WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR 032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.8N 124.9E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 382 NM SOUTHWEST OF BUSAN, SOUTH KOREA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT TY
12W CONTINUES TO HOLD BACK PERSISTENT DRY AIR INTRUSION FROM THE
WEST, AND HAS MAINTAINED A SMALL, APPROXIMATELY 45NM WIDE CDO WITH
A 10NM EYE FEATURE. THE EYE FEATURE HAS WINKED IN AND OUT OVER THE
COURSE OF THE PAST SIX HOURS, BUT THE OVERALL STRUCTURE, EYE AND
CLOUD TOP TEMPERATURES ARE THE SAME AS THEY WERE SIX HOURS AGO.
THUS THE INITIAL INTENSITY REMAINS SET SLIGHTLY ABOVE THE T5.5
DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND KNES,
EXTRAPOLATING EARLIER SAR DATA AND IN VIEW OF THE OVERALL
CONSISTENT STRUCTURE. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON AGENCY FIX POSITIONS AND EXTRAPOLATION OF THE
MOST RECENT 042202Z SSMIS 91GHZ MICROWAVE IMAGE. THE MICROWAVE DATA
SUGGESTS A BIT OF A DOWN-TRACK TILT WITH HEIGHT, NOT SURPRISING
GIVEN THE STRONG POLEWARD OUTFLOW AND THE CIMSS SHEAR ANALYSIS
SHOWING A DUE SOUTH SHEAR VECTOR. THE MICROWAVE IMAGERY ALSO
INDICATES THE OUTER EYEWALL IS NOT CLOSED, AND THERE IS LITTLE TO
NO SPIRAL BANDING INTO THE INNER CORE OF THE SYSTEM. THE
ENVIRONMENT REMAINS FAVORABLE, THOUGH NOT FOR MUCH LONGER.
CONVERGENT FLOW, ACCOMPANYING VERY DRY UPPER-LEVEL AIR, IS STARTING
TO SHOW UP TO THE NORTHWEST OVER THE SOUTHERN YELLOW SEA AND
ALREADY IMPINGING OUTFLOW IN THAT DIRECTION. THE PRIMARY OUTFLOW
NOW IS POLEWARD INTO THE JET MAX RACING ACROSS THE BOHAI GULF AND
EQUATORWARD TO THE EAST AND SOUTH. SHEAR REMAINS LOW (LESS THAN 5
KTS) AND THUS THE OUTFLOW IS STILL KING OF THE MOUNTAIN AND
PROVIDING AMPLE SUPPORT FOR MAINTAINING THE INTENSITY. THE SYSTEM
IS STILL EXHIBITING TROCHOIDAL MOTION BUT THE TRACK MADE GOOD
REMAINS JUST EAST OF DUE NORTH OVER THE PAST SIX HOURS.

INITIAL WIND RADII BASIS: PERSISTENCE AND SURFACE OBSERVATIONS

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 101 KTS AT 042109Z
   CIMSS ADT: 101 KTS AT 050010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 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: TY 12W LOOKS TO HAVE STARTED, ALBEIT SLOWLY,
TO TURN ONTO A MORE NORTH-NORTHEAST HEADING AS IT BEGINS TO ROUND
THE RIDGE AXIS AND BEGIN TO ACCELERATE. TRACK SPEEDS ARE NOW UP TO
12 KNOTS AND THE SYSTEM IS MOVING JUST SLIGHTLY EAST OF DUE NORTH.
THIS TREND WILL CONTINUE OVER THE NEXT 12 HOURS AND BY TAU 12 THE
SYSTEM WILL BE JUST SOUTHEAST OF CHEJU DO, MOVING RAPIDLY NORTHEAST
TOWARDS THE BUSAN AREA. LANDFALL IN THE VICINITY OF BUSAN IS
ANTICIPATED BETWEEN TAUS 18 AND 21. AFTER CLIPPING SOUTHEASTERN
KOREA, THE SYSTEM MOVES RAPIDLY INTO THE SEA OF JAPAN WHILE
TRANSITIONING TO AN EXTRA-TROPICAL CYCLONE. THE SYSTEM HAS LIKELY
REACHED PEAK INTENSITY, AND WHILE THE OVERALL ENVIRONMENT REMAINS
GENERALLY FAVORABLE, THE WINDOW OF OPPORTUNITY FOR INTENSIFICATION
IS GETTING SMALLER BY THE HOUR. FROM HERE ON OUT THE ENVIRONMENT IS
EXPECTED TO BECOME INCREASINGLY HOSTILE; SSTS BEGIN TO DROP OFF
SHARPLY AS THE SYSTEM APPROACHES THE SOUTH KOREAN COAST, AND SHEAR
IS FORECAST TO DRAMATICALLY AND SHARPLY INCREASE BEFORE TAU 12. SO
WHILE THE OUTFLOW IS CURRENTLY THE DOMINANT PARTY IN THE
OUTFLOW-SHEAR RELATIONSHIP, SHEAR WILL QUICKLY SUPPLANT IT AFTER
TAU 12, AND WILL BEGIN TO BLOW THE SYSTEM APART AROUND TAU 18. AT
THE SAME TIME, THE SYSTEM WILL BEGIN TO COUPLE WITH A VERY STRONG,
NEGATIVELY TILTED 500MB TROUGH AND SUPPORTING 200MB JET MAX EXITING
THE BASE OF THE TROUGH AND BEGIN A RAPID TRANSITION TO AN
EXTRA-TROPICAL LOW. THE TRANSITION PROCESS WILL BE EXCEPTIONALLY
QUICK, LEAVING A STRONG TYPHOON-STRENGTH EXTRA-TROPICAL LOW IN THE
SEA OF JAPAN NO LATER THAN TAU 36. DUE TO THE VERY STRONG
BAROCLINIC FORCING ASSOCIATED WITH THE APPROACHING MID-LATITUDE
SYSTEM, MAXIMUM SUSTAINED WINDS WILL BE HIGHER THAN WOULD OTHERWISE
BE EXPECTED FOR SUCH A SYSTEM AND ARE EXPECTED TO BE 85-95 KNOTS AS
THE SYSTEM CROSSES OVER THE SOUTHERN COAST OF KOREA. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
VERY TIGHT AGREEMENT THROUGH THE FORECAST PERIOD, WITH LESS THAN
50NM SPREAD AT LANDFALL, INCREASING MODESTLY TO 90NM BY THE END OF
THE FORECAST. THIS RUN INTRODUCES SOME MODEST ALONG-TRACK SPREAD,
UP TO 110NM AT TAU 24 INCREASING FURTHER THROUGH THE END OF THE
FORECAST, THUS A FAIR AMOUNT OF UNCERTAINTY IN THE TIMING OF THE
LANDFALL AND CLOSEST APPROACH TO BUSAN HAS CREPT INTO THE FORECAST.
WITH THE EXCEPTION OF THE TRACK SPEED UNCERTAINTY, OVERALL TRACK
CONFIDENCE IS HIGH. INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH
THIS RUN, AND THE GUIDANCE IS SPREAD ACROSS A 75-90 KNOT ENVELOPE
AT TAU 24. THE JTWC FORECAST LIES CLOSE TO THE MULTI-MODEL
CONSENSUS WITH HIGH CONFIDENCE. 

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