Tropical Storm PEIPAH Advisory 15.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN)
WARNING NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED APPROXIMATELY
226 NM EAST OF SAIPAN, HAS TRACKED NORTHWESTWARD AT 11 KNOTS (KTS)
OVER THE PAST SIX HOURS. AN EXPOSED LOW LEVEL CIRCULATION CENTER
(LLCC) IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY PROVIDES HIGH
CONFIDENCE IN THE INITIAL POSITION. AT 25 KTS, THE INITIAL INTENSITY
IS CONSISTENT WITH THE PGTW DVORAK CURRENT INTENSITY ESTIMATE OF
T1.0 (25 KTS) AND A PARTIAL 142318Z METOP-A ASCAT IMAGE THAT SHOWED
25 KTS TO THE EAST OF THE INITIAL POSITION. STRONG (40-50 KT)
VERTICAL WIND SHEAR (VWS) IS OFFSETTING EXCELLENT EQUATORWARD
OUTFLOW AND WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURE (SST) TO
MAKE THE ENVIRONMENT UNFAVORABLE. TD 17W IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF A SHALLOW, NORTHWEST-TO-SOUTHEAST ORIENTED
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. FOR THE DURATION OF THE FORECAST, TD 17W WILL TRACK
NORTHWESTWARD ALONG THE PERIPHERY OF THE STR. THE UNFAVORABLE
ENVIRONMENT IS EXPECTED TO KEEP INTENSITY TO 30 KTS OR LESS UNTIL
THE SYSTEM DISSIPATES BY TAU 48. THE INTENSITY FORECAST IS
CONSISTENT WITH AVAILABLE INTENSITY AIDS. NUMERICAL MODEL GUIDANCE
IS IN FAIR AGREEMENT WITH MINOR DIFFERENCES IN ALONG TRACK SPEED.
THE JTWC TRACK FORECAST CLOSELY FOLLOWS CONSENSUS WITH FAIR
CONFIDENCE BASED ON THE MODEL GUIDANCE.//
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