WDPN32 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI) 
WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 494 NM 
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED EASTWARD AT 05 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) REVEALS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER 
(LLCC) WITH FLARING CONVECTION STARTING TO WRAP INTO THE CENTER; THE 
SYSTEM HAS REMAINED QUASISTATIONARY OVER THE PAST SIX HOURS. THE 
INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE LOW-
LEVEL BANDING WRAPPING INTO THE OBSCURED LLCC, GENERAL POSITIONING 
IS FURTHER SUPPORTED BY A 022207Z SSMIS 91GHZ MICROWAVE IMAGE. THE 
INITIAL INTENSITY OF 35KTS IS BASED ON THE DVORAK ESTIMATES OF 
T2.5/35KTS FROM PGTW, KNES, AND RJTD. THE ENVIRONMENT IS FAVORABLE 
FOR DEVELOPMENT WITH LOW (5-15KT) VERTICAL WIND SHEAR (VWS) AND WARM 
(29-30C) SEA SURFACE TEMPERATURES (SST), HOWEVER THE UPPER LEVEL 
OUTFLOW IS LIMITED WITH ONLY WEAK WESTERLY OUTFLOW AT THIS TIME. THE 
CYCLONE IS CURRENTLY QUASISTATIONARY LOCATED IN A COL AREA BETWEEN 
TWO SUBTROPICAL RIDGES (STR), ONE TO THE EAST-NORTHEAST AND A SECOND 
TO THE WEST-NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 23W WILL REMAIN QUASISTATIONARY THROUGH TAU 36 WITH NO 
DOMINANT STEERING MECHANISM AS IT CONTINUES TO SLOWLY MEANDER AROUND 
THE COL IT IS CURRENTLY LOCATED NEAR. BETWEEN TAUS 36 AND 48 THE STR 
TO THE EAST-NORTHEAST OF THE SYSTEM WILL BUILD AND TAKE OVER AS THE 
PRIMARY STEERING MECHANISM SENDING TS 23W WESTWARD. A FAVORABLE 
ENVIRONMENT CONSISTING OF LOW (5-15KT) VWS, WARM (28C) SST, AND 
DECENT UPPER LEVEL OUTFLOW TO THE WEST WILL PROMOTE STEADY 
INTENSIFICATION TO A PEAK OF 60 KTS AT TAU 72. NUMERICAL MODELS HAVE 
COME TOGETHER SLIGHTLY FROM THE LAST RUN, HOWEVER THEY STILL HAVE A 
SPREAD OF 250NM AT TAU 72, LENDING FAIR CONFIDENCE TO THIS PORTION 
OF THE JTWC FORECAST TRACK. 
   C. IN THE EXTENDED TAUS, THE PRIMARY STR WILL STEER TS 23W WEST-
NORTHWESTWARD THROUGH THE LUZON STRAIT, AND INTO THE SOUTH CHINA SEA 
(SCS) TURNING TO THE WEST-SOUTHWEST BETWEEN TAUS 96 AND 120. THE 
ENVIRONMENT WILL DETERIORATE DUE TO DECREASED DIVERGENCE ALOFT AND 
COOLING SST IN THE SCS, WEAKENING THE SYSTEM TO 45KTS BY TAU 120. 
NUMERICAL MODELS SIGNIFICANTLY DIVERGE WITH A SPREAD OF 650 NM BY 
TAU 120 AND LARGE DIFFERENCES IN THE TRACK SPEED AND THE TIMING OF 
THE SOUTHWESTWARD TURN, LENDING LOW CONFIDENCE IN THE EXTENDED 
PORTION OF THE JTWC FORECAST THAT IS LAID NEAR THE MULTI-MODEL 
CONSENSUS.// 
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