WDPN31 PGTW 161500 
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC// 
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W WARNING NR/ 
05// 
RMKS/ 
1. FOR METEOROLOGISTS. 
2. PROGNOSTIC REASONING FOR 161200Z0 AUG TO 191200Z3 AUG 02. 
   A. TROPICAL DEPRESSION (TD) 20W, LOCATED APPROXIMATELY 420 NM 
SOUTH OF HONG KONG, CHINA, HAS TRACKED NORTHEASTWARD AT 02 
KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 
161130Z2 ENHANCED INFRARED SATELLITE IMAGERY, 161045Z7 QUIKSCAT AND 
A 161034Z5 SPECIAL SENSOR MICROWAVE IMAGER (SSM/I) PASS. THE WARNING 
INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 25 
KNOTS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND THE RECENT 
SSM/I PASS REVEAL A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER 
(LLCC) WITH CONVECTION DISPLACED SOUTH-SOUTHWEST OF THE LLCC. THE 
QUIKSCAT PASS INDICATES ENHANCED WESTERLY WINDS IN THE SOUTHERN 
SEMICIRCLE OF THE LLCC.
   B. TD 20W IS EXPECTED TO TRACK SLOWLY TO THE NORTH AND THEN 
NORTH-NORTHWESTWARD UNDER RELATIVELY WEAK STEERING FLOW IN THE SOUTH 
CHINA SEA. THE AVAILABLE DYNAMIC AIDS CONSISTING OF NOGAPS (NGPS), 
UKMET (EGRR), JAPANESE GLOBAL (JGSM) AND AVIATION (AVN) MODELS AGREE
WITH THIS SCENARIO. OUR FORECAST IS BASED ON A BLEND OF PERSISTENCE,
CLIMATOLOGY, AND THE AVAILABLE AIDS. 
   C. TD 20W IS FORECAST TO DEVELOP AT A LESS THAN CLIMATOLOGICAL 
RATE THROUGHOUT THE FORECAST PERIOD. ONLY MINIMAL INTENSIFICATION IS
EXPECTED AS IT TRACKS SLOWLY IN THE SOUTH CHINA SEA WITH STRONG
WESTERLIES AND MODERATE VERTICAL WIND SHEAR TO THE SOUTH. 
   D. SYSTEM DOES NOT MEET WIND RADII CRITERIA.
FORECAST TEAM: BRYANT/JACOBS/HEATH/SHERRY/NUTONGLA//

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