WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.0N 146.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 420 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 04W (MUN) WITH GREATLY IMPROVED CENTRAL CONVECTION THAT
IS NOW TIGHTLY WRAPPING INTO THE CENTER OF THE CIRCULATION. THE
LOW-LEVEL STRUCTURE ALSO APPEARS TO HAVE IMPROVED COMPARED TO 6
HOURS AGO, AS IS EVIDENT IN THE 042246Z GMI 37 GHZ MICROWAVE IMAGE
WHICH SHOWS A NEARLY COMPLETE MICROWAVE EYE FEATURE. ENVIRONMENTAL
ANALYSIS INDICATES THAT 04W IS IN A FAVORABLE ENVIRONMENT
CHARACTERIZED BY STRONG EASTWARD AND EQUATORWARD OUTFLOW, LOW
(10-15 KTS) VERTICAL WIND SHEAR, AND WARM (27-28 C) SEA SURFACE
TEMPERATURES. THE DRY AIR THAT WAS PREVIOUSLY WITHIN THE SOUTHERN
SEMICIRCLE HAS NOW MOISTENED AND IS REPLACED WITH CYCLING DEEP
CONVECTION. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE MENTIONED GMI MICROWAVE IMAGE AND THE ANIMATED MSI.
THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW. THE INTENSITY IS ASSESSED TO BE HIGHER THAN WHAT MANY OF THE 
ESTIMATES SUGGEST DUE TO THE COMPACT NATURE OF THE CIRCULATION AND A 
RELATIVELY SMALL POCKET OF CONVECTION COMPARED TO AN AVERAGE SYSTEM 
OF THE SAME INTENSITY.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE TO THE SOUTH AND SOUTHEAST.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 34 KTS AT 050000Z
   CIMSS AIDT: 56 KTS AT 050000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG EQUATORWARD AND EASTWARD

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 05W IS FORECAST TO TRACK EAST-NORTHEASTWARD
THROUGH TAU 24 BEFORE MAKING A TURN NORTHWARD AS RIDGING BUILDS IN
TO THE EAST OF THE SYSTEM. 04W WILL THEN CONTINUE ON A GENERALLY
NORTH-NORTHWESTWARD TRACK THROUGH TAU 72, ALONG THE WESTERN
PERIPHERY OF THE RIDGE EXTENSION. AFTER TAU 72, THE SYSTEM IS
FORECAST TO ROUND THE RIDGE AXIS AND TURN TOWARD THE NORTHEAST,
WHICH WILL COMPLETE THE S-TYPE TRACK. SUBTROPICAL TRANSITION WILL
BEGIN AROUND TAU 72 AND COMPLETE BY TAU 96 AS THE VORTEX SHALLOWS,
BECOMES ENGULFED BY DRY AIR, AND ENTERS VERY COLD OCEAN
TEMPERATURES. REGARDING INTENSITY, 04W IS FORECAST TO INTENSIFY
OVER THE NEXT 24 HOURS TO A PEAK OF 65 KTS AS OUTFLOW REMAINS
ROBUST AND SHEAR REMAINS LOW. AFTER TAU 24, SEA SURFACE
TEMPERATURES WILL BEGIN TO DROP AND SHEAR WILL BEGIN TO RISE AS THE
VORTEX GAINS LATITUDE, CAUSING A WEAKENING TREND TO PERSIST THROUGH
THE REMAINDER OF THE FORECAST PERIOD. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT WITH A 180 NM CROSS-TRACK SPREAD AT TAU 72. AFTER TAU 72,
ALONG-TRACK SPREAD BEGINS TO INCREASE DUE TO DIFFERING INTERACTIONS
WITH THE UPPER-LEVEL ENVIRONMENT. THE JTWC TRACK FORECAST IS PLACED
WITH OVERALL MEDIUM CONFIDENCE, CLOSE TO THE CONSENSUS. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT WITH ALL MODELS DEPICTING
INTENSIFICATION THROUGH TAU 24 AND WEAKENING THEREAFTER WITHIN A
TIGHT (10 KTS) ENVELOPE. AS A RESULT, THE JTWC INTENSITY FORECAST
IS PLACED WITH HIGH CONFIDENCE.

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