WDIO31 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08B (EIGHT) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.5N 82.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 162 NM SOUTHEAST OF CHENNAI, INDIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TC 08W HAS GATHERED ITSELF AND CONSOLIDATED UPSTREAM OF THE
SOUTHEAST COAST OF INDIA. THE SYSTEM DEVELOPED SLOWLY OVER THE
PAST FEW DAYS DUE TO STIMULATION FROM A PEAKING PHASE THREE OF THE
MJO.  WITHOUT THE BOOST FROM THE MJO THE SYSTEM WOULD NOT LIKELY
HAVE DEEPENED BEYOND DEPRESSION STATUS. BUT OVER THE PAST FOUR
HOURS CONVECTION DEEPENED AND TIGHTENED AROUND THE LOW LEVEL
CIRCULATION CENTER (LLCC), LEAVING A BROAD DOUGHNUT HOLE THAT LENDS
CONFIDENCE TO BOTH THE POSITION AND DVORAK ASSESSMENTS. THE
INTENSITY ASSESSMENT IS BASED ON DVORAKS AND INFERRED FROM SURFACE
PRESSURE REPORTS ALONG THE EAST COAST OF INDIA AS WELL AS MODEL
FIELDS. TC 08B IS IN AN EXCELLENT ENVIRONMENT FOR DEEPENING. ANIMATED
WATER VAPOR IMAGERY SHOWS SPECTACULAR OUTFLOW, WITH THE POLEWARD
FLANK TAPPING INTO A VIGOROUS SUBTROPICAL JET THAT IS ARCHING OVER
MYANMAR AND SOUTHERN CHINA.  EQUATORWARD OUTFLOW IS ALSO VIGOROUS.
TOTAL PRECIPITABLE WATER LOOPS FROM CIMSS SHOW DEEP MOISTURE IS NOW
WRAPPING AROUND THE ENTIRE CIRCULATION AS WELL AS A BROAD BELT OF
EQUATORIAL WESTERLIES CONTINUING TO FEED MOISTURE INTO THE SYSTEM.
THE ENVIRONMENT BETWEEN THE STORM AND THE COAST IS COMPLETELY
SATURATED WITH DEEP MOISTURE. 28 TO 29 DEGREE SEA WATER
TEMPERATURES AND DECENT OCEAN HEAT CONTENT VALUES LIE ALONG TRACK
UNDERNEATH LOW VERTICAL WINDSHEAR (VWS) VALUES. WINDSHEAR INCREASES
SHARPLY NORTH OF CHENNAI, BUT IN THE NEAR TERM, EVEN THOUGH THE
SHEAR INCREASES NORTH OF THE 13TH LATITUDE, THE ENHANCED EXHAUST
WILL ALLOW THE SYSTEM TO DEVELOP FURTHER.

INITIAL WIND RADII BASIS: AVERAGE DISTANCE TO BANDING FEATURES IN A
022243Z SSMIS 37V. 

CURRENT STEERING MECHANISM: THE SOUTHWESTERN FLANK OF THE
SUBTROPICAL RIDGE WHICH EXTENDS FROM OVER RANGOON THROUGH THE
VISAKHAPATNAM AREA. 

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE 08B WILL TAKE A STEADY BEND
TO THE NORTH-NORTHWEST, SKIRTING THE PONDICHERRY COAST WHILE
DEEPENING THANKS TO A VERY FAVORABLE ENVIRONMENT. THE SYSTEM WILL
INTENSIFY FREELY UP UNTIL LAND INTERACTION BEGINS TO WEAR ON IT NEAR
THE COAST. THE PARALLEL BEARING TO THE COAST AND THE LARGER THAN
AVERAGE TRACK GUIDANCE SPREAD MAKE FOR LOWER CERTAINTY AS TO
PRECISELY WHERE, AND AT WHAT INTENSITY, THE SYSTEM WILL COME
ASHORE.  BUT HIGH TROPICAL STORM STRENGTH WINDS APPROACHING TYPHOON
STRENGTH JUST PRIOR TO LANDFALL ARE PLAUSIBLE. ONCE INLAND, THE
SYSTEM WILL BEGIN RAPID DECAY, BUT THE RISK OF RE-EMERGENCE OVER
THE NORTHERN BAY OF BENGAL REMAINS POSSIBLE. EVEN IF TC O8B DOES
TRACK BACK INTO THE NORTHERN BAY OF BENGAL, HOWEVER, COOLER SEA
WATER AND VERY HIGH VWS WILL CAP INTENSIFICATION MAKING
RE-INTENSIFICATION UNLIKELY. THE MUCH MORE LIKELY SCENARIO IS THAT
OF THE SYSTEM MOVING ASHORE NEAR 05DEC0600Z, NEAR ONGOLE, AND
DISSIPATING OVER LAND BY 07DEC1200Z AS IT SHEARS AND CHOKES ON DRY
MID-LEVEL AIR.  

MODEL DISCUSSION: ECMWF HAS BEEN OUTPERFORMING GFS IN THIS CASE.
GFS BEGAN WITH THE TRACK CURLING OVER BANGLADESH BUT HAS GRADUALLY
WALKED WEST AND JOINED THE PACK. WITH THE LATEST RUNS ALL GUIDANCE
IS INDICATING A LAND STRIKE BETWEEN CHENNAI AND VISAKHAPATNAM, WITH
DECAY OVER THE SUBCONTINENT THROUGH THE EXTENDED RANGE.  TRACK
GUIDANCE IS FINE THROUGH THE FIRST 24 HOURS BUT AFTER THAT THERE IS
A SIGNIFICANT DROP-OFF DUE TO A LARGER-THAN-AVERAGE CROSS-TRACK
SPREAD.  THE JTWC FORECAST LEANS INSIDE AND RIGHT OF CONSENSUS,
FAVORING THE ECMWF ENSEMBLE AND THE H-FAS. THOSE MODELS STEER THE
STORM, OR WHAT IS LEFT OF IT, BACK TO SEA NEAR THE 20TH LATITUDE
AFTER THE END OF THE FIVE DAY FORECAST. THE TRACK ENDS JUST PRIOR
TO THAT AND DISSIPATION OVER LAND REMAINS THE EXPECTATION. THE
INTENSITY FORECAST GOES SLIGHTLY HIGHER THAN CONSENSUS THROUGH
LANDFALL IN CONSIDERATION OF THE FAVORABLE ENVIRONMENT, THEN
DECAYS THE STORM FASTER THAN GUIDANCE BASED ON THE OBSERVED
TENDENCY OF THE GUIDANCE TO UNDER-FACTOR THE INFLUENCE OF THE
RUGGED TERRAIN IN EASTERN INDIA. GUIDANCE IS EXPECTED TO CONGEAL AS
THE STORM MATURES, GIVING HIGHER CERTAINTY.  



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