WDPS32 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 16P (KEVIN) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.5S 177.3E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 389 NM SOUTH OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 23 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER HAVING PEAKED AT AN AMAZING 140 KNOTS YESTERDAY, TC 16P
(KEVIN) IS NOW RAPIDLY WEAKENING AND UNDERGOING SUBTROPICAL
TRANSITION (STT). ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY DEPICTS A SIGNIFICANTLY DETERIORATED CONVECTIVE STRUCTURE,
WITH WEAK DISORGANIZED CONVECTION BEING SHEARED TO THE SOUTHEAST OF
THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). WHILE THE LLCC
REMAINS OBSCURED BY THE CONVECTIVE BLOWOFF, AN 041718Z SSMIS
MICROWAVE IMAGE REVEALED THE SYSTEM STILL HAS AN INTACT LOW LEVEL
VORTEX STRUCTURE, WITH A SMALL BUT WELL-DEFINED MICROWAVE EYE
VISIBLE IN THE 37GHZ BAND, WHICH PROVIDED HIGH CONFIDENCE TO THE
INITIAL POSITION. THE 91GHZ FREQUENCY REVEALED SIGNIFICANT EROSION
OF THE EYEWALL ACROSS THE NORTHWEST SECTOR OF THE SYSTEM, NO
SURPRISE GIVEN STRONG NORTHWESTERLY SHEAR. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE, HEDGED SLIGHTLY LOWER THAN THE
AGENCY CURRENT INTENSITY ESTIMATES DUE TO THE SHARP DROP IN FINAL-T
NUMBERS FROM ALL AGENCIES. FAVORABLE ENVIRONMENTAL CONDITIONS ARE
RAPIDLY GIVING WAY TO VERY UNFAVORABLE CONDITIONS AS THE SYSTEM
RAPIDLY MOVES SOUTHEASTWARD ALONG THE SOUTHWEST PERIPHERY OF THE
SUBTROPICAL RIDGE (STR). CIMSS VWS ESTIMATES ARE ALREADY OVER 37
KNOTS AND GOING HIGHER, WHILE SSTS HAVE DROPPED OFF TO THE 25-26C
RANGE. ADDITIONALLY, A LARGE AMOUNT OF MID-LEVEL DRY AIR IS LURKING
OUT TO THE WEST, WAITING FOR THE OPPORTUNITY TO RUSH IN AND SMOTHER
TC KEVIN. OUTFLOW REMAINS VERY STRONG TO POLEWARD, BUT THE SHEAR IS
STARTING TO EXERT THE STRONGER INFLUENCE, MARKING THE BEGINNING OF
THE END OF TC KEVIN.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   PHFO: T6.5 - 127 KTS
   CIMSS ADT: 102 KTS AT 041730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30+ KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TC 16P IS TRACKING SOUTHEASTWARD AT A GOOD
CLIP OF ABOUT 23 KNOTS. SOME ADDITIONAL ACCELERATION IS EXPECTED
OVER THE NEXT 12 HOURS BUT THEN THE SYSTEM WILL SLOW DOWN AS THE
STEERING LEVEL COMES DOWN AND THE GRADIENT BEGINS TO WEAKEN.
REGARDLESS HOWEVER, NO SIGNIFICANT DEVIATION FROM THE SOUTHEAST
TRACK IS EXPECTED THROUGH THE FORECAST PERIOD. IN TERMS OF
INTENSITY, THE SYSTEM HAS ENTERED A PERIOD OF RAPID WEAKENING, AS
THE STRONG VWS TEARS APART THE CORE AND THE SYSTEM MOVES OVER
WATERS WITH A SIGNIFICANT SHORTFALL IN AVAILABLE HEAT CONTENT. OVER
THE NEXT 24 HOURS, THE SYSTEM WILL BE DECAPITATED BY THE SHEAR AND
THE DRY AIR MASS CURRENTLY LYING IN WAIT TO THE WEST WILL MOVE IN
OVER TOP OF THE SYSTEM, ROBBING IT OF ANY CHANCE OF RECOVERY AND
LEAVING BEHIND A NAKED LLCC. THE SYSTEM HAS ALREADY STARTED TO SHOW
SIGNS OF STT BUT WILL BEGIN THE STT PROCESS IN EARNEST WITHIN THE
NEXT 12 HOURS AS IT SLIDES TOWARDS THE SOUTHEAST. STT IS EXPECTED
TO BE VERY QUICK, WITH TC 16P TRANSITIONING TO A STORM-FORCE
SUBTROPICAL LOW NO LATER TAU 36, AND POTENTIALLY AS EARLY AS TAU
24.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY TIGHT AGREEMENT THROUGH
THE SHORT DURATION OF THE FORECAST, AND THE JTWC FORECAST LIES
CLOSE TO THE CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH THE JTWC FORECAST LYING A
SHADE HIGHER THAN THE BULK OF THE GUIDANCE, AS THE MODELS GENERALLY
WEAKEN THESE TYPES OF SYSTEMS TOO FAST. CONFIDENCE REMAINS HIGH IN
THE OVERALL INTENSITY FORECAST. 

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