Advisories

WDIO31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01B (ONE) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8N 83.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 391 NM SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
RADAR IMAGERY FROM THE INDIA METEOROLOGICAL DEPARTMENT INDICATES
TROPICAL CYCLONE (TC) 01B JUST OFF THE COAST OF VISAKHAPATNAM AS IT
SLOWLY MOVES NORTHWESTWARD. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS THE LOW LEVEL CIRCULATION CENTER (LLCC)
REMAINING OBSCURED BY CONVECTION CONFINED TO THE SOUTHWESTERN FLANK
AS MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR (VWS) ACTS UPON
THE SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON RADAR IMAGERY, AND THE INITIAL INTENSITY IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE SPREAD OF SURFACE OBSERVATIONS FROM
VISAKHAPATNAM REPORTING 10-15 KTS, SUGGESTING A LOWER INTENSITY THAN
DEPICTED IN DVORAK FIXES AS THE DVORAK METHOD STRUGGLES WITH
SYSTEMS NEAR LAND.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 53 KTS AT 231800Z
   CIMSS AIDT: 48 KTS AT 231700Z
   CIMSS D-MINT: 49 KTS AT 231645Z
   CIMSS D-PRINT: 47 KTS AT 231800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: TERRAIN INTERACTION

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 01B IS FORECAST TO MAKE LANDFALL OVER INDIA
WITHIN THE NEXT 12 HOURS AS IT IS SLOWLY STEERED NORTHWESTWARD BY
THE SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. INTENSITY IS
FORECAST TO DECREASE FOR THE REMAINDER OF THE FORECAST PERIOD AS
IMMINENT LANDFALL REMOVES THE ENERGY SOURCE OF THE TC AND CONTINUED 
MODERATE TO HIGH VWS IS EXPECTED TO DETERIORATE THE VORTEX, 
DISSIPATING 01B AS A TROPICAL CYCLONE BY TAU 24.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT ON A
NORTHWESTWARD TRACK FOR THE REMAINDER OF THE FORECAST PERIOD. THE
OFFICIAL JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE,
SLIGHTLY SLOWER BUT IN LINE WITH THE MULTI-MODEL CONSENSUS AS 01B
APPROACHES THE HIGHER TERRAIN OF THE INDIAN COAST. MODEL INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT ON A WEAKENING FOR THE REMAINDER
OF THE FORECAST PERIOD, SUPPORTING THE OFFICIAL JTWC INTENSITY
FORECAST WITH HIGH CONFIDENCE.

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