WDPN33 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (KRATHON) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 123.9E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 488 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 20W
(KRATHON) OPENED UP A BROAD, RAGGEDLY-DEFINED EYE SEVERAL HOURS AGO
WHICH HAS SINCE BECOME CLOUD-FILLED. THE OUTFLOW COULD BE DESCRIBED
AS MODERATE RADIAL BUT IS MOST PRONOUNCED IN THE EQUATROWARD
DIRECTION DUE TO ITS BROAD EXTENT REACHING THE VIGOROUS
NORTHEASTERLY FLOW OVER THE PHILPPINES. THE SYSTEM IS HINTING AT
OPENING UP A POLEWARD OUTFLOW CHANNEL INTO THE MID-LATITUDE
WESTERLIES, BUT IT HAS NOT YET CONNECTED WITH THIS MECHANISM. DEEP
CONVECTION IS EVIDENT, PARTICULARLY ON THE NORTHEAST SIDE WITHIN AN
INNER AND OUTER BAND, BUT THE OVERALL SYMMETRY SUGGESTS THE SYSTEM
IS QUICKLY BECOMING BETTER ORGANIZED. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON PLACEMENT WITHIN THE VERY
BROAD, RAGGED EYE EVIDENT ON ANIMATED MSI IMAGERY. THE INITIAL
INTENSITY OF 80 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A
BLEND OF THE CURRENT INTENSITY AND DVORAK ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING BY A SUBTROPICAL RIDGE TO
THE DISTANT NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 97 KTS AT 290530Z
   CIMSS AIDT: 83 KTS AT 290530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-30 CELSIUS
   OUTFLOW: STRONG 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: THE SYSTEM IS EXPECTED TO CONTINUE
STRENGTHENING AT RAPID INTENSIFICATION (RI) LEVELS THROUGHOUT THE
DURATION OF ITS EXPECTED TRACK SLOWLY NORTHWESTWARD, PASSING
THROUGH THE LUZON STRAIT OVER EXCESSIVELY WARM SSTS AND FAVORABLE
VERTICAL WIND SHEAR VALUES OF 5-10 KTS. THE HIGH OCEAN HEAT CONTENT
VALUES ACROSS THE LUZON STRAIT ALLEVIATE CONCERN OF A DEPLETION OF
WARM WATER FUELING THE INTENSIFICATION. THE PERIOD OF STRENGTHENING
WILL LEVEL OFF BY TAU 48 DUE TO INCREASING LAND INTERACTION TAIWAN.
THE EXPECTED TRACK WILL CURVE SHARPLY TO THE NORTHEAST AND TAKE THE
CORE OF THE SYSTEM ACROSS THE SOUTHERN (HENGCHUN) PENINSULA OF
TAIWAN. A QUICK DECAY IN KRATHON'S STRENGTH WILL OCCUR NEAR TAU 72
AND AFTER. THE WIND FIELD, WHICH IS ALREADY EXTENSIVE FOR THIS
SYTEM, WILL GRADUALLY EXPAND WITH THE ONSET OF INTENSITY DECLINE.
TYPHOON KRATHON WILL BEGIN TO ACCELATE NORTHEASTWARD THROUGH THE
EAST CHINA SEA AS THE SUBTROPICAL RIDGE TO THE EAST LATCHES ON AS
THE DOMINANT STEERING INFLUENCE DRIVER. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS LARGELY
PREDICTING A NEARLY RIGHT-ANGLE TURN SOUTH OF TAIWAN WITH SOME OF
THE LESS RELIABLE MODELS PULLING THE CONSENSUS TOO FAR WEST AT THIS
PIVOT POINT. THERE IS GOOD AGREEMENT WITH A NORTHEASTWARD TRACK
FOLLOWING A POSSIBLE LANDFALL IN SOUTHERN TAIWAN NEAR TAU 60. THE
UNCERTAINTY REGARDING LANDFALL INTRODUCES A GREATER CHANCE FOR
TRACK ERRORS AFTER TAU 72 AND IS REFLECTED IN THE POOR AGREEMENT IN
INDIVIDUAL TRACKERS RUN-TO-RUN AND THEIR OVERALL CONSENSUS.
INTENSITY GUIDANCE IS SUPPORTIVE OF THE IMMEDIATE RAPID
INTENSIFICATION PERIOD. DEVELOPMENT BEGINS TO LEVEL OFF BY TAU 48,
WHEN THE NUMERICAL MODELS BEGIN TO ACCOUNT FOR THE LAND INTERACTION
NEAR TAIWAN. INTENSITY GUIDANCE IS IN GOOD AGREEEMENT WITH THE
TIMING AND RATE OF DECLINE THROUGH TAU 120. UNCERTAINTIES IN THE
FORECAST ARE DUE TO THE INITIAL INTENSITY UNCERTANTIES STEMMING
FROM LACK OF DATA AND ALSO DUE TO THE UNKNOWN EXTENT OF LAND
INTERACTION WITH TAIWAN.  

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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