Tropical Storm TEMBIN Advisory 12月26日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (TEMBIN) WARNING NR
21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 33W (TEMBIN), LOCATED APPROXIMATELY 148 NM
SOUTH-SOUTHWEST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WESTWARD
AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS A FULLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH LITTLE TO NO ASSOCIATED DEEP CONVECTION. WHAT
CONVECTION THERE IS, IS SHEARED OVER 150 NM TO THE NORTHWEST OVER
SOUTHERN CAMBODIA. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE ANIMATED INFRARED SATELLITE IMAGERY AND IS
SUPPORTED BY A 251448Z AMSU-B 89GHZ MICROWAVE IMAGE, WITH SHALLOW
BANDING WRAPPING INTO THE LLCC. THE INITIAL INTENSITY IS ASSESSED AT
40 KNOTS, WHICH IS SUPPORTED BY THE DVORAK FINAL-T INTENSITY
ESTIMATES OF T2.5 (35 KNOTS) FROM PGTW AND KNES, HEDGED SLIGHTLY
HIGHER DUE TO PREVIOUS SCATTEROMETER DATA INDICATING A BROAD AREA OF
40 KNOT WINDS TRAPPED BETWEEN THE LLCC AND THE VIETNAM COAST.
ENVIRONMENTAL CONDITIONS REMAIN MARGINAL WITH MODERATE (20-25 KNOTS)
VERTICAL WIND SHEAR (VWS), GOOD POLEWARD OUTFLOW AND MARGINAL VALUES
OF SST NEAR 26C. WHILE THESE FACTORS ARE GENERALLY SUPPORTIVE OF
DEVELOPMENT, AN UPPER-LEVEL TROUGH HAS DEVELOPED OVER THE PAST SIX
HOURS JUST TO THE SOUTHEAST TS 33W, WHICH IS INDUCING CONVERGENT
FLOW OVER THE SYSTEM AND CONTRIBUTING TO ITS WEAKENING. TS 33W IS
TRACKING STEADILY WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE EAST-
WEST ORIENTED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 33W WILL CONTINUE TO TRACK WESTWARD, PASSING NEAR OR JUST
OVER THE SOUTHERN TIP OF VIETNAM WITHIN THE NEXT 12 HOURS, THEN TURN
TO A MORE WEST-NORTHWESTWARD TRACK THROUGH THE REMAINDER OF THE
FORECAST PERIOD. TS 33W IS FORECAST TO CONTINUE TO SLOWLY WEAKEN DUE
TO PERSISTENT MODERATE VWS AND CONVERGENT FLOW ALOFT AS IT TRACKS
GULF OF THAILAND. BY TAU 36, THE SYSTEM WILL BE A MINIMAL TROPICAL
DEPRESSION AND IS FORECAST TO DISSIPATE AS IT CROSSES THE MALAY
PENINSULA, FULLY DISSIPATING IN THE EASTERN BAY OF BENGAL BY TAU 48.
DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH THE FORECAST
PERIOD, LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.//
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