WDPN31 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MA-ON)            
WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.7N 116.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 213 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES AN EXPOSED
LOW-LEVEL CIRCULATION CENTER (LLCC) DECOUPLED FROM THE
RAPIDLY-DECAYING DEEP CONVECTION, WHICH IS SHEARING TO THE
SOUTHWEST DUE TO HIGH NORTHEASTERLY VERTICAL WIND SHEAR (VWS). A 
240552Z
ATMS 88.2GHZ MICROWAVE IMAGE SHOWS LIMITED CURVED BANDING OVER THE
SOUTHERN SEMICIRCLE WITH A WEAKLY-DEFINED LLCC ON THE NORTHERN EDGE
OF THE CONVECTION. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON MSI. ENVIRONMENTAL CONDITIONS HAVE DEGRADED
OVER THE PAST SIX HOURS WITH PERSISTENT, STRONG VWS OFFSET SLIGHTLY
BY VIGOROUS EQUATORWARD OUTFLOW AND WARM SST VALUES. THE INITIAL
INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
PGTW DVORAK ESTIMATE. BASED ON THE RAPIDLY WEAKENING CONVECTIVE
STRUCTURE, BOTH THE KNES AND RJTD DVORAK INTENSITY ESTIMATES ARE
ASSESSED AS BEING TOO HIGH AND WERE POSITIONED IN THE DEEP
CONVECTION SOUTH OF THE NOW DECOUPLED AND EXPOSED LLCC.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 50 KTS AT 240501Z
   CIMSS ADT: 47 KTS AT 240540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30+ KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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: TS 10W IS FORECAST TO TRACK GENERALLY
WEST-NORTHWESTWARD THROUGH THE FORECAST PERIOD WITH LANDFALL
EXPECTED NEAR TAU 24. TS 10W WILL GRADUALLY WEAKEN OVER THE NEXT
DAY AS IT TRACKS UNDER HIGH NORTHEASTERLY VERTICAL WIND SHEAR.
AFTER TAU 24, THE SYSTEM WILL RAPIDLY DISSIPATE AS IT TRACKS
INLAND.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
WITH A 30-40NM SPREAD IN SOLUTIONS THROUGH THE FORECAST PERIOD,
THEREFORE THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.
THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST DUE TO
THE SPREAD IN INTENSITY GUIDANCE AT TAU 12. PEAK INTENSITIES RANGE
FROM 53 TO 70 KNOTS WITH HWRF ON THE HIGH END OF THE GUIDANCE,
HOWEVER, THE 240000Z HWRF SHIPS OUTPUT INDICATES SHEAR MAGNITUDE IN
THE 35-40 KNOT RANGE, WHICH SHOULD HINDER INTENSIFICATION. THE JTWC
FORECAST IS PLACED AT THE LOWER RANGE OF GUIDANCE WITH THE
EXPECTATION THAT THE SYSTEM WILL CONTINUE TO STRUGGLE TO ORGANIZE. 

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