WDPN33 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (NALGAE) 
WARNING NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 13W (NALGAE), LOCATED APPROXIMATELY 536 NM EAST-
NORTHEAST OF MINAMI TORI SHIMA, HAS TRACKED NORTH-NORTHWESTWARD AT 
07 KNOTS OVER THE PAST SIX HOURS.  ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER 
WITH WEAK BANDING CONVECTION.  THERE IS HIGH CONFIDENCE IN THE 
INITIAL POSITION BASED ON THE EXPOSED LOW LEVEL AND RECENT SATELLITE 
FIXES. THE INITIAL
INTENSITY OF 40 KNOTS IS BASED ON A 032222Z METOP-B ASCAT IMAGE 
SHOWING A COUPLE 40 KNOT WIND BARBS IN A REGION OF 35 KNOTS ON THE 
NORTHERN PERIPHERY, WHILE SUBJECTIVE DVORAK ESTIMATES HAVE BEEN LOW 
WITH AGENCIES REPORTING T2.0 TO 2.5 (30 TO 35 KNOTS). UPPER-LEVEL 
ANALYSIS INDICATES THAT A TUTT CELL IS DEVELOPING JUST SOUTHWEST OF 
THE SYSTEM, WHICH IS HINDERING CONVECTIVE DEVELOPMENT. OTHERWISE, 
VERTICAL WIND SHEAR IS LOW AND SSTS MODERATELY SUPPORT DEVELOPMENT 
AT 27 TO 28 CELSIUS. 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.
   B. TS NALGAE IS FORECAST TO CONTINUE TRACKING NORTH-NORTHWESTWARD 
ALONG THE WESTERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD. 
NEAR TAU 36, THE SYSTEM WILL TRACK WITHIN THE LEADING PERIPHERY OF A 
SHARP SHORTWAVE TROUGH AND WILL BEGIN EXTRA-TROPICAL TRANSITION
(ETT). AFTER TAU 36, TS 13W WILL TRACK OVER COOLER SST (24 TO 25C)
AND WILL GAIN WEAK FRONTAL CHARACTERISTICS, COMPLETING ETT BY TAU 48.
DYNAMIC MODEL GUIDANCE IS IN VERY GOOD AGREEMENT, THEREFORE, THERE 
IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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