Tropical Storm HALONG Advisory dim, 31.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HALONG) WARNING NR
14//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (HALONG), LOCATED APPROXIMATELY 323 NM NORTH-
NORTHEAST OF YAP, HAS TRACKED WEST-SOUTHWESTWARD AT 08 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR)
REVEALS THE CENTRAL CONVECTION HAS BEEN STRUGGLING OVER THE LOW LEVEL
CIRCULATION CENTER (LLCC) AND THE NORTHERN HALF OF THE SYSTEM AS
VERTICAL WIND SHEAR (VWS) REMAINS AT HIGH LEVELS (20 TO 30 KNOTS). A
RECENT 311214Z ASCAT PASS INDICATES A FAIRLY SYMMETRIC STRUCTURE IN
THE EASTERN HALF OF THE SYSTEM AND HAS BEEN USED TO ASSESS THE WIND
FIELD AT THE 1200Z AND 1800Z BEST TRACK POSITIONS. CURRENT POSITION
IS BASED ON THE EIR LOOP AND THE TRACKING OF THE EXPOSED LLCC, TAKING
INTO ACCOUNT THE DEVELOPMENT OF DEEP CONVECTION OBSCURING THE LLCC.
DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD HAVE COME INTO BETTER
AGREEMENT OVER THE PAST SIX HOURS, ALL INCREASING DUE TO IMPROVED
CONVECTIVE DEVELOPMENT NEAR THE CENTER OF THE SYSTEM. UPPER LEVEL
ANALYSIS INDICATES THE NORTHERLY FLOW ASSOCIATED WITH THE ANTICYCLONE
TO THE NORTHWEST OF TS 11W IS MAINTAINING THE HIGH LEVELS OF VWS,
AND THE DIFFICULTIES THE SYSTEM IS FACING WITH BECOMING MORE
VERTICALLY ALIGNED. TS 11W IS TRACKING WESTWARD ALONG THE SOUTHERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 11W IS EXPECTED TO TRACK WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE STR THROUGH TAU 36. AFTER TAU 36, THE STR
IS EXPECTED TO MODIFY AND WEAKEN WHICH WILL ALLOW FOR A TRANSITION
INTO A MORE NORTHWESTWARD TRACK THROUGH TAU 72. MODEL GUIDANCE
SUGGESTS A SLIGHT WEAKENING OF THE VWS TO MODERATE LEVELS (20 TO 25
KNOTS) THROUGH TAU 72 WITH AN UPPER LEVEL TROUGH TO THE NORTHEAST OF
THE LLCC ANTICIPATED TO ENHANCE THE EASTERN OUTFLOW CHANNEL. THERE IS
SOME VARIATION IN THE GUIDANCE REGARDING THE MAXIMUM INTENSITY. THIS
FORECAST HAS DROPPED THE MAXIMUM TO 85 KNOTS AT TAU 72 BASED ON THE
CONSENSUS OF INTENSITY GUIDANCE.
   C. TS HALONG IS EXPECTED TO TRACK NORTH-NORTHWESTWARD ALONG THE
WEAKENED PERIPHERY OF THE STR IN THE EXTENDED TAUS AND SLOWLY WEAKEN
AS IT TRACKS INTO NORTHERLY UPPER-LEVEL FLOW AND VWS ASSOCIATED WITH
A BROAD UPPER-LEVEL HIGH TO THE NORTHWEST. NUMERIC MODEL GUIDANCE IS
IN FAIRLY TIGHT AGREEMENT THROUGH TAU 48 AND SLIGHTLY DIVERGES AFTER
WHICH WITH SOME DISAGREEMENT IN THE EXTENT OF THE RIDGE AS IT
MODIFIES AND WEAKENS. DUE TO THIS UNCERTAINTY IN THE MOVEMENT OF THE
RIDGE, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST.//
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