WDIO32 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (DITWAH) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.0N 80.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 926 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 04 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD,
RAGGED, AND FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) AS
TROPICAL CYCLONE (TC) 05B CONTINUES TO TRACK NORTHWARD OVER SRI
LANKA. PERSISTENT CONVECTION IS CONFINED TO THE NORTHERN AND
WESTERN QUADRANTS WHILE THE SOUTHERN PERIPHERY IS ERODED BY DRY AIR
ENTRAINMENT AND TERRAIN INTERACTION. A SURFACE STATION FROM MANNAR,
SRI LANKA IS REPORTING 13KTS FROM THE NORTH-NORTHWEST, SUPPORTING
THE INTIAL POSITION. A PARTIAL METOP-C ASCAT PASS FROM 281613Z
REVEALS THAT THE EASTERNMOST EXTENT OF THE BROAD LLCC LIES OFF THE
EAST COAST OF SRI LANKA, AND A PATCH OF 30-35 KTS DISPLACED
APPROXIMATELY 130NM NORTHEAST FROM THE CENTER. AS A RESULT, THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
RAGGED NATURE OF THE LLCC IN ANIMATED EIR.

INITIAL WIND RADII BASIS: PERSISTENCE AND A 281613Z PARTIAL METOP-C
SCATTEROMETER IMAGE

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) CENTERED OVER
SOUTHEAST ASIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS D-MINT: 36 KTS AT 281913Z
   CIMSS D-PRINT: 38 KTS AT 281830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT AND TERRAIN INTERACTION

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 05B (DITWAH) WILL CONTINUE ON A GENERALLY
NORTHWARD TRACK FOR THE DURATION OF THE FORECAST PERIOD, WITH
REEMERGENCE OVER WATER EXPECTED TO OCCUR PRIOR TO TAU 12. DITWAH IS
FORECAST TO MAINTAIN INTENSITY WHILE TRACKING OVER SRI LANKA SINCE
THE LOW-LYING, FLAT COASTAL TERRAIN CONTRIBUTES MILD FRICTIONAL
EFFECTS. BEGINNING AROUND TAU 24, THE SOUTHERLY VERTICAL WIND SHEAR
IS EXPECTED TO INCREASE TO 20-25 KTS, PROHIBITING INTENSIFICATION,
EXPEDITING DRY AIR ENTRAINMENT, AND ULTIMATELY LEADING TO
DISSIPATION NO LATER THAN TAU 48.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN
AGREEMENT ON A GENERALLY NORTHWARD TRACK FOR THE DURATION OF THE
FORECAST PERIOD, BUT THERE IS SOME DISAGREEMENT ON HOW CLOSE TO THE
INDIAN COAST 05B WILL TRACK. ECMWF MODELS (DETERMINISTIC AND
ENSEMBLE MEAN) ARE THE WESTERN BOUNDARY OF THE MODEL ENVELOPE,
TRACKING 05B NORTH-NORTHWESTWARD UNTIL LANDFALL IN SOUTHEASTERN
INDIA. NAVGEM IS THE EASTERN BOUNDARY OF THE ENVELOPE, PREDICTING A
NORTH-NORTHEASTWARD TRACK AWAY FROM THE COAST. THE REMAINDER OF
MODEL GUIDANCE AND THE MULTI-MODEL CONSENSUS ARE IN GOOD AGREEMENT
ON A DUE NORTHWARD TRACK, SUPPORTING THE JTWC TRACK FORECAST.
OVERALL, THE JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE.
RELIABLE INTENSITY GUIDANCE IS IN MODERATE AGREEMENT THAT 05B WILL 
MAINTAIN INTENSITY AT BORDERLINE TROPICAL STORM STRENGTH
BEFORE DIPPING BELOW 35 KTS PRIOR TO TAU 48. THE ONLY OUTLIER IS
COAMPS-TC, BOTH THE GFS AND NAVGEM BASED MODELS, WHICH ARE
PREDICTING INTENSIFICATION.

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