WDIO32 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (DITWAH) WARNING 
NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.2N 80.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 863 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 05B WITH A COMPLETELY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND CONVECTION CONFINED PRIMARILY TO THE NORTHERN PERIPHERY.
ENVIRONMENTAL ANALYSIS INDICATES THAT 05B IS IN A MARGINAL 
ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW ALOFT OFFSET
AND WARM (28-29 C) SEA SURFACE TEMPERATURES OFFSET BY MODERATE
(15-20 KTS) SOUTHEASTERLY VERTICAL WIND SHEAR AND SIGNIFICANT DRY
AIR ENTRAINMENT. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON THE EXPOSED LLCC IN ANIMATED EIR IMAGERY. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE CENTERED OVER SOUTHERN MYANMAR.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS SATCON: 35 KTS AT 291030Z
   CIMSS ADT: 28 KTS AT 291200Z
   CIMSS AIDT: 29 KTS AT 291200Z
   CIMSS D-PRINT: 30 KTS AT 291200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT WITHIN THE EASTERN SEMICIRCLE

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 05B IS FORECAST TO TRACK NORTHWARD, ALONG
THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE CENTERED OVER
SOUTHERN MYANMAR THROUGHOUT THE FORECAST PERIOD. THE SYSTEM IS
FORECAST TO TRACK JUST OFF THE EASTERN COAST OF INDIA, AND PASSING
EAST OF CHENNAI AROUND TAU 36. REGARDING INTENSITY, 05B IS FORECAST
TO MAINTAIN ITS CURRENT INTENSITY THROUGH TAU 36 AS SHEAR REMAINS
WITHIN THE 15-20 KNOT RANGE. AROUND TAU 36, SOUTHERLY SHEAR
INCREASES TO AROUND 25 KTS AND SIGNIFICANT AMOUNTS OF DRY BEGIN TO
ENTRAIN INTO THE VORTEX FROM THE WEST. THESE TWO FACTORS ARE
EXPECTED TO WEAKEN THE SYSTEM BELOW WARNING CRITERIA AROUND TAU 48.
THE PROXIMITY TO THE COAST OF INDIA WILL BE A MAJOR FACTOR IN
INTENSITY. IF THE VORTEX CLIPS THE COAST, A QUICKER DISSIPATION
TIMELINE MAY ENSUE.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH AN 85 NM CROSS-TRACK
SPREAD AT TAU 48. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. INTENSITY GUIDANCE
AGREES ON A STEADY INTENSITY THROUGH TAU 36-48 BEFORE STEADY
WEAKENING. THE JTWC INTENSITY FORECAST IS ALSO PLACED CLOSE TO THE
CONSENSUS WITH HIGH CONFIDENCE.

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