WDIO32 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06B (SIX)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.5N 87.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 395 NM SOUTHWEST OF CHITTAGONG
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 06B (SIX) AS HAVING GRADUALLY CONSOLIDATED WITH
PERSISTENT CENTRALIZED CONVECTION OVER THE PAST SIX HOURS.
COMPLETELY OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC), THE
270NM WIDE VISIBLE CLOUD CANOPY SHOWS EVIDENCE OF MODERATE
SOUTHERLY SHEAR ALOFT WITH THIN, WISPY CLOUD FILAMENTS DRIFTING
NORTHWARD INTO THE POLEWARD OUTFLOW CHANNEL. FLARING CONVECTION
OVER THE LLCC APPEARS TO BE ATTEMPTING TO COALESCE BUT HAS REMAINED
ASYMMETRIC, FAVORING THE SOUTHEASTERN SEMICIRCLE. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A 230600Z
METEOSAT-9 IR-BD IMAGE. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON A 230340Z METOP-B ASCAT
PARTIAL-PASS IMAGE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: STR EAST OF TC 06B

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 06B IS FORECAST TO TRACK NORTHEASTWARD OVER
THE NEXT 48 HOURS.  THROUGH TAU 12, THE SYSTEM WILL TAKE ADVANTAGE
OF A FAVORABLE ENVIRONMENT AND GRADUALLY INTENSIFY.  AFTER TAU 12,
SEA SURFACE TEMPERATURES DROP SLIGHTLY AND VERTICAL WIND SHEAR 
INCREASES (45KTS BY TAU 48). ADDITIONALLY, A SHORTWAVE TROUGH IS 
FORECAST TO DIG SOUTH FROM THE NORTH OVER THE NORTHERN BAY OF BENGAL 
(TAU 12) AND IS ANTICIPATED TO RAPIDLY WEAKEN TC 06B WITH THE 
INTRODUCTION OF DEEP-LAYER WESTERLY FLOW. COMPLETE DISSIPATION IS 
FORECAST TO OCCUR PRIOR TO TAU 48. 

MODEL DISCUSSION: GLOBAL NUMERICAL MODELS ARE IN EXCEPTIONAL
AGREEMENT THAT TC 06B WILL TRACK NORTHEASTWARD THROUGH TAU 48, WITH
THE JTWC CONSENSUS SHOWING A CROSS-TRACK SPREAD OF JUST 28NM AT TAU
48. THERE IS, HOWEVER, SIGNIFICANT UNCERTAINTY PRESENTED IN TRACK
SPEED, WITH AN ALONG-TRACK SPREAD OF 216NM BETWEEN GALWEM AND GFS.
THIS UNCERTAINTY CONTRIBUTES TO A TRACK FORECAST CONFIDENCE OF
MEDIUM. INTENSITY GUIDANCE IS IN VERY GOOD AGREEMENT THAT TC 06B
WILL CONTINUE TO GRADUALLY INTENSIFY TO NEAR 45 KTS BY TAU 12,
FOLLOWED BY A WEAKENING TREND TO 20 KTS BY TAU 48. GIVEN THE
VARIABILITY IN TRACK SPEED, THE FORECAST CONFIDENCE FOR INTENSITY
IS ALSO MEDIUM.

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