WDPN31 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 02W (SEPAT) WARNING 
NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.7N 141.4E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 86 NM EAST-NORTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL DEPRESSION
(TD) 02W (SEPAT). THE SYSTEM IS COMPACT, WITH SPIRAL BANDS OF DEEP
CONVECTION WRAPPING INTO THE CENTER, HOWEVER CONVECTION IS SHALLOW
AND DOES NOT PERSIST FOR TOO LONG. ENVIRONMENTAL CONDITIONS ARE
BECOMING INCREASINGLY UNFAVORABLE FOR TROPICAL DEVELOPMENT. AS THE
SYSTEM MOVES POLEWARD AND EASTWARD, SEA SURFACE TEMPERATURES (SST)
ARE DECREASING, AND ARE CURRENTLY BELOW 23 C. VERTICAL WIND SHEAR
(VWS) IS ALSO INCREASING AND IS CURRENTLY ANALYZED AS MODERATE
(15-20 KTS). ADDITIONALLY, TD 02W IS CURRENTLY UNDERGOING AN 
EXTRATROPICAL TRANSITION, WHILE POSITIONED AHEAD OF AN INCOMING DEEP-
LAYER TROUGH FROM THE WEST. THE INITIAL POSITION OF THE SYSTEM IS 
DETERMINED WITH HIGH CONFIDENCE BASED ON THE CLEAR LLCC VISIBLE IN 
SATELLITE IMAGERY. THE INITIAL INTENSITY IS ESTIMATED AT 25 KNOTS WITH 
MEDIUM CONFIDENCE, SUPPORTED BY BOTH AGENCY DVORAK ESTIMATES AND 
AUTOMATED ANALYSIS TOOLS.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS ADT: 32 KTS AT 252030Z
   CIMSS AIDT: 39 KTS AT 252030Z
   CIMSS D-MINT: 27 KTS AT 252043Z
   CIMSS D-PRINT: 27 KTS AT 252250Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 22-23 CELSIUS
   OUTFLOW: WEAK RADIAL
   OTHER FACTORS: SYSTEM IS UNDERGOING AN EXTRATROPICAL TRANSITION

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD SEPAT HAS CROSSED THE AXIS OF A STR TO THE
SOUTHEAST AND THE FORECAST TRACK INDICATES THAT THE SYSTEM WILL 
FURTHER ACCELERATE NORTHEASTWARD ALONG THE NORTHWESTERN EDGE OF THE 
RIDGE AND AWAY FROM MAINLAND JAPAN. AS THE SYSTEM CONTINUES TO 
INTERACT WITH THE BAROCLINIC ZONE, IT IS FORECAST TO SLOWLY INTENSIFY, 
DRIVEN BY THE BAROCLINIC FORCING. THE SYSTEM IS FORECAST TO COMPLETE 
THE EXTRATROPICAL TRANSITION WITHIN THE NEXT 24 HOURS.

MODEL DISCUSSION: JTWC TRACK FORECAST CARRIES HIGH CONFIDENCE, AS
NUMERICAL MODEL GUIDANCE IS CLOSELY ALIGNED, WITH A CROSS-TRACK
SPREAD OF 60 NM BY TAU 24. HOWEVER, THERE IS SOME UNCERTAINTY
ASSOCIATED WITH THE ACCELERATION RATE OF THE SYSTEM, AS INDICATED
BY THE ALONG-TRACK GUIDANCE SPREAD OF 90 NM AT THE END OF THE
FORECAST PERIOD. THE INTENSITY FORECAST IS GIVEN MEDIUM CONFIDENCE.
WHILE ALL AVAILABLE MODELS SUGGEST STRENGTHENING THROUGH TAU 24, THE 
DEGREE OF INTENSIFICATION DIFFERS AND THE SPREAD IS 15-20 KTS BETWEEN 
THE MOST CONSERVATIVE HAFS, AND MOST AGGRESSIVE STATISTICAL-DYNAMICAL
MODEL. THE JTWC INTENSITY FORECAST CLOSELY FOLLOWS THE MULTI-MODEL
CONSENSUS.

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