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Amer. Catholic Historical Society, Philadelphia, Pa. (in press.) 



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Hydrographic Oi^ce, Washington, D.C., 1944. 



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193fi, pp. 349-360. 

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1938, pp. 1337-1416. 



TROPICAL CYCLONES OF THE WESTERN NORTH PACIFIC 



By Captain Merle P. Woodall, U. S. Air Force 



Air Weather Service units located at Harmon AFB, Guam ; Haneda 

 AFB, Tokyo ; Kadena AFB, Okinawa ; Clark AFB, Manila ; and 

 Kaingwan i\FB, Shanghai, comprised the Typhoon Warning Netw^ork of 

 the 2143d Air Weather Wing in 1947. The Haneda Weather Central 

 was the Typhoon Warning Centre, charged with overall direction and 

 operation of the Typhoon Warning Network until 1st September, at 

 which time this function was transferred to Harmon Weather Central. 

 The 514th Weather Reconnaisance Squadron (VLR) at North Guam 

 AFB performed reconnaissance of typhoons beginning 1st September. 

 This material is drawn from post-analysis reports made by the Typhoon 

 Warning Network. 



There were 26 tropical cyclones of sufficient intensity to warrant the 

 exchange of Bulletins among the stations of the Typhoon Warning Net- 

 work, Of these, 19 were of typhoon intensity (maximum winds over 

 65 K), and 7 of tropical storm intensity (maximum winds over 27 knots, 

 but less than 66 K). From these records some observations on the origin, 

 movement, and dissipation can be made. 



The problem of anticipating the formation of tropical cyclones was 

 not too difficult. Most of them were suspected several days in advance, 

 and in all cases they were found in sufficient time to issue forecasts to 

 interested agencies. According to analyses made, all tropical cyclones of 

 1947, except those which formed in the wake of another tropical cyclone, 

 originated at the junction of an easterly wave and the ITC often inten- 

 sified by a trough in the westerlies. In no case was one observed to form 

 in a strictly homogenous air mass. Formation of typhoons did not appear 

 to be limited to island areas. 



Forecasting the movement of tropical cyclones was the most difficult 

 problem encountered. No accepted method of forecasting was reliable 

 in all cases, and using every technique available the path and rate of 

 movement of many of the typhoons was impossible to forecast accurately. 

 Even by post-analysis the path of Rosalind, or the deceleration of Gwen, 

 is difficult to explain. To approach the problem of forecasting track and 

 speed of movement, some new hypotheses on steering principles will be 

 considered and the usually accepted rules examined. 



The most popular method of predicting the movement of typhoons is 

 by the use of the steering wind of the free air current. From a study of 

 those in 1947 it was found that forecasting the movement of typhoons in 

 the Pacific by the direction of flow of the free air current above the typ- 

 hoon is practical only for those which do not extend above the 500 mb. 

 level, since upper air data above that level is very sparse, and since it is 

 doubtful if the free air current steers the very deep lows. Of the typhoons 

 and tropical storms of 1947, in only three cases did the 700 mb. wind flow 



31 



