WDPN31 PGTW 040900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) 
WARNING NR 029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.0N 124.6E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 174 NM WEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SMALL 10NM
EYE SURROUNDED BY SPIRAL BANDS OF DEEP CONVECTION. THE WESTERN
PERIPHERY OF THE SYSTEM CONTINUES TO SHOW SIGNS OF DRY AIR
ENTERTAINMENT BUT THIS HAS NOT PREVENTED 12W FROM CONSOLIDATING AND
INTENSIFYING. A 040430Z AMSR2 89GHZ MICROWAVE IMAGE REVEALS THAT TY
12W HAS A SMALL COMPACT INNER CORE WITH A SIZABLE MOAT AND MUCH
LARGER SECONDARY EYEWALL. SHORT TERM POSITIONING REMAINS DIFFICULT
DUE TO A SIZABLE AMOUNT OF TROCHOIDAL MOTION AS THE SYSTEM
PROPAGATES NORTHWARD. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON MSI AND AMSR2 IMAGERY. THE INITIAL INTENSITY OF
105 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PGTW, KNES
AND CIMSS ADT ALL INDICATING 102 KTS WITH AN UPWARD TREND OVER THE
PAST SEVERAL HOURS.

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: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 102 KTS AT 040610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: POSSIBLE EYE WALL REPLACEMENT CYCLE, DRY AIR
ENTERTAINMENT TO THE 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: STILL TRACKING GENERALLY NORTHWARD UNDER THE
STEERING INFLUENCE OF THE STR TO THE EAST, TY 12W HAS SHOWN
CONSISTENT CONSOLIDATION AND INTENSIFICATION OVER THE PAST SEVERAL
HOURS. THROUGH TAU 12, THE SYSTEMS ENVIRONMENT WILL REMAIN HIGHLY
FAVORABLE, CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES
(29C-30C), LOW VERTICAL WIND SHEAR (10-15KTS) AND VIGOROUS
DUAL-CHANNEL OUTFLOW BOTH POLEWARD AND EQUATORWARD. UNFORTUNATELY
FOR 12W, THE CURRENT CONCENTRIC EYEWALL SETUP, AND INCREASING
M-PERC EYEWALL REPLACEMENT CYCLE (ERC) PROBABILITIES SUGGEST THAT
ERC WILL TAKE PLACE IN THE NEAR FUTURE AND THE SYSTEMS INTENSITY
WILL LIKELY NOT RECOVER. BECAUSE OF THIS, TY 12W IS LIKELY TO REACH
PEAK INTENSITY WITHIN THE NEXT 12-18 HOURS. BY TAU 24, THE SYSTEM
WILL STEADY UP ON A GENERALLY NORTHEASTWARD TRACK AS IT ROUNDS THE
STR AND ACCELERATES TOWARDS THE KOREAN PENINSULA. NEAR TAU 36, NOW
OVER COOLER WATERS AND INTERACTING WITH THE PENINSULA ITSELF 12W
WILL CONTINUE TO WEAKEN, ALL THE WHILE THE STRONG UPPER-LEVEL LOW
AND TROUGH MOVING IN FROM THE WEST WILL BOMBARD THE SYSTEM WITH
VERTICAL WIND SHEAR AND FURTHER ACCELERATE 12W NORTHEASTWARD. THIS
INTERACTION WITH THE PASSING TROUGH WILL BEGIN TO ROB THE SYSTEM OF
ITS TROPICAL CHARACTERISTICS AND THEREBY START EXTRATROPICAL
TRANSITION (ETT) AS THE SYSTEM PASSES OVER THE SOUTHERN COAST OF
SOUTH KOREA. BY TAU 48 THE SYSTEM WILL STILL HAVE MUCH OF ITS
FORMER INTENSITY AS IT PROGRESSES THROUGH ETT. NEAR TAU 72, NOW
DEVOID OF ITS TROPICAL CHARACTERISTICS AND FULLY INCORPORATED IN
THE MIDLATITUDE TROUGH, 12W IS FORECAST TO COMPLETE ETT.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT THROUGH
TAU 48 WITH A 100NM SPREAD IN THE SOLUTION, BY TAU 72 THERE IS
ADDITIONAL CROSS TRACK DISCREPANCY AS VARIOUS MODELS ATTEMPT TO
RESOLVE THE COMPLETION OF ETT. DUE TO THIS TIGHT AGREEMENT THE JTWC
FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE. RELIABLE MODEL
INTENSITY GUIDANCE IS IN FAIR AGREEMENT WITH SEVERAL RAPID
INTENSIFICATION AIDS TRIGGERING DUE TO THE ABOVE MENTIONED HIGHLY
FAVORABLE ENVIRONMENT, HOWEVER, DECAY-SHIPS (NVGM AND GFS) HAVE
SHOWN A CONSISTENTLY OPPOSING STORY WITH STAGNATION AND WEAKENING
THROUGH THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS
THEREFORE PLACED WITH MEDIUM CONFIDENCE DUE TO THE UNCLEAR EXTENT
THAT ERC WILL PLAY IN THE SYSTEMS SHORT TERM INTENSIFICATION TREND
AND THEREFOR ITS LONG TERM FORECAST INTENSITY.

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