A Study of Several Typhoons in the West Pacific, 1945" CAPT. KENNETH P. KIDD, A.C.

Cherry St., Alcoa, Tennessee

AND

CAPT. CHARLES K. REED, A.C.

622 Delaware Ave., St. Paul, Minn.

N THIS PAPER is presented a brief study Storm Grace formed south of Marcus Is- I of some of the typhoons affecting mili- land about 15 August 1945, moved in a NW tary operations in the Southwest Pa- direction, and entered SE Honshu near To- cific in 1945 with an emphasis upon their kyo on the night of 22 August, giving wide- origin and movement. Selected analyzed spread rain and a minimum barometric pres- daily surface charts are included. The sure near Tokyo of 986 mb. The direction temperate-latitude areas of the analyses have and speed of movement of Grace indicated been checked with data later obtained from the presence of a large high-pressure cell the files of the Japanese Central Meteoro- to the northeast of the storm—a fact that logical Observatory. Excellent data from was helpful in the forecasting of the move- Army and Navy typhoon reconnaissance ment of Ruth. Upon passage over Honshu planes enabled reliable lifixes'' of the posi- Grace filled rapidly, and her influence on tions of the typhoon centers to be obtained. the other typhoons declined accordingly Since no detailed records were available from after 23 August. land stations over which the centers of the At the time of formation of Grace the ITC typhoons passed, the actual maximum in- (intertropic zone of convergence) extended tensity of the typhoons was estimated from through Luzon and into a large area of low the winds and extrapolated pressures re- pressure and weak winds in the vicinity of ported by the aircraft. On the charts, sur- 17°N 130°E. Development of the low did face data include wind, sky cover, weather, not take place for several days because the pressure and 24-hour pressure change. flow of easterlies did not penetrate west of Wind speeds are represented by 10-knot 135°E and because the westerlies were un- barbs. Heights of winds-aloft reports are usually weak. given in thousands of feet. Aircraft reports Gradually the SE trades in the Palau and include weather and the height of plane (in southern Philippines area retreated in favor hundreds of feet), plotted above the time of an increasing flow of Indian westerlies, (OCT). which by 20 August had swept over the entire Philippines and was continuing ENE TYPHOONS RUTH AND SUSAN T (ALSO TESS in a narrowing stream. On this day a fresh AND GRACE), 22-27, AUGUST 1945 surge was noted in the westerlies, marked by (Figs. 2 to 4) winds of 25-40 knots over the South China Sea. These four tropical cyclones of storm of typhoon intensity that appeared almost si- On 21 August Grace was located 250 miles multaneously present a most spectacular and NE of Iwo Jima with a trough extending interesting example of formation and move- SW to join the ITC. At this time the low ment. The presence of typhoons Ruth and pressure area east of Luzon was greatly elongated along the ITC near 21 °N. Easter- Susan caused a 48-hour delay in Supreme lies to north of the low were weak (10 knots, Allied Commander MacArthur's plans to up to 15,000 feet) while the flow of Equa- land occupation forces in Japan. torial air south of the low had strengthened * Published with permission of the War Department. to 20 to 25 knots. As the surge of Equa- t The Army Air Forces Weather centrals in the SW torial air turned NEward near the eastern Pacific in 1945 began the custom of identifying tropical storms by first names of wives of their commanding end of the elongated low, the pressure began officers.—Ed.

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC to fall in tlie forward left edge of the surge third typhoon (Tess) was found 75 miles and storm Buth developed there on 22 Au- south of Hong Kong on 24 August moving gust (FIG. 2). It has been noted in other NNEward. These typhoons developed very instances that when a strong surge of Equa- rapidly and in each case the area of strong torial air juts sharply into another wind winds had but a short radius. This behavior stream to the north, tropical cyclonic devel- is quite in contrast to that of some other opment has taken or is taking place. 1945 typhoons of the SW Pacific, which de- The mountains of northern Luzon act as veloped only very slowly by a gradual a barrier to the flow of the SW monsoon, strengthening of the winds about a large sometimes splitting the stream and causing area of low pressure and often with the the formation of a small typhoon just NW strongest winds appearing first a great dis- of Luzon. Streamline charts for the 8000- tance from the center. foot level for 22 August can be analyzed to Also of particular interest in the cases of show three tongues of SW monsoon: one Buth and Susan is the unequal distribution wide stream flowing across the southern of strong winds around the periphery of the Philippines toward the newly formed storm typhoons. In both typhoons the strongest Buth; a second narrow stream flowing winds were first found in the southern quad- swiftly up the west side of Luzon (winds rants and gradually moved counterclockwise at Laoag reached 50 knots from the SSW into the NE quadrant (FIGS. 2 and 4). below 10,000 feet) ; a third narrow stream Relatively weak winds were found in their turning NNEward around 17 °N 114°E. NW quadrants, and also in the area between Each of the tongues was associated with the the typhoons where horizontal shear pre- development of a typhoon in the ITC, for a vented strong opposing winds. The migra- second typhoon (Susan) was found near tion of the strong-gradient region to the NE 22°N 124°E on the morning of 23 August quadrant of Buth was associated with the (FIG. 3) moving in an ENE direction and a disappearance of the trough leading to Grace

