WDPN31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.8N 145.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 593 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 04W (MUN) EXHIBITS A LOPSIDED APPEARANCE IN THE
LATEST ANIMATED ENHANCED INFRARED (EIR) SATELLITE LOOP. DEEP
CONVECTION HAS FLARED WEST OF THE PREVIOUSLY EXPOSED LOW LEVEL 
CIRCULATION CENTER (LLCC) OVER THE PAST FEW HOURS. BASED
ON THE LATEST CIRA UPPER-LEVEL DERIVED MOTION VECTOR (ULDMV)
PRODUCT, THE ASSOCIATED OUTFLOW HAS STARTED TO PUSH EASTWARD
AGAINST THE PREVAILING SOUTHWESTERLY UPPER-LEVEL FLOW, CREATING AN 
OPPORTUNITY FOR THE LLCC TO RE-ALIGN WITH THE CONVECTION. THOUGH HARD 
TO DEFINITIVELY DETERMINE WITHOUT RECENT MICROWAVE IMAGERY, THE 
STRONGEST UPDRAFTS AND COLDEST CLOUD TOPS ARE STILL NOT VERTICALLY 
ALIGNED WITH THE LLCC DUE TO SOME MID-LEVEL NORTHEASTERLY SHEAR. A 
021546Z AMSR2 89GHZ MICROWAVE IMAGE CAPTURED THE SETUP PRIOR TO THE 
LLCC MOVING UNDER THE CONVECTION, WITH THE VORTEX REMAINING THE DRY, 
RELATIVELY CLEAR AIR TO THE EAST OF THE CONVECTIVE ACTIVITY. THE 
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
EXTRAPOLATION OF THE AMSR2 IMAGE, AS WELL AS TRACKING OF THE VORTEX IN 
ANIMATED SHORTWAVE INFRARED (SWIR) IMAGERY. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON EXTRAPOLATION OF AN EARLIER 
ASCAT PASS, AS WELL AS THE OBJECTIVE AND SUBJECTIVE INTENSITY 
ESTIMATES NOTED ABOVE. THE ENVIRONMENT IS STEADILY IMPROVING, NOW THAT 
THE TUTT-CELL HAS STARTED TO MOVE AWAY AND DISSIPATE, OPENING UP A 
MUCH STRONGER, DIVERGENT POLEWARD OUTFLOW CHANNEL AND SSTS REMAIN 
SUFFICIENTLY WARM TO SUPPORT DEVELOPMENT. THE MAIN HINDRANCE AT THE 
MOMENT REMAINS THE SIGNIFICANT WEDGE OF DRY AIR, EVIDENT IN THE TOTAL
PRECIPITABLE WATER (TPW) LOOP, EXTENDING NORTHWARD ALONG THE
EASTERN PERIPHERY OF THE VORTEX. THE LATEST SOUNDING FROM
CHICHIJIMA, ON THE WESTERN EDGE OF THE CONVECTIVE SHIELD, INDICATES
THIS DRY MID-LEVEL AIR EXTENDS OUT TO THE WEST AS WELL, SUCH THAT
TS 04W IS COCOONED IN A VERY SMALL POCKET OF RELATIVELY MOIST AIR.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WEST-NORTHWEST PERIPHERY OF AN
ELONGATED RIDGING PATTERN EXTENDING FROM SOUTHWEST OF GUAM
NORTHEASTWARD TO 40N 178E. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 021730Z
   CIMSS AIDT: 41 KTS AT 021730Z
   CIMSS D-PRINT: 36 KTS AT 021820Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR IN THE EASTERN PORTION OF THE
SYSTEM. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: ADDED SUBTROPICAL TRANSITION AT THE
END OF THE FORECAST. 

