WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) 
WARNING NR 033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.1N 125.5E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 301 NM SOUTHWEST OF BUSAN, SOUTH KOREA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A WELL
DEFINED, TIGHTLY WRAPPED CIRCULATION WHO'S EYE HAS SLOWLY FILLED
OVER THE PAST FEW HOURS. A 050514Z AMSR2 89GHZ COLOR COMPOSITE
MICROWAVE IMAGE REVEALS THAT 12W HAS MAINTAINED A SMALL CORE
SURROUNDED BY AN INTERMITTENT SECONDARY EYEWALL LIKE FEATURE THAT
HAS FRAGMENTED AND REFORMED SEVERAL TIMES OVER THE PAST 12-24
HOURS. THIS CORE STRUCTURE WHILE CERTAINLY A-TYPICAL HAS ALLOWED
12W TO DELAY ITS IMPENDING WEAKENING. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON MSI AND AMSR2 IMAGERY. THE
INITIAL INTENSITY OF 105 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE NOTABLE DECLINE OF ALL AGENCY DVORAK INTENSITY
ESTIMATES, WHILE THE SYSTEMS CORE STRUCTURE APPEARS MOSTLY INTACT. 
FURTHERMORE, WHILE AGENCY DVORAK INTENSITY ESTIMATES WILL GENERALLY
MAKE AN INITIAL DROP WHEN AN EYE FILLS, CIMSS ADT AND SATCON HAVE
ALSO DROPPED.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 101 KTS AT 050439Z
   CIMSS ADT: 94 KTS AT 050540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: CONVERGENCE AND DRY MID TO UPPER-LEVEL AIR TO THE
NORTHWEST.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: HAVING STEADIED UP ON A NORTH-NORTHEASTWARD
HEADING, 12W IS NEARING THE PRECIPICE OF ITS FINAL WEAKENING STAGE.
THOUGH THE SYSTEM HAS MAINTAINED A STRONG CORE STRUCTURE, A VAST
FIELD OF CONVERGENT FLOW AND UPPER LEVEL DRY AIR HAS CONTINUED
IMPINGING THE WESTERN FLANK OF 12W. OVER THE NEXT 12 HOURS, TRACK
SPEEDS WILL CONTINUE TO INCREASE AS THE SYSTEM CONTINUES TO ROUND
THE STR, AND CLOSES ON 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. SHORTLY
AFTER TAU 12, AS THE SYSTEMS PASSES OVER THE KOREAN PENINSULA IT
BEGINS TO INTERACT WITH A VERY STRONG, MIDLATITUDE TROUGH AND
UPPERLEVEL JET MAX AND BEGINS A RAPID TRANSITION TO AN
EXTRA-TROPICAL LOW. BY TAU 24, NOW WELL INTO 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. SHORTLY AFTER 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 NO LATER THAN TAU 36. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH THE
JTWC FORECAST TRACK, SHOWING A GENERALLY NORTH-NORTHEASTWARD TRACK
THROUGH THE FORECAST PERIOD. BY TAU 36 THERE IS A SLIGHT AMOUNT OF
CROSS TRACK VARIANCE AS MODELS ATTEMPT TO RESOLVE THE MOVEMENT OF
THE EXTRA-TROPICAL LOW. FOR THESE 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//
NNNN