WDPN33 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (KRATHON) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.9N 119.4E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 224 NM SOUTH-SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAGGED EYE
FEATURED THAT IS CLOUD-FILLED AND COMPLETELY EXPOSES THE LOW-LEVEL
CIRCULATION CENTER (LLCC). THE ERRATIC AND QUASI-STATIONARY MOTION
HAS CONTINUED TO UPWELL COOLER WATER BELOW 26C. THE COOL WATER IS
PRIMARILY DRIVING THE GRADUAL WEAKENING TREND WHILE THE ENVIRONMENT
IS OTHERWISE FAVORABLE FOR INTENSIFICATION. UPPER-LEVEL OUTFLOW
REMAINS EQUATORWARD BUT MODERATE INTO DIFFLUENT NORTHEASTERLY FLOW.
AN EARLIER 020212Z METOP-C ASCAT IMAGE IN BETWEEN VALID TIMES
SUPPORTS THE CURRENT TRACK POSITION AND ASSISTED IN IDENTIFYING THE
WIND RADII. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE AFOREMENTIONED MSI AND SCATTEROMETRY. THE INITIAL
INTENSITY OF 100 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
SUBTROPICAL RIDGES TO THE EAST AND WEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T6.0 - 115 KTS
   CIMSS SATCON: 106 KTS AT 020211Z
   CIMSS ADT: 99 KTS AT 020530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TYPHOON (TY) 20W WILL REMAIN IN A COMPETING
STEERING ENVIRONMENT FOR THE NEXT 24 HOURS AS IT REMAINS PINNED
BETWEEN TWO SUBTROPICAL RIDGES TO THE EAST AND WEST. DURING THIS
TIME, THE MOTION WILL CONTINUE TO BE ERRATIC BUT OVERALL
NORTHEASTWARD. AFTER LANDFALL BETWEEN TAU 12-24, THE EASTERN RIDGE
WILL PULL THE TYPHOON NORTHEASTWARD OVER THE MOUNTAINOUS TERRAIN OF
TAIWAN. THE SYSTEM WILL CONTINUE TO GRADUALLY WEAKEN TO 90KTS
BEFORE LANDFALL AS COOLER WATERS RISE TO THE SURFACE DUE TO THE
SLOW STORM MOTION. AFTER THE SYSTEM MAKES LANDFALL, THE INTENSITY
WILL DROP STARKLY DUE TO TOPOGRAPHIC INTERACTION WHILE TY 20W
PASSES OVER TAIWAN. ULTIMATELY, THE SYSTEM WILL DISSIPATE OVER LAND
BY TAU 72.

MODEL DISCUSSION: DETERMINISTIC MODEL AGREEMENT HAS IMPROVED OVER
THE LAST SIX HOURS. GFS, WHICH IN PREVIOUS RUNS WAS AN OUTLIER WITH
A WESTWARD TRACK, NOW ALIGNS WITH THE OVERALL NORTHEASTWARD TRACK
WITH THE BULK OF THE JTWC MULTI-MODEL CONSENSUS MEMBERS.
NEVERTHELESS, THERE IS STILL A LARGE SPREAD ACROSS MODEL SOLUTIONS
AFTER LANDFALL DUE TO VARIABILITY IN THE TRACK AS THE SYSTEM
INTERACTS WITH LAND. THE JTWC FORECAST LIES CLOSELY TO THE
CONSENSUS MEAN FOR THE FIRST 48 HOURS AND EAST OF THE MEAN AT TAU
72. THE INTENSITY GUIDANCE IS IN TIGHT AGREEMENT AND HAS A
CONSISTENT TREND OF GRADUAL WEAKENING ACROSS ALL CONSENSUS MEMBERS.

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