WDIO32 PGTW 270300
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: 6.6N 81.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 1046 NM SOUTH-SOUTHWEST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
ORGANIZING SPIRAL BANDS OF DEEP CONVECTION WRAPPING INTO A FULLY
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH
TROPICAL CYCLONE (TC) 05B. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE ANIMATED SHORTWAVE INFRARED
SATELLITE LOOP, WHILE THE INITIAL INTENSITY OF 35 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON A 261940Z GCOMW1 AMSR2 AND A 261820Z
OCEANSAT-3 PASSES SHOWING DISTINCT BANDS OF 30-35 KT WINDS,
PARTICULARLY OVER THE SOUTHERN SEMICIRCLE OF THE CIRCULATION, AS
WELL AS TO THE NORTHEAST. WITH THE LLCC ASSESSED OVER LAND, THE
ENVIRONMENTAL CONDITIONS ARE ANALYZED AS MARGINAL, WITH LOW (10-15
KTS) VERTICAL WIND SHEAR (VWS) AND ROBUST DUAL-CHANNEL OUTFLOW. AS
THE CONVECTIVE BANDS EXTEND WELL OVER WATER, THE WARM (28-29 C) SEA
SURFACE TEMPERATURES (SST) ARE ALSO BENEFICIAL, ESPECIALLY ONCE THE
SYSTEM RE-EMERGES OVER WATER.

INITIAL WIND RADII BASIS: A 261940Z GCOMW1 AMSR2 AND A 261820Z
OCEANSAT-3 PASSES

CURRENT STEERING MECHANISM: WEAK RIDGING TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   KNES: T2.0 - 30 KTS
   DEMS: T1.5 - 25 KTS
   CIMSS D-PRINT: 29 KTS AT 270000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 05B IS FORECAST TO TRACK NORTHWARD THROUGH
ITS LIFESPAN. DURING THE INITIAL 48 HOURS THE LLCC IS EXPECTED TO
BE LOCATED OVER LAND, AS THE SYSTEM IS MAINLY STEERED BY WEAK
RIDGING TO THE EAST. THE CIRCULATION IS BROAD, WITH 34 KT WIND
RADII EXTENDING WELL OUTSIDE OF THE PERIMETER OF SRI LANKA. AS
SUCH, THE SYSTEM IS EXPECTED TO MAINTAIN INTENSITY, WHILE THE LLCC
TRANSLATES ACROSS THE ISLAND. AROUND TAU 48, TC 05B IS EXPECTED TO
RE-EMERGE OVER WATER JUST NORTH OR NORTHEAST OF SRI LANKA.
SIMULTANEOUSLY, A SUBTROPICAL RIDGE (STR) INITIALLY CENTERED TO THE
NORTH WILL RETROGRADE EASTWARD AND ASSUME THE PRIMARY STEERING,
PUSHING THE SYSTEM FURTHER NORTH. THIS WILL OPEN A SHORT WINDOW OF
OPPORTUNITY FOR SLIGHT INTENSIFICATION. HOWEVER, AS THE SYSTEM
APPROACHES LAND, THE FRICTIONAL EFFECTS OF TERRAIN INTERACTION,
COMBINED WITH INCREASING VERTICAL SHEAR, AS WELL AS DRY AIR
ENTRAINMENT WILL RESULT IN A WEAKENING TREND. THE SYSTEM WILL BEGIN
DISSIPATING AS SOON AS IT MAKES LANDFALL OVER THE SOUTHEASTERN
COAST OF INDIA, WHICH IS CURRENTLY EXPECTED BETWEEN TAUS 72 AND 96.

MODEL DISCUSSION: NUMERICAL MODEL SHORT-TERM TRACK GUIDANCE IS IN
VERY GOOD AGREEMENT AS WITNESSED BY A CROSS-TRACK SPREAD OF 65-75
NM THROUGHOUT THE FORECAST PERIOD. THE ONLY MINOR OUTLIER IS
GALWEM, WHICH PREDICTS A MORE EASTERN TRACK, WHICH EXTENDS THE
CROSS-TRACK SPREAD OF THE GUIDANCE ENVELOPE TO 100 NM. OVERALL
TRACK FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE, DUE TO
UNCERTAINTY ASSOCIATED WITH THE INITIAL POSITION, AS WELL AS THE
ALONG-TRACK SPREAD INCREASING TO 135 NM BY TAU 96 INDICATING
UNCERTAINTY RELATED TO THE TIMELINE OF RE-EMERGENCE OVER WATER
AND IN RETURN, LANDFALL OVER INDIA. INTENSITY GUIDANCE IS ALSO
ASSESSED WITH MEDIUM CONFIDENCE, AS ALL CONSENSUS MEMBERS INDICATE
MAINTAINED INTENSITY, WITH A POTENTIAL FOR SLIGHT INCREASES THOUGH
TAU 60, FOLLOWED BY A WEAKENING TREND AFTERWARDS, AND DISSIPATION
BETWEEN TAUS 96 AND 120. THE CONSENSUS ENVELOPE SPREAD IS 25 KTS,
MAINLY DUE TO NAVGEM-DRIVEN COAMPS-TC INDICATING PEAK INTENSITY OF
60 KTS. OFFICIAL JTWC FORECAST CLOSELY FOLLOWS THE MULTI-MODEL
CONSENSUS THROUGHOUT THE FORECAST.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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