Tropical Storm HALONG Advisory Tue Jul 29

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HALONG) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (HALONG), LOCATED APPROXIMATELY 134 NM
EAST OF ANDERSEN AFB, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
INDICATES THAT TS 11W HAS CONTINUED TO CONSOLIDATE WITH IMPROVED
CONVECTIVE BANDING. A 291146Z GMI IMAGE DEPICTS TIGHTLY-CURVED
BANDING WRAPPING INTO A SMALL MICROWAVE EYE FEATURE, THEREFORE,
THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION, WHICH IS ALSO
SUPPORTED BY RADAR FIXES. A 291114Z ASCAT IMAGE SHOWS 45 TO 50 KNOT
CORE WINDS WITH EXTENSIVE 30 TO 35-KNOT WINDS OVER THE SOUTHERN SEMI-
CIRCLE. THE INITIAL INTENSITY IS ASSESSED AT 55 KNOTS BASED ON THE
ASCAT IMAGE, CONVECTIVE STRUCTURE AND DVORAK INTENSITY ESTIMATE OF
55 KNOTS FROM PGTW. UPPER-LEVEL ANALYSIS INDICATES ENHANCED OUTFLOW
SUPPORTED BY A TUTT CELL TO THE NORTHEAST AND A WEAK TUTT CELL TO
THE WEST. TS 11W TRACKED NORTH-NORTHWESTWARD FROM 29/06Z TO 29/09Z
THEN TURNED WESTWARD. RECENT RADAR FIXES CONTINUE TO INDICATE A
WESTWARD TRACK AS OF 1330Z. TS 11W IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. NO SIGNIFICANT CHANGES TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING. DUE TO THE SHORT-TERM INCREASE IN
TRACK SPEED, THE CPA TO GUAM HAS CHANGED BY 7 HOURS. ADDITIONALLY,
PEAK INTENSITY HAS BEEN INCREASED TO 105 KNOTS.
   B. AS THE MONSOON DEPRESSION (INVEST 96W) TRACKS NORTH-
NORTHWESTWARD TOWARD OKINAWA, THE STR IS FORECAST TO BUILD NORTH OF
THE SYSTEM PROVIDING A WESTWARD TO WEST-NORTHWESTWARD STEERING
INFLUENCE THROUGH TAU 36. AFTER TAU 36, THE STR SHOULD MAINTAIN A
NORTHWEST-SOUTHEAST ORIENTATION, WHICH WILL STEER TS 11W
NORTHWESTWARD THROUGH TAU 72. DYNAMIC GUIDANCE IS IN TIGHT AGREEMENT
WITH A 100 NM SPREAD IN SOLUTIONS NEAR TAU 72. TS 11W IS FORECAST TO
INTENSIFY THROUGH TAU 72 TO A PEAK INTENSITY OF 105 KNOTS.
ENVIRONMENTAL CONDITIONS ARE CURRENTLY FAVORABLE BUT THE OVERALL
SYNOPTIC PATTERN IS COMPLEX WITH TUTT CELLS ENHANCING THE OUTFLOW,
THEREFORE, THERE IS MODERATE UNCERTAINTY IN THE INTENSITY FORECAST.
   C. IN THE EXTENDED TAUS, UNCERTAINTY IN THE TRACK INCREASES
SLIGHTLY AS THE DYNAMIC GUIDANCE DIVERGES. NAVGEM PRESENTS THE MOST
UNREALISTIC SCENARIO WITH A NORTHWARD TRACK INTO THE STR, THEREFORE,
THE JTWC FORECAST FAVORS A NORTHWESTWARD TRACK CLOSER TO ECMWF AND
GFS. TS HALONG SHOULD WEAKEN AFTER TAU 96 AS IT ENCOUNTERS
INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH UPPER-LEVEL NORTHERLY
FLOW ALONG THE EASTERN FLANK OF THE UPPER-LEVEL HIGH. DUE TO THE
INCREASED UNCERTAINTY IN THE TRACK AND INTENSITY FORECAST AT THE
EXTENDED TAUS, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC
FORECAST.//
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