Tropical Storm HALONG Advisory Thu Jul 31

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HALONG) WARNING NR
08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (HALONG), LOCATED APPROXIMATELY 38 NM
NORTHWEST OF ANDERSEN AFB, HAS TRACKED WEST-NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH CURVED DEEP CONVECTIVE BANDING OVER THE SOUTHERN SEMI-
CIRCLE. A 300457Z SSMI 37 GHZ IMAGE, HOWEVER, INDICATES A WELL-
DEFINED LLCC WITH A SMALL MICROWAVE EYE. THIS IMAGE SHOWS STRONGER,
DEEPER CONVECTIVE BANDING OVER THE SOUTHERN SEMI-CIRCLE, WHICH
CORRESPONDS TO THE 300034Z ASCAT PARTIAL IMAGE SHOWING WEAKER WINDS
OVER THE NORTHERN SEMI-CIRCLE AND NEAR GALE-FORCE WINDS OVER THE
SOUTHERN SEMI-CIRCLE. OVER THE PAST 24 HOURS, THE TUTT HAS WEAKENED
AND SHIFTED EAST ALLOWING INCREASING UPPER-LEVEL NORTHERLY FLOW TO
AFFECT THE SYSTEM. RECENT ANIMATED WATER VAPOR IMAGERY CURRENTLY
DEPICTS THIS NORTHERLY, CONVERGENT FLOW IMPINGING ON THE NORTHERN
PERIPHERY OF THE SYSTEM, WHICH HAS LED TO THE RECENT WEAKENING TREND
AND SHEARING OF DEEP CONVECTION SOUTHWARD. BASED ON THE EXPOSED LLCC
AND RECENT RADAR FIXES, THERE IS HIGH CONFIDENCE IN THE CURRENT
POSITION (30/12Z). THE INITIAL INTENSITY REMAINS ASSESSED AT 55
KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF 55 KNOTS. IF
THE SYSTEM CONTINUES TO WEAKEN, THE INTENSITY WILL LIKELY BE
DECREASED ON THE 30/12Z JTWC WARNING. TS 11W IS TRACKING WEST-
NORTHWESTWARD 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 WESTWARD TO WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 36. AFTER TAU
36, THE STR IS EXPECTED TO RE-ORIENT POLEWARD AS THE MONSOON
DEPRESSION (INVEST 96W) TRACKS TOWARD WESTERN JAPAN AND THE SYSTEM
SHOULD TURN NORTHWESTWARD. DYNAMIC MODEL GUIDANCE IS IN TIGHT
AGREEMENT THROUGH TAU 48 BUT DIVERGE AFTER TAU 48 WITH UKMO AND
COAMPS-TC TRACKING THE SYSTEM WEST-NORTHWESTWARD. THE BULK OF THE
GUIDANCE SUPPORTS THE NORTHWESTWARD TURN AND MAKES MORE
METEOROLOGICAL SENSE WITH THE RESPECT TO HOW THE MONSOON DEPRESSION
WILL INFLUENCE THE STEERING PATTERN. TS 11W IS FORECAST TO MAINTAIN
INTENSITY THROUGH TAU 24 AS IT STRUGGLES WITH THE NORTHERLY VERTICAL
WIND SHEAR (VWS) BUT SHOULD BEGIN TO SLOWLY INTENSIFY BY TAU 36 AS
THE VWS RELAXES.
   C. TS HALONG IS EXPECTED TO TRACK SLOWLY NORTH-NORTHWESTWARD
ALONG THE WESTERN PERIPHERY OF THE STR IN THE EXTENDED TAUS. WITH
THE EXCEPTION OF COAMPS-TC AND UKMO, THE MODEL GUIDANCE SUPPORTS THE
JTWC FORECAST TRACK. TS 11W IS FORECAST TO WEAKEN AS IT TRACKS INTO
NORTHERLY UPPER-LEVEL FLOW AND INCREASING VWS ASSOCIATED WITH A
BROAD UPPER-LEVEL HIGH TO THE NORTHWEST. DUE TO THE UNCERTAINTY IN
THE TRACK SPEEDS AND INTENSITY FORECAST, THERE IS OVERALL LOW
CONFIDENCE IN THE JTWC FORECAST.//
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