WDIO31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02B (ASANI) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 86.1E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 532 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPANSIVE
SYSTEM THAT SPANS OVER 500NM WITH ITS CIRRUS CANOPY STRETCHING
WESTWARD ALL THE WAY TO THE NORTH INDIAN OCEAN. THE CENTRAL DENSE
OVERCAST HAS BEGUN TO ELONGATE AND BECOME MORE ASYMMETRICAL AND
CONTINUED TO OBSCURE THE LOW LEVEL CIRCULATION (LLC). THE MSI LOOP
ALSO SHOWS STRONGER PRESSURE ALONG THE EASTERN SIDE, AN INDICATION
OF INCREASED EASTERLY VERTICAL WIND SHEAR (VWS). THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON AN EXPOSED LLC IN
THE 082229Z SSMIS 91GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS 
PLACED WITH MEDIUM CONFIDENCE BASED ON THE PGTW AND ADT DVORAK 
ESTIMATES AND REFLECTS THE DEGRADED 6-HR CONVECTIVE STRUCTURE.

INITIAL WIND RADII BASIS: EXTRAPOLATION FROM RECENT SCATTEROMETER
DATA.

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST AND EAST.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   CIMSS ADT: 49 KTS AT 082115Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 ASANI IS EXPECTED TO CONTINUE TRACKING
NORTHWESTWARD ALONG THE PERIPHERY OF THE STR THROUGH TAU 24 UNDER
THE STEERING INFLUENCE OF THE STR. AFTERWARD, IT WILL TURN MORE
NORTHWARD THEN NORTHEASTWARD AS IT ROUNDS THE AXIS OF THE STR AS IT
RECEDES IN RESPONSE TO AN APPROACHING MID-LATITUDE SHORTWAVE
TROUGH. THE UNFAVORABLE ENVIRONMENT, DUE TO HIGH VWS AND COOL DRY
AIR ENTRAINMENT FROM THE NORTH WILL CONTINUE TO GRADUALLY WEAKEN
THE CYCLONE TO DISSIPATION BY TAU 120 AFTER IT MAKES LANDFALL OVER 
WESTERN BANGLADESH.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN AGREEMENT WITH THE
FORECAST RECURVING TRACK WITH NAVGEM AND AFUM ON THE LEFT AND
GFS ON THE RIGHT MARGIN OF THE ENVELOPE. IN VIEW OF THIS, THERE IS
MEDIUM CONFIDENCE IN THE JTWC FORECAST TRACK THAT IS LAID CLOSE TO 
THE MODEL CONSENSUS. THERE IS ALSO MEDIUM CONFIDENCE IN THE FORECAST 
INTENSITIES THAT ARE ALSO HELD CLOSE TO THE MODEL CONSENSUS.


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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