WDXS32 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (DINGANI) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1S 81.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 755 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A COMPACT
SYSTEM THAT HAS MAINTAINED OVERALL CONVECTIVE SIGNATURE WITH THE
CENTRAL CONVECTION SLIGHTLY OFFSET WESTWARD FROM THE LOW-LEVEL
CIRCULATION AND THIN FEEDER BANDS TRAILING FROM THE SOUTH. THE
INITIAL POSITION AND INTENSITY ARE PLACED WITH HIGH CONFIDENCE
BASED ON EXTRAPOLATION FROM THE 101559Z DIRECT ASCAT PASS AND IS
CONSISTENT WITH AUTOMATED DVORAK ESTIMATES AND THE SUSTAINED EIR
SIGNATURE. ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT
WITH MODERATE POLEWARD OUTFLOW OFFSET BY MODERATE VERTICAL WIND
SHEAR AND TEPID SSTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTH.  


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 47 KTS AT 101421Z
   CIMSS ADT: 45 KTS AT 101500Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 DINGANI WILL CONTINUE ON ITS CURRENT
WESTWARD TRACK UP TO TAU 24; AFTERWARD, IT WILL TURN MORE
SOUTHWESTWARD AS THE STR RECEDES. VWS IS EXPECTED TO RELAX A
BIT AND THE POLEWARD OUTFLOW TO INCREASE, FUELING A GRADUAL
INTENSIFICATION PHASE TO A PEAK OF 70KTS BY TAU 48. AFTER TAU 48,
COOLING SST AND INCREASING VWS WILL BEGIN TO ERODE THE SYSTEM AND
BY TAU 72, WILL BE REDUCED TO 45KTS AS IT PASSES TO THE SOUTH OF
RODRIGUES ISLAND, MAURITIUS.  

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH AN EVEN AND GRADUAL SPREAD TO 280NM BY TAU 120. AFUM IS THE
ERRATIC RIGHT-OF-TRACK OUTLIER DIVERGING 90 DEGREES NORTHWESTWARD
FROM THE PACK BEGINNING AT TAU 36. THE JTWC TRACK FORECAST IS LAID
WITH MEDIUM CONFIDENCE TO THE LEFT OF CONSENSUS TO OFFSET AFUM. THE
INTENSITY FORECAST IS ALSO AT MEDIUM CONFIDENCE FOR THE DURATION OF
THE FORECAST. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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