WDIO31 PGTW 170300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07B (SEVEN) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.3N 88.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 141 NM SOUTH-SOUTHEAST OF KOLKATA, INDIA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A MASS OF
DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC)
ALONG WITH FLARING CONVECTION DISPLACED OVER THE NORTHERN AND
EASTERN PERIPHERIES. MSI SHOWS THAT TROPICAL CYCLONE (TC) 07B IS
MAINTAINING AN INNER CORE OF DEEP CONVECTION. HIGH VERTICAL WIND
SHEAR HAS CONTINUED TO BE PERSISTENT OVER THE PAST SIX HOURS BUT
HAS NOT DISRUPTED THE DEEP CONVECTION NEAR THE LLCC. THE INITIAL
POSITION IS BASED ON THE MSI IMAGERY AS WELL AS AGENCY POSITION
FIXES AND PLACED WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY
REMAINS AT 35 KTS BASED ON A COMBINATION OF OBJECTIVE ADT (35 KTS),
AIDT (35 KTS), DPRINT (33 KTS) AND SUBJECTIVE DVORAK INTENSITY
ESTIMATES RANGING FROM T2.0 (30 KTS) AND T2.5 (35 KTS). THE
ENVIRONMENTAL CONDITIONS REMAIN 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: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 170000Z

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

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 07B WILL CONTINUE TRACKING NORTHEASTWARD
ALONG THE WESTERN SIDE OF THE DEEP-LAYER SUBTROPICAL STEERING RIDGE
TO THE EAST, WITH LANDFALL EXPECTED WITHIN THE NEXT 12 HOURS IN THE
VICINITY OF KUAKATA, BANGLADESH. WIND SHEAR WILL REMAIN HIGH DURING
THE REMAINING TIME BEFORE LANDFALL IN BANGLADESH. HOWEVER, SOME
ADDITIONAL SLIGHT INTENSIFICATION IS POSSIBLE IF THE INNER CORE OF
CONVECTION CAN BECOME BETTER ORGANIZED AND OFFSET THE HOSTILE HIGH
LEVELS OF WIND SHEAR. AFTER TAU 12, THE SYSTEM IS EXPECTED TO
GRADUALLY WEAKEN NEAR THE BANGLADESH COAST, WITH DISSIPATION
EXPECTED TO INITIATE. THE SYSTEM WILL CONTINUE TO TRACK GENERALLY
NORTH-NORTHEASTWARD WHILE SLOWLY WEAKENING DUE TO LAND INTERACTION
BEFORE DISSIPATING BY TAU 24.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
OVERALL GOOD AGREEMENT THROUGH THE FORECAST PERIOD. BOTH THE GFS
AND ECMWF ENSEMBLE MEAN ARE IN GOOD AGREEMENT, STAYING WITHIN THE
GUIDANCE ENVELOPE AND NEAR THE MULTI-MODEL CONSENSUS. THEREFORE,
THE JTWC TRACK FORECAST FOLLOWS CLOSE TO THE MULTI-MODEL CONSENSUS,
PROVIDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. THE INTENSITY
GUIDANCE IS IN GENERAL GOOD AGREEMENT, EXCEPT HWRF, WHICH PEAKS
NEAR 40 KNOTS WITHIN THE NEXT 12 HOURS. ALL INTENSITY GUIDANCE
MEMBERS SHOW A STEADY DECREASING TREND AFTER TAU 12. OVERALL, THE
JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE.

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