Types and Cycles of Summer Weather Citation Carlmark, Carl Wilbert and Whitfield, Hervey Haydon (1941) Types and Cycles of Summer Weather. Master's thesis, California Institute of Technology. doi:10.7907/143t-fb38. https://resolver.caltech.edu/CaltechTHESIS:02102025-213843694 Abstract No abstract. Item Type: Thesis (Master's thesis) Subject Keywords: (Meteorology) Degree Grantor: California Institute of Technology Division: Engineering and Applied Science Major Option: Meteorology Thesis Availability: Public (worldwide access) Research Advisor(s): Unknown, Unknown Thesis Committee: Unknown, Unknown Defense Date: 21 May 1941 Record Number: CaltechTHESIS:02102025-213843694 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:02102025-213843694 DOI: 10.7907/143t-fb38 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 16992 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 11 Feb 2025 17:07 Last Modified: 11 Feb 2025 17:16 Thesis Files PDF - Final Version See Usage Policy. 11MB Repository Staff Only: item control page

'rYPES Al"\JD CYCIES OF SUMBER WEATHER By Capt. G. N. Carlmark and Lieut. H. He Whitfield California Institute of Technology May 21, 1941 TYPES AND CYCLES OF SUMMER VJEATHER In this research, the three swnmer months, June, July and August of 1938, 1939 and 1940 were investigated in an attempt to pick out some definite weather types which could be used in any summer month of any year. The attempt was madeto pick out the types without reference to any past types ,f.ound in wint·er months. This was done by going through the daily synoptic charts and trying to find a periodicity in the movement of frontal systems or pressure centers. The days were counted from the time frontogenesis began in the Western part of the Continent until the resulting wave left .the Atlantic Coast. Only the most definite pictures were taken and finally called types, as there were numerous periods vlhere no definite ·sequence or movement of the systems could be observed. These generally were . in transition stages from one type to another. The enclosed tables which give a picture of the daily synoptic charts as to location, shape and movement of the systems were devised before attempting to pick ·o1,1.t any of the types. This was done to see if there was any sequence in the movement of the centers or any relation between the type of weather prevalent on the Continent and the shape, position and intensity of the anticyclones and frontal systems in the Pacific and in Canada. There were finally four different types picked out. t'hese have been called, for the sake of convenience, B-w, R, 9-day, and 16-day types. TJe reason for giving them different names was that all had different length periods; i.e., 6, 3, 9 and 16 days respectively. Other than that, their general characteristics and appearance were practically the same. It is believed that the difference in length of period is largely due to the shape and location and intensity of of the Pacific Anti-cyclone. J:t'or example, it was observed that when the Pacific anti-cyclone was large and fairly intense with an East-West orientation, fronts on the Continent were more persistent and also had an East-West orientation. On the other hand when the Pacific - Anticyclone was fairly broken dovm and displaced far to the West, fronts passed rapidly across the Gontinent and off the Atlantic Coast. Also the location of low centers and frontal systems in the Pacific and their intensity seems to have an important part in the period of these types. For cycles or types of the same period, it was noted that the synoptic charts apparently had the same conformation, that is, except for small variations, the day by day appearance of the weather maps was identical. For cycles that