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC (FIG. 2) and with the blocking action of pressures and steep pressure gradients indi- the high-pressure area northeast of Iwo Jima. cated that the strongest winds were migrat- The migration of the area of strong winds ing into the NE quadrant. about Susan, however, resulted from the Ruth reached typhoon intensity before movement of Ruth to the north. entering Honshu, with winds of 60 to 65 The trajectory of each typhoon paral- knots reported near the center and with an leled step by step approximately the direc- estimated central pressure of 986 mb. tions of the strongest '' environment-winds'' Susan was somewhat more intense with 80- near its periphery. The initial movement knot winds reported 26 August and an es- in each case was ENE with a gradual re- timated central pressure of 980 mb. In- curvature to the NNW, when the rising sufficient data are available from coastal

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC stations of southern Honshu for a more and dissipated within an area covered by accurate picture of the intensity of Rutli and Army and Navy typhoon reconnaissance Susan as they passed inland. Both typhoons planes—the complete life-history lasting 8 passed over the mountains of Honshu and days. recurved NE across the Sea of Japan. In September-October a bulge of the ITC north of its normal position in the Marianas TYPHOON JEAN, 25 SEPTEMBER TO is always viewed with suspicion, especially 2 OCTOBER 1945 if the ITC between the Marianas and the {Figs. 5 to 8) Philippines is at the same time south of the normal position. The northward bulge of Jean was one of the five most severe ty- the ITC is owing to the advance or surge phoons of the Pacific in 1945. She appears of the Equatorial air, and is also assisted in this study because she formed, developed, by any SEly component of the trades where

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC they are deflected 011 the east side of a pass- On the 700-mb chart there was a split in ing Easterly or Induced Trough. The the Pacific High near 140°E, the western southerly position of the ITC west of the cell being centered about 20 °N 130 °E. bulge indicates that the northern trades are Slightly to the east of this 700-mb trough, a blowing from ENE or NE in that area and surface trough extending NNE from the thus in a position favorable for producing ITC at its northward bulge was moving cyclonic shear with respect to the Equatorial slowly to the west. The easterlies between air. On 24 September such a counterclock- Philippines and east of Guam were blowing wise shifting of the orientation of the ITC at around 10 knots, up to 20,000 feet. The was observed. The ITC now extended from base of the westerlies dipped down to 30,000 Truk to a northermost position at 12 °N feet over the Marianas. Indian westerlies 142°E, thence WSW toward Samar. in the South China Sea had been diverted

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC into a small storm approaching Hainan trough which was located west of that sta- island, so that the flow of air south of the tion in the levels below 20,000 feet and to ITC was very weak in the area between east of the station at 30,000 to 40,000 feet. Palau and the Sulu Sea. The Equatorial air This trough extended NNE from the depres- in the bulge appeared to be mainly recurved sion (named Jean). Its vertical axis had trades from the southern hemisphere. evidently reversed slope since the previous As the air streams in the region were day, the lower 20,000 feet of the trough weak, the depression associated with the having shifted westward while the upper bulge of the ITC moved slowly (about 6 trough (in the westerlies) moved eastward. knots) to the WNW and had deepened only The effect of divergence aloft over the sur- about 1 mb by the next day. On 25 Septem- face low was shown by general surface- ber (FIG. 5) winds at Guam indicated a pressure fall in all quadrants of Jean. In

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC addition to the pressure falls, the develop- By 26 September (FIG. 6) the circulation ment of Jean was accompanied by strength- about Jean had reached storm intensity. ening of the southwest flow at Ulithi and Ship 025 located near the center reported by the ITC acquiring an orientation from surface wind of force 6 and a 24-hour pres- the Marianas to Samar. sure change of —• 5.0 mb. Winds at this ship Wind shifts with height at Palau and indicated that the axis of the low tilted to Ulithi as shown in FIG. 5 are quite common the southeast. Pressure falls in the center when the ITC is north of those stations. of the cyclone during the past 24 hours had Such a wind shift presumably indicates that been about 4 mb. With this decrease in cen- the Equatorial air is cooler than the trade tral pressure there was a tightening of the easterlies to the north. pressure gradient within 300 miles of the

