WDIO31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (ASANI) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 84.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 531 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS INTENSE, 
FLARING CONVECTIVE BURSTS WITHIN A CENTRAL DENSE OVERCAST (CDO)
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC), WHICH IS
POSITIONED UNDER THE NORTHEASTERN EDGE OF THE CDO. ANIMATED WATER
VAPOR IMAGERY REVEALS AN AREA OF INTENSE DEEP CONVECTION AS THE
SYSTEM ENTERS ITS CONVECTIVE MAXIMUM. A 091921Z ATMS SERIES MICROWAVE
IMAGE INDICATES THE BULK OF THE CONVECTION IS BEING SHEARED TO THE
WEST AS THE SYSTEM APPROACHES LAND. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE ATMS IMAGERY. THE INITIAL
INTENSITY OF 55 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN
AGREEMENT OF AGENCY DVORAK INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS ADT: 57 KTS AT 091815Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG WESTWARD
   OTHER FACTORS: LAND INTERACTION WITH SOUTHEAST INDIA

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 02B REMAINS UNDER THE STEERING INFLUENCE OF
THE STR ENTRENCHED TO THE NORTHEAST. CURRENT MODEL GUIDANCE
INDICATES THAT THROUGH TAU 36 THE STR WILL MAINTAIN ITS INFLUENCE 
BEFORE EVENTUALLY ERODING AS A MIDLATITUDE TROUGH DEEPENS TO THE 
NORTH ALLOWING THE SYSTEM TO RECURVE. THE SYSTEM WILL TURN POLEWARD 
NEAR VISAKHAPATNAM BY TAU 48 WITHIN A COMPETING STEERING 
ENVIRONMENT. 
TC 02B WILL WEAKEN STEADILY DURING THIS PERIOD UNDER PERSISTENT 
EASTERLY VWS (25-30 KNOTS) AND INTERACTION WITH LAND. AFTER TAU 48, 
UPPER-LEVEL WESTERLIES ARE EXPECTED TO PUSH INTO THE BAY OF BENGAL 
WITH THE STR WEAKENING AND SHIFTING EAST. THIS SHOULD ALLOW THE 
SYSTEM TO ACCELERATE NORTHEASTWARD TOWARD BANGLADESH ALONG THE 
NORTHWESTERN PERIPHERY OF THE STR. TC 02B WILL BE EMBEDDED WITHIN 
THE UPPER-LEVEL WESTERLIES IN A MARGINAL ENVIRONMENT WITH DRY AIR 
ENTRAINING INTO THE SYSTEM AND LAND INTERACTION TEARING THE SYSTEMS
LOW LEVEL STRUCTURE APART AND IS EXPECTED TO CONTINUE TO WEAKEN AND
EVENTUALLY DISSIPATE OVER THE NORTHERN BAY OF BENGAL.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO STRUGGLE
WITH THIS COMPLEX STEERING ENVIRONMENT WITH SIGNIFICANT UNCERTAINTY
IN THE JTWC FORECAST TRACK. IN GENERAL, MODEL GUIDANCE IS IN POOR
AGREEMENT AND SHOWS A LARGE SPREAD IN SOLUTIONS. THE 091200Z ECMWF
ENSEMBLE (EPS) STRIKE PROBABILITY PRODUCT, IS NOW INDICATING A
BIFURCATION WITH LANDFALL NEAR VISAKHAPATNAM AND DISSIPATION OR A
SHARP NORTHEASTWARD RECURVE AND TRACK ALONG THE COAST OF 
NORTHEASTERN 
INDIA AND EVENTUAL DISSIPATION NEAR BANGLADESH. THE BULK OF THE 
RELIABLE INTENSITY GUIDANCE INDICATES GOOD AGREEMENT ON STEADY 
WEAKENING WITH A WEAK TROPICAL CYCLONE IN THE EXTENDED PERIOD THUS 
OVERALL MEDIUM CONFIDENCE. MODEL GUIDANCE DOES INDICATE, HOWEVER, 
SIGNIFICANT RAINFALL SPREADING ACROSS EASTERN INDIA AND THE NORTHERN 
BAY OF BENGAL INTO BANGLADESH AND MYANMAR.



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