WDPN33 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (NEOGURI) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.5N 153.1E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 381 NM NORTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON NEOGURI HAS BECOME ASYMMETRIC DURING THE PAST SIX HOURS AND
IS NOW A LOP-SIDED SYSTEM WITH SIGNIFICANTLY MORE DEEP MOISTURE AND
STRONGER WINDS OVER THE EASTERN SEMICIRCLE. THE FORMER EYE IS CLOUD
FILLED BUT STILL DISCERNABLE. ALTHOUGH NO DRY AIR IS GETTING INTO
THE CORE, DRY NORTHERLIES ARE FLOWING ALONG THE WESTERN SIDE OF THE
SYSTEM AND CONFINING THE FAVORABLE ENVIRONMENT TO A NARROW
CORRIDOR. THE SYSTEM IS TRAPPED BETWEEN A SPLIT SUBTROPICAL RIDGE,
WITH THE WESTERN EXTENSION CURRENTLY DOMINATING. THE LAST FIVE FIXES
HAVE SHOWN A MOVEMENT TO THE EAST-NORTHEAST, WHEREAS YESTERDAY THE
SYSTEM WAS TRACKING NORTHWEST. UPWELLING CAUSED BY SLOW MOVEMENT
BETWEEN THE COMPETING STEERING FORCES HAS BECOME THE PRIMARY
WEAKENING FORCE. A DEEP SHORT WAVE TROF TRACKING OVER THE TOP OF
THE SYSTEM IS ENHANCING POLEWARD OUTFLOW BUT THE GRADIENT 
LEVEL BAROCLINIC ZONE IS DISPLACED FAR POLEWARD, LEAVING TYPHOON 
NEOGURI TRAPPED IN A NARROW ENVIRONMENT SURROUNDED BY DRY AIR. THE
INTENSITY IS ASSESSED BY THE JTWC DVORAK OF T4.5 AND RAISED
SLIGHTLY DUE TO A 221959Z SAR PASS SHOWING VALUES RANGING FROM 80 TO 
90 KTS IN THE POLEWARD EYEWALL. THE PARTIAL SAR IMAGE IS FACTORED INTO 
THE INTENSITY ASSESSMENT BUT DISCOUNTED SLIGHTLY DUE TO MUCH LOWER
DVORAKS AND OBJECTIVE ASSESSMENTS.

INITIAL WIND RADII BASIS: A 221959Z SAR IMAGE AND A 222236Z ASCAT
IMAGE. 

CURRENT STEERING MECHANISM: THE SYSTEM IS CURRENTLY BEING FORCED
EASTWARD BY AN EASTERN EXTENSION OF A SPLIT SUBTROPICAL RIDGE, WITH
THE WESTERN PORTION OF THE RIDGE SETTLED OVER THE DATELINE. THE TWO
RIDGES WILL COMPETE FOR INFLUENCE OVER THE NEXT 72 HOURS.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 70 KTS AT 222322Z
   CIMSS ADT: 63 KTS AT 222020Z
   CIMSS AIDT: 73 KTS AT 222020Z
   CIMSS D-MINT: 69 KTS AT 222310Z
   CIMSS D-PRINT: 55 KTS AT 230140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: UPWELLING DUE TO THE SLOW MOVEMENT OF THE SYSTEM
AND DRY AIR ALONG THE WESTERN SEMICIRCLE.  

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: THE WESTERN SUBTROPICAL RIDGE BUILDING OVER
JAPAN WILL CONTINUE TO SHOVE NEOGURI EASTWARD THROUGH THE NEXT 48
HOURS.  AFTER THAT THE EASTERN RIDGE, ANCHORED IN A H500
ANTICYCLONE OVER THE DATELINE NEAR 36N, WILL BUILD IN AND SHOVE THE
SYSTEM BACK TO THE WEST, RESULTING IN A CHECK-MARK PATTERN ON THE
TRACK. UPWELLING WILL GRADUALLY ERODE THE SYSTEM TO BELOW TYPHOON
STRENGTH AS IT TURNS TO THE WEST. ONCE THE SYSTEM TRACKS NORTH OF
THE RIDGE AXIS, IT WILL ROLL OVER AND TRACK NORTHEAST IN A TYPICAL
RECURVATURE SCENARIO. EXTRA-TROPICAL TRANSITION WILL BE AN
INORDINATELY SLOW PROCESS HOWEVER, DUE TO THE FAR POLEWARD
DISPLACEMENT OF THE BAROCLINIC ZONE. INTERACTION WITH THE POLAR
FRONT JET WILL NOT BE STRONG UNTIL THE VORTEX TRACKS NORTH OF THE
40TH LATITUDE. AS THE SYSTEM ENTERS ITS TERMINAL LEG TO THE
NORTHEAST, DRY AIR ENTRAINMENT WILL BECOME THE DOMINANT CAUSE OF
WEAKENING. THE EXTRA-TROPICAL TRANSITION PROCESS WILL BE GRADUAL
AND NOT COMPLETED UNTIL BEYOND THE END OF THE FORECAST PERIOD. 

MODEL DISCUSSION: TRACK GUIDANCE HAS BEEN COMING INTO MUCH BETTER
AGREEMENT AND THE SCENARIO OF A WESTWARD TRACK HAS ALL BUT
DISAPPEARED, LENDING MUCH GREATER CONFIDENCE TO THE TRACK FORECAST. 
THE INTENSITY GUIDANCE HAS ALSO COME INTO ALIGNMENT, SHOWING A STEADY 
DECLINE UNTIL THE SYSTEM BEGINS TO INTERACT WITH THE POLAR FRONT IN 
THE EXTREME LATE PERIOD OF THE FORECAST. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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