vmre a.like a general picture of the sequence of v,eather events was dra"Vm up. t;ype. This picture was called a A type is represented by several small maps to shov; the aver- age progression of weather events during the period of the cycle. Explanation of the Tables After repeatedly looking t P-rrough the fil•e of large ·maps in the Meteorology Department of the California Institute of Technology in the search for types and cycles, it became apparent that certain dominant features were characteristic of the summer maps. If these certain dominant features ' were tabulated it was thought that the weather sit~ uation for as long a period as a month could be comprehended at a glance. Also the influence of these dominant features upon the per- sistence and change of types could be studied more easily and carefully vdthout the necessity of handling large and bulky maps. Vfith .· this end in view a worksheet was constructed for each month to be used in a statistical siludyof' the characteristics of each type. This table shows the exact day of the month each type began and ended, and the number of · days in each cycle. It is thm.i'ght that such a table a~:f' this worksheet might aid in future research to discover the indica- ~ipns for a change in tY9e or the reasons for a lone or short period. In order that this statistical tabulation of data \,n the worksheet c0nvey an impression to the mind of the reader of the characteristics of the vreather map, some explanation of the headings in the table and the entries thereafter is necessary: Date: 4:30 a.m. maps were the da}ly reference, but in the case where this map vias missing, ·the fraction 11 ½11 indicates the use' of the evening map. The type of weather persisting a fter the beginn"ing of any cycle is indicated. Day of Cycle: The criterion for the length of cycle is the number of days betw¢en, thein~~ption of the wave and its passage off the Atlantic coast of the Unit"ed States. Invariably the place of frontogenesis and first appearance of the wave- was in the tvest central 'part· bf the 'Ufij_ted States. An average position 6f ·the start of these sumr1er vvaves would be the lddatiori of thestates of Colorado and Kansas. It will be noted that .t here. is.. sometimes a double entry such as ttl/8 11 under a certain date. This means that · before the- wave of the previous cycle had passed ·· off the Atlantic Coast, the new <'iave of the follovdng cycle · had already formed. : Aleutiah' Low: If the Aleutian low was centered at -latitude 60 degrees, it was ~11~.~±".~~t.?-.:3 _normal; if above 60 degrees, high; if at 50 degrees, low; and if at 4o · degrees, extremely low ( a chenk mark vtith the subscript 11x11 • in the row with the heading 111ow11 ) . --Th(;l. __ ·invasion .of Tropical Gulf air into the interior of the United States and its ·contact · there itrith Polar Pacific air ·t,hat had come over the mountains from the west, or with Polar Continental air that had . rus hed down from the north, was responsible for "Johe start of the··vrai.re arid ' the beginning of the cycle. 11 Starts 11 ·means ·- that the circulation was · favorable for . the commencement of a 'fiow of Tropical Gulf air over Texas.- -It may have already invaded the coastal region of Texas. . ,,,-- ""' 1 1Deepll air having reached as far refers to the inflow of Tropical 'f ulr/ · .. .... / as northern Texas, Oklahoma and Kansas. ••• 11 Boundary 11 signifies that the wave which now extends over most of the Central and Eastern States in lJ,,. /.. 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J.- I- I- I- '- J- '-- I- I- L- I.- I- i- L.. I.- L- l J. I- I- i- /_ /.. w I-- /...J..l-1- I- i- L 1- I- I- /.. I- L- /... I- t- J. J_ L- L L L- S ,., , 2 3 ,,., 2 3 Lf- ~2.34-S-6 7 I 1 3 ' t S t 7 ' l w w wC J.