Tropical Storm TWENTYEIGHT Advisory Sex, 11-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT)
WARNING NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 28W (TWENTYEIGHT), LOCATED APPROXIMATELY
284 NM NORTHEAST OF POHNPEI, HAS TRACKED WESTWARD AT 15 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A
COMPLETE DISSIPATION OF THE DEEP CONVECTION ASSOCIATED WITH A WEAK
LOW LEVEL CIRCULATION CENTER (LLCC). THE WEAK LLCC IS EVIDENT IN AN
110606Z GPM 89GHZ MICROWAVE IMAGE WHICH SUPPORTS THE CURRENT
POSITION WITH GOOD CONFIDENCE. THE INTENSITY HAS BEEN HELD AT 30
KNOTS BASED ON THE DEFINED LLCC IN THE GPM IMAGE; HOWEVER, THE
INTENSITY COULD BE LOWER. TD 28W IS LOCATED SOUTH OF THE UPPER LEVEL
RIDGE UNDER STRONG EASTERLY FLOW. LIMITED DIVERGENCE ALOFT AND LOW
TO MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR (VWS) IS RESPONSIBLE
FOR THE WANING CONVECTION. THE CYCLONE IS TRACKING WESTWARD WITH THE
EASTERLY FLOW ASSOCIATED WITH THE DEEP-LAYERED SUB-TROPICAL RIDGE
(STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST TRACK
PHILOSOPHY; HOWEVER, THE PEAK INTENSITY IN THE EXTENDED FORECAST HAS
BEEN DECREASED.
   B. TD 28W IS EXPECTED TO TRACK WESTWARD UNDER THE INFLUENCE OF
THE STR TO THE NORTH OVER THE NEXT 72 HOURS. THE UPPER-LEVEL
ENVIRONMENT WILL REMAIN MOSTLY UNCHANGED WHICH WILL CAUSE THE
CONVECTIVE STRUCTURE TO CONTINUE TO STRUGGLE WITH ONLY SLIGHT
INTENSIFICATION POSSIBLE.
   C. IN THE EXTENDED FORECAST, THE STR WILL REMAIN THE DOMINANT
STEERING MECHANISM FORCING THE CYCLONE ON A GENERALLY WEST-
NORTHWESTWARD TRACK. ENVIRONMENTAL CONDITIONS WILL REMAIN MARGINAL
THROUGH THE END OF THE FORECAST PERIOD KEEPING THE CYCLONE AT A WEAK
TROPICAL STORM STRENGTH. DYNAMIC MODEL GUIDANCE IS IN DECENT
AGREEMENT ON THE WEST-NORTHWESTWARD TRACK; HOWEVER, THERE ARE SOME
DIFFERENCES IN THE FORWARD SPEED AND THE DEGREE OF THE NORTHWESTWARD
COURSE. THE EARLY INSTABILITY IN THE MODEL GUIDANCE PROVIDES LOW
CONFIDENCE IN THE JTWC FORECAST.//
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