WDIO31 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (SITRANG)      
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0N 90.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 119 NM SOUTHWEST OF CHITTAGONG, BANGLADESH
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A PARTIALLY 
EXPOSED, BROAD LOW-LEVEL CIRCULATION CENTER (LLCC) WITH A LARGE REGION 
OF INTENSE DEEP CONVECTION PERSISTING OVER THE NORTHERN SEMICIRCLE. 
UPPER-LEVEL ANALYSIS SHOWS STRONG DIFFLUENT FLOW BETWEEN A SHARP UPPER-
LEVEL TROUGH OVER CENTRAL INDIA AND A BROAD ANTICYCLONE TO THE EAST NEAR 
21N 95E. WINDS WITHIN THIS WEDGE OF DIFFLUENT UPPER-LEVEL FLOW RANGE 
FROM 50-70 KNOTS, WHICH IS FUELING THE INTENSE CONVECTION ACROSS 
NORTHEAST INDIA AND BANGLADESH. A 241145Z SSMIS 91GHZ COLOR COMPOSITE 
MICROWAVE IMAGE REVEALS SHALLOW BANDING WRAPPING INTO A BROAD, DEFINED 
LLCC WITH DEEP CONVECTION SHEARED ABOUT 70NM NORTH. THE INITIAL POSITION 
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE SSMIS IMAGE. THE INITIAL
INTENSITY OF 45 KTS IS BASED ON THE HIGHER END OF THE DVORAK ESTIMATES 
AND THE CIMSS ADT ESTIMATE.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T3.0 - 45 KTS
   CIMSS SATCON: 43 KTS AT 240740Z
   CIMSS ADT: 47 KTS AT 240915Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: INTERACTION WITH LAND

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TROPICAL CYCLONE (TC) 05B IS FORECAST TO TRACK 
NORTH-NORTHEASTWARD THROUGH THE FORECAST PERIOD ALONG THE WESTERN 
PERIPHERY OF THE NORTH-SOUTH ORIENTED STR. TC 05B WILL MAKE LANDFALL IN 
ABOUT THREE HOURS OVER SOUTHEASTERN BANGLADESH WITH RAPID WEAKENING AND 
DISSIPATION EXPECTED DUE TO INTERACTION WITH LAND AND INCREASING 
VERTICAL WIND SHEAR. 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 45NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 12 BUT DIVERGES AFTER 
TAU 12 AS THE SYSTEM RAPIDLY WEAKENS OVERLAND. THE 240600Z ECMWF (EPS) 
AND GFS (GEFS) ENSEMBLES ARE IN TIGHT AGREEMENT WITH A TRACK OVER THE 
SOUTHEASTERN COAST OF BANGLADESH. THUS, THERE IS HIGH CONFIDENCE IN THE 
JTWC TRACK FORECAST. RELIABLE INTENSITY GUIDANCE SUPPORTS A RAPID 
WEAKENING TREND THROUGH THE FORECAST PERIOD.  

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