WDPN33 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (NEOGURI) WARNING NR 
034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.6N 154.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 445 NM NORTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM NEOGURI HAS MOVED SOUTHEASTWARD FOR TWO CONSECUTIVE
FIXES, CONFIRMING THAT IT IS ENTERING ITS TERMINAL LEG AND
BEGINNING A LONG SLOW RUN TOWARDS EXTRA-TROPICAL TRANSITION
(ETT). THE SYSTEM IS NOW POLEWARD OF THE SUBTROPICAL RIDGE AXIS AND
BEGINNING TO RIDE THE NORTHWESTERN FLANK OF THE SUBTROPICAL RIDGE,
WHICH IS ANCHORED IN AN ANTICYCLONE CENTERED OVER THE DATELINE.
MOVEMENT IS STILL SLOW BUT INCREASING, AND IT HAS INCREASED ENOUGH
TO LEAVE BEHIND THE UPWELLING THAT WAS LIMITING DEVELOPMENT. 
ALTHOUGH ANIMATED ENHANCED INFRARED IMAGERY REVEALS A LOP-SIDED
SYSTEM WITH THE MAJORITY OF THE DEEP CONVECTION OVER THE SOUTHEAST
QUADRANT, A 261509Z AMSR2 SERIES SHOWS THAT CONVECTIVE BANDING
STILL ENCIRCLES THE LOW LEVEL CIRCULATION CENTER (LLCC). THERE IS,
HOWEVER, SUBSTANTIAL SUPPRESSION OF THE BANDING ALONG THE WESTERN
HEMISPHERE OF THE SYSTEM. VENTING TO THE NORTHEAST IS EVIDENT IN
THE WATER VAPOR ANIMATION AND IS HELPING TO KEEP THE SYSTEM
VIGOROUS. AGENCY FIXES FROM PGTW, RCTP, AND RJTD ARE REMARKABLY TIGHT
IN LOCATION CONSIDERING THE DIFFICULTIES ASSOCIATED WITH NIGHT TIME
FIXING IN INFRARED IMAGERY. THE INTENSITY IS ASSESSED PRIMARILY
ON THE AGENCY DVORAKS, WHICH ARE AT OR NEAR 55KTS, AND THEN TWEAKED
DOWNWARDS A NOTCH IN CONSIDERATION OF A 26119Z ASCAT PARTIAL AND AN
EARLIER SAR PASS AND A 51KT SATCON ASSESSMENT.

INITIAL WIND RADII BASIS: PERSISTENCE FROM A 260739Z SAR IMAGE.

CURRENT STEERING MECHANISM: THE WESTERN FLANK OF A SPLIT
SUBTROPICAL RIDGE, WHICH IS ANCHORED IN 5990M H500 QS OVER THE
DATELINE AND 34N. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 52 KTS AT 261552Z
   CIMSS ADT: 39 KTS AT 261730Z
   CIMSS AIDT: 56 KTS AT 261730Z
   CIMSS D-MINT: 44 KTS AT 261552Z
   CIMSS D-PRINT: 50 KTS AT 261830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TROPICAL STORM NEOGURI WILL ACCELERATE TO THE
NORTHEAST. BECAUSE THE BAROCLINIC ZONE IS POLEWARD OF THE 40TH
LATITUDE,  IT WILL BE SOME TIME BEFORE THE EXTRA-TROPICAL TRANSITION
PROCESS BEGINS, BUT WITH THE PATTERN AMPLIFYING AND THE BAROCLINIC
ZONE DROPPING EQUATORWARD, THE PROCESS SHOULD BE UNDERWAY BY TAU
36, AS THE VORTEX CROSSES 35N. UNTIL THEN, THE SYSTEM WILL INTENSIFY
SHARPLY DUE TO THE WARM WATERS AND EXCELLENT POLEWARD OUTFLOW,
REACHING LOW TYPHOON STRENGTH. THE ETT PROCESS WILL BE GRADUAL AND
WILL NOT BE FULLY COMPLETED UNTIL THE VORTEX CROSSES THE 40TH
LATITUDE, WHERE IT WILL BECOME A HIGH-STORM FORCE TO LOW-TYPHOON
FORCE MID-LATITUDE STORM.    

MODEL DISCUSSION: TRACKERS ARE TIGHT AND THERE IS VERY LITTLE
ALONG-TRACK SPREAD DESPITE THE ACCELERATION. INTENSITY GUIDANCE IS
ALSO UNANIMOUS IN SHOWING A STEEP INTENSIFICATION THROUGH THE FIRST
36 HOURS, WITH SOME AIDS INCLUDING HAFS-A REACHING 90KTS NEAR TAU
36. THE JTWC INTENSITY FORECAST FOLLOWS THE SAME TREND BUT LIMITS
THE PEAK TO LOW TYPHOON STRENGTH.  

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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