- J.. 2 J Rp .- ,,u--lre-r w C. BrJRDER we EC Above 60' /,.. F (J I- L. L- F F /_ /_ L. 0 C w L "' F F F f F F F F F w wwcc £ t:E C. C. EE W WW I- '- L F F L W C C WE C. C AIR !'J,4S5 S. Pfo [& •• T;, POSITION 1-#/G,.H /H X X 3 3 3 1 I I X X I I I 2. .2. 2 1- I I I X X X IH 1 I I I I,, IH ,, ., . . ,, ., .. ,, .. .. .. ., . .. Pp ., .. . X J? Pc. • • •• /} Pc /t! R MASS IV. Pe- . . .. . Tc, . . ,. ,, ,' i Po , Tfl i • TCT '• ,. ,, 7' X ~ . " ' .. " ., fPAC. c OV,BP.EAK l- J_ -~ ~...... Low ...,~ ~~<% HIGH C.AN . ROCl<lfS FA ON P- E. AST £ ~ :t:Cl ._!,""I:" < ~ ~ 3 S 3.S S S S:I f".t 2n b I 2 .3 S I H 2 H t, t 6 I 1 H 1 3 I / .2 2 2 I, 7 I 1 7 2,'Zi. I.Bi. 6H 7H 'l 'I// S- S S,72,Z S S S 7,8,3 8 ~ 3 ~ 6 2, 3 ~ LOW ?OS. ~.3~.21,2 'g 9 1/- J gtt 1 t C: w C. WW C. wE Vy w w E w wC ~~ Above 611° ~~ .J w C. CE£ C E £ C C E C £ w C C E EE BORD£ R E E NON£ WAVE OCL. WAV£ ?os. STARTS '6 DEEP t-- 80/JNDARY -..I ll.i --.1 L,. I DAY OF CYt.L[ ~ 3 4- S -<=. HIG-H NORMAL ~~ ::::::. ~ ? TYPE 191/-0_ JULY I 23 Lf-S6 7 g q DATE rvore-s .,.:,,, ft/'o T e (e., \ / V&fe (,a. ) ~~ p of RP signifies tha t this type although similar to the R type is not identical in that a pc outbreak is involvea The subscript b~ August 26~31, 1938. from east to west over northern U. s. ---c ompare similar period lows form over Hudson Bay area and that two wave systems extend waves extendi ng SE- NW off California coast---note at same time tha t Not ice breakdown of Pacific High with lows for mi n g there and air coming :wEX over the Rocky Mountains. ' in creating the wave instead of the normal way by a bulge of pp a) : I /..,( <,j(,trr, f' "' o r e, y.. • r r _ __ e )(. .5 ~e M7'~ (g.. j for July /'1 '/0 NOJJ/£ ~ l t- J._ I- I- LL /.. L- 1-L L '- I- t. I t. LL L. I., ~~ I- I- J_ I- I- L L L/../.../-. '- I- 0 L L O D AlR MASS .S. Ter Hi<rH Po s IT, o N p1,. c.. I- t- '- '- • " " ' ·• ~ ' fu. X X ~ ~ " " '' • ., " " &4 ?o '' X. Po {c, '' '• A ~ ' IH 2 .2 ~ ~ 2- 2 / /. 'f I IH I I 2 2 2 .2 2 / 3 I I f 2 2 X / 2. 2 X X. AIR MAS5 /V. R .. Pr • •• • " •• " X x Pr " .. " P<:. •• " •• • " • " x fr R. . •• x Pp • HI G- H Pc. 0/JTP, REAK o..~ ~ ~ ,!, -' ~ ~~ WA-VE Pos. s,, s,, S,J s., 2 3 S S X X X 1 6 6 / I 2 2 'f . /If 2H 1 3 ½I I ~ 3 7,'l 2,S' 3 3 LOW POS. q 'f- S 6 ti i ~ 1 q I 2 3 x tr ,,,.1 s s gH 7,1 g s;, 6H 7 i ~s s 6 S" (, bl( 7H 7 < f' w w s ~ Above ttJ° C C WC C W w E W W C cwww WE w W C E £ £ CE f £ E E WEWE C C. £ .J ~ Bt1RDER E E WE [_ ~ ~ Ahove r,c• W WE C. IC c C C £ E WE C ~ ~ BORDER E E E CE C c. C [ WE C Cf E WE W W c f-P,O/V T F'A~ T FFFFF 'AN. f{OCJ<JE"S F F F F F f F f F F 0 L 0 J_ 0 v:z: ~ L tJ W L- 0 L- LSTARTS J~10EEP t--t- 1- '-I- Ih. BOVNDARY L 'J._ /,,. NOJi£ 'WA V£ OCL, Il- /.. '- J. '- L /... ~ ~ -l L...! "' L~ W I q 4-0 AV&V ST _, \ r ··~·~ DATE I ~ 3 f S f:, 7 Z C/ 10 II 12 13 l'f- IS/!:, 17 I F 19 20 21222321/ 2s-11, 272'! 2.'13o J I TYPE [3v, lBw 8w IRf 9 1 DAY Of CYCLE I 1 3 4- s b 1 I' I 2 3 'f s 6 7 , 2 3 '{- s 6 2 3 'fl 2 3 'f s b 7 z /.... '- L L- /,,. ~ HIG-1-1 tL /.... /... L... L IL I- It- I- '- L L L- L I L L I- L 1- '- I L /,, /.. L~ S N~RMAL r oar B-w 'f'l;pe This type is so called B-w because of t he shape of t he Pacific Anticyclone and als o in that it follows the general appearance of the accepted B-type. The Pacific anticyclone is generally a wedge shape, orientated in a Nort~;t,-South~ direction with the NE part extendi ng into t he continent at British Col UDbi a . It has a six day sequence or it takes six: days for a front which is formed bet ween ·tg and Pp, east of t he Rockies, to move across the continent and leave t he Atlantic Coast. The movement of this wave i s apparently aided by an antic;yclone vmich breaks off f rom the Paci f ic anticyclone in the Pacifi c Northwest