WDIO32 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (DITWAH) WARNING 
NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.9N 80.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 878 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 05B WITH A COMPLETELY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND DEEP CONVECTION CONFINED TO THE NORTHERN PERIPHERY.
ENVIRONMENTAL ANALYSIS INDICATES THAT 05B IS IN A MARGINAL
ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT,
MODERATE (15-20 KTS) SOUTHEASTERLY VERTICAL WIND SHEAR, DRY AIR
ENTRAINMENT, AND WARM (28-29 C) SEA SURFACE TEMPERATURES. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
ANIMATED MSI. 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: 39 KTS AT 290737Z
   CIMSS ADT: 35 KTS AT 290600Z
   CIMSS AIDT: 32 KTS AT 290600Z
   CIMSS D-MINT: 33 KTS AT 290737Z
   CIMSS D-PRINT: 30 KTS AT 290600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE 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 DRY BEGINS TO ENTRAIN INTO THE VORTEX FROM THE
WEST. THESE TWO FACTORS ARE EXPECTED TO WEAKEN THE SYSTEM BELOW
WARNING CRITERIA AROUND TAU 48. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF NAVGEM, WHICH TRACKS THE VORTEX OFF
TO THE NORTHEAST RATHER THAN NORTHWARD. EXCLUDING NAVGEM, THERE IS
A 75 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. MODELS DO SHOW A POTENTIAL FOR THE VORTEX
TO MAINTAIN 35 KTS FOR SLIGHTLY LONGER THAN TAU 48 THOUGH. DUE TO
THIS POSSIBILITY, THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM
CONFIDENCE.

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