WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 04W (FOUR) WARNING 
NR 002//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 04W (FOUR), LOCATED APPROXIMATELY 67
NM SOUTHWEST OF PALAU, HAS TRACKED WESTWARD AT 07 KNOTS OVER THE 
PAST SIX HOURS. ANIMATED ENHANCED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) SHOWS OVERALL CONSOLIDATION EVEN AS THE CENTRAL CONVECTION 
SLIGHTLY WARMED UP, WITH THE FEEDER BANDS, MOSTLY FROM THE NORTHWEST 
AND SOUTH, WRAPPING TIGHTER INTO A DEFINED LOW LEVEL CIRCULATION 
(LLC). A PARTIAL 292115Z SSMIS 91GHZ MICROWAVE SATELLITE PASS 
INDICATES THE FRAGMENTED CONVECTION ARE OFFSET SOUTHWARD OF THE LLC. 
THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON LOW 
CLOUD TRACING IN THE MSI LOOP AND ON AN OBSCURED LLC FEATURE IN THE 
AFOREMENTIONED MICROWAVE IMAGERY AND LINED UP WELL WITH THE WIND 
OBSERVATION FROM PALAU. THE INITIAL INTENSITY OF 30KTS IS SET WITH 
FAIR CONFIDENCE BASED ON AN OVERALL ASSESSMENT OF DVORAK ESTIMATES 
OF T2.0/30KTS (PGTW), T2.1/31KTS (ADT), T2.5/35KTS (KNES) AND 
REFLECTS THE SLIGHT INTENSIFICATION. TD 04W REMAINS IN A FAVORABLE 
ENVIRONMENT WITH GOOD EASTWARD AND EQUATORWARD OUTFLOW, LOW (10-
15KTS) VERTICAL WIND SHEAR (VWS) ALOFT, AND VERY WARM (30-31C) SEA 
SURFACE TEMPERATURES (SST) IN THE PHILIPPINE SEA. THE CYCLONE IS 
TRACKING ALONG THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE 
(STR) TO THE EAST-NORTHEAST. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 04W WILL TRACK MORE NORTHWESTWARD OVER THE NEXT 72 HOURS 
UNDER THE STEERING INFLUENCE OF THE STR. THE SYSTEM IS FORECAST TO 
STEADILY INTENSIFY UNDER THE AFOREMENTIONED FAVORABLE CONDITIONS, 
AND BY TAU 72, WILL REACH TYPHOON INTENSITY OF 65KTS. THE FORECAST 
TRACK IS LAID SLIGHTLY TO THE LEFT AND AHEAD OF MODEL CONSENSUS 
DURING THE FIRST 36 HOURS TO OFFSET THE GFS TRACKER BEING SLOW AND 
TO THE RIGHT OF THE MODEL ENVELOPE. AFTER TAU 36, THE FORECAST TRACK 
IS MORE TO THE RIGHT OF FORECAST CONSENSUS, TO OFFSET NVGM BEING THE 
EXTREME LEFT OUTLIER WITH A WEST-NORTHWESTWARD TRACK TOWARD THE 
NORTHEAST PORTION OF THE PHILIPPINE ISLANDS.
   C. AFTER TAU 72, TD 04W WILL CONTINUE ON ITS NORTHWESTWARD TRACK 
UNDER THE SAME STR; HOWEVER, BY TAU 96, THE SYSTEM WILL BEGIN TO 
ROUND THE RIDGE AXIS THEN ACCELERATE NORTHEASTWARD. THE FAVORABLE 
CONDITIONS WILL PERSIST AND INTENSIFY THE CYCLONE TO 75KTS BY TAU 
96. AFTERWARD, AS IT BECOMES EXPOSED TO INCREASED POLEWARD OUTFLOW 
ASSOCIATED WITH THE PREVAILING WESTERLIES UNDER THE POLAR FRONT JET, 
THE SYSTEM WILL PEAK AROUND TAU 102 THEN SYSTEM WILL BEGIN TO DECAY 
DUE TO INCREASING VWS DOWN TO 65KTS BY TAU 120. NUMERICAL MODELS 
REMAIN IN GOOD AGREEMENT, LENDING ALSO FAIR CONFIDENCE IN THE 
EXTENDED PORTION OF THE JTWC FORECAST TRACK.//
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