Tropical Storm VICENTE Advisory Pzt, 23.07.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (VICENTE) WARNING
NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 09W (VICENTE), LOCATED APPROXIMATELY 175 NM SOUTH
OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 04 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS
BUILDING CENTRAL CONVECTION WITH FORMATIVE BANDING OVER THE
SOUTHERN SEMI-CIRCLE OF THE LOW-LEVEL CIRCULATION CENTER (LLCC).
THE CURRENT POSITION IS BASED ON A 221820Z AMSU-B IMAGE WITH HIGH
CONFIDENCE. THE CURRENT INTENSITY IS BASED ON A BLEND OF THE
SUBJECTIVE DVORAK ESTIMATES OF 45 KNOTS FROM PGTW/RJTD/KNES, AND
OBJECTIVE ESTIMATES FROM THE 221800Z SATCON OF 61 KNOTS (COMPRISED
OF CIMSS AMSU = 65 KNOTS, ADT = 53 KNOTS). A RE-ANALYSIS OF THE
PAST 18 HOUR MICROWAVE AND SCATTEROMETER DATA SUGGESTS THAT TS 09W
HAS DEFINITELY SLOWED DOWN AND DIPPED SLIGHTLY SOUTHWESTWARD.
HOWEVER, THE DEGREE OF SOUTHWESTWARD DIP IS NOT AS MUCH AS
PREVIOUSLY THOUGHT AND RECENT TRACK MOTION SUGGESTS A RETURN TO
WEST-NORTHWESTWARD MOTION. UPPER-LEVEL ANALYSIS SHOWS AN
ANTICYCLONE TO THE NORTHEAST AND A STRONG POINT SOURCE OF
DIVERGENCE TO THE SOUTHEAST OF THE LLCC. THESE FEATURES ARE CAUSING
MODERATE (10-15 KNOTS) NORTH-NORTHEASTERLY VERTICAL WIND SHEAR OVER
THE LLCC AND GOOD DIVERGENCE TO THE WEST IN AN EQUATORWARD OUTFLOW
CHANNEL. ANIMATED WATER VAPOR IMAGERY SHOWS NO SIGNS OF A POLEWARD
OUTFLOW CHANNEL. TS 09W IS CURRENTLY BEING STEERED BY THE
SOUTHWESTERN PERIPHERY OF THE MID- TO UPPER-LEVEL SUBTROPICAL RIDGE
(STR) CENTERED FAR TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IT SEEMS AS THOUGH THE TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL CENTERED NEAR 19N 136E HAS ALTERED THE ORIENTATION OF
THE SOUTHWESTERN PERIPHERY OF THE STEERING STR CAUSING TS 09W TO
TRACK MORE NORTH THAN PREVIOUSLY THOUGHT. THE SYSTEM SHOULD TRACK
TOWARDS THE COASTLINE EAST OF THE LUICHOW PENINSULA AND CONTINUE TO
INTENSIFY TO MINIMAL TYPHOON STRENGTH BEFORE MAKING LANDFALL AT TAU
36. DURING TAUS 48-72, TS 09W SHOULD SLOWLY SPIN-DOWN DUE TO LAND
INTERACTION. THE MAJORITY OF NUMERICAL MODEL GUIDANCE IS IN
EXCELLENT AGREEMENT UP TO THE LANDFALL POINT WITH THE EXCEPTION OF
THE MORE POELWARD WBAR. THEREFORE, THE OFFICIAL JTWC TRACK FORECAST
IS HELD SLIGHTLY LEFT OF THE MODEL CONSENSUS TO OFFSET THE WBAR AND
MAINTAINED SLIGHTLY FASTER DUE TO DIFFERING TRACK SPEEDS IN THE
LATER TAUS. HIGH CONFIDENCE STILL REMAINS IN THE FORECAST TRACK.//
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