and pushes the wave acros s the continent. This anticyclon e generally breaks- off on about the s econd or third day of t he cycle. In t his type, occlusions are also passing t hrough the Gulf of Alaska r ath er r apidly and pass ing over the continent far to the North through Canada . Fronts in t he United States are generally 'l'g--Pp fronts , and pass t hrough the central part of the United States. This t ype i s fairly dry, the great est a11ounts of precipitation occuring in the Northwest where the occlusions first hit the continent. The f ront through the United States does not cause much precipitation. There is no pre ci pitation at a l l through California and t he Great Basin. This type was by f ar t he most distinct and most pr evalent through out t he three years studied in t his res earch . I t occ urred mos tly in 1938 but was also i n evidence through 1939 and 1940, I t occurred t en times consecutivel y in the t hree surruner months of 1938; f our times in 1939 and four times in 1940, t i1e sequence ·was disrupted only when t he R - Type (3 Days) This type has been named Ras a matter of convenience although it is quite similar to the B-w, the chief difference being that it has a three - day cycle or takes three days for the front formed East of the Hockies to clear the Atlantic Coast. In appearance and action it is the san1e as the B-w. The Pacific anticyclone is oriented Northeast-Southwest along the Pacific Coast and there is a break-9f..f of this high in British Columbia generally on the first day of the cycle and this broken off anticyclone travels rapidly across the continent pushing the Tg - Pp front ahead of it. In this type there are occlusions entering the continent through the Gulf of Alaska but in contrast to the B-w type, do not form a lov, pressure trough through Ganaq,a; there is an anticyclone in Canada in the same place that there was low pressure in .the B-w type. This type was rather infr~quent in occurrence, but generally seemed to oc.::ur ue.1. u .ce or a0:,he end of a series of B-w types. Also the antiJ:' / cyclone that broke off of the Pacific high is more intense than in the B-w type. This type occurred six times durimg 1938 and twice in 1939. It did not occur in 1940. 9 - Day Type This nine day type is also similar in appearance to the B-w type but has a longer cycle. The Pacific anticyclone covers a more exten- sive area a.nd does not have the usual Northeast-Southvrest orientation, but does have the characteristic bulge in the Pacific anticyclone in the Northwest and this bulge breaks off on the second or third day and also on about the seventh or eighth day of the cycle. The first broken off anticyclone moves rapidly across the continent just above the Tg - Pn front -which has formed in the Central p:i.rt of the U. S. a..'1d lies in an E -W direction. The second anticyclone which breaks off on the seventh day forms a front East of the Canadian Rockies, between itself and the first anticyclone. This second anticyclone begins to move across the continent and cleans bot_r,i waves _off the Atlantic Coast. The chief characteristics to be recognized in this type is the large anticyclone in the Pacific and the fact that there are no active Aleutian Lows or fronts passing through the Gulf of Alaska. The only fronts passing through enter Alaska from the Straits of Siberia. This type was also infrequent in occru:lence, being found only in 1939, v,here it occurred five times consecutively. It was preceded by an odd type similar to an E and was followed by a l::J-v-1 type. This type caused a greater amount of Preci:oitation in the central part of the United States than the other two types already discussed. 