WDPN31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.8N 148.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 385 NM EAST OF NARITA AIRPORT
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER OF TROPICAL STORM (TS) 04W
(MUN) SURROUNDED BY SHALLOW BANDS OF CONVECTION. THE SYSTEM IS
CURRENTLY TRACKING NORTH-NORTHWESTWARD UNDER THE INFLUENCE OF A
SUBTROPICAL RIDGE TO THE EAST. TS 04W IS MAINTAINING STRUCTURAL
VORTEX INTEGRITY DESPITE 35+ KTS VERTICAL WIND SHEAR (VWS), AS WELL
AS SIGNIFICANT DRY AIR SURROUNDING THE VORTEX. ADDITIONAL 
ENVIRONMENTAL 
ANALYSIS REVEALS WEAK EQUATORWARD OUTFLOW CHANNEL AND COOLING (24-25 
C) 
SEA SURFACE TEMPERATURES (SST) IN THE PATH OF TS MUN. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC 
PRESENT IN VISIBLE SATELLITE IMAGERY. THE INITIAL INTENSITY OF 35 KTS 
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION OF DVORAK 
FIXES AND OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 062334Z METOP-C ASCAT UHR PASS

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 43 KTS AT 070236Z
   CIMSS ADT: 33 KTS AT 070520Z
   CIMSS AIDT: 39 KTS AT 070520Z
   CIMSS D-MINT: 28 KTS AT 070708Z
   CIMSS D-PRINT: 30 KTS AT 070630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30+ KTS
   SST: 24-25 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT

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: TS 04W IS FORECAST TO BEGIN ROUNDING THE AXIS
OF A STR TO THE EAST WITHIN THE NEXT 6-12 HOURS, WHILE
SIMULTANEOUSLY WEAKENING DUE TO INCREASINGLY HOSTILE ENVIRONMENT
DISCUSSED EARLIER. SUBTROPICAL TRANSITION IS EXPECTED TO BEGIN
AROUND TAU 24 AND IS FORECAST TO COMPLETE BY TAU 36, AT THE
CONCLUSION OF THE CURRENT FORECAST PERIOD. AT THAT TIME, THE SYSTEM
IS EXPECTED TO WEAKEN TO 25 KTS.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT AS INDICATED BY A 15 NM CROSS-TRACK SPREAD AT TAU 12,
EXPANDING TO 95 NM BY TAU 24. BEYOND THAT, FORECAST DIVERGENCE
INCREASES DUE TO DIFFERENCES IN REPRESENTATIONS OF THE SYSTEM
INTERACTION WITH THE BAROCLINIC ZONE AND ASSOCIATED UPPER-LEVEL,
WESTERLY FLOW. GFS DETERMINISTIC MODEL IS PROJECTING THE TIGHTEST AND
QUICKEST TURN, WHILE ECMWF AND ECMWF ENSEMBLE PREDICT A SLOWER AND
MORE GRADUAL TURN. JTWC TRACK FORECAST IS THEREFORE ASSESSED WITH
OVERALL MEDIUM CONFIDENCE AND IS LAID CLOSE TO THE MULTI-MODEL
CONSENSUS. INTENSITY GUIDANCE IS ASSESSED WITH GOOD CONFIDENCE,
WITH ALL MODELS SUPPORTING A FORECAST OF PROGRESSIVE WEAKENING. 

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