WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (CHAMPI) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.6N 140.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 379 NM SOUTH OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS AN EXPOSED, TIGHTLY 
WRAPPED LOW LEVEL CIRCULATION (LLC) WITH SHALLOW BANDING AND DEEP 
CONVECTION STARTING TO FLARE OVER THE CENTER. A 232304Z 89GHZ MHS 
MICROWAVE IMAGE SHOWS FRAGMENTED BANDING WRAPPING INTO A DEFINED LLC. 
A 231933Z 91GHZ SSMIS IMAGE DEPICTS A MICROWAVE EYE FEATURE WITH 
TIGHTLY CURVED BANDING, HOWEVER, THIS FEATURE WAS SHORT-LIVED AND 
DEGRADED SIGNIFICANTLY SINCE THAT TIME. THE HIGH CONFIDENCE IN THE 
INITIAL POSITION IS BASED ON THE WELL DEFINED NATURE OF THE CENTER IN 
VISIBLE IMAGERY. THERE IS SOME UNCERTAINTY IN THE INITIAL INTENSITY 
DUE THE RAPIDLY EVOLVING CONVECTIVE STRUCTURE OVER THE PAST SIX HOURS. 
THE INITIAL INTENSITY IS BASED ON THE PGTW AND RJTD DVORAK CURRENT 
INTENSITY ESTIMATES AND A 232311Z PARTIAL ASCAT-A IMAGE SHOWING 35-40 
KT WINDS OVER EASTERN SEMICIRCLE. OVERALL THE ENVIRONMENT IS 
FAVORABLE, HOWEVER, POLEWARD OUTFLOW IS WEAK AND THERE IS DRY OVER THE 
WESTERN SEMICIRCLE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 43 KTS AT 232340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: WEAK POLEWARD OUTFLOW

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 06W (CHAMPI) WILL CONTINUE
TRACKING NORTHWARD DURING THE NEXT 48 HOURS AS IT ROUNDS THE
PERIPHERY OF THE SUBTROPICAL RIDGE TO THE EAST. AT THIS POINT, THE
CYCLONE WILL TURN SLIGHTLY NORTHEASTWARD AS IT NEARS THE BAIU
FRONTAL BOUNDARY SOUTHEAST OF JAPAN. THE JTWC INTENSITY FORECAST
CALLS FOR STEADY INTENSIFICATION TO A PEAK OF 70 KTS AROUND TAU 36 AS 
LOW TO MODERATE SHEAR PERSISTS, WHICH SHOULD ALLOW AN INNER CONVECTIVE 
CORE TO ORGANIZE. PERIODIC INGESTION OF DRY AIR AND LIMITED OUTFLOW IS 
LIKELY TO LIMIT INTENSIFICATION TO SOME EXTENT. AFTER TAU 48, THE 
CYCLONE WILL PASS INTO COOLER WATERS OF 18-20C, AND INTERACTION WITH 
THE BAIU FRONTAL BOUNDARY WILL INCREASE VERTICAL SHEAR. THESE FACTORS 
WILL LEAD TO WEAKENING TO 45 KTS BY THE TIME OF EXTRATROPICAL 
TRANSITION AROUND TAU 96.

MODEL DISCUSSION: THE JTWC FORECAST IS IN LINE WITH THE MULTI-MODEL
CONSENSUS AND IS CONSISTENT WITH THE PREVIOUS FORECAST TRACK.
CONFIDENCE IN THE FORECAST TRACK IS MEDIUM DUE TO MODEL SPREADING
IN THE LATER TAUS WITH A CROSS TRACK SPREAD OF 200 NM AT TAU
72 AND 335 NM AT TAU 96. THERE IS UNCERTAINTY IN THE INTENSITY
FORECAST WITH SOME POTENTIAL FOR A HIGHER PEAK INTENSITY AS
INDICATED BY THE HWRF GUIDANCE SHOWING A PEAK NEAR 85 KTS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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