WDIO32 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (DITWAH) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.9N 81.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 972 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 05B (DITWAH) AND ITS BROAD CIRCULATION, WITH WIND
FIELD EXTENDING WELL BEYOND THE PERIMETER OF SRI LANKA. THE LOW-LEVEL 
CIRCULATION CENTER (LLCC) OF THE SYSTEM IS CURRENTLY POSITIONED OVER 
LAND WITH MEDIUM CONFIDENCE, UTILIZING ANIMATED SHORTWAVE INFRARED 
SATELLITE IMAGERY LOOP, AS WELL AS WIND SHIFT OBSERVED AT THE 
BATTICALOA STATION. THE INITIAL INTENSITY OF 35 KTS, AS WELL AS THE 
WIND RADII ARE ASSESSED WITH HIGH CONFIDENCE BASED ON A 261634Z METOP-
C AND A 261551Z METOP-B ASCAT PASSES. ENVIRONMENTAL ANALYSIS REVEALS  
MARGINAL CONDITIONS, WITH MODERATE DUAL CHANNEL OUTFLOW, LOW (10-15
KTS) VERTICAL WIND SHEAR (VWS) OFFSET BY FRICTIONAL EFFECTS OF LAND
INTERACTION.

INITIAL WIND RADII BASIS: A 261634Z METOP-C AND A 261551Z METOP-B
ASCAT PASSES

CURRENT STEERING MECHANISM: LOW-LEVEL RIDGING TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS D-PRINT: 41 KTS AT 271800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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 DITWAH IS FORECAST TO CONTINUE TRACKING
NORTHWARD UNDER THE INFLUENCE OF LOW-LEVEL RIDGING CENTERED TO THE
EAST. THE CENTER OF THE SYSTEM IS EXPECTED TO REMAIN OVER LAND
UNTIL SHORTLY AFTER TAU 24, WHILE MAINTAINING INTENSITY ALONG THE
TRANSIT. AFTER THAT, POSITIVE IMPACTS OF WARM (28-29 C) SEA SURFACE
TEMPERATURES (SST) AND REDUCED FRICTIONAL EFFECTS WILL BE OFFSET BY
INCREASING SOUTHERLY VWS, ULTIMATELY RESULTING IN A WEAKENING TREND
AND DISSIPATION BETWEEN TAUS 72 AND 96. TOWARDS THE END OF THE
FORECAST PERIOD, THE SYSTEM WILL BEGIN ROUNDING THE NORTHWESTERN
PERIPHERY OF THE RIDGE TO THE EAST, HOWEVER IT IS LIKELY THAT THE
CIRCULATION WILL DISSIPATE PRIOR TO THE COMPLETION OF THE TURN.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT IN REGARD TO THE NORTHWARD TRACK, HOWEVER THE FORECAST IS
ASSESSED WITH MEDIUM CONFIDENCE DUE TO UNCERTAINTY ASSOCIATED WITH
THE TRACK OVER SRI LANKA. THE CROSS-TRACK SPREAD AT TAU 12 IS
APPROXIMATELY 90 NM. ONCE THE SYSTEM RE-EMERGES OVER WATER, GUIDANCE 
BECOMES TIGHTER, AS WITNESSED BY THE CROSS-TRACK SPREAD REDUCED TO 70 
NM. INTENSITY GUIDANCE IS ALSO IN GENERALLY GOOD AGREEMENT, WITH 
MAJORITY OF THE MODELS INDICATING A WEAKENING TREND WITH TIME. THE 
MAJOR OUTLIER IS NAVGEM DRIVEN COAMPS-TC WHICH DEPICTS A STRENGTHENING 
TO A PEAK OF 50-55 KTS, WHILE THE SYSTEM IS OVER WATER. OTHER MODELS 
DEPICT ONLY A POTENTIAL FOR A 5 KTS INCREASE, WHILE HOVERING AROUND 
25-35 KTS. AS SUCH, JTWC OFFICIAL FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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