WDPN31 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (NAKRI) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.7N 136.5E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 257 NM SOUTHEAST OF IWAKUNI
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 29W (NAKRI) WITH IMPROVING CIRCULATION WRAPPED BY DEEP 
CONVECTION. TY NAKRI CONTINUES TO STRENGTHEN AS WITNESSED BY
INCREASED RATE OF CONVECTION AND A COOLING TREND EVIDENT IN THE EIR.
THE TRANSLATION SPEED OF THE SYSTEM HAS REMAINED FAIRLY CONSISTENT
AS IT ROUNDS THE NORTHERN PERIPHERY OF A STR TO THE SOUTHEAST. TY
NAKRI HAS STARTED TO ENCOUNTER SLIGHTLY LESS FAVORABLE ENVIRONMENTAL 
CONDITIONS WITH VERTICAL WINDS SHEAR (VWS) INCREASING TO 10-15 KTS 
AND SEA SURFACE TEMPERATURES COOLING TO BETWEEN 27-28 C. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR AND A 121229Z 
METOP-C ASCAT DATA. THE INITIAL INTENSITY IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE AFOREMENTIONED SCATTEROMETRY DATA AND THE 
AGENCY FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: 121229Z METOP-C ASCAT DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.0 - 65 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TY NAKRI HAS CONTINUED TO TRACK NORTHEAST
UNDER THE INFLUENCE OF A STR TO THE SOUTHEAST. THE SYSTEM HAS
CONTINUED TO IMPROVE OVER THE PAST 6 HOURS AND WILL CONTINUE TO
IMPROVE TILL AROUND TAU 24 HAVING ACHIEVED A PEAK INTENSITY OF 75
KNOTS. SLIGHTLY DETERIORATING ENVIRONMENTAL CONDITIONS ARE NOT YET
SIGNIFICANT ENOUGH TO DEGRADE THE STRONG SYSTEM. EXPECTATION IS FOR
THE DRY AIR TO START WRAPPING INTO THE CORE WITHIN THE NEXT 24
HOURS. SIMULTANEOUSLY AROUND TAU 48, TY NAKRI WILL ENCOUNTER MORE
UNFAVORABLE WIND SHEAR (30-40 KTS) RESULTING IN A WEAKENING TREND
AND KICKING OFF EXTRATROPICAL TRANSITION (ETT), WHICH IS EXPECTED
TO CONCLUDE BY TAU 72.

MODEL DISCUSSION: MODEL CONSENSUS REMAINS IN TIGHT AGREEMENT ON THE
FORECASTED TRACK WITH A CROSS-TRACK SPREAD UNDER 40 NM TILL JUST
PAST TAU 48. THE JTWC FORECAST TRACK IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE HAS
ALSO COME INTO TIGHTER AGREEMENT WITH A PEAK INTENSITY OF 75 KNOTS
AROUND TAU 24 FOLLOWED BY A GRADUAL WEAKENING TREND. THE JTWC
FORECASTED INTENSITY IS PLACED SLIGHTLY ABOVE THAT OF THE MULTI-MODEL
CONSENSUS WITH CONSIDERATION FOR THE SLIGHTLY MORE AGGRESSIVE HAFS-A, 
WHICH ALSO MAINTAINS 50-60 KT WIND SPEEDS FOR A BIT LONGER THAN OTHER 
MODEL GUIDANCE. THE 72 HR FORECASTED INTENSITY IS THUS PLACED WITH 
MEDIUM CONFIDENCE.

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