WDIO31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (FIVE)       
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.8N 88.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 435 NM SOUTH-SOUTHWEST OF CHITTAGONG,
     BANGLADESH
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 9 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION WITH EXTENSIVE DEEP
CONVECTION OVER THE NORTHERN SEMICIRCLE. A 231200Z SSMIS 91GHZ
MICROWAVE IMAGE REVEALS SHALLOW BANDING WRAPPING TIGHTLY INTO A
DEFINED LOW-LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE INITIAL
POSITION WITH HIGH CONFIDENCE, AND EXTENSIVE CURVED CONVECTIVE
BANDING OVER THE NORTHERN SEMICIRCLE FUELED BY THE STRONG POLEWARD
OUTFLOW. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE PGTW AND KNES DVORAK ESTIMATES.
ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE WITH STRONG POLEWARD
OUTFLOW, ENHANCED BY A SHARP UPPER-LEVEL TROUGH POSITIONED OVER
CENTRAL INDIA, LOW VERTICAL WIND SHEAR AND WARM SST VALUES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 05B IS FORECAST TO
RAPIDLY CONSOLIDATE UNDER HIGHLY FAVORABLE CONDITIONS AS IT TRACKS
POLEWARD ALONG THE WESTERN PERIPHERY OF THE NORTH-SOUTH ORIENTED
STR. TC 05B SHOULD CONSOLIDATE QUICKLY WITH A SHARP INCREASE TO A
PEAK OF 55 KNOTS WITHIN THE NEXT 24 HOURS. AFTER TAU 24,
INTERACTION WITH LAND AND INCREASING VERTICAL WIND SHEAR WILL
CONTRIBUTE TO A STEADY WEAKENING TREND AND EVENTUAL DISSIPATION
OVER BANGLADESH BY TAU 48. HOWEVER, THE LARGE SYSTEM IS EXPECTED TO
PRODUCE HEAVY RAINFALL ACROSS BANGLADESH, INCLUDING THE EASTERN
REGION NEAR CHITTAGONG AND COX'S BAZAR.      

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
WITH A 70-80NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 36 TO TAU 48.
ADDITIONALLY, THE 230000Z ECMWF (EPS) ENSEMBLE AND THE 230600Z
(GEFS) ENSEMBLE ARE IN TIGHT AGREEMENT WITH A TRACK OVER THE
SOUTHERN COAST OF BANGLADESH. THUS, THERE IS HIGH CONFIDENCE IN THE
JTWC TRACK FORECAST. THE 230000Z COAMPS-TC ENSEMBLE INDICATES AN
80-100 PERCENT PROBABILITY OF A STRONG TROPICAL STORM-STRENGTH (50-63 
KNOTS) SYSTEM DEVELOPING WITHIN THE NEXT 30 HOURS WITH A LOW 
PROBABILITY OF A WEAK TYPHOON AT TAU 24. INTENSITY GUIDANCE CURRENTLY 
RANGES FROM A PEAK OF 45 TO 58 KNOTS AT TAU 24 WITH HWRF SHOWING THE
HIGHEST PEAK AT TAU 12 (64 KNOTS) AND TAU 24 (63 KNOTS). THE JTWC
FORECAST IS HEDGED BELOW THE AGGRESSIVE HWRF SOLUTION WITH A PEAK
OF 55 KNOTS BUT THERE IS A POSSIBILITY OF A WEAK TYPHOON IF THE
SYSTEM CAN DEVELOP CORE CONVECTION PRIOR TO LANDFALL.        

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