WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (FIVE)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
    12JUN21. TROPICAL DEPRESSION 05W (FIVE), LOCATED APPROXIMATELY 
29 NM EAST OF SANYA, HAINAN, CHINA, HAS TRACKED WESTWARD AT 14 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) INDICATES A LOW LEVEL CIRCULATION (LLC) RESIDES UNDER THE 
NORTHEAST PERIPHERY OF A BROAD AREA OF CONVECTION. THE INITIAL 
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE AFOREMENTIONED 
MSI, AN 112330Z PGTW FIX, AND A 120020Z GMI 37GHZ IMAGE. THE INITIAL 
INTENSITY OF 25KTS IS SET WITH FAIR CONFIDENCE BASED ON MULTIPLE 
AGENCY DVORAK ESTIMATES OF T1.0/25KTS (PGTW/KNES) AND T2.0/30KTS 
(RJTD). THE SYSTEM IS IN A MARGINAL ENVIRONMENT WITH GOOD WESTWARD 
AND EQUATORWARD OUTFLOW AND VERY WARM (30-31C) SEA SURFACE 
TEMPERATURES (SSTS), OFFSET BY MODERATE (15-20KTS) VERTICAL WIND 
SHEAR (VWS). THE SYSTEM IS TRACKING ALONG THE WESTERN PERIPHERY OF 
THE SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING BULLETIN ON THIS 
SYSTEM AND SETS THE FORECAST PHILOSOPHY.
   B. TD 05W (FIVE) WILL CONTINUE ITS WEST-NORTHWEST TRACK ALONG THE 
WESTERN PERIPHERY OF THE STR. SHORTLY BEFORE TAU 06, TD 05W WILL 
MAKE LANDFALL OVER THE SOUTHERN PORTION OF HAINAN ISLAND AND UNDERGO 
SLIGHT WEAKENING AS IT INTERACTS WITH THE RUGGED TERRAIN. BY TAU 12, 
INTENSITY IS FORECAST TO INCREASE TO 35KTS AS THE SYSTEM MOVES IN A 
FAVORABLE ENVIRONMENT FOR FURTHER TROPICAL DEVELOPMENT WITH LOW (5-
10KTS) VWS AND VERY WARM (30-31C) SSTS OF THE GULF OF TONKIN. BY TAU 
24, TD 05W WILL REACH MAX INTENSITY OF 40KTS BEFORE LANDFALL NEAR 
SAM SON, VIETNAM. BY TAU 36, THE SYSTEM WILL WEAKEN TO 30KTS AS IT 
MOVES FURTHER INLAND AND BEGINS DISSIPATING. BY TAU 48, TD 05W WILL 
ROUND THE RIDGE AXIS AND FULLY DISSIPATE. NUMERICAL MODELS ARE IN 
GOOD AGREEMENT, SPREADING TO 24 NM AT TAU 12 AND 76 NM AT TAU 30 
NEAR LANDFALL, LENDING FAIR CONFIDENCE TO THE JTWC TRACK FORECAST. 
THE JTWC FORECAST TRACK IS PLACED SLIGHTLY LEFT OF MODEL CONSENSUS 
TO ACCOUNT FOR THE EXCESS OF NORTHEASTERLY WIND SHEAR IN MID AND 
UPPER LEVELS.//
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