WDPN33 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (NEOGURI) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.5N 152.8E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 383 NM NORTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON NEOGURI IS A LOP-SIDED SYSTEM WITH SIGNIFICANTLY MORE DEEP
MOISTURE AND STRONGER WINDS OVER THE SOUTHEASTERN AND NORTHEASTERN
QUADRANTS. 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 TWO SEPARATE MANIFESTATIONS OF THE SUBTROPICAL RIDGE, WITH
THE WESTERN EXTENSION CURRENTLY DOMINATING. THE LAST FOUR FIXES
HAVE SHOWN A MOVEMENT TO THE NORTHEAST, WHEREAS YESTERDAY THE
SYSTEM WAS TRACKING NORTHWEST. THE COMPETING STEERING FORCES HAVE
RESULTED IN SLOW MOVEMENT THAT CAUSED UPWELLING AND WEAKENED THE 
STORM BY 30KTS DURING THE PAST 24 HOURS. A DEEP SHORT WAVE TROF IS 
APPROACHING THE SYSTEM AND ENHANCING POLEWARD OUTFLOW BUT THE GRADIENT 
LEVEL BAROCLINIC ZONE IS DISPLACED FAR POLEWARD, LEAVING TYPHOON 
NEOGURI TRAPPED IN A NARROW ENVIRONMENT AND FLANKED BY DRY AIR ON THE 
WESTERN SIDE. THE INTENSITY IS ASSESSED BY THE JTWC DVORAK OF T4.5 AND 
RAISED SLIGHTLY DUE TO DMINT OF 81KTS AND SATCON AT 86KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: AT THE MOMENT THE SYSTEM IS 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: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 86 KTS AT 221527Z
   CIMSS ADT: 67 KTS AT 221730Z
   CIMSS AIDT: 76 KTS AT 221730Z
   CIMSS D-MINT: 81 KTS AT 221527Z
   CIMSS D-PRINT: 67 KTS AT 221930Z

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.


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: THE EASTERN RIDGE WILL CONTINUE TO SHOVE NEOGURI
EASTWARD THROUGH THE NEXT 48 HOURS.  AFTER THAT THE WESTERN RIDGE WILL
BUILD IN AND SHOVE THE SYSTEM BACK TO THE WEST, RESULTING IN THE
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 NEAR TAU 48, IT WILL ROLL
OVER AND TRACK NORTHEAST IN A TYPICAL RECURVATURE SCENARIO. UPWELLING 
WILL ACT TO WEAKEN THE SYSTEM FOR THE FIRST 48 HOURS, THEN DRY AIR 
ENTRAINMENT WILL BECOME THE DOMINANT FORCE TO WEAKEN THE SYSTEM AFTER 
THAT. THE EXTREME POLEWARD DISPLACEMENT OF THE BAROCLINIC ZONE, 
HOWEVER, ILL DELAY THE EXTRA-TROPICAL TRANSITION PROCESS UNTIL VERY 
LATE IN THE FORECAST PERIOD. 

MODEL DISCUSSION: THE BIFURCATED TRACK GUIDANCE THAT HAD BEEN
REDUCING CONFIDENCE IN THE TRACK IS NO LONGER AN ISSUE, LENDING
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: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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