WDIO31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01B (ONE) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 89.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 235 NM SOUTH-SOUTHEAST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
EXTENSIVE DEEP CONVECTIVE BANDING ALONG THE SOUTHERN AND EASTERN
PERIPHERIES OF A BROAD LOW-LEVEL CIRCULATION EVIDENT IN RECENT
MICROWAVE SATELLITE IMAGERY, INCLUDING A 251153Z SSMIS PASS. THE
SYSTEM CENTER IS MOSTLY DEVOID OF CONVECTIVE ACTIVITY. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON RECENT MICROWAVE
SATELLITE IMAGERY INCLUDING THE AFOREMENTIONED SSMIS PASS AND A
250953Z SSMIS PASS. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON 251217Z RCM-3 SAR DATA INDICATING 35
KNOT WINDS EMBEDDED WITHIN THE SOUTHERN AND EASTERN PORTIONS OF THE
CIRCULATION AND IS CONSISTENT WITH SEA LEVEL PRESSURE OBSERVATIONS
OF 990 MB FROM BUOYS POSITIONED NEAR THE STORM CENTER.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGING (STR) TO THE EAST

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 31-32 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 01B IS EXPECTED TO STEADILY CONSOLIDATE AND
INTENSIFY AS IT MOVES INTO A NARROW ZONE OF LOW VERTICAL WIND SHEAR
IN THE NORTHERN PORTION OF THE BAY OF BENGAL UNDER THE CONTINUED
STEERING INFLUENCE OF DEEP-LAYER RIDGING TO THE EAST. WHILE REDUCED
VERTICAL WIND SHEAR, PASSAGE OVER VERY WARM WATER, AND PERSISTENT
EQUATORWARD OUTFLOW WILL SUPPORT CONTINUED INTENSIFICATION, THE
CIRCULATION WILL TAKE SOME TIME TO CONSOLIDATE GIVEN ITS CURRENT
BROAD LOW-LEVEL STRUCTURE. REGARDLESS OF PEAK CORE WIND SPEEDS,
IMPACTS FROM DISTURBED WEATHER ASSOCIATED WITH TC 01B, INCLUDING
GUSTY WINDS AND HEAVY RAINFALL, WILL LIKELY BE WIDESPREAD GIVEN THE
SIZE OF THE SYSTEM AND ANTICIPATED LANDFALL AROUND TAU 24.
FOLLOWING LANDFALL, THE SYSTEM WILL STEADILY WEAKEN AND DISSIPATE
BELOW THE WARNING THRESHOLD INTENSITY OF 35 KNOTS BY TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL TRACK FORECASTS ARE IN GOOD
AGREEMENT REGARDING THE OVERALL FORECAST SCENARIO AND TIMING OF
LANDFALL. THE UKMET GLOBAL AND ENSEMBLE MEAN TRACKERS DEPICT
LANDFALL A BIT FARTHER TO THE EAST, CLOSER TO CHITTAGONG, THAN THE
PRIMARY GROUPING, WHICH CONSISTS OF THE ECMWF DETERMINISTIC MODEL
AND ENSEMBLE MEAN, GEFS, GEFS MEAN, AND NAVGEM SOLUTIONS. HOWEVER,
GIVEN THE SIZE OF THE SYSTEM, IMPACTS FROM THE SYSTEM WILL LIKELY
BE WIDESPREAD FROM THE CENTER. INTENSITY FORECAST GUIDANCE, INCLUDING 
HAFS AND COAMPS-TC MESOSCALE MODEL SOLUTIONS, FIRMLY SUPPORT THE PRE-
LANDFALL INTENSIFICATION SCENARIO, AND THE CURRENT FORECAST INDICATES 
AN INTENSIFICATION RATE NEAR THE MULTI-MODEL CONSENSUS WITH HIGH 
CONFIDENCE.

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