WDPN31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) 
WARNING NR 034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.5N 126.5E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 203 NM SOUTHWEST OF BUSAN, SOUTH KOREA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 41 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
DEFIANTLY WELL DEFINED CIRCULATION WITH CLOUD BANDS FINALLY SHOWING
SIGNS OF WEAKENING. A 050921Z SSMIS 91GHZ MICROWAVE SATELLITE IMAGE
REVEALS THAT THE SYSTEMS DEEP CONVECTIVE ELEMENTS ARE ALMOST
EXCLUSIVELY TO THE NORTH AND SOUTH OF THE LLCC, AND THE SYSTEMS
CORE REMAINS WELL DEFINED. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON EIR AND SSMIS IMAGERY. WITH THE LOSS OF
THE EYE IN THE PREVIOUS FORECAST, AND THE SYSTEM NOW SHOWING SIGNS
OF MORE SIGNIFICANT DRY AIR ENTERTAINMENT AND SHEAR, AGENCY DVORAK
VALUES HAVE AGGRESSIVELY FALLEN. AS HAS BEEN PREVIOUSLY FORECAST,
12W WILL INITIALLY WEAKEN GRADUALLY AND THEREFOR WOULD NOT BE
PROPERLY REPRESENTED BY DVORAK INTENSITY ESTIMATES. AS EXPECTED,
AGENCY DVORAK ESTIMATES ARE TOO AGGRESSIVELY WEAKENING THE SYSTEM,
ALL SHOWING T4.0-4.5 AND AS A RESULT THE JTWC FORECAST TRACK IS
PLACED AT A HIGHER MORE CONSERVATIVE 100 KNOTS WITH MEDIUM
CONFIDENCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS ADT: 79 KTS AT 051140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: STILL TRACKING GENERALLY NORTH-NORTHEASTWARD
UNDER THE STEERING INFLUENCE OF THE STR TO THE EAST, THE ENVIRONMENT 
SURROUNDING 12W WILL CONTINUE TO GET MORE HOSTILE. AS IS EVIDENT IN 
THE EIR IMAGERY, THE FIELD OF CONVERGENT FLOW AND UPPER LEVEL DRY AIR 
MOVING OVER THE YELLOW SEA HAS CONTINUED TO ERODE THE WESTERN FLANK 
OF 12W, AND HAS NOW METASTASIZED TO OTHER AREAS OF THE SYSTEM. AS THE 
12W CONTINUES TO ROUND THE STR AND CONTINUES TO INCREASE SPEED, IT 
WILL CLOSE ON THE SOUTHERN COAST OF THE KOREAN PENINSULA. AS THIS 
HAPPENS THE ENVIRONMENT WILL CONTINUE TO RAPIDLY DEGRADE 
CHARACTERIZED BY FALLING SEA SURFACE TEMPERATURES, INCREASING 
VERTICAL WIND SHEAR AND DRY AIR ENTERTAINMENT WHICH WILL ALL WEAKEN 
THE SYSTEM. NEAR TAU 6, AS THE SYSTEM BEGINS TO PASS OVER THE KOREAN 
PENINSULA IT INTERACTS WITH A VERY STRONG, MID-LATITUDE TROUGH AND 
UPPER-LEVEL JET MAX AND BEGINS A RAPID TRANSITION TO AN EXTRA-
TROPICAL LOW. BY TAU 12, NOW IN THE SEA OF JAPAN, 12W WILL STILL HAVE 
MUCH OF ITS FORMER INTENSITY DUE TO THE EXTREME DYNAMICAL FORCES 
ASSOCIATED WITH THE TROUGH AND SPEED OF TRANSITION. NEAR TAU 24, 12W 
WILL BE ROBED OF ITS LAST REMAINING TROPICAL CHARACTERISTICS, LEAVING 
A STRONG STORM-STRENGTH EXTRA-TROPICAL LOW IN THE SEA OF JAPAN.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH THE
JTWC FORECAST TRACK, SHOWING A GENERALLY NORTH-NORTHEASTWARD TRACK
THROUGH THE FORECAST PERIOD. FOR THIS REASONS THE JTWC FORECAST
TRACK IS PLACED WITH HIGH CONFIDENCE. RELIABLE MODEL INTENSITY
GUIDANCE IS IN GOOD AGREEMENT WITH THE JTWC FORECAST INTENSITY
GUIDANCE, WITH ALL MEMBERS WEAKENING 12W OVER THE NEXT 12 HOURS,
AFTER WHICH ALL MEMBERS SHARPLY WEAKEN THE SYSTEM THROUGH THE
FORECAST PERIOD. FOR THIS REASON THE JTWC FORECAST INTENSITY IS
ALSO PLACED WITH HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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