WDPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MINDULLE) WARNING NR 031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.7N 136.4E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 543 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND WATER VAPOR
IMAGERY CONFIRM THAT TYPHOON 20W IS ON AN IRREDEEMABLE WEAKENING
TREND. CLOUD TOPS ARE WARMING AND THE LARGE 40NM EYE IS TAKING ON
AN IRREGULAR SHAPE AND BECOMING CLOUD FILLED. THE SYSTEM HAS
TRACKED NORTHEAST AT AN INCREASING SPEED OF ADVANCEMENT (S.O.A.) 
FOR TWO CONSECUTIVE FIX
CYCLES AND IS TRACKING THROUGH A REGION OF STEADILY DECREASING SEA
SURFACE TEMPERATURES. BOTH SUBJECTIVE AND OBJECTIVE DVORAK
ESTIMATES ARE ON A CLEAR DOWNWARD TREND AND DRY AIR FEEDING INTO
THE SYSTEM FROM THE NORTH IS NOW WRAPPING ALL THE WAY AROUND TO THE
NORTHEASTERN QUADRANT. THE INITIAL INTENSITY ASSESSMENT IS BASED ON
A COMBINATION OF AGENCY DVORAKS, ADT, AND SATCON, WHICH ONLY VARY
FROM 99KTS TO 104KTS. OBSERVATIONS FROM KITA DAITO JIMA CONFIRM
WHAT THE RADIUS OF GALE FORCE WINDS AT ANALYSIS TIME WAS CORRECT,
AT LEAST OVER THE WESTERN SEMICIRCLE.

INITIAL WIND RADII BASIS: PERSISTENCE. 

CURRENT STEERING MECHANISM: A HIGH AMPLITUDE RIDGE OVER THE
MARIANAS ANCHORED BY A 5910M 500MB HEIGHT CENTER JUST NORTHEAST OF
SAIPAN AND HEIGHT FALLS ALONG THE 135TH MERIDIAN. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 104 KTS AT 300010Z
   CIMSS ADT: 99 KTS AT 292340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 HAS ROLLED OVER TO THE NORTHEAST
AND IS TRANSITING INTO THE MIDDLE LATITUDES AT A LEISURELY PACE DUE
TO WEAK STEERING FORCES. A WEDGE OF DRIER TROPICAL AIR OVER THE
RYUKUS IS SEPARATING THE STORM FROM THE MID-LATITUDE WESTERLIES,
MAKING FOR A SLOWER-THAN-USUAL PACE OF EXTRA-TROPICAL TRANSITION.
PHASE-BASED DIAGRAMS INDICATE THAT THE SYSTEM WILL MAINTAIN ITS
WARM CORE EVEN AFTER DEVELOPING THE FRONTAL
CHARACTERISTICS OF A WARM OCCLUSION (A SECLUSION AS OPPOSED TO AN
OCCLUSION). THE PROCESS WILL BE WELL UNDERWAY AS THE SYSTEM TRACKS
SEAWARD OF THE KANTO PLAIN. COUPLED MODELS INDICATE THAT 20W HAS
SEEN ITS WARMEST WATERS AND WILL TRACK THROUGH PROGRESSIVELY COOLER
SEA WATERS, ALTHOUGH SEA SURFACE TEMPERATURES REMAIN ABOVE 27C UP
THROUGH THE 30TH LATITUDE. DESPITE THE SUBSTANTIATIVE SURFACE
TEMPERATURES, HOWEVER, OCEAN HEAT CONTENT FALLS DRAMATICALLY AFTER
TAU 36. THE EXTRA-TROPICAL TRANSITION PERIOD WILL COMMENCE BY TAU
24 BUT WILL NOT BE FULLY COMPLETE UNTIL ABOUT TAU 54, HENCE THE
EXTENDED TRACK THROUGH TAU 72. 
 

MODEL DISCUSSION: TRACK GUIDANCE HAS BEEN OUTSTANDING AND INTENSITY
GUIDANCE HAS BEEN EXCELLENT DURING THIS STORM. WITH EACH
SUCCESSIVE RUN, THE GUIDANCE TIGHTENS EVEN FURTHER. THE JTWC TRACK
FORECAST STAYS STRAIGHT ON THE MULTI-MODEL CONSENSUS. THE INTENSITY
FORECAST STAYS 5-10 KTS ABOVE CONSENSUS AS ACTUAL INTENSITY HAS
BEEN SLIGHTLY ABOVE GUIDANCE FOR THE PAST 48 HOURS. 


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