Tropical Storm MITAG Advisory Wed Oct 02

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (MITAG) WARNING NR
020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 19W (MITAG), LOCATED APPROXIMATELY 320 NM
SOUTHWEST OF PUSAN, SOUTH KOREA, HAS TRACKED NORTHEASTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. DESPITE THE RAPID DECAY OF DEEP
CONVECTION OVER THE PAST 12 HOURS, ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS TIGHTLY-CURVED LOW-LEVEL BANDING WRAPPING INTO A
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE
CURRENT POSITION WITH HIGH CONFIDENCE. THIS WELL-DEFINED LOW-LEVEL
STRUCTURE IS ALSO EVIDENT IN A 012309Z SSMIS 91GHZ COLOR COMPOSITE
IMAGE WITH LIMITED DEEP CONVECTION SHEARED WELL NORTH OF THE CENTER.
A 020118Z ASCAT-B IMAGE INDICATES 40-45 KNOT WINDS (10-MINUTE
AVERAGE) OVER THE EASTERN SEMICIRCLE WITH EXTENSIVE GALE-FORCE
WINDS. THE CURRENT INTENSITY IS ASSESSED SLIGHTLY HIGHER AT 55 KNOTS
BASED ON CURRENT INTENSITY ESTIMATES OF 3.5 (55 KNOTS) CONSISTENT
WITH A 012308Z SATCON ESTIMATE OF 50 KNOTS. THE SYSTEM IS CURRENTLY
LOCATED WITHIN A BROAD UPPER-LEVEL SUBTROPICAL TROUGH, WHICH IS
CONTRIBUTING TO THE RAPID DECAY OF THE DEEP CONVECTIVE STRUCTURE AND
PRODUCING STRONG (30-35 KNOTS) SOUTHWESTERLY VERTICAL WIND SHEAR
(VWS). SST VALUES ARE MARGINAL AT 24-25C. TS 19W IS TRACKING ALONG
THE NORTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED
TO THE SOUTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII HAVE
BEEN ADJUSTED BASED ON AVAILABLE SURFACE AND SHIP OBSERVATIONS.
   B. TS 19W IS FORECAST TO ACCELERATE NORTH-NORTHEASTWARD TO
NORTHEASTWARD THROUGH TAU 24 AS IT ROUNDS THE STR AXIS. TS 19W WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 24 AS IT INTERACTS
WITH THE MIDLATITUDE WESTERLIES AND BAROCLINIC ZONE. THE SYSTEM
SHOULD GRADUALLY WEAKEN DUE TO INCREASING VWS, COOLER SST AND
INTERACTION WITH LAND. 19W WILL TRACK OVER THE SEA OF JAPAN AFTER
TAU 30 AND WILL COMPLETE ETT NEAR TAU 48 AS IT GAINS FRONTAL
CHARACTERISTICS AND BECOMES EMBEDDED WITHIN STRONG MIDLATITUDE
WESTERLY FLOW. SST VALUES WILL DECREASE TO LESS THAN 24C, WHICH WILL
FURTHER AID IN WEAKENING THE SYSTEM. NUMERICAL MODEL GUIDANCE
REMAINS IN TIGHT AGREEMENT WITH A 70NM SPREAD IN SOLUTIONS AT TAU
36, THEREFORE, THERE IS HIGH CONFIDENCE (LOW UNCERTAINTY) IN THE
JTWC FORECAST TRACK THROUGH TAU 36. AFTER TAU 48, THIS COLD-CORE
EXTRA-TROPICAL LOW WILL ACCELERATE EAST-NORTHEASTWARD OVER NORTHERN
HONSHU. THE SYSTEM IS STILL EXPECTED TO MAINTAIN GALE-FORCE WINDS.
DUE TO THE BROAD NATURE OF THIS LOW AND THE LARGE SPREAD IN THE
NUMERICAL MODELS, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE
JTWC FORECAST TRACK.//
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