WDPN31 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.7N 149.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 481 NM EAST-SOUTHEAST OF NARITA AIRPORT
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS)
04W (MUN) WITH WELL DEFINED, BUT SHALLOW CONVECTIVE SPIRAL BANDS.
THE SYSTEM IS STRUGGLING TO SUSTAIN DEEP CONVECTION DUE TO SIGNIFICANT 
DRY AIR ENTRAINMENT, BUT MANAGES TO MAINTAIN STRUCTURALLY SOUND LOW-
LEVEL VORTEX AT THE MOMENT. ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS 
BORDERLINE WARM (26-27 C) SEA SURFACE TEMPERATURES (SST), LOW (5-10 
KTS) VERTICAL WIND SHEAR AND MODERATE, PRIMARILY EQUATORWARD UPPER 
LEVEL OUTFLOW. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE LLCC LOCATION PRESENT IN VISIBLE SATELLITE IMAGERY, AS 
WELL AS EXTRAPOLATION FROM A 060316Z GCOMW1 AMSR2 37 GHZ MICROWAVE 
PASS. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM 
CONFIDENCE BASED ON THE AGENCY DVORAK AND AUTOMATED FIXES LISTED 
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: RIDGING TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 53 KTS AT 060530Z
   CIMSS ADT: 34 KTS AT 060530Z
   CIMSS AIDT: 42 KTS AT 060530Z
   CIMSS D-MINT: 48 KTS AT 060551Z
   CIMSS D-PRINT: 49 KTS AT 060600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: PERSISTENT AND SIGNIFICANT DRY AIR ENTRAINMENT 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 04W IS FORECAST TO TRACK NORTHWARD IN
RESPONSE TO CONTINUOUSLY BUILDING RIDGING TO THE EAST OF THE
SYSTEM. AS A RESULT, AFTER TAU 12, THE SYSTEM WILL SHIFT TOWARD THE
NORTHWEST. BETWEEN TAUS 24 AND 36, TS MUN IS EXPECTED TO ROUND THE
AXIS OF THE RIDGE AND BEGIN TRANSITING NORTHEASTWARD, WHILE
EVENTUALLY BECOMING EMBEDDED IN A DEEP-LAYER WESTERLY FLOW. THE
SYSTEM IS FORECAST TO BEGIN ITS SUBTROPICAL TRANSITION AROUND TAU
36, WITH COMPLETION EXPECTED BY TAU 48. IN REGARD TO INTENSITY, TS
04W IS CURRENTLY IN A MARGINAL ENVIRONMENT, WHICH IS SOON EXPECTED
TO BECOME INCREASINGLY HOSTILE. WHILE VWS IS EXPECTED TO INCREASE
TO OVER 30 KTS BY TAU 12, THE SYSTEM IS EXPECTED TO BE COMPLETELY
SURROUNDED BY DRY AIR WITHIN THE NEXT 36 HOURS. ADDITIONALLY, SST
WILL DROP TO BELOW 20 C BEFORE THE END OF THE FORECAST PERIOD, 
RESULTING IN STEADY WEAKENING OF THE STORM.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT FOR THE NEXT 24 HOURS, AS WITNESSED BY A CROSS-TRACK
SPREAD OF 50 NM AT TAU 24. HOWEVER UNCERTAINTY INCREASES
AFTERWARDS, DRIVEN BY DIFFERENCES IN UPPER-LEVEL ENVIRONMENT
INTERACTION ASSESSMENT BY THE MODELS. WHILE NAVGEM AND JGSM PREDICT
A TIGHTER AND QUICKER TURN, OTHER MODELS LIKE EMCWF AND ECMWF
ENSEMBLE PREDICT A WIDER AND SLOWER TURN TOWARD THE NORTHEAST.
JTWC TRACK FORECAST IS LAID CLOSE TO THE CONSENSUS WITH MEDIUM
CONFIDENCE. IN TERMS OF INTENSITY, JTWC FORECAST IS ASSESSED WITH
HIGH CONFIDENCE DRIVEN BY TIGHT AGREEMENT AMONG ALL CONSENSUS
MEMBER, INDICATING STEADY WEAKENING THROUGH TAU 48.

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