WDIO31 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07B (SEVEN) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.3N 88.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 199 NM SOUTH OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED, WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH DEEP CONVECTION FLARING OVER THE NORTHERN SEMICIRCLE. A
161546Z ASCAT-C BULLSEYE IMAGE REVEALS A SLIGHTLY ELONGATED
CIRCULATION WITH A SWATH OF 30 TO 35 KNOT WINDS OVER THE
NORTHWESTERN AND EASTERN SEMICIRCLE, WHICH SUPPORTS THE INITIAL
INTENSITY ASSESSMENT OF 35 KNOTS. THEREFORE, THE INITIAL INTENSITY
IS PLACED WITH HIGH CONFIDENCE, HEDGED SLIGHTLY HIGHER THAN THE
PGTW AGENCY DVORAK INTENSITY ESTIMATE OF T2.0 (30 KNOTS). THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
ASCAT-C ALONG WITH THE EIR IMAGERY, WHICH INDICATES A GENERAL
NORTHEASTWARD TRACK MOTION. ENVIRONMENTAL ANALYSIS INDICATES A
MARGINALLY FAVORABLE ENVIRONMENT WITH HIGH (30+ KNOTS) VERTICAL
WIND SHEAR (VWS), OFFSET BY WARM (28-29 C) SEA SURFACE TEMPERATURES
(SSTS) AND ROBUST DIFFLUENT POLEWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA. 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE EAST.

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 30+ KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 07B (SEVEN) IS FORECAST
TO TRACK NORTHEASTWARD ALONG THE WESTERN SIDE OF THE DEEP-LAYER
SUBTROPICAL STEERING RIDGE TO THE EAST, WITH LANDFALL EXPECTED
WITHIN THE NEXT 24 HOURS IN THE VICINITY OF KUAKATA, BANGLADESH.
DUE TO THE MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS, THE
SYSTEM IS EXPECTED TO INTENSIFY SLIGHTLY TO A PEAK NEAR 40 KNOTS BY
TAU 12. HOWEVER, THE SYSTEM IS EXPECTED TO GRADUALLY WEAKEN AS IT
APPROACHES THE BANGLADESH COAST, WITH DISSIPATION EXPECTED TO
INITIATE BY TAU 24. AFTER LANDFALL, THE SYSTEM WILL CONTINUE TO
TRACK GENERALLY NORTH-NORTHEASTWARD WHILE SLOWLY WEAKENING DUE TO
LAND INTERACTION BEFORE DISSIPATING NO LATER THAN TAU 36.

MODEL DISCUSSION: NUMERICAL TRACK GUIDANCE IS IN OVERALL GOOD
AGREEMENT THROUGH THE FORECAST PERIOD, WITH THE JTWC TRACK FORECAST
FOLLOWING CLOSE TO THE MULTI-MODEL CONSENSUS, PROVIDING HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK. THE INTENSITY GUIDANCE IS
ALSO IN GENERAL GOOD AGREEMENT. HOWEVER, THE JTWC FORECAST DEVIATES
ABOUT FIVE KNOTS HIGHER IN THE FIRST 12 HOURS, MORE IN LINE WITH
THE HWRF PEAK INTENSITY BY TAU 12 AFTER TAU 12, ALL INTENSITY
GUIDANCE MEMBERS SHOW A STEADY DECREASING TREND. OVERALL, THE JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE AND ALIGNS
WELL WITH THE GUIDANCE PACKAGE.

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