WDIO31 PGTW 010900
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: 15.9N 86.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 416 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH CONVECTION
DISPLACED FAR TO THE SOUTHWEST. A 010327Z METOP-B ASCAT IMAGE
REVEALS AN ELONGATED CIRCULATION WITH THE STRONGEST WINDS (30-35
KTS) CONFINED TO THE SOUTHERN SEMICIRCLE. ENVIRONMENTAL ANALYSIS
INDICATES A MARGINAL ENVIRONMENT, CHARACTERIZED BY MODERATE 
EQUATORWARD OUTFLOW ALOFT AND WARM SEA SURFACE TEMPERATURES (29-30C), 
OFFSET BY MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR AND A BROAD 
WIND FIELD. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED 
ON THE FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) IN ANIMATED 
IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE AFOREMENTIONED 010327Z ASCAT DATA.

INITIAL WIND RADII BASIS: 010327Z METOP-B SCATTEROMETER DATA

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) TO THE EAST
OF THE SYSTEM

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T1.5 - 25 KTS
   CIMSS D-PRINT: 23 KTS AT 010600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: VERY BROAD WIND FIELD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 01B IS FORECAST TO TRACK
NORTHWESTWARD FOR THE DURATION OF THE FORECAST PERIOD, UNDER THE
INFLUENCE OF THE STR TO ITS EAST. 01B WILL REMAIN IN A MARGINAL 
ENVIRONMENT LEADING UP TO LANDFALL, WHICH WILL STALL INTENSIFICATION 
GREATER THAN GALE-FORCE WINDS. THE WIND FIELD IS ANTICIPATED TO 
REMAIN BROAD, FURTHER HINDERING DEVELOPMENT. AS A RESULT, TC 01B IS 
EXPECTED TO MAINTAIN ITS INTENSITY OF 35 KTS UNTIL LANDFALL IN 
NORTHEASTERN INDIA. AFTER LANDFALL, DISSIPATION IS IMMINENT.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THAT 01B WILL CONTINUE ITS NORTHWESTWARD MOTION AND MAKE
LANDFALL JUST BEFORE TAU 36, SUPPORTING THE JTWC TRACK FORECAST
WITH HIGH CONFIDENCE. RELIABLE INTENSITY GUIDANCE IS ALSO IN STRONG
AGREEMENT THAT 01B WILL PEAK AT 35 KTS. THE JTWC INTENSITY FORECAST 
FOLLOWS SUIT, MAINTAINING 35 KTS THROUGH TAU 24 BEFORE WEAKENING OVER 
LAND.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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