WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (SEPAT) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.3N 141.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 366 NM SOUTH OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: 
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT,
WITH SYMMETRICAL LOW-LEVEL BANDING FEATURES WRAPPING INTO A DEFINED 
LOW LEVEL CIRCULATION CENTER (LLCC). CONVECTIVE ACTIVITY HAS WANED 
SIGNIFICANTLY OVER THE LAST HOUR OR TWO, WITH THE LLCC ONCE AGAIN 
BECOMING EXPOSED. ANIMATED WATER VAPOR IMAGERY SHOWS THAT THE UPPER-
LEVEL OUTFLOW IS CONSTRAINED TO THE SOUTHWEST, PINCHED BETWEEN 
NORTHERLY FLOW COMING SOUTHWARD FROM JAPAN AND STRONG SOUTHERLY FLOW 
EMANATING NORTHWARD OUT OF THE TUTT-CELL TO THE SOUTHWEST. A 240138Z 
GMI MICROWAVE PASS REVEALS WEAK AND SCATTERED DEEP CONVECTIVE 
ACTIVITY, WHILE THE 37GHZ CHANNEL REVEALS SOLID LOW-LEVEL BANDING 
FEATURES AND A DEFINED CENTER. COMPARISON OF THE TWO CHANNELS REVEALS 
SIGNIFICANT VORTEX TILT, NORTHWARD WITH HEIGHT, DUE TO THE INCREASING 
SOUTHERLY SHEAR. THE INITIAL POSITION, IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE ANIMATED MSI AND EXTRAPOLATION TO THE LLCC 
DEFINED IN THE AFOREMENTIONED MICROWAVE IMAGERY. THE INITIAL 
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE 
AND OBJECTIVE INTENSITY ESTIMATES OUTLINED ABOVE. THE ENVIRONMENT IS 
BECOMING INCREASINGLY HOSTILE, WITH SHEAR INCREASING AND OUTFLOW 
DECREASING AS THE SYSTEM TRACKS NORTHWARD, OFFSETTING THE FAVORABLE 
OCEAN ENVIRONMENT.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER THE NORTHERN PACIFIC.

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 42 KTS AT 232223Z
   CIMSS ADT: 33 KTS AT 232020Z
   CIMSS AIDT: 37 KTS AT 232020Z
   CIMSS D-MINT: 39 KTS AT 232114Z
   CIMSS D-PRINT: 37 KTS AT 240100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: WEAK WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TS 02W IS ANTICIPATED TO CONTINUE TRACKING
TOWARDS THE NORTHWEST AT A STEADILY DECREASING SPEED AS IT
APPROACHES THE STR AXIS OVER THE NEXT 24 HOURS. THE SYSTEM IS
EXPECTED TO REACH THE RIDGE AXIS BY TAU 24, AND THEREAFTER WILL
ACCELERATE NORTHEASTWARD ALONG THE NORTHWESTERN SIDE OF THE RIDGE 
THROUGH THE REMAINDER OF THE FORECAST PERIOD. TS 02W IS EXPECTED TO 
BRUSH THE EASTERN COAST OF THE BOSO PENINSULA BETWEEN TAUS 36 AND 48 
AS IT ACCELERATES NORTHEASTWARD. DUE TO INCREASING CONVERGENCE ALOFT 
AS WELL AS INCREASING SHEAR, TS 02W IS FORECAST TO WEAKEN OVER THE 
NEXT 12 HOURS, THEN MAINTAIN THAT INTENSITY AS IT APPROACHES EASTERN 
HONSHU. THE SYSTEM CROSSES THE 26C ISOTHERM BY TAU 36 AS A WEAK 
TROPICAL STORM, JUST BEGINNING THE EARLY PHASES OF EXTRATROPICAL 
TRANSITION (ETT). AS THE SYSTEM REACHES CPA TO YOKOSUKA, IT WILL 
BEGIN INTERACTING WITH THE DIVERGENT REGION AHEAD OF A NEGATIVELY 
TILTED MAJOR SHORTWAVE TROUGH APPROACHING FROM THE WEST. THE RAPID 
INCREASE IN OUTFLOW ALOFT, COUPLED WITH SOME BAROCLINIC FORCING, WILL 
RESULT IN AN INCREASE IN INTENSITY AS THE SYSTEM UNDERGOES ETT TO THE 
NORTHEAST OF TOKYO. TS 02W IS FORECAST TO COMPLETE ETT SHORTLY AFTER 
TAU 48 AS IT MOVES INTO PHASE WITH THE MAJOR SHORTWAVE TROUGH AND 
BEGINS TO DEVELOP FRONTAL CHARACTERISTICS.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT, WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD THROUGH TAU 
48. MODEL SPREAD INCREASES AFTER TAU 48, DURING THE ETT AND RECURVE 
PHASE, UP TO APPROXIMATELY 200NM BY THE END OF THE FORECAST. THE JTWC 
FORECAST REMAINS CONSISTENT WITH THE PREVIOUS TRACK AND THE ECMWF 
TRACKER, PLACED WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS MIXED, 
WITH BOTH DECAY-SHIPS MODELS INDICATING INTENSIFICATION THROUGH TAU 
48, WHILE THE REMAINDER OF THE GUIDANCE PACKAGE INDICATES WEAKENING 
THROUGH 24, STEADY-STATE TO TAU 36 AND REINTENSIFICATION AFTER TAU 36 
AS THE SYSTEM BEGINS ETT. THE JTWC FORECAST CLOSELY TRACKS THE HAFS-A 
MEMBER THROUGH THE FORECAST PERIOD WITH MEDIUM CONFIDENCE.

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