WDPN32 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 33W (TEMBIN) WARNING NR 18//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 33W (TEMBIN), LOCATED APPROXIMATELY 253 NM EAST-
SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WESTWARD AT 11
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A HIGHLY SHEARED AND RAPIDLY WEAKENING SYSTEM, WITH
ALL DEEP CONVECTIVE ACTIVITY SHEARED OVER 100 NM TO THE NORTHWEST
OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE HIGH RESOLUTION VISIBLE
IMAGERY SHOWING A FULLY EXPOSED LLCC EVIDENT THROUGH A THIN CIRRUS
DECK. THE INITIAL POSITION IS CONFIRMED BY ANALYSIS OF A 242345Z
SSMIS 91GHZ MULTI-POLARITY MICROWAVE IMAGE, WHICH REVEALS A VERY
DISTINCT MICROWAVE EYE FEATURE IN THE LOWER LEVELS. ENVIRONMENTAL
ANALYSIS IS INDICATIVE OF A NON-SUPPORTIVE ENVIRONMENT, WITH HIGH
SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) AND ONLY WEAKLY SUPPORTIVE
SEA SURFACE TEMPERATURES OF 26 DEG CELSIUS. POLEWARD OUTFLOW
REMAINS STRONG, BUT IS BEING OFFSET BY THE STRONG SHEAR. THE
INITIAL INTENSITY HAS DROPPED SIGNIFICANTLY AND IS NOW ASSESSED AT
65 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T4.0 (65
KNOTS). THE MOST RECENT CIMSS SATCON ESTIMATE OF 74 KNOTS AND
RECENT ADVANCED DVORAK TECHNIQUE (ADT) ESTIMATE OF T4.7 (83 KNOTS)
ARE NOT REPRESENTATIVE, AS THEY ARE TRACKING THE DEEP CONVECTION
WHICH IS OVER 150 NM DISPLACED FROM THE LLCC. TY 33W HAS JOGGED
SLIGHTLY TO THE SOUTH OF WEST OVER THE PAST SIX HOURS AND SLOWED
SIGNIFICANTLY, LEADING TO A RELOCATION OF THE LLCC ON THIS WARNING.
THE SYSTEM CONTINUES TO TRACK GENERALLY WESTWARD OVER THE LONG TERM
ALONG THE SOUTHERN PERIPHERY OF AN EAST-WEST ORIENTED SUBTROPICAL
RIDGE CENTERED NEAR 20 DEG NORTH.
3. FORECAST REASONING.
A. EVEN IN LIGHT OF THE RELOCATION, THERE IS NO SIGNIFICANT
CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TY 33W WILL CONTINUE TO TRACK WESTWARD UNDER THE INFLUENCE OF
THE STEERING RIDGE ANCHORED ALONG 20 DEG NORTH THROUGH THE FORECAST
PERIOD. TY 33W HAS BEGUN TO RAPIDLY DETERIORATE UNDER INCREASING
SHEAR AND WILL CONTINUE THIS TREND THOUGH THE NEXT 24 HOURS AS IT
MOVES JUST SOUTH OF THE SOUTHERN TIP OF VIETNAM. AFTER TAU 24, THE
WEAKENING WILL SLOW SOMEWHAT AS POLEWARD OUTFLOW IMPROVES AND SSTS
INCREASE, BUT CONTINUING TO BE OFFSET BY STRONG VWS. THE SYSTEM IS
NO LONGER EXPECTED TO MAKE LANDFALL IN VIETNAM AND IS FORECAST TO
MAKE INITIAL LANDFALL ALONG THE CENTRAL THAILAND COASTLINE NEAR TAU
60 AS A WEAK TROPICAL DEPRESSION. TERRAIN INTERACTION WILL FURTHER
WEAKEN TY 33W AS IT CROSSES OVER THE MALAY PENINSULA AND IS
EXPECTED TO DISSIPATE BY TAU 72 IN THE EASTERN BAY OF BENGAL.
DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 LEADING
TO HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.//
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