WDPN32 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (ATSANI) 
WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 23W (ATSANI), LOCATED APPROXIMATELY 
622 NM EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
ENHANCED 3.9UM INFRARED (EIR) SATELLITE IMAGERY SHOWS A WEAK 
SYSTEM THAT HAS MAINTAINED AN OVERALL POORLY-ORGANIZED 
CONVECTIVE STRUCTURE. THE INITIAL POSITION IS PLACED WITH FAIR 
CONFIDENCE BASED ON LOW-CLOUD TRACING INTO AN OBSCURED LOW LEVEL 
CIRCULATION IN THE EIR LOOP. THE INITIAL INTENSITY OF 30 KTS IS 
BASED ON AGENCY DVORAK ESTIMATES OF T2.0/30KTS FROM PGTW, RJTD,
AND KNES. THE ENVIRONMENT IS OVERALL UNFAVORABLE WITH MODERATE 
(20-25KT) VERTICAL WIND SHEAR (VWS) AND WEAK OUTFLOW ALOFT OFFSET 
SLIGHTLY BY WARM (29-30C) SEA SURFACE TEMPERATURES (SST). THE 
CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-
LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TD 23W WILL CONTINUE ON ITS CURRENT TRACK IN THE 
PHILIPPINE SEA, STEERED BY THE STR, AND BY TAU 24, WILL REACH 
A COL AREA SOUTH OF A SHORTWAVE MIDLATITUDE TROUGH AND BETWEEN
THE STEERING STR AND A SECONDARY STR TO THE NORTHWEST, WHERE 
IT WILL REMAIN IN A QUASI-STATIONARY (QS) STATE UP TO TAU 72. 
THE ENVIRONMENT IS FORECAST TO IMPROVE AS VWS WEAKENS AND 
POLEWARD OUTFLOW INCREASES, FUELING A STEADY INTENSIFICATION 
TO 65KTS BY TAU 72. NUMERICAL MODELS ARE IN GOOD AGREEMENT UP 
TO TAU 24 WITH NAVGEM THE SOLE OUTLIER TO THE RIGHT. AFTERWARD, 
THE MODELS DIVERGE SIGNIFICANTLY WITH VARYING SOLUTIONS IN THE 
DURATION OF QS STATE IN THE COL, LENDING LOW CONFIDENCE IN THIS 
PORTION OF THE JTWC FORECAST TRACK. 
   C. IN THE EXTENDED TAUS, THE PRIMARY STR WILL BUILD AND SLOWLY
DRIVE TD 23W WESTWARD. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
IMPROVE FURTHER WITH DECREASED VWS (10-15KTS) AND THE ADDITION 
OF AN EQUATORWARD OUTFLOW CHANNEL. THESE CONDITIONS, COUPLED WITH 
CONTINUED WARM SST, WILL ALLOW FOR FURTHER INTENSIFICATION TO 
80KTS AS IT APPROACHED THE LUZON STRAIT. AFTERWARD, INCREASING 
VWS AND COOLER SST IN THE LUZON STRAIT AND INTO THE SOUTH CHINA 
SEA WILL GRADUALLY WEAKEN THE SYSTEM DOWN TO 70KTS BY TAU 120. 
NUMERICAL MODELS SIGNIFICANTLY DIVERGE TO OVER 700 NM BY TAU 120
WITH AFUM AND UEMN SUGGESTING A RECURVATURE INTO JAPAN, LENDING 
LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST 
TRACK.//
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