FORECAST DISCUSSION: TS 04W IS EXPECTED TO FOLLOW A CLASSIC S-TYPE
TRACK, OFTEN ASSOCIATED WITH A REVERSE-ORIENTED MONSOON TROF
SETUP, THROUGHOUT THE FORECAST PERIOD. IN THE NEAR-TERM, TS 04W WILL 
CONTINUE TRACKING NORTH-NORTHWEST TO NORTH OVER THE NEXT 24 TO 36 
HOURS, ALONG THE WESTERN SIDE OF AN EXTENSIVE RIDGING PATTERN
THAT EXTENDS FROM SOUTHWEST OF GUAM ALL THE WAY TO 40N NEAR THE
DATELINE. THE SOUTHWESTERN PORTION OF THIS RIDGE COMPLEX IS
FORECAST TO BUILD SIGNIFICANTLY AFTER TAU 24, AND BY TAU 48, A VERY
LARGE AND VERY STRONG SUBTROPICAL RIDGE (STR) WILL DEVELOP OVER THE
NORTHERN MARIANAS. SIMULTANEOUSLY, AN UPPER-LEVEL TROF WILL MOVE
FROM WEST-EAST TO THE NORTH OF TS 04W, ERODING AND PUSHING THE
NORTHERN PORTION OF THE RIDGE FURTHER EAST. THIS WILL ALLOW TS 04W
TO QUICKLY TRANSITION TO A MORE EAST-NORTHEASTWARD TRACK AFTER TAU
36. BEYOND TAU 60, THE OPPOSITE PATTERN BEGINS TO TAKE SHAPE, WITH
THE STR PUSHING WEST INTO THE PHILIPPINE SEA, WHILE THE RIDGE TO
THE NORTHEAST OF TS 04W BEGINS TO BUILD, WITH THE GFS INDICATING
DEVELOPMENT OF REX BLOCK PATTERN NEAR THE DATELINE. AS THIS RIDGE
BUILDS AND ORIENTS ALONG A NORTH-SOUTH AXIS, TS 04W WILL TURN
POLEWARD AFTER TAU 72, TURNING NORTHWESTWARD BY THE END OF THE
FORECAST PERIOD AS THE RIDGE CONTINUES TO BUILD AND SHIFT WEST. IN
TERMS OF INTENSITY, THE PERSISTENT DRY AIR TO THE EAST WILL INHIBIT
SIGNIFICANT INTENSIFICATION IN THE NEAR-TERM, EVEN IF THE CURRENT
CONVECTIVE BURST CAN PERSIST. THE MAJORITY OF THE MODELS DEPICT A
STEADY MOISTENING OF THE ENVIRONMENT BEGINNING AROUND TAU 24, WHICH
WILL ALLOW FOR A SLOW INTENSIFICATION TREND TO ABOUT TAU 48. THE
APPROACH OF AN UPPER-LEVEL TROF AROUND TAU 48 WILL LEAD TO IMPROVED
POLEWARD AND EASTWARD OUTFLOW, AND TS 04W IS EXPECTED TO INTENSIFY 
FAIRLY QUICKLY THROUGH TAU 72 UNDER THESE MORE FAVORABLE CONDITIONS.
SHORTLY AFTER TAU 72 HOWEVER, ANOTHER, MUCH STRONGER TROF AND
ASSOCIATED DEFORMATION ZONE WILL PUSH DOWN OVER TS 04W, INTRODUCING
SIGNIFICANT NORTHEASTERLY SHEAR WHICH WILL START THE WEAKENING
TREND. AS THE SYSTEM PASSES 35N, IT WILL MOVE INTO COOLER WATERS,
INGEST SIGNIFICANT DRY AIR INTO THE VORTEX AND CONTINUE TO SUFFER
THE EFFECTS OF STRONG SHEAR, STEADILY WEAKENING THROUGH THE END OF
THE FORECAST. THE SYSTEM IS EXPECTED TO REMAIN WARM-CORE THROUGHOUT
THE FORECAST PERIOD, THOUGH AS IT SHALLOWS OUT, WILL SLOWLY BEGIN
TO TRANSITION TO A SUBTROPICAL LOW AFTER TAU 96. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GENERAL
AGREEMENT ON THE OVERALL S-TYPE TRACK SCENARIO, THOUGH MODEL SPREAD
IS SIGNIFICANT. AS EARLY AS TAU 24, THE GFS AND GEFS BEGIN TO
DIVERGE FROM THE REMAINDER OF THE MODEL PACKAGE, WITH A SHARPER
EASTWARD TURN, TRACK THE SYSTEM EAST ROUGHLY ALONG 30N. THE
REMAINDER OF THE GUIDANCE IS CLOSELY PACKED ABOUT THE MEAN, WITH A
CONSISTENT CROSS-TRACK SPREAD OF ABOUT 130NM FROM TAU 36 TO TAU 72,
BETWEEN THE EGRR ON THE LEFT SIDE AND GFS ON THE RIGHT SIDE OF THE
ENVELOPE. THE JTWC FORECAST IS POSITIONED CLOSE TO THE CONSENSUS
MEAN AND ECMWF TRACKER THROUGH TAU 72. AFTER TAU 72, THE GFS AND
GEFS REJOIN THE ECMWF, EGRR AND ECMWF ENSEMBLE IN TRACKING THE
SYSTEM NORTH, THEN NORTHWESTWARD, WHILE THE NAVGEM, JGSM AND THE
EC-AIFS PUSH THE SYSTEM STRAIGHT NORTH-NORTHEASTWARD. THE JTWC
FORECAST IS POSITIONED EAST OF THE TIGHTEST GROUPING OF MODELS BUT
FOLLOWS THE OVERALL SHAPE OF THE TRAJECTORY. INTENSITY GUIDANCE IS
IN STRONG AGREEMENT ON THE OVERALL INTENSITY TREND AND TIMING BUT
DIFFERS IN THE PEAK INTENSITY. ALL OF THE GUIDANCE PEAKS AT TAU 72,
WITH A RANGE BETWEEN 60 KNOTS FOR THE HWRF, 75 KNOTS FOR THE
HAFS-A, AND 85 KNOTS FOR THE COAMPS-TC (GFS). THE CTR1 RAPID
INTENSIFICATION (RI) AID REACHES EVEN HIGHER, AT 95 KNOTS. THE
CONSENSUS MEAN IS COMING IN AROUND 65-70 KNOTS, AND THE JTWC
FORECAST IS SITUATED NEAR THE MEAN THROUGH THE FORECAST PERIOD. 


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