WDPN33 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (NALGAE) 
WARNING NR 11//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 13W (NALGAE), LOCATED APPROXIMATELY 519 NM 
NORTH-NORTHWEST OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY AND A 031111Z GPM IMAGE DEPICT FORMATIVE CONVECTIVE BANDING 
OVER THE EASTERN SEMI-CIRCLE OF THE BROAD LOW-LEVEL CIRCULATION 
CENTER (LLCC). A 030955Z ASCAT IMAGE SHOWS 35 TO 40 KNOT WINDS OVER 
THE NORTHEAST QUADRANT OF THE CIRCULATION WITH 30 TO 35 KNOT WINDS 
ELSEWHERE. THIS ASCAT IMAGE SHOWS A WELL-DEFINED CENTER AND SUPPORTS 
THE INITIAL POSITION AND INITIAL INTENSITY ASSESSMENT OF 40 KNOTS 
WITH GOOD CONFIDENCE. UPPER-LEVEL ANALYSIS INDICATES THAT THE SYSTEM 
IS LOCATED UNDER AN UPPER LOW, WHICH IS HINDERING CONVECTIVE 
DEVELOPMENT. TS 13W IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF A 
LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE 
NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST TRACK PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII HAVE BEEN 
ADJUSTED SIGNIFICANTLY LARGER BASED ON A DETAILED ANALYSIS OF A 
RECENT ASCAT IMAGE.
   B. TS 13W IS FORECAST TO CONTINUE TRACKING NORTH-NORTHWESTWARD 
ALONG THE WESTERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD. 
NEAR TAU 48, THE SYSTEM WILL TRACK WITHIN THE LEADING PERIPHERY OF A 
SHARP SHORTWAVE TROUGH AND WILL BEGIN A GRADUAL EXTRA-TROPICAL 
TRANSITION (ETT). AFTER TAU 48, TS 13W WILL TRACK OVER COOLER SST 
(24 TO 25C) AND WILL GAIN WEAK FRONTAL CHARACTERISTICS, COMPLETING 
ETT BY TAU 72. DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT, THEREFORE, 
THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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