Tropical Storm HALONG Advisory vie, 01-08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HALONG) WARNING
NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (HALONG), LOCATED APPROXIMATELY 313 NM NORTH
OF YAP, FSM, HAS TRACKED WESTWARD AT 06 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL AND WATER VAPOR SATELLITE IMAGERY
SHOWS THE SYSTEM CONTINUES TO BE AFFECTED BY STRONG (30-40 KNOT)
NORTHERLY VERTICAL WIND SHEAR (VWS), INDUCING A SLIGHTLY EXPOSED
LOW LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS BASED ON THE
ABOVE ANIMATION WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS A
CONSENSUS OF DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER
LEVEL ANALYSIS INDICATES THE SYSTEM IS WELL SOUTH OF THE RIDGE AXIS
IN AN AREA OF HIGH VWS. HOWEVER, THESE SAME WINDS ARE PROVIDING
STRONG EQUATORWARD OUTFLOW FOR THE SYSTEM. THE CYCLONE IS TRACKING
ALONG THE SOUTHERN PERIPHERY OF A WEAK SUBTROPICAL RIDGE (STR)
LOCATED IN THE EASTERN PHILIPPINE SEA.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 11W IS EXPECTED TO CONTINUE ITS WEST TO WEST-NORTHWEST
TRACK AS IT REMAINS UNDER THE INFLUENCE OF THE STR TO THE NORTH
OVER THE NEXT 24-36 HOURS. BETWEEN TAU 36 AND 72, EXPECT TS HALONG
TO ROUND THE SOUTHWEST EXTENSION OF THE STR AND SLOWLY TURN MORE
NORTHWESTWARD. AS THE VWS WILL WEAKEN AND ALLOW FOR A MORE
FAVORABLE UPPER-LEVEL ENVIRONMENT, 11W WILL INTENSIFY AT A FASTER
RATE BETWEEN TAU 36 AND 72, REACHING A PEAK INTENSITY OF 85 KNOTS
BY TAU 72.
   C. TS HALONG WILL GENERALLY TRACK NORTHWESTWARD THROUGH THE
REMAINDER OF THE FORECAST PERIOD. AFTER TAU 120, EXPECT THE MONSOON
DEPRESSION CURRENTLY AFFECTING THE EAST CHINA SEA TO BE ABSORBED IN
AN UPPER LEVEL TROUGH AND MODIFY THE STR WHICH WILL BE OVER
MAINLAND JAPAN. NUMERIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH
TAU 72, WITH SOME DIVERGENCE IN THE MODELS IN THE LATER TAUS WITH
REGARD TO THE LEADING STEERING ENVIRONMENT. GFS AND ECMWF AGREE
THAT THE RIDGE DEVELOPING TO THE EAST OF JAPAN WILL BE MAIN FACTOR,
LENDING TO A RECURVE SCENARIO OVER SOUTHERN JAPAN, WHILE NAVGEM HAS
THE HIGH OVER MAINLAND CHINA AFFECTING THE STORMS TRACK, BRINGING
THE SYSTEM INTO THE YELLOW SEA. THIS LENDS AN OVERALL LOW
CONFIDENCE IN THE JTWC TRACK FORECAST.//
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