Advisories

WDIO31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01B (ONE) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8N 84.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 359 NM SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 01B AS A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH A PLUME OF DEEP CONVECTION SHEARED TO THE
SOUTHWEST. THE 230337Z ASCAT DATA REVEALS THE CIRCULATION IS
RELATIVELY COMPACT WITH HIGHEST WIND SPEEDS CONFINED TO THE
SOUTHERN QUADRANT. ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY
FAVORABLE ENVIRONMENT, CHARACTERIZED BY VERY WARM (29 C - 30 C) SEA
SURFACE TEMPERATURES, AND DECENT OUTFLOW ALOFT, OFFSET BY LAND
INTERACTION AND MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR
(VWS). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED
ON THE PARTIALLY EXPOSED LLCC AND EXTRAPOLATION FROM THE 230337Z
ASCAT DATA. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE 230337Z ASCAT DATA.

INITIAL WIND RADII BASIS: ADJUSTED WIND RADII USING THE 230337Z
ASCAT DATA

CURRENT STEERING MECHANISM: A WEAK MID-LEVEL SUBTROPICAL RIDGE
(STR) CENTERED FAR TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS SATCON: 41 KTS AT 230158Z
   CIMSS ADT: 45 KTS AT 230300Z
   CIMSS AIDT: 43 KTS AT 230200Z
   CIMSS D-MINT: 40 KTS AT 230414Z
   CIMSS D-PRINT: 35 KTS AT 230400Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: LAND INTERACTION

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 01B IS FORECAST TO CONTINUE TRACKING SLOWLY
NORTHWESTWARD WHILE IT REMAINS IN A WEAK STEERING ENVIRONMENT ON
THE FRINGES OF A MID-LAYER STR CENTERED FAR TO THE NORTHEAST. 01B
IS FORECAST TO MAKE LANDFALL NORTHEAST OF VISAKHAPATNAM JUST AFTER
TAU 12. REGARDING INTENSITY, 01B IS LIKELY CURRENTLY AT ITS PEAK
INTENSITY, AS THE ENVIRONMENT IS EXPECTED TO CONTINUE TO
DETERIORATE AS THE SYSTEM APPROACHES THE COAST. AROUND TAU 12, VWS
IS EXPECTED TO CLIMB TO 30 KTS AND INCREASED LAND INTERACTION WILL
ACCELERATE WEAKENING. DISSIPATION OVER LAND IS EXPECTED NO LATER
THEN TAU 36, BUT LIKELY SOONER.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 36, SUPPORTING THE JTWC TRACK FORECAST WITH
HIGH CONFIDENCE. LIKEWISE, RELIABLE INTENSITY AIDS ARE IN STRONG
AGREEMENT ON A STEADY WEAKENING TREND THROUGH THE END OF THE
FORECAST PERIOD. AS A RESULT, THE JTWC INTENSITY FORECAST IS
ASSESSED WITH HIGH CONFIDENCE.

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