WDPN31 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.6N 144.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 428 NM SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
STORM, WHICH APPEARS TO BE MAKING A SLOW BUT STEADY COMEBACK. OVER
THE COURSE OF THE PREVIOUS 12 HOURS, A SERIES OF MICROWAVE IMAGES
REVEALED AN ASYMMETRIC STRUCTURE, WITH WEAK CONVECTION DISPLACED TO
THE EAST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). OVER THE PAST
FEW HOURS, THE LLCC APPEARS TO BE SLOWING WORKING ITS WAY BACK
UNDER THE CONVECTION AND ASSOCIATED MID-LEVEL VORTEX. THE LATEST
MSI SUGGESTS THE MID-LEVEL VORTEX IS STRENGTHENING AND IF THE TWO
CAN ALIGN, WE MAY SEE ANOTHER ROUND OF INTENSIFICATION. THERE HAS
NOT BEEN A GOOD MICROWAVE PASS FOR MORE THAN SIX HOURS, THUS THE
CONFIDENCE IN THE INITIAL POSITION IS LOW. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE, CONSISTENT WITH THE PGTW CURRENT
INTENSITY ESTIMATE OF T3.5, AND THE SATCON ESTIMATE OF 52 KNOTS.
OVERALL, THE ENVIRONMENT APPEARS TO BE IMPROVING, WITH VERY LOW
VWS, GOOD RADIAL OUTFLOW ALOFT, THOUGH THE OUTFLOW IS CURRENTLY
CONFINED TO A SMALL REGION IN VICINITY OF THE STORM ITSELF, AND
WARM SSTS. THERE REMAINS SOME LINGERING DRY AIR, PARTICULARLY ON
THE WESTERN SIDE OF THE CIRCULATION, BUT THE INNER-CORE CONTINUES
TO BE SUFFICIENTLY MOIST TO SUPPORT PERSISTENT CONVECTIVE ACTIVITY.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP LAYER
SUBTROPICAL RIDGE (STR) COMPLEX EXTENDING FROM EAST OF THE SYSTEM
SOUTHWESTWARD TO THE CENTRAL MARIANAS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 52 KTS AT 040000Z
   CIMSS ADT: 39 KTS AT 040000Z
   CIMSS AIDT: 42 KTS AT 040020Z
   CIMSS D-PRINT: 49 KTS AT 040000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK RADIAL
   OTHER FACTORS: LINGERING DRY MID-LEVEL AIR, PARTICULARLY TO THE
WEST.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TROPICAL STORM (TS) 04W (MUN) IS TRAVELING
ALMOST DUE NORTH, ALONG THE WESTERN SIDE OF THE STEERING RIDGE.
HOWEVER, THE NORTHERN EXTENSION OF THIS STEERING RIDGE IS RAPIDLY
WEAKENING, IN FAVOR OF A BUILDING RIDGE OVER THE CENTRAL MARIANAS.
OVER THE COURSE OF THE NEXT 12 HOURS, TS 04W WILL GRADUALLY TURN
TOWARDS THE EAST-NORTHEAST, DRIVEN ALONG THE NORTHERN SIDE OF THE
BUILDING RIDGE TO THE SOUTH. AFTER TAU 48, THE STR TO THE SOUTH
MOVES WESTWARD WHILE A DEEP-LAYER BUBBLE HIGH DEVELOPS EAST OF TS
04W, DRIVING THE SYSTEM POLEWARD FROM TAU 48 TO TAU 96. AFTER TAU
96, THE SYSTEM WILL TRACK INTO A BREAK IN THE RIDGE AND BE CAUGHT
UP IN THE MID-LATITUDE WESTERLIES AND QUICKLY TURN TO THE
NORTHEAST. IN TERMS OF INTENSITY, AS SEEN IN THE MOST RECENT MSI
AND IR LOOPS, THE VORTEX MAY BE TRYING TO REALIGN AT THE MOMENT. AS
THIS PROCESS COMPLETES AND POLEWARD OUTFLOW IMPROVES, THERE SHOULD
BE ENOUGH WARM WATER LEFT TO SUPPORT A SLOW BUT STEADY
INTENSIFICATION OVER THE NEXT 36 HOURS. AROUND TAU 60, A STRONG
MID-LATITUDE TROF AND DEFORMATION ZONE WILL MOVE IN FROM THE
NORTHWEST, USHERING IN A SHARP INCREASE IN SHEAR AND DRY MID-LEVEL
AIR, EFFECTIVELY DECAPITATING AND SMOTHERING TS 04W. THIS WILL MARK
THE ONSET OF BOTH SUBTROPICAL TRANSITION (STT) AND A RAPID
WEAKENING TREND, WHICH WILL CONTINUE THROUGH THE REMAINDER OF THE
FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE SHOWS LITTLE CHANGE
FROM THE PREVIOUS RUN. NAVGEM, GALWEM AND JGSM CONTINUE TO RACE THE
SYSTEM TOWARDS THE NORTHEAST AFTER TAU 72, IN LINE WITH THEIR KNOWN
BIASES. CONSIDERED AS UNREALISTIC, THESE MODELS HAVE BEEN
DISCOUNTED. THE REMAINDER OF THE GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 48, WITH EVEN THE GFS AND GEFS MOVING INTO BETTER
AGREEMENT WITH THE REST OF THE CONSENSUS. AFTER TAU 72, THE GFS
BREAKS OFF FROM THE PACK HOWEVER, AND TRACKS FAR TO THE NORTHWEST
BEFORE TURNING NORTH AT TAU 96, ALONG THE 144E LONGITUDE LINE. THE
REMAINDER OF THE GUIDANCE PACKAGE TURNS NORTH-NORTHWESTWARD AFTER
TAU 72 BEFORE TURNING NORTHEAST AFTER TAU 96. THE JTWC FORECAST IS
POSITIONED CLOSE TO THE CONSENSUS MEAN THROUGH THE FORECAST PERIOD.
INTENSITY GUIDANCE IS IN GOOD AGREEMENT ON THE OVERALL TREND LINE,
WITH A RANGE OF PEAK INTENSITIES BETWEEN 60-75 KNOTS. THE JTWC
FORECAST IS CONSISTENT WITH THE CONSENSUS MEAN THROUGH THE
FORECAST. 

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