WDIO31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (SITRANG) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.7N 89.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 312 NM SOUTH-SOUTHWEST OF CHITTAGONG,
BANGLADESH
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A VERY
LARGE CYCLONE (600NM+ DIAMETER) SPANNING MOST OF THE BAY OF BENGAL
WITH BROAD AND DEEP RAIN BANDS AHEAD AND TO THE RIGHT OF A WIDE
CENTRAL DENSE OVERCAST THAT IS OFFSET NORTHWARD BUT STILL OBSCURING
THE LOW LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS BASED ON A
RAGGED BUT DEFINED MICROWAVE LLC FEATURE IN THE 232348Z GPM 89GHZ
IMAGE. THE INITIAL INTENSITY IS BASED ON AGENCY AND AUTOMATED
DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 231815Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC SITRANG WILL CONTINUE ON ITS
NORTH-NORTHEASTWARD TRACK ALONG THE NORTH-WESTERN EDGE OF THE STR
AND MAKE LANDFALL OVER BANGLADESH, APPROXIMATELY 54NM TO THE WEST
OF CHITTAGONG, A FEW HOURS BEFORE TAU 24. THE FAVORABLE ENVIRONMENT
WILL FUEL AN INTENSIFICATION TO A PEAK OF 50KTS BY TAU 12.
AFTERWARD, INCREASING VWS AND EVENTUAL LANDFALL WILL RAPIDLY ERODE
THE SYSTEM DOWN TO 35KTS AT LANDFALL, THEN DISSIPATION BY TAU 36. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY TIGHT AGREEMENT WITH
VERY MINIMAL AND GRADUAL SPREAD TO 90NM BY TAU 36, LENDING HIGH
CONFIDENCE IN THE JTWC TRACK FORECAST. 


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