WDPN31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (JANGMI) WARNING NR 
026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.2N 133.1E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 136 NM SOUTH-SOUTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 25 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY PRESENTS
TROPICAL STORM (TS) 06W (JANGMI) RAPIDLY TRANSLATING ALONG THE
SOUTHERN COASTLINE OF JAPAN. THE LOW-LEVEL CIRCULATION CENTER
(LLCC) IS VIRTUALLY FULLY EXPOSED WITH AN ASYMMETRIC DECOUPLING OF
THE CONVECTIVE STRUCTURE DRIVEN BY MODERATE TO HIGH (20-25 KTS)
VERTICAL WIND SHEAR (VWS), WHICH HAS DISPLACED THE BULK OF THE
ACTIVE DEEP CONVECTION POLEWARD AND EASTWARD. INJECTED DRY AIR IS
PROVEN BY MID-LEVEL THERMODYNAMIC SENSING, EVIDENCING INTENSE
DRY-AIR ENTRAINMENT ON THE SOUTHWEST FLANK ORIGINATING FROM AN
UPSTREAM SYNOPTIC-SCALE DRY AIR MASS LOCATED TO THE WEST. WHILE THE
TRANSLATION OVER THE WARM KUROSHIO CURRENT PROVIDED SOME RESIDUAL
OCEAN HEAT CONTENT (OHC), THE LLCC IS NOW TRANSITING OVER MUCH
COOLER (24-25 C) SEA SURFACE TEMPERATURES (SST), WHILE APPROACHING
AREA WITH SSTS LOWER THAN 24 C. AIDING IN THE SUSTAINMENT OF THE
STORM IS PERSISTENT AND ROBUST DIVERGENT OUTFLOW, TEMPORARILY
ENHANCED BY A PASSING UPPER-LEVEL TROUGH TO THE NORTH. EIR IMAGERY
AND JMA RADAR DATA CONFIRM THE CURRENT INITIAL POSITION WITH MEDIUM
CONFIDENCE, WHILE THE INTENSITY ESTIMATION OF 50 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON RECENT 45-50 KT SURFACE OBSERVATIONS 
FROM CAPE MUROTO, JAPAN.  DVORAK ESTIMATES ARE CURRENTLY 
UNDERESTIMATING SURFACE MAXIMUM WINDS DUE TO HIGH VERTICAL WIND SHEAR 
AND ASSOCIATED DECOUPLING OF THE DEEP CONVECTION.
INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 32 KTS AT 021200Z
   CIMSS AIDT: 38 KTS AT 021200Z
   CIMSS D-PRINT: 38 KTS AT 021200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE SOUTH AND WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 06W IS PROPAGATING TO THE NORTHEAST ALONG
THE NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTHEAST. THE LLCC IS EXPECTED TO FOLLOW A TRACK
SOUTH OF THE JAPANESE MAINLAND, WHERE BRIEF CYCLONIC LANDFALLS ARE
POSSIBLE ACROSS THE KII PENINSULA, THE HEAD OF SURUGA BAY, AND THE
SOUTHERN PORTION OF THE GREATER TOKYO METROPOLITAN REGION.
STRUCTURAL ASYMMETRY WILL CONCENTRATE THE MAXIMUM SEVERE WINDS
CHIEFLY WITHIN THE EASTERN SEMICIRCLE. TRANSLATIONAL VELOCITY WILL
CONTINUE TO ACCELERATE OVER THE NEXT 24-36 HOURS, AS THE SYSTEM
COMMENCES EXTRATROPICAL TRANSITION (ETT). THE INTENSITY IS EXPECTED
TO INITIALLY REMAIN AROUND 50 KTS, WITH WEAKENING BEGINNING AS SOON
AS TAU 24. POST-ETT, THE THERMAL STRUCTURE WILL RAPIDLY DEGENERATE
AS THE STORM ALIGNS UNDERNEATH A SUBTROPICAL JET MAXIMUM, CAUSING
DESTRUCTIVE VERTICAL WIND SHEAR (VWS). THE SYSTEM IS EXPECTED TO
BEGIN SLOWING DOWN AROUND TAU 36, AS A RESULT OF COMPLETE DECOUPLING 
AND GRADUAL DECAY. SYSTEMIC DECAY WILL BE FURTHER CATALYZED BY LOW SST 
VALUES COUPLING WITH UNABATED SOUTHWEST-QUADRANT DRY AIR ENTRAINMENT. 

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION TRACK GUIDANCE SHOWS
MINIMAL SPATIAL VARIATION, YIELDING HIGH TRACK CONSENSUS WITH AN
ENVELOPE SPREAD OF ONLY 60 NM IN THE VICINITY OF YOKOSUKA, JAPAN.
ALL OF THE CONSENSUS MEMBERS PREDICT THE TRACK IN CLOSE PROXIMITY,
BUT SOUTHEAST OF TOKYO, JAPAN. THE JTWC FORECAST TRACK IS
ESTABLISHED WITH HIGH CONFIDENCE, ALIGNING COHESIVELY WITH THE
MULTI-MODEL CONSENSUS. INTENSITY PREDICTIONS CONVEY MEDIUM
CONFIDENCE DUE TO METHODOLOGICAL DISCREPANCIES.
STATISTICAL-DYNAMICAL MODELS PORTRAY RAPID DECAY, WHEREAS ALL OTHER
PHYSICS-BASED MODELS DELAY DECAY NEARLY UNTIL POST-ETT STAGES.
ACCORDINGLY, THE CONSERVATIVE JTWC INTENSITY FORECAST IS POSITIONED
SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS, AND CLOSER TO THE
HIGH-RESOLUTION MESOSCALE DYNAMICAL GUIDANCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM//
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