WDXS31 PGTW 281500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (BATSIRAI) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3S 73.4E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 1032 NM EAST OF ST DENIS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER THAT IS POSITIONED UNDER THE
NORTHERN EDGE OF THE PRIMARY DEEP CONVECTIVE BAND. A 281213Z SSMIS
91GHZ MICROWAVE IMAGE DEPICTS A COMPACT SYSTEM WITH THE BULK OF THE
CONVECTIVE BANDING OVER THE SOUTHERN SEMICIRCLE. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI AND SSMIS
IMAGE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE FMEE DVORAK ESTIMATE AND THE CIMSS ADT
ESTIMATE. ENVIRONMENTAL CONDITIONS REMAIN GENERALLY FAVORABLE WITH
LOW VERTICAL WIND SHEAR AND MODERATE POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR).

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   FMEE: T3.0 - 45 KTS
   CIMSS SATCON: 50 KTS AT 280902Z
   CIMSS ADT: 45 KTS AT 281215Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 08S IS FORECAST TO TURN WEST-SOUTHWESTWARD
AS THE STR WEAKENS IN RESPONSE TO AN APPROACHING MAJOR SHORTWAVE
TROUGH. HOWEVER, THE TROUGH WILL QUICKLY PROPAGATE EASTWARD AND A
WESTERN STR IS EXPECTED TO BUILD TO THE SOUTHWEST TURNING THE
SYSTEM WEST-NORTHWESTWARD THROUGH TAU 72. POLEWARD OUTFLOW WILL
IMPROVE AND ALLOW THE SYSTEM TO INTENSIFY TO 75 KNOTS BY TAU 72.
AFTER TAU 72, THE STR WILL WEAKEN AND REALIGN PRODUCING A MORE
WESTWARD TO WEST-SOUTHWESTWARD TRACK. ENVIRONMENTAL CONDITIONS WILL
DEGRADE WITH INCREASING VERTICAL WIND SHEAR AND WEAK DIFFLUENCE,
THEREFORE THE SYSTEM IS FORECAST TO GRADUALLY WEAKEN. 

MODEL DISCUSSION: THE JTWC FORECAST TRACK IS CONSISTENT WITH THE
PREVIOUS FORECAST AND IS POSITIONED CLOSE TO THE ECMWF AND GFS
SOLUTIONS. THERE IS A LARGE SPREAD IN BOTH DETERMINISTIC AND
ENSEMBLE MODEL OUTPUT WITH SEVERAL MODELS (NAVGEM, UEMN AND AFUM) 
INDICATING A SHARP, UNREALISTIC POLEWARD TRACK AND THE REMAINING 
GUIDANCE INDICATING SIGNIFICANT UNCERTAINTY IN THE EXTENDED PERIOD 
FORECAST. RELIABLE INTENSITY GUIDANCE SUPPORTS THE INTENSIFICATION 
TREND THROUGH TAU 72 WITH HWRF INDICATING A PEAK OF 80 KNOTS AT TAU 
60. THE JTWC INTENSITY FORECAST IS SLIGHTLY HIGHER THAN THE JTWC 
INTENSITY CONSENSUS (ICNW) THROUGH TAU 72. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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