WDIO32 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06B (HAMOON) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8N 89.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 174 NM SOUTH-SOUTHEAST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT THE
INNER CORE OF CYCLONE 06B (HAMOON) HAS BECOME BETTER ORGANIZED
DURING THE PAST SIX HOURS, AND A PERIOD OF QUICK INTENSIFICATION
HAS LIKELY OCCURRED. A NEARLY SYMMETRIC MASS OF DEEP CONVECTION
WITH CLOUD TOPS COLDER THAN -80 DEGREES CELSIUS HAS DEVELOPED, WITH
AN EMBEDDED CENTER MANIFESTING AS A SLIGHT WARM DIMPLE. A 240002Z
GPM MICROWAVE PASS REVEALED A CLOSED EYEWALL COLOCATED WITH THE
AFOREMENTIONED DIMPLE. VERTICAL SHEAR HAS INCREASED TO 20-25 KT,
BUT HAS APPARENTLY NOT YET AFFECTED THE CORE CONVECTIVE STRUCTURE.
STRONG UPPER-LEVEL OUTFLOW INTO A JET STREAK OVER SOUTHERN CHINA IS
FACILITATING THIS DEVELOPMENT OF THE INNER CORE. THE INITIAL
INTENSITY IS RAISED TO 70 KT BASED ON A BLEND OF AGENCY DVORAK
ESTIMATES AND OBJECTIVE SATELLITE-BASED ESTIMATES FROM CIMSS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   CIMSS SATCON: 60 KTS AT 231945Z
   CIMSS ADT: 59 KTS AT 232100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE INTENSITY FORECAST FOR THE FIRST
24 HOURS HAS BEEN ADJUSTED 15-20 KT UPWARD DUE TO THE INCREASE IN
THE INITIAL INTENSITY.

FORECAST DISCUSSION: CYCLONE 06B (HAMOON) TOOK ADVANTAGE OF SEVERAL
HOURS OF STRONG POLEWARD OUTFLOW AND LOW TO MODERATE VERTICAL
SHEAR, AND HAS QUICKLY INTENSIFIED DURING THE PAST 6-12 HOURS.
VERTICAL SHEAR IS INCREASING, HOWEVER, AND ALL MODELS EXPECT
SIGNIFICANT DISRUPTION OF THE INNER CORE TO BEGIN IMMINENTLY.
INDEED, HAFS, ECMWF, AND GFS ALL SHOW FULL DECOUPLING OF THE VORTEX
PRIOR TO LANDFALL AS IT BECOMES IMMERSED IN THE MID-LATITUDE
WESTERLIES. GIVEN THE RECENT STRENGTHENING TREND, THE LANDFALL
INTENSITY MAY BE SENSITIVE TO HOW QUICKLY HAMOON REACHES THE
COASTLINE, AS THE LONGER THAT TAKES, THE MORE TIME ELEVATED SHEAR
WILL HAVE TO ADVERSELY IMPACT THE STORM. THE JTWC FORECAST HAS BEEN
SHIFTED SLIGHTLY EASTWARD, AND SHOWS LANDFALL IN BANGLADESH IN
ABOUT 48 HOURS WITH AN INTENSITY OF 40 KT. DISSIPATION WILL QUICKLY
FOLLOW AS THE VORTEX MOVES INLAND.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE
MULTI-MODEL CONSENSUS, WHICH HAS SHIFTED SLIGHTLY EASTWARD SINCE
THE PREVIOUS FORECAST. THE JTWC INTENSITY FORECAST IS ALSO CLOSE TO
THE MULTI-MODEL CONSENSUS, WHICH REMAINS TIGHTLY CLUSTERED AROUND A
STEEP WEAKENING TREND THROUGH LANDFALL.

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