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC center. But all the winds reported from Jean to the north Avould be slow and would 19 °N to 25 °N in the area north of Jean depend upon the pressure and wind field remained light. In view of these light winds north of 20 °N. and the pressure falls over the region from North of 25°N there had been a rapid the East China Sea to Iwo Jima little in- eastward movement of pressure systems. crease in speed of movement was likely. The high north of Korea had moved to the With a tropical cyclone in this area rapid eastern part of the Sea of Japan. A polar pressure rises at Guam and Saipan are indi- front x>receding this high had a weak por- cations of the southward projection of the tion oriented, from Iwo Jima through Oki- Pacific High to the east and rapid movement nawa with a wave developing south of of the cyclone to the north. But without Shanghai. The recurvature of Jean to the the pressure rises at Guam, any movement of N within 48 to 72 hours depended in part

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC upon the rate of movement of this wave of Indian westerlies joining the diverted SE and the intensity it would develop while trades in that area. Divergence had in- south of Honshu. With pressure systems creased aloft as evidenced by an estimated moving rapidly eastward, development of 9-mb drop in central pressure within the waves between the China coast and 140 °E past 24 hours. Ship 025 (14°N 136°E) indi- is not as likely as when a large high lies cated cross-isobar winds at angles of 30° over China and the eastward motion of to 40°. Such a cross-isobaric flow in west- pressure system is less rapid. ward-moving tropical cyclones has been no- Aircraft reported winds of 50 knots to ticed most frequently in the SE quadrant the SE of the center of Jean on the morning and is associated with deepening of the of the 27th. A strengthening of the flow cyclone and with a pronounced elongation of Equatorial air into the southern quad- of the isobars to the WSW. rants of Jean had continued, with a tongue A complete wind pattern at 20,000 feet

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC was not available as an aid in forecasting mum waves, 45 to 50 feet high, were ob- the movement of Jean. West winds at Oki- served 40 miles north of the center. nawa and Iwo Jima suggested a curvature The eccentric surface isobaric pattern toward the north. The strong winds in the (FIG. 7) is an excellent case for illustrating eastern periphery of Jean as compared with the low-level convergence of air in the east- the weaker ones to the west also suggested ern quadrants. This interpretation is con- an increase in the northward component of sistent with the observation of maximum movement. Pressure falls to the north of rainfall and turbulence reported there. A Jean were consistent with this change in hodographic inspection of wind reports at trajectory. But Jean had been moving ship 025 (14°N 136°E) and ship 114 (22°N slowly and no rapid acceleration was in evi- 134°E) shows cool-air advection below 10,- dence; hence, the outlook for complete re- 000 feet with a tilt of the axis of the cy- curvature would for at least the next two clone to the east. (See also winds for ship days depend mainly upon the changing con- 025 in FIG. 6.) ditions north of 25°N. Quite interesting on this day were the Jean curved from WNW to NW and ac- large pressure rises N and E of Jean. The celerated from 6 to 8 knots, reaching ty- causes of the build up of this large high- phoon intensity by the morning of 28 Sep- pressure area were not obvious to the writers. tember with 70-knot winds reported. Ty- The effect of these pressure changes on Jean phoon reconnaissance searches described the were more easily understood. Winds around eye of the typhoon as being 35 miles in the northern and eastern periphery of Jean diameter with a smooth sea and thin broken increased at the surface and also aloft. to overcast altostratus and broken strato- With the greatest packing of surface isobars cumulus. Heavy rain was found within 150 in the NE quadrant and the pressure rises miles of the center in southern quadrants, and strong easterly winds aloft at Okinawa, while clear blue sky appeared abruptly north an accelerated movement of Jean in a WNW of 20°N 130°E. direction was expected. In the 700-mb sur- By this time it was evident that the shal- face the westerlies in the trough associated low frontal wave had moved so rapidly east- with the front in China did not extend south ward from Shanghai to Tokyo that Jean had of 30 °N. NE winds present at that level not been forced northward into the shallow over SE China were expected to strengthen Westerlies Trough. However, a peculiar di- as the Asiatic High continued to push rap- gression in the track of Jean toward the idly to the SE. north between 27 and 28 September attests The synoptic map for 30 September con- to some influence of the extratropical low. tained an unusually strong isobaric gradient Pressure rises at Iwo Jima and Okinawa, from northern China to the center of Jean, and the east winds to 50,000 feet at Okinawa then located 150 miles northeast of Luzon on 28 September favored a return of Jean (FIG. 1). On this day typhoon "recco" toward a more westerly path. planes brought back a picture of 90 knot On 29 September (FIG. 7) Navy weather winds, 11 extremely severe turbulence,'9 heavy reconnaissance planes found that the eye rain and very high seas. So much difficulty had decreased to 15 miles in diameter and did the reccos have battling the severe condi- that the central pressure (obtained by radio tions within Jean that reports by planes altimeter and reduced from about 900 feet from Manila and Okinawa were not in above the sea surface) had lowered to 971 complete agreement. A "Venturi" effect mb. The eye contained confused seas and was quite pronounced along the southeastern broken to overcast stra.tocumulus with bases tip of Formosa where conditions were re- at 500 feet and tops at 3000 to 4000 feet. ported unusually severe. Turbulence was reported as extreme in the It can be seen from FIG. 1 that, while SE quadrant, where winds continued to cut development was taking place within Jean sharply across the isobars. Maximum winds between 27 and 30 September, she accel- of 75 to 80 knots were reported. The maxi- erated from 6 to 13 knots. The greatest

