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
11//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TROPICAL STORM 11W (HALONG), LOCATED APPROXIMATELY 181 NM WEST-
NORTHWEST OF NAVSTA GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS STRONG UPPER LEVEL ANTICYCLONIC FLOW, TO THE NORTH-
NORTHWEST OF THE LOW LEVEL CIRCULATION CENTER (LLCC), HAS CREATED
HIGH LEVELS (30 PLUS KNOTS) OF VERTICAL WIND SHEAR (VWS). DEEP
CONVECTION REMAINS ISOLATED TO THE SOUTHEASTERN QUADRANT AND THE LLCC
HAS BEEN FULLY EXPOSED OVER THE PAST SIX HOURS. THE POSITIONING IS
BASED ON THE FULLY EXPOSED LLCC IN MSI. INTENSITY HAS BEEN MAINTAINED
AT 45 KNOTS BASED ON THE WEAKENING DVORAK ESTIMATES FROM PGTW, KNES,
AND RJTD BALANCED BY THE PERSISTENCE STRUCTURE OF THE LLCC. 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 NORTHWESTWARD UNDER THE STEERING
INFLUENCE OF THE STR THROUGH TAU 48. RECENT GUIDANCE SHOWS THE STR
WILL BUILD WESTWARD AS THE MONSOON DEPRESSION (INVEST 96W) TRACKS
TOWARD SOUTH KOREA. AFTER TAU 48, THE MONSOON DEPRESSION WILL BEGIN
TO INTERACT WITH THE MID-LATITUDE FLOW, EVENTUALLY BEING ABSORBED
WITHIN THE WESTERLY JET AND TRACKING OVER THE SEA OF JAPAN. THIS
WILL CAUSE THE STR TO SHIFT, ALLOWING FOR A MORE NORTHWESTWARD
TRACK PAST TAU 72. THE HIGH LEVELS OF VWS WILL PREVENT A QUICK
INTENSIFICATION THROUGH TAU 48. CURRENT INDICATIONS ARE THAT AS THE
SYSTEM MOVES TO THE WEST, THE UPPER LEVEL ENVIRONMENT WILL SEE
MARGINAL IMPROVEMENTS, ALLOWING A DECREASE IN VWS AND A PERIOD OF
QUICKER INTENSIFICATION THROUGH TAU 72.
   C. TS HALONG IS EXPECTED TO TRACK SLOWLY NORTHWESTWARD ALONG THE
WESTERN PERIPHERY OF THE STR IN THE EXTENDED TAUS. WITH THE EXCEPTION
OF GFNI, COTI, AND WBAR, 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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