16 - Day Type This type was picked out because it persisted over a sixteen day period; hovrever, it may or may not be a definit5:) type as it w.::i.s found only once in the three years studied. Its distinguishing characteristic was the lows in the Pacific. These were at much lower l atitudes and the Aleutian low was of much lower pressure t han usual. The Pacific anticyclone is displaced farther . to the south and does not cover as an extensive area as in the other types. There is a large Ga.i.7.adian Hi gh , generally in the west ern par t of Canada .or over Alaska. r·rontal systems arriving at the Pacif ic c oast from .L'lorthern California to \vashington cause . large amounts .of precipitation in those areas. Active fronts ar e formed ~ast of the Rockies in the United States between Pp and Tg air. waves travel along this front through -the central part of the United States from west to east. A long front extends from about Wyoming through the Great Lakes ;irea and to New England. Greatest amounts of precipitation occur in the Roc.k ies in Idaho, l,;[ontana and Wyor:tlng, and in the North Central States. As the cycle pregresses t he 1wc1.ves on the front in the United States are pushed Southeastward by Pp air v,rhich has broken off of the . .- ,, ,..,,, Pacific anticyclone, leaving the Atlantic Coast on the ;( is teenth \;day. --~-/ i ,./ y The end or cleanine up of this type vras aided by a Pc outbreal{ which entered t he United States through the Great Lakes area . Other features of the picture of this type are very nearly the same as t he other types, the Ber muda high being centered just East of the Florida Coast. In comparison to the accepted types t his follows more clos ely t o the E-type t han any others observed. It did not occur i n any of the other years and only during the first half of June in 19/+0. CONCLUSIONS DRAWN FROM TABLE OF TABULATION For 9 Day Type: The Pacific High bulge and invasion of Pp air on the continent takes place at a lower latitude than it does for the 6-day i::3-w type, that is, south of t he Columbian Gorge. The Aleutian Low is normal or at a lovrer than normal latitude or there is no low pres ent. No front is present east of the Canadian Rocky Mountains. On the t hird or fourt h day a boundary of 'l'g air i s along the Appalachian Mountains. For B-w~: The Pacific Hi gh bulge breaks off on the 2nd or 3rd day, causing Pp air to cross the mountains in the vicinity of the Columbian Gorge. This air that is detached joins in the circulation of the Continent. -- "·"\ The Aleutian Low is in the normal position or at a) higher latitude . .• Centers of low pres sure exist in Canada at latitude 60 degrees or above. General: A Pc outbr eak vlill terminat e any succession of t;'.rpes or i.3- w or 9-day and t he followin g type will be H or Rp. For the shorter cycles of weather (R or Rp) the interacting air masses ar e generally Pc and Tg or Ta ; for the longer cycles , Pp and Tg or Ta. Conclusions (continued) General: If, during the sumrner months, lows form in t he Pacific off the L:alifornia Uoast t he weather situation on the continent becomes confus ed and cannot very well be t yped. At the beginning of any cycle the Pacific Anticyclone is usually in the (1) position and by the end of the cycle has develo:ped to t he 'Q2) or even (3) position. No front is present east of the Canadian Rocky Mountains during the long 9-day Type. This front is pres ent during the Rand B-w '1'ypes usually at t he end of one cycle and t he beginning of another TYPE NUMBER OF TIMES OCCURHED AVER.AGE LENG'rH CYCLE ( DAYS ) MAXIMUM NUMBER OF SUC~ESSIVE CYCLES ------- 11 -------------- 4 ----------- 4 --------9-Day --------16-Day --------- 21 ------------- 6.l2 6 --------------------------- 9½ ------------ 10 ------------ 4 ------------ 0 R or Rp B-w 1 16