'o thc Gulf of Mexico,generally coincident with the area of below normal surface temperatures (fig. 4). Few records wereestablished inthe East beyond several ncwdaily minimumtemperatures. At Norfolk, Va., :L new- all-time FICTRE3.-llean 700-mb. contours (solid) and dckpartures from minimumfor June of 48' F. wasrecorded on tl~c 17th; normal(dottctl), both in tens of feetfor (A) June 1-15, 1961, recordlow monthlymean tcmperaturee werereported and (B) Jnne 16-30, 1961. Retrogression of the trough in the East and intensificationof the ridge in the Westwere important at Louisville, Ky. (68.9' F.) and Vicksburg, Miss. factors during June. (75.1' F.), and the coldest June since 1903 was reported at Shreveport, TAL. In contrast to the East, temperatureswere exceptionally warm in t'he West. A large area was 6'-10' F. warmer than normal (fig. 4). This region was located under ttlc upper level ridge where subsidence WRS widespread and whereheights exceeded rlormdby as much as 170 ft. (fig. 1).Many areas in the West reported heat waves ofvwrJ+lg duration, but one of thc most intcnse was at

TABLE].--New monthly maximum trmperature rerords in .June 1961.

Maximum Location trmperature (OF.)

FIGURE4.-I>cparture of average temperature from normal (OF.) forJune 1061. Manynew temperature records mwe estab- lished, especially inthe West. (From [5].)

Unauthenticated | Downloaded 09/26/21 06:48 AM UTC 371

FIGURE5,”L)eparture of average temperature from ~~orrr~al(OF.) for (A) June 1-15, 1961, and (B) -30, 1961. Note that (B) most closely resembles figure 4.

JALSVegas, Xev., where the daily maximum temperature ranged from 110’ to 113’ F. from to 26. ,\lost cities in JIontana hntl the w:lrnlest June of record. Othcr spectwulttr records include new maximum temperatures for June as shown in talh 1. Above normaltemperatures were not confined to thc United States.The core of m:trm thicknessand uhove normttl heights extended northrvard to the Beaufort Sea. Repxtsfrom the (hrdi:m J\Teteorological Branch, Department of Transport,indicate that temperatures exceeded normal by 6’ to So E’. fromsouthcrn Albcrta to Great Slave hl

Unauthenticated | Downloaded 09/26/21 06:48 AM UTC 372 MONTHLY WEATHER REVIEW SEPTEMBER1961

A PERCENTAGE OF NORMALPRECIPITATION SEPT. 1960-JUNE 1961 I

arlornalous windconlponents. In addition,tcnlpcr:rturcs were fairly cool (figs. 2 and 4) from t,he surl':wc to 700 II!~. andthe influx of moisture at the sur4'tlc~\ (C'hart XI ol' [31 was moderatelystrong from the GulL of Jlr...;ic-o to Oklahoma.Thus, conditions were optirllu~rlTor over- runningand heavy precipitationin this arcs. Iiccortl amounts for June,were observed at Wwo md h1dcrlc, Tex., and Shrcveport, Lit. The distribution of precipitation can also be cotlsitlcrd as a function of fronttdwtivity. Figure 7 sllo\vs an axis of mnxirnmu front,al frequency from Texas to southcm Alabama t,o North Cnro1in:l. The 1oc:ttion ol' this uveragc frontal zone corresponds well to the area of 1te:~vy prccipi- tation, as would be espectcd. However, the uea of mi xi mum frontal occurrence from North Dakota to the T,ower Great Lakes shorn a higher frequency thnn that in the South,yet t,he precipitation "fit" wasrelatively poor, exceptin New York andPennsylvania. The flow ut alllevels west of the troughat 700 mb. cor1t:lined a northerly component, carrying dry air into the countr:;. Therefore,fronts in tlre West were ineffecative in pro- ducingrain of any consequence, a nlajor f:lc.tor in t'lw perpetuat'ion of drought' in this area. DROUGHT Asignificant shortage of prr:cipitnt,ion in the last tcn monthshas produced n drought of p:trticularseverity inportions of the States shown in figure SA (from [SI). The 700-1nh. mean circulat,ion for most, of tlre United Statesand Canada for the period Septembw 1960 to June 1961 (fig. 8B) was prepared in order to detect any correspondence between the flow and the drought'. Anonl- alousprecipitation is not uniquely defined by mean 700-mb. contours,but there are components of this

