WDIO31 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04B (FOUR) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.0N 80.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 717 NM SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A LARGE AREA OF DEEP
CONVECTION EAST AND NORTHEAST OF A FULLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE MSI LOOP AND A 110550Z GMI 89GHZ IMAGE. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED AND AN EARLIER 110355Z BULLSEYE METOP-B ASCAT PASS AND
MULTIPLE AGENCY DVORAK ESTIMATES BETWEEN A T1.5 (25KTS) AND T2.0
(30KTS). THE ENVIRONMENT IS OVERALL MARGINALLY FAVORABLE WITH
MODERATE POLEWARD OUTFLOW, WARM (28-29 CELCIUS) SEA SURFACE
TEMPERATURES, ALL BEING OFFSET BY MODERATE TO STRONG VERTICAL WIND
SHEAR.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   DEMS: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION:  TC 04B IS EXPECTED TO CONTINUE ON A
WEST-NORTHWEST TRACK TOWARDS THE COAST OF INDIA AND MAKE LANDFALL
NEAR CHENNAI, INDIA WITHIN THE NEXT 6 HOURS. TC 04B IS EXPECTED TO
MAINTAIN CURRENT INTENSITY UNTIL IT REACHES LAND WHERE IT WILL
BEGIN TO WEAKEN AND ERODE AS IT INTERACTS WITH THE TERRAIN THROUGH
TAU 12. AFTER TAU 12, TC 04B WILL TRACK WESTERLY ACROSS THE INDIAN
PENINSULA, RAPIDLY DISSIPATE OVER THE ROUGHER TERRAIN IN CENTRAL
INDIA NEAR TAU 24. THE REMNANTS OF TC 04B WILL CONTINUE TRACKING 
OVER INDIA AND MAY MOVE OVER THE ARABIAN SEA, HOWEVER, THERE IS LOW 
PROBABILITY OF REGENERATION.

MODEL DISCUSSION: GUIDANCE FOR THE SHORT TRACK IS IN GENERALLY FAIR
AGREEMENT, EXCEPT FOR NAVGEM AND AFUM MODEL GUIDANCE, WHICH ARE THE
FAR LEFT OUTLIERS AND TURN THE TC TO THE WEST-SOUTHWEST PRIOR TO
LANDFALL. THE JTWC FORECAST LIES WITHIN THE TIGHTEST GROUPING OF
MODELS OF ECMWF, GFS, AND UKMET LYING JUST TO THE RIGHT OF THE
CONSENSUS MEAN WITH MEDIUM CONFIDENCE. THE INTENSITY GUIDANCE IS
ALSO IN FAIR AGREEMENT WITH A STEADY WEAKENING AFTER LANDFALL. 

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