Unauthenticated | Downloaded 09/24/21 10:51 AM UTC acceleration occurred when or just after she China. Warm air from the east overran the was forced from a NW to a WNW path. colder air over China, causing a large area Jean decreased in intensity with passage of rainfall (FIG. 8). The introduction of the over the southern tip of Formosa. The esti- cP air into the typhoon tended to suppress mated central pressure increased 15 to 20 vertical currents, owing to the relative sta- mb while the diameter of the closed 1000-mb bility and dryness of the new air, and caused isobar showed little change. Just west of Jean to fill very rapidly. On 2 October Formosa Jean ran headlong into a cold cP Jean had degenerated to a weak NE-SW high that had been moving SEward across elongated extratropical low.

Candidates for Membership All candidates whose names have appeared in the lists published already, in the June, October, and November BULLETINS, 1945, have now been elected; and membership cards are being sent out. Hereafter, instead of publishing the names of candidates in a special note in the BULLETIN, they will appear currently in the minutes of the Council, to be published from month to month. Thus the 13th and 14th lists of candidates for professional membership and the 8th and 9th lists for ordinary membership appeared in the minutes of the Council for January 12 and 22, 1946, in the March BULLETIN. The 15th to 17th lists of candidates for professional membership and the 10th to 13th lists of candidates for ordinary member- ship appear in the minutes of the Council for February 5 and March 6 and 19, below. Some applicants for professional membership will find their names appearing in the lists of candidates for ordinary membership [sustaining class], which does not necessarily mean that their applications for the professional grade have been rejected, but that the informa- tion in the hands of the Committee on Admissions and Council failed to indicate that the candidate was yet able to meet the requirements for professional membership (as stated in the constiution and interpreted by the Committee and Council). In each case, the appli- cant is merely placed in the Member class pending receipt of further information or the candidate's attainment of further qualifications.—C. F. Broolcs, Secy.

Minutes of the Council First Meeting on January 29, 1946, in New York A quorum meeting of the Council was held January 29th in Room 205 of the American Museum of Natural History from 12:30 to 1:40 p.m., with the following Councilors present: President Rossby, Messrs. Buell, Burhoe, Byers, Houghton, Middleton, Orville, Reicliel- derfer, Stone, Wexler and Brooks, Secy. The following votes Avere unanimously adopted. 1. Voted, to appoint a committee on special problems: Capt. II. T. Orville, Dr. F. W. Reichelderfer, Dr. C.-G. Rossby, Col. D. N. Yates, and the President, ex officio, chairman. 2. Voted, to request the new president himself or through a delegate or delegates to carry out final negotiations with the American Institute of Physics for quarters for the office of the Executive Secretary in their building in New York and to present a definite proposal to the Council. [This came to nothing, owing to the problem it would give the Institute relative to their present tax-exempt status.] 3. Voted, that the American Meteorological Society assist the U. S. Weather Bureau by rendering opinions as to the professional competence of applicants for teletype service for general private practice of meteorology. 4. Voted, to designate the Committee on Professional Ethics and Standards to investi- gate all applications for teletype service and to make recommendations to the Council,

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