Unauthenticated | Downloaded 09/26/21 06:48 AM UTC SEPTEMBER1961 MONTHLY WEBTHER REVIEIV 373

REFERENCES 4. by. H. Klein, “l’rirlcipal Tracks and hlean Frequencies of Cyclones :md Anticvclolles inthe Xorthern Hemisphere,” 1. IT.S. Weather Bureau, “Norrnal Weather Charts for t,he Northern IT.S. WcnthcrBurcnu, Research Paper So. 40, Washington, Hemisphere,” Technical Paper No. 21, Washington, D.C., 1952, I).C., 1957, (io pp. 74 pp. 5. IT.S. W(,atherHureau, V‘eekly TVcath~r and Crop Bulletin, 2. R. H. Gclhard,“The Weather and Circulation of - AVulior~nliC!lwtmary, vol. XLVIIT, SOS.2T slid 28, July 3 Pcrsistent Cool Weatherin the ITnited States,” Monthly arid 10, 1961. Weather KeaiPw, vol. SO, No. 8, Ang. 1961, pp. 299-305. 6. C. K.Stidd, “Thc, I-se of CorrelatiouFields in Relating Pre- 3. l-.S. WeatherBureau, Clirrmtological Duta-L\‘ational hSctm?nury, ripitation to Chculntion,” Journal of Md,eorology, vol. 11, vol.12, h-0. 6, June 1961, Charts IX and X. So. 3, June 1!)54, pp. 203-213.

Weather Bureau Technical News

ISOTOPE-POWEREDAUTOMATIC WEATHER STATION

The latest devclopment in the tLutorntLtic obscrvatiorl of weathcr is the incorporationof :t radio-isotope pon-cr plant into thc apparnt’us of autorn;lticstations. This :dloms unnttcntled oper:ttion of tllestation up to thc limit of iostrurnerlt life, tmtl c1imin:ttcs tllc tliffkultios rnct, with in other nutom.:rtic st’ationsfrom ltrck of n continuous pon-er source. ‘Fhc first’ such station was sct up in August 011 or near Graham Island in the Can:tc\ian Arctic nbout~half- way betwwntllc Joint C)i~n~tlia~l-Unitetl States Arctic WeatherStations at Eurelm :md Resolute. I’owcr is gcncratcd by tlle heat spont:rncously produced by radio activc decay of pcllcts of strontium-90, in theform of st,rontium titanate, enclosed in n srnall(5-inch) shicltlcd cylindricd capsule. The heat is tr:tnsformctl dircct157 into a continuous flow of electricit’y by 60 pairs of thcrmo- couplcs arrangrcl like spokes around the cylindrical heat source. The whole gencrator is shieldcd in 4.4 inches of lead and c,overcd by an outcr skin of st’airllcss stccl. 7‘11~ overalldimrnsiorls are 20 incheslong by 18inchcs in dinmetcr. The gcncratorcylindcr is the bot,tom elcmrnt in a larger cylindrical container 8 fcct long. The top conrpart- mcrlts of this house theclectricsl tappttratus, recording equipment, radio transmitters, and the barometer. Excess heatfrom the gencrator serves tomnintairl an intcrior operatingtemperature of 70” F. The arlcmomcter and thermometer are cxposetl on a mast beside thc cylinder, the lower 5 feet of which is buried in the ground. Observations of wind direction (to nearest 10’ llr:ttling), wind speed (0 t,o 150 Id. f 1 kt., 1 and 8 minute :Ivcr:ge), pressure (28.00 to 32.00 in., f 0.02 in.), and tcmpernturc (-75’ to +120” P.,11” F.) is transmittctl bJ- radio in 8 bit binary digital formonce every 3 hours simult’tmeously on two frequencies, 3.36 and 4.97 megacycles. The trans- mitter out>putis 250 watts on each frequency with range up to 1500 miles depending on the frequency. The trttrls- mission consists of call letters nrld data measurements plus one repeat. Provision has beerr made in the package for

Unauthenticated | Downloaded 09/26/21 06:48 AM UTC