WDPN33 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (KRATHON) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.5N 119.3E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 248 NM SOUTH-SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EYE THAT
REMAINS WELL-DEFINED ON VISIBLE AND IR IMAGERY, BUT THE SURROUNDING
EYEWALL HAS BECOME WARMER AND MORE FRAGMENTED OVER THE PAST SIX
HOURS IN BOTH IR IMAGERY AND MICROWAVE OVERPASSES FROM SSMIS AT
012252Z AND WSF-M AT 012247Z. NUMERICAL OCEAN MODELING FROM MOM6
COUPLED TO HAFS-A CONTINUES TO SHOW THAT DYNAMIC OCEAN COOLING IS
LIKELY ONGOING BENEATH THE STORM, WHICH CONTINUES TO BE NEARLY
STATIONARY, AND THIS IS LIKELY THE PRIMARY DRIVER OF THE ONGOING
WEAKENING TREND. THE ENVIRONMENT IS OTHERWISE FAVORABLE WITH LIGHT
VERTICAL SHEAR AND DEEP MOISTURE. THE INITIAL INTENSITY IS LOWERED
TO 100 KT BASED ON A BLEND OF AGENCY DVORAK ESTIMATES AND OBJECTIVE
SATELLITE-BASED INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.5 - 127 KTS
   CIMSS ADT: 104 KTS AT 012330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON 20W (KRATHON) CONTINUES TO BE NEARLY
STATIONARY SOUTHWEST OF TAIWAN, LEADING TO DYNAMIC OCEAN COOLING
BENEATH THE STORM ACCORDING TO NUMERICAL OCEAN MODELING. THIS IS
LIKELY DRIVING THE ONGOING WEAKENING TREND AS THE INNER CORE
GRADUALLY LOSES ITS FUEL SOURCE. COMBINED WITH INCREASING PROXIMITY
TO TAIWAN, THIS IS EXPECTED TO CAUSE STEADY WEAKENING OVER THE NEXT
12-24 HOURS AS KRATHON SLOWLY APPROACHES TAIWAN. THE TRACK FORECAST
REMAINS CHALLENGING AS KRATHON REMAINS MIRED BETWEEN RIDGES TO ITS
WEST AND EAST, RESULTING IN WEAK STEERING CURRENTS. DYNAMICAL
MODELS REMAIN DIVERGENT IN THEIR HANDLING OF THE WEAKENING TYPHOON,
WITH MOST TAKING IT NORTHEASTWARD OVER TAIWAN, WHILE THE GFS AND
ABOUT 60 PERCENT OF THE GFS ENSEMBLE MEMBERS ARE TURNING IT
SOUTHWESTWARD AWAY FROM TAIWAN AS IT BECOMES EMBEDDED IN THE
NORTHEASTERLY COOL SURGE BELT FUNNELING THROUGH THE TAIWAN
STRAIGHT. THE JTWC FORECAST CONTINUES TO ASSESS THE GFS SOLUTION AS
AN OUTLIER AND FOLLOWS THE BULK OF THE GUIDANCE INLAND OVER TAIWAN
WITHIN 24 HOURS, CONTINUING A NORTHEASTWARD OR NORTHWARD CRAWL
THROUGHOUT THE 96-HOUR FORECAST PERIOD. A MULTI-DAY PERIOD OVER THE
TAIWANESE TOPOGRAPHY WOULD LEAD TO RAPID WEAKENING, THOUGH WINDS TO
THE WEST AND NORTH OF THE STORM CENTER MAY REMAIN ELEVATED DUE TO
THE NEARBY NORTHEASTERLY SURGE EVENT, ESPECIALLY IN THE TAIWAN
STRAIGHT. THE JTWC FORECAST SHOWS DISSIPATION BY 96 HOURS, AS THE
CIRCULATION WILL LIKELY OPEN UP AND BECOME ABSORBED INTO THE
BROADER NORTHEASTERLY SURGE FLOW AND FRONTAL ZONE. IT IS ALSO
POSSIBLE THAT DISSIPATION COULD OCCUR SOONER THAN 96 HOURS. GIVEN
THE WEAK STEERING CURRENTS AND HIGH MODEL TRACK SPREAD, THERE IS
LOWER THAN AVERAGE CONFIDENCE IN THE TRACK FORECAST. THE INTENSITY
FORECAST CONFIDENCE HAS BEEN INCREASED TO MEDIUM DUE TO INCREASING
MODEL AGREEMENT THAT INTERACTION WITH TAIWAN AND THE NORTHEASTERLY
SURGE EVENT WILL LEAD TO DRAMATIC WEAKENING OF THE STORM.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO A BLEND OF
THE ECMWF, ECMWF ENSEMBLE MEAN, HAFS-A, AND THE CLUSTER OF GFS
ENSEMBLE MEMBERS WHICH TRACK OVER TAIWAN. THE JTWC INTENSITY
FORECAST IS CLOSE TO THE MULTI-MODEL CONSENSUS.

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