Tropical Storm HALONG Advisory vie, 08-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (HALONG) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (HALONG), LOCATED APPROXIMATELY 142 NM WEST-
SOUTHWEST OF MINAMI TORI SHIMA, JAPAN, HAS TRACKED NORTHEASTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS A LARGE AREA OF EXPANDING DEEP CONVECTION
PERSISTING OVER AND TO THE NORTH OF THE LOW-LEVEL CIRCULATION CENTER
(LLCC). A 070520Z SSMI 85GHZ MICROWAVE IMAGE INDICATES A PARTIALLY-
EXPOSED LLCC WITH CURVED DEEP CONVECTIVE BANDING OVER THE NORTHERN
SEMICIRCLE, WHICH SUPPORTS THE CURRENT POSITION WITH FAIR
CONFIDENCE. UPPER-LEVEL ANALYSIS REVEALS A MARGINALLY-FAVORABLE
ENVIRONMENT WITH LOW TO MODERATE (10 TO 20 KNOTS) SOUTHERLY VERTICAL
WIND SHEAR (VWS) OFFSET BY ROBUST POLEWARD OUTFLOW. BASED ON THE
WEAKENING CONVECTIVE STRUCTURE AND INCREASING VWS, THE CURRENT
INTENSITY IS ASSESSED AT 90 KNOTS BASED ON THE LOWER END OF DVORAK
CURRENT INTENSITY ESTIMATES RANGING FROM 5.0-5.5 (90-102 KNOTS). TY
24W IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 24W (HALONG) WILL ACCELERATE POLEWARD WHILE GRADUALLY
TURNING NORTHEASTWARD TO EAST-NORTHEASTWARD. THE ENVIRONMENT WILL
BECOME MORE UNFAVORABLE WITH INCREASING VWS AND COOLING SSTS, WHICH
SUPPORTS THE WEAKENING TREND. BY TAU 24, THE SYSTEM WILL ENCOUNTER
THE BAROCLINIC ZONE AND BEGIN EXTRA-TROPICAL TRANSITION (ETT). THESE
COMBINED DYNAMICS WILL CONTRIBUTE TO ITS RAPID DECAY, AND BY TAU 48
WILL BE REDUCED TO A STORM-FORCE COLD CORE LOW WITH AN EXPANSIVE
WIND FIELD AS IT COMPLETES ETT. THE NUMERICAL MODELS ARE IN GOOD
AGREEMENT, LENDING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.//
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