WDPN31 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (MERBOK) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.0N 162.2E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 522 NM NORTH-NORTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTIVE BANDING WRAPPING CYCLONICALLY AROUND A CONSOLIDATED
LOW-LEVEL CIRCULATION CENTER (LLCC). A 131712Z GMI 89GHZ MICROWAVE
IMAGE REVEALS CONVECTIVE BANDING IN ALL QUADRANTS WRAPPING INTO A
WELL DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON RECENT SATELLITE
FIXES FROM PGTW, KNES AND RJTD, AS WELL AS 121712Z 37GHZ IMAGERY
SHOWING A LOW-LEVEL MICROWAVE EYE FEATURE. THE INITIAL INTENSITY OF
65 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON RECENT AUTOMATED
AND SUBJECTIVE DVORAK INTENSITY ESTIMATES AS WELL AS RECENT AMSR2
PASS COVERING THE EASTERN PORTION OF THE CIRCULATION. ADDITIONALLY,
VERTICAL WIND SHEAR IS LOW ALONG WITH WARM SST (29-30C) VALUES
WHICH ARE FAVORABLE FOR FURTHER INTENSIFICATION AND DEVELOPMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUB-TROPICAL
RIDGE (STR) TO THE EAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   CIMSS SATCON: 62 KTS AT 131300Z
   CIMSS ADT: 55 KTS AT 131430Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TYPHOON 15W WILL CONTINUE TO TRACK POLEWARD ON 
THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST
THROUGH TAU 12. BY TAU 24, THE SYSTEM WILL BEGIN TO TURN AND
TRACK NORTH-NORTHEAST FOR THE REMAINDER OF THE FORECAST PERIOD
FOLLOWING THE FLOW OF THE SUBTROPICAL RIDGE TO THE EAST. AS THIS
TAKES PLACE, STEADY INTENSIFICATION WILL LIKELY CONTINUE FOR THE
NEXT 36 HOURS AS THE SYSTEM TRANSITS IN FAVORABLE ENVIRONMENTAL
FACTORS CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES (SST)
(28-29C), LOW VERTICAL WIND SHEAR AND A OUTFLOW PATTERN WHICH IS
GENERALLY SUPPORTIVE. THEREAFTER, SST VALUES WILL BEGIN COOLING
ALONG-TRACK AND INCREASING VERTICAL WIND SHEAR (VWS) ASSOCIATED
WITH A MID-LATITUDE TROUGH APPROACHING FROM THE NORTHWEST WILL
INDUCE WEAKENING. BY TAU 48, TYPHOON 15W WILL BECOME FULLY EMBEDDED
IN THE AFOREMENTIONED TROUGH INDUCING BAROCLINIC INTERACTION AND
COMPLETE EXTRATROPICAL TRANSITION.

MODEL DISCUSSION: NUMERICAL MODEL TRACK FORECASTS REMAIN IN TIGHT
AGREEMENT THROUGH THE ENTIRETY OF THE FORECAST PERIOD. FOR THIS
REASON THE JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE IS IN FAIR AGREEMENT AS WELL, THE BULK OF THE
GUIDANCE AGREES ON THE TIMING OF THE INTENSIFICATION PERIOD, ALONG
WITH HIGH EXTRATROPICAL TRANSITION INTENSITY. THEREFORE, THE JTWC
FORECAST INTENSITY IS PLACED WITH MEDIUM CONFIDENCE.


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