WDIO31 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05B (FIVE) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 86.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 532 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WELL
DEFINED MID-LEVEL ROTATION SIGNATURE, WITH STRONG FLARING
CONVECTION DISPLACED TO THE NORTHWEST OF THE ASSESSED LOW LEVEL
CIRCULATION CENTER. WHILE THE DEEPEST OF THE CONVECTION IS
DISPLACED A BIT TO THE NORTHWEST, THE LOW LEVEL CIRCULATION CENTER
(LLCC) HAS TUCKED UNDER THE SOUTHEASTERN CORNER OF THE CONVECTIVE
ENVELOPE. THE INITIAL POSITION IS PLACED WITH ONLY MEDIUM
CONFIDENCE DUE TO A LACK OF RECENT SCATTEROMETER DATA AND
INCONCLUSIVE MICROWAVE DATA FROM 022116Z. THE INITIAL INTENSITY IS
ASSESSED AT A GENEROUS 35 KNOTS WITH LOW CONFIDENCE BASED ON A PGTW
FIX AT 0000Z OF T2.5 (35 KTS) WITH A .40 WRAP. DEMS IS FIXING AT
T2.0 (30 KTS). THE SYSTEM IS TRACKING QUICKLY NORTHWEST ALONG THE
WESTERN PERIPHERY OF DEEP SUBTROPICAL RIDGE CENTERED OVER NORTHERN
THAILAND. THE ENVIRONMENT IS MARGINALLY FAVORABLE, TRENDING
FAVORABLE, WITH WARM SSTS (28-29C) AND ROBUST POLEWARD OUTFLOW. AT
THE CURRENT TIME, VWS IS MODEST, THE CIMSS ANALYSIS DEPICTING A
SMALL POCKET OF LOW SHEAR IN DIRECT VICINITY OF THE LLCC, COCOONED
WITHIN A LARGER AREA OF MODERATE TO HIGH EASTERLY SHEAR. THE
ENVIRONMENTAL EASTERLY FLOW IS HIGHLY DIVERGENT NEAR THE SYSTEM,
PROVIDING STRONG SUPPORT FOR THE ENHANCED CONVECTION, BUT IS
RESULTING IN A WESTWARD TILT WITH HEIGHT OF THE VORTEX BASED ON GFS
AND HWRF CROSS-SECTIONS.

INITIAL WIND RADII BASIS: OTHER 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
STR CENTERED OVER NORTHERN THAILAND. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: VORTEX TILT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 05B HAS SLOWLY BUT STEADILY CONSOLIDATED
OVER THE PREVIOUS TWO DAYS, AND HAS NOW REACHED WARNING CRITERIA.
THE SYSTEM IS CURRENTLY TRACKING QUICKLY TOWARDS THE NORTHWEST
ALONG THE SOUTHWEST SIDE OF A DEEP STR TO THE EAST. OVER THE NEXT
24 HOURS, THE SYSTEM WILL SLOW AS IT REACHES THE RIDGE AXIS, ROUND
THE AXIS NEAR TAU 36, THEN ACCELERATE NORTH THEN NORTHEAST THROUGH
THE REMAINDER OF THE FORECAST. THE FORECAST CALLS FOR THE SYSTEM TO
MAKE LANDFALL NEAR TAU 48, THEN SKIRT THE COASTLINE AND PASSING
NEAR KOLKATA BETWEEN TAUS 72 AND 96 BEFORE MOVING INTO CENTRAL
BANGLADESH BY THE END OF THE FORECAST. DUE TO THE PERSISTENT
EASTERLY UPPER-LEVEL FLOW, THE VORTEX OR CORE OF THE SYSTEM IS
TILTED A BIT TO THE WEST. WHILE UPPER-LEVEL FLOW IS EXPECTED TO
SLACKEN SLIGHTLY OVER THE NEXT 24 HOURS, THE VORTEX TILT IS
FORECAST TO REMAIN IN PLACE, WHICH WILL ACT AS A BRAKING MECHANISM
ON THE RATE OF INTENSIFICATION, EVEN IN LIGHT OF THE ROBUST
POLEWARD OUTFLOW IN THE BASE OF A PASSING MID-LATITUDE TROUGH. THUS
THE SYSTEM IS FORECAST TO INTENSIFY AT A LESS THAN CLIMATOLOGICAL
RATE, PEAKING AT 50 KNOTS BY TAU 36, JUST OFFSHORE OF
VISAKHAPATNAM, INDIA. INCREASING SHEAR, DRY AIR ENTRAINING IN FROM
THE INDIA SUBCONTINENT AND FRICTIONAL EFFECTS OVER LAND WILL
CONSPIRE TO STEADILY WEAKEN AND ULTIMATELY DISSIPATE THE SYSTEM
OVER BANGLADESH BY TAU 96. 

MODEL DISCUSSION: TRACK GUIDANCE, WITH THE EXCEPTION OF GFS, IS IN
GOOD AGREEMENT ON THE OVERALL SCENARIO, WITH CROSS-TRACK SPREAD
INCREASING AFTER TAU 24, PLACING THE ECMWF AND ECMWF ENSEMBLE
TRACKERS OVER LAND BY TAU 36. THE REMAINDER OF THE TRACKERS KEEP
THE CENTER OFFSHORE UNTIL TAU 48. THE GFS TURNS THE SYSTEM SHARPLY
EASTWARD AFTER TAU 12, WITH A LANDFALL NEAR CHITTAGONG, BUT THIS
SCENARIO IS UNREALISTIC AS THE SYSTEM IS UNLIKELY TO TRACK DIRECTLY
INTO THE STRONG RIDGE. THE JTWC FORECAST LIES JUST INSIDE AND
SLIGHTLY FASTER THAN THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE.
INTENSITY GUIDANCE IS MIXED, WITH THE SHIPS GUIDANCE INDICATING A
PEAK INTENSITY NEAR 65 KNOTS, WHILE THE COAMPS-TC SUGGESTS A PEAK
CLOSER TO 45 KNOTS. THE JTWC FORECAST CLOSELY TRACKS THE HWRF
SOLUTION, JUST SLIGHTLY LOWER THAN CONSENSUS THROUGH TAU 36, THEN
SLIGHTLY ABOVE IT THEREAFTER. OVERALL CONFIDENCE IS LOW DUE TO
UNCERTAINTIES WITH THE AMOUNT OF LAND INTERACTION, WHICH IS
DEPENDENT UPON THE EXACT TRACK.   

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