Tropical Storm HALONG Advisory Wed Jul 30

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (HALONG) WARNING NR
07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (HALONG), LOCATED APPROXIMATELY 37 NM
EAST-NORTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD
AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH DEEP CENTRAL CONVECTION SLIGHTLY DISPLACED
SOUTHWARD. A 292345Z METOP-B MICROWAVE IMAGE REVEALS TIGHTLY-CURVED
BANDING WRAPPING TOWARDS THE WELL-DEFINED LLCC. THE CURRENT POSITION
IS BASED ON THE MSI, ABOVE MENTIONED MICROWAVE IMAGE AS WELL AS
RADAR FIXES WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 55 KNOTS
IS BASED ON CONSISTENT DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW
AND KNES. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS NOW LOCATED
IN AN AREA WITH MODERATE (15 TO 25 KNOT) VERTICAL WIND SHEAR (VWS)
OFFSET BY EXCELLENT EQUATORWARD OUTFLOW. TS 11W IS TRACKING WEST-
NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE
(STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THE JTWC FORECAST INTENSITY HAS DECREASED DUE TO PERSISTENT
MODERATE VWS AND AN OVERALL DECREASE IN DYNAMICAL-NUMERICAL MODEL
GUIDANCE. THEREFORE, THE PEAK INTENSITY HAS BEEN REDUCED TO 95 KNOTS
AT TAU 72.
   B. TS 11W IS EXPECTED TO TRACK WESTWARD TO WEST-NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR THROUGH TAU 36. BY TAU 36,
AN UPPER-LEVEL TROUGH MOVING OVER FROM THE NORTHWEST MODIFIES THE
STR, CAUSING TS HALONG TO SHIFT NORTHWESTWARD THROUGH THE REMAINDER
OF THE FORECAST PERIOD. DESPITE THE PERSISTENT MODERATE VWS, UPPER-
LEVEL CONDITIONS ARE EXPECTED TO IMPROVE ALLOWING THE SYSTEM TO
INTENSIFY AND LEADING TO A PEAK INTENSITY OF 95 KNOTS BY TAU 72.
ADDITIONALLY, WARM SEA SURFACE TEMPERATURES ALONG THE TRACK ARE
CONDUCIVE FOR DEVELOPMENT.
   C. TS HALONG IS EXPECTED TO WEAKEN BY TAU 96 AS THE SYSTEM
ENCOUNTERS INCREASING VWS ASSOCIATED WITH UPPER-LEVEL NORTHERLY FLOW
ALONG THE EASTERN FLANK OF THE UPPER-LEVEL HIGH. AVAILABLE MODEL
GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 AND DIVERGES AFTERWARD.
DUE TO THE UNCERTAINTY IN THE TRACK SPEEDS AND INTENSITY FORECAST AT
THE EXTENDED TAUS, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC
FORECAST.//
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