WDPN32 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (MALIKSI) WARNING 
NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 20W (MALIKSI), LOCATED APPROXIMATELY 470 NM SOUTH-
SOUTHEAST OF TOKYO, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 21 
KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON 
RECENT SATELLITE FIXES FROM PGTW AND RJTD. THE CURRENT INTENSITY OF 
45 KNOTS IS BASED ON CONGRUENT DVORAK INTENSITY ESTIMATES FROM 
MULTIPLE REPORTING AGENCIES. RECENT ANIMATED INFRARED SATELLITE 
IMAGERY CONTINUES TO SHOW THE DEEP CONVECTION IS ISOLATED TO THE 
EASTERN SEMI-CIRCLE OF A BROAD LOW-LEVEL CIRCULATION CENTER WITH 
SOME SPARSE CONVECTION NEAR THE CENTER AND IS INCREASINGLY STARTING 
TO LOOK EXTRATROPICAL. A 030812Z SSMIS 91GHZ MICROWAVE IMAGE ALSO 
SUPPORTS THIS. TS 20W IS LOCATED NORTH OF AN UPPER- LEVEL 
ANTICYCLONE IN AN AREA OF INCREASING VERTICAL WIND SHEAR AND STRONG 
POLEWARD OUTFLOW. THE SYSTEM IS TRACKING POLEWARD ALONG THE 
NORTHWESTERN PERIPHERY OF A SUBTROPICAL STEERING RIDGE TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 20W IS FORECAST TO MAINTAIN INTENSITY IN THE NEXT 24 HOURS 
DUE TO INCREASING POLEWARD OUTFLOW AHEAD OF AN APPROACHING MID-
LATITUDE TROUGH TO THE WEST, WHICH WILL OFFSET THE INCREASING 
VERTICAL WIND SHEAR. TS 20W WILL ACCELERATE POLEWARD IN THE GRADIENT 
BETWEEN THE CURRENT STEERING RIDGE AND THE APPROACHING MID-LATITUDE 
TROUGH.  EXTRATROPICAL TRANSITION IS FORECASTED FOR THE NEXT 24 
HOURS AND TS 20W WILL BE AN EXTRATROPICAL LOW BY TAU 36 BEING FULLY 
EMBEDDED IN THE BAROCLINIC ZONE. DYNAMIC MODEL GUIDANCE REMAINS IN 
GOOD AGREEMENT. THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC 
FORECAST TRACK, WHICH IS POSITIONED SLIGHTLY TO THE RIGHT OF AND 
FASTER THAN THE MULTI-MODEL CONSENSUS.//
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