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
13//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (HALONG), LOCATED APPROXIMATELY 266 NM WEST-
NORTHWEST OF NAVSTA GUAM, HAS TRACKED WESTWARD AT 08 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR)
REVEALS INCREASING DEEP CONVECTION AS A CENTRAL DENSE OVERCAST
FEATURE HAS DEVELOPED WHICH HAS OBSCURED THE PREVIOUSLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC). A 311037Z SSMIS MICROWAVE IMAGE
SHOWS AN INCREASE IN CONSOLIDATION AS DEEP CONVECTIVE BANDING HAS
BECOME MORE DEFINED WHILE BEGINNING TO WRAP TIGHTER INTO THE LLCC.
THE INITIAL POSITION IS BASED UPON THE MICROWAVE IMAGE AND A
POSITION FIX FROM PGTW WITH GOOD CONFIDENCE. THE INITIAL INTENSITY
HAS BEEN INCREASED TO 50 KNOTS DUE TO THE INCREASE IN CONSOLIDATION
WHILE DVORAK CURRENT INTENSITY ESTIMATES REMAIN AT 45 KNOTS FROM
PGTW AND RJTD. UPPER LEVEL ANALYSIS, ALONG WITH WATER VAPOR IMAGERY,
DEPICTS STRONG (25 TO 30 KNOTS) VERTICAL WIND SHEAR (VWS) CONTINUES
TO ACT UPON THE SYSTEM, WHICH IS SLIGHTLY BEING OFFSET BY VIGOROUS
EQUATORWARD OUTFLOW AS THE CONVECTION CONTINUES TO GROW. 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. THE STRONG
EQUATORWARD OUTFLOW, DESPITE THE NORTHERLY VWS, WILL ALLOW FOR A
GRADUAL INTENSIFICATION REACHING 95 KNOTS BY TAU 72.
   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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