WDPN31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (THIRTEEN) 
WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 13W (THIRTEEN), LOCATED APPROXIMATELY 136 NM 
EAST-NORTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 14 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) REVEALS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER 
(LLCC) WITH DEEP CONVECTION LIMITED TO THE WESTERN SEMICIRCLE. THE 
INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE AND IS BASED ON THE 
MSI LOOP AND A 222229Z SSMIS 91 GHZ IMAGE SHOWING WEAK BANDING. THE 
INITIAL INTENSITY OF 30 KNOTS IS BASED ON A PGTW DVORAK CURRENT 
INTENSITY ESTIMATE OF T2.0 (30 KNOTS). ENVIRONMENTAL ANALYSIS SHOWS 
THAT TD 13W HAS A WEAK EQUATORWARD OUTFLOW CHANNEL AND NORTHERLY 
VERTICAL WIND SHEAR BETWEEN 15 AND 20 KNOTS. SEA SURFACE 
TEMPERATURES REMAIN FAVORABLE, RANGING BETWEEN 28 TO 29 DEGREES 
CELSIUS. TD 13W IS TRACKING GENERALLY NORTH-NORTHWESTWARD ALONG THE 
SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) LOCATED TO THE 
NORTHEAST. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 13W WILL CONTINUE TO TRACK GENERALLY NORTHWARD AROUND THE 
PERIPHERY OF THE STR TO THE NORTHEAST. TD 13W WILL SLOWLY WEAKEN TO 
BELOW WARNING THRESHOLD BY TAU 36 DUE TO CONTINUED MARGINAL 
ENVIRONMENTAL CONDITIONS. DYNAMIC MODEL GUIDANCE IS IN GOOD 
AGREEMENT AND THE FORECAST TRACK CLOSELY FOLLOWS THE CONSENSUS. 
BASED ON THE LOW UNCERTAINTY IN THE MODEL GUIDANCE, THERE IS HIGH 
CONFIDENCE IN THE JTWC FORECAST TRACK.//
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