WDIO31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04B (FENGAL) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.1N 80.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 61 NM SOUTH-SOUTHWEST OF CHENNAI, INDIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 04B HAS CONTINUED TO VERY SLOWLY HEAD TOWARDS
THE COAST OF SOUTHEASTERN INDIA BUT REMAINS SITUATED JUST OFF THE
COAST AS OF THE 0000Z HOUR. ANIMATED SHORTWAVE INFRARED (SWIR) AND
THE FIRST FEW FRAMES OF VISIBLE SATELLITE IMAGERY SHOW A WEAKLY
DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) A FEW MILES EAST OF
PUDUCHERRY. DUE TO PARALLAX ERROR, THE DETERMINATION OF WHETHER
THE SYSTEM IS OVER LAND OR OFFSHORE DEPENDS UP ON WHICH SATELLITE
IS USED. THE INITIAL POSITION IS DETERMINED WITH HIGH CONFIDENCE
USING THE EXPOSED LLCC IN THE METEOSAT-9 SWIR IMAGERY. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, PRIMARILY BASED ON
PERSISTENCE AND THE OVERALL WORSENING STRUCTURAL PRESENTATION, WITH
ONLY ONE FIX AVAILABLE FROM PGTW, AT T2.0. THE ENVIRONMENT REMAINS
UNFAVORABLE, WITH MARGINAL SSTS, MODERATE TO HIGH EASTERLY SHEAR
AND STRONG POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 41 KTS AT 010000Z
   CIMSS AIDT: 34 KTS AT 300000Z
   CIMSS D-PRINT: 43 KTS AT 010000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: HIGH MID-LEVEL SHEAR

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 04B HAS TRACKED TOWARDS THE COAST AT ABOUT
TWO KNOTS OVER THE PAST SIX HOURS, DRIFTING IN A WEAK STEERING
PATTERN. THE SYSTEM IS SITUATED WITHIN A BROAD AREA OF CYCLONIC
ROTATION, WITH RIDGING TO THE NORTHEAST AND NORTHWEST. IN A RATHER
ABRUPT CHANGE, THE LATEST GFS RUN HAS GIVEN UP ON TAKING THE SYSTEM
TO THE EAST IN THE NEAR-TERM, AS IT HAS BEEN DOING FOR THE LAST
COUPLE OF DAYS. THE RIDGING TO THE NORTHWEST IS NOW EXPECTED TO
BUILD SOUTHEASTWARD ALONG THE SOUTHERN SLOPES OF THE HIMALAYAS AT A
MUCH FASTER RATE THAN IN EARLIER RUNS, WHICH WILL ALLOW TC 04B TO
TRACK WESTWARD THROUGH THE SHORT DURATION OF THE FORECAST PERIOD.
THE SYSTEM HAS CONTINUED TO WEAKEN AS IT CONTINUES TO UPWELL
RELATIVELY COOL WATERS TO THE SURFACE AND SUCCUMBS TO THE
PERSISTENT EASTERLY SHEAR. ONCE IT MOVES ASHORE IN THE NEXT FEW
HOURS, IT WILL RAPIDLY WEAKEN AND DISSIPATE WITHIN THE NEXT 18 TO
24 HOURS. TRACK SPEEDS WILL BE SLOW THROUGH THE FORECAST, BUT THE
REMNANTS OF TC FENGAL WILL ACCELERATE AFTER TAU 24, AND CROSS THE
SOUTHERN PORTION OF THE INDIAN SUBCONTINENT BEFORE MOVING INTO THE
NORTH ARABIAN SEA (NAS) AROUND TAU 60, WHERE IT WILL NEED TO BE
CLOSELY MONITORED FOR POSSIBLE REINTENSIFICATION. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE HAS COME INTO BETTER
AGREEMENT WITH THIS MODEL RUN. AS MENTIONED ABOVE, THE GFS NO
LONGER SHOWS THE SYSTEM MOVING BACK TO THE EAST AND NOW SLOWLY
MOVES THE SYSTEM INLAND THROUGH TAU 24, THEN ACCELERATES WESTWARD
INTO THE NAS BY TAU 60. THE REMAINDER OF THE CONSENSUS MEMBERS,
WITH THE EXCEPTION OF NAVGEM, DEPICT A SIMILAR TRACK TO THE GFS,
PROVIDING INCREASED CONFIDENCE TO THE JTWC FORECAST, WHICH LIES
CLOSE TO THE CONSENSUS MEAN. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THAT THE SYSTEM WILL STEADILY WEAKEN THROUGH THE FORECAST
AND DISSIPATE NO LATER THAN TAU 24. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
NNNN