WDPN31 PGTW 210300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W WARNING NR 18//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. REMARKS: RECENT ANIMATED MULTISPECTRAL IMAGERY SHOWS A BROAD 
CIRCULATION WITH DEEP CONVECTION ALONG A CONVERGENT INFLOW BOUNDARY 
ALONG THE SOUTH SIDE OF THE LOW LEVEL CIRCULATION CENTER (LLCC) BUT 
VERY LITTLE CONVECTION OVER THE CENTER AND THE NORTHERN SIDE. A 
202300Z SSMIS PASS SHOWS A SIMILAR DEPICTION WITH DEEP CONVECTION TO 
THE SOUTH WITH VERY LITTLE DEFINITION OF THE CIRCULATION NEAR THE 
CENTER. UPPER LEVEL ANALYSIS HAS THE SYSTEM UNDER THE SOUTHEASTERN 
SIDE OF THE UPPER-LEVEL RIDGE IN AN AREA OF CONVERGENT FLOW AND 
UNDER A MODERATE AMOUNT (20KTS) OF VERTICAL WIND SHEAR. THE SYSTEM 
IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF THE ASIATIC 
HIGH LOCATED OVER SOUTHEASTERN CHINA. POSITION IS BASED ON THE 
POSITION FIX FROM PGTW, AND INTENSITY WAS HELD A LITTLE HIGHER THAN 
THE PGTW FIX. THE PGTW DVORAK INTENSITY WAS DETERMINED TO BE 
SLIGHTLY UNREPRESENTATIVE OF THE CURRENT INTENSITY DUE TO THE 
SUPPRESSION OF CONVECTION BY THE UPPER LEVEL CONVERGENCE. THE 20/12Z 
POSITION WAS DOWNGRADED FROM A 35KT TS POSITION TO A 30KT TD 
POSITION.
3. FORECAST REASONING.
   A. THERE ARE NO CHANGES TO THE FORECAST PHILOSOPHY. 
   B. AS TD 06W CONTINUES TO TRACK TO THE WEST, THE ASIATIC HIGH IS 
FORECASTED TO DRIFT TO THE EAST, WEAKEN, AND EVENTUALLY BECOME 
ABSORBED BY THE MID-PACIFIC HIGH OVER THE NEXT 24 TO 36 HOURS. AS 
THIS HAPPENS, TD 06W WILL START TO GAIN LATITUDE INTO THE WEAKNESS 
IN THE SUBTROPICAL RIDGE TO THE WEST OF THE ASIATIC HIGH/MID-PACIFIC 
HIGH BEFORE MAKING LANDFALL WEST OF HONG KONG. THE RELATIVELY 
UNFAVORABLE UPPER LEVEL ENVIRONMENT WILL CONTINUE TO HAMPER 
DEVELOPMENT, AND 06W IS EXPECTED TO REMAIN A TD BEFORE DISSIPATING 
OVER LAND. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 
48. GFS IS THE EASTERN OUTLIER AND IT GAINS LATITUDE RATHER QUICKLY 
BEFORE FLATTENING OUT AND UKMET IS THE WESTERN OUTLIER SKIRTING THE 
COAST INTO THE GULF OF TONKIN. JGSM, NOGAPS, WBAR, AND ECMWF ARE ALL 
CLUSTERED TOGETHER NEAR THIS FORECAST.
//
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