WDPN31 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (CHAMPI) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1N 139.4E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 246 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CONSOLIDATING YET STILL ASYMMETRIC CIRCULATION WITH DEEP FLARING
CONVECTION SUSTAINED OVER THE CENTER. A 242359Z 89 GHZ MHS
MICROWAVE IMAGE SHOWS CONVECTIVE BANDING WRAPPING INTO THE WESTERN
SEMICIRCLE OF THE SYSTEM FROM THE NORTH BUT SHOWS NO EVIDENCE OF A
SUSTAINED STRONG INNER CORE AS OF YET. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON A 250005Z ASCAT IMAGE SHOWING
A DEFINED BUT ASYMMETRIC CIRCULATION WITH 45-50 KT WINDS WRAPPING
INTO THE CENTER. THE INITIAL INTENSITY IS BASED ON THE PGTW AND
RJTD DVORAK CURRENT INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 57 KTS AT 242340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 06W WILL CONTINUE TO TRACK
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST AS IT REMAINS IN A FAVORABLE ENVIRONMENT WITH LOW
VERTICAL WIND SHEAR (VWS), WARM (28-30C) SEA SURFACE TEMPERATURES
(SSTS), AND NEAR-RADIAL OUTFLOW ALLOWING 06W TO REACH A PEAK
INTENSITY OF 85 KTS BY TAU 36. AS THE SYSTEM CONTINUES TO TURN MORE
NORTH-NORTHEASTWARD AROUND THE STR, COOLER SSTS OF 23-25C AND
INCREASING VWS FROM THE WESTERLIES WILL BEGIN TO WEAKEN 06W. NEAR
TAU 48, THE SYSTEM WILL BEGIN EXTRATROPICAL TRANSITION WITH
COMPLETION BY TAU 72 AS THE SYSTEM TRACKS NEAR THE UPPER-LEVEL JET
AND TRANSITIONS INTO AN EXTRATROPICAL LOW ON THE BAIU FRONT. 

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS SLIGHTLY EAST OF THE
MULTI-MODEL CONSENSUS DUE TO THE WESTERN OUTLIERS JGSM AND NVGM. 
HOWEVER, THERE IS OVERALL GOOD AGREEMENT IN THE NUMERICAL MODEL 
GUIDANCE WITH A 65 NM CROSS-TRACK SPREAD AT TAU 48 LENDING TO HIGH 
CONFIDENCE IN THE JTWC FORECAST TRACK. THE JTWC INTENSITY FORECAST AND 
PEAK INTENSITY ARE NOW IN LINE WITH THE HWRF GUIDANCE AND SLIGHTLY 
HIGHER THAN THE INTENSITY CONSENSUS.


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