Tropical Storm THIRTYSIX Advisory Pzt, 31.12.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 36W (THIRTYSIX)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 35W (THIRTYFIVE), LOCATED APPROXIMATELY
375 NM EAST-SOUTHEAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED
WESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) SHOWS A CONSOLIDATING SYSTEM WITH FLARING
CONVECTION SLIGHTLY SHEARED NORTHWESTWARD OF THE LOW LEVEL
CIRCULATION (LLC). FORMATIVE BANDS ALONG THE SOUTHERN FLANK CAN BE
SEEN FEEDING INTO THE LLC. THE INITIAL POSITION IS PLACED WITH FAIR
CONFIDENCE BASED ON THE MSI LOOP. THE INITIAL INTENSITY OF 25 KNOTS
IS BASED ON THE DVORAK ESTIMATE OF T1.5/25KTS FROM PGTW. UPPER LEVEL
ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF MODERATE (20-25 KNOTS)
SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY EXCELLENT POLEWARD
OUTFLOW. SEA SURFACE TEMPERATURES IN THE SOUTH CHINA SEA AND INTO THE
GULF OF THAILAND ARE VERY CONDUCIVE AT 28-29 CELSIUS. TD 35W IS
TRACKING ALONG THE SOUTHEASTERN PERIPHERY OF A SUBTROPICAL RIDGE
(STR) ANCHORED TO THE NORTHWEST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE ON THIS SYSTEM
AND SETS THE FORECAST PHILOSOPHY.
   B. TD 36W IS EXPECTED TO TRACK SOUTHWESTWARD THEN NORTHWESTWARD
TOWARD THE GULF OF THAILAND AROUND THE SOUTHERN PERIPHERY OF THE STR.
THE VWS IS EXPECTED TO DECREASE AND ALLOW A MODEST INTENSIFICATION TO
A PEAK OF 45 KNOTS BY TAU 72 AS IT ENTERS THE GULF OF THAILAND.
   C. AFTER TAU 72, VWS WILL ONCE AGAIN PICK UP. THIS, IN ADDITION TO
LAND INTERACTION AS TD 35W CROSSES THE MALAY PENINSULA AFTER TAU 96
WILL CAUSE A STEADY WEAKENING DOWN TO 30 KNOTS BY TAU 120. THE
AVAILABLE NUMERICAL GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH GRADUAL
SPREADING TO 250 NM BY TAU 120 WITH HWRF ON THE LEFT AND NAVGEM ON
THE RIGHT MARGIN OF THE MODEL ENVELOPE. HOWEVER, DUE TO THE FORMATIVE
NATURE OF THE SYSTEM, THERE IS LOW CONFIDENCE IN THIS INITIAL JTWC
TRACK FORECAST THAT IS LAID CLOSE TO THE MODEL CONSENSUS.//
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