WDPN31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.8N 126.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 141 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 07W (MEKKHALA) FIGHTING AGAINST THE LOW TO MODERATE
(15-20 KTS) VERTICAL WIND SHEAR (VWS), EVIDENT BY THE RADIALLY
EXPANDING CIRRUS FILAMENTS. THE VWS HAS REDUCED IN THE LAST 6
HOURS, CAUSING 07W TO REMAIN TILTED WHILE REMAINING ATTACHED TO THE
DEEP CONVECTIVE STRUCTURE. THE LOW-LEVEL CIRCULATION CENTER REMAINS
OBSCURED BY CENTRAL DENSE OVERCAST (CDO), BUT ONLY BARELY, AS THE
TIGHTEST LOW-LEVEL CLOUD BANDING AROUND THE CENTER IS BEGINNING TO
POP OUT FROM UNDER THE NORTHERN FRINGES OF THE CDO. A 250442Z AMSR2
MICROWAVE IMAGE REVEALS THAT THE BULK OF DEEP CONVECTION IS
CONFINED TO THE SOUTHEASTERN QUADRANT, CONSISTENT WITH THE VWS
MAGNITUDE AND DIRECTION. ENVIRONMENTAL ANALYSIS REVEALS AN
UNFAVORABLE ENVIRONMENT CHARACTERIZED BY THE VWS, MODERATE OUTFLOW,
AND DRY AIR ENTRAINMENT IN THE NORTHERN HEMISPHERE, MARGINALLY
OFFSET BUT THE WARM (28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
AFOREMENTIONED 250442Z AMSR2 DATA AND LOWER-LEVEL CLOUD BANDING
PRESENT IN ANIMATED MSI. THE INITIAL INTENSITY OF 50 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK FIXES AND
CIMSS OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 53 KTS AT 250630Z
   CIMSS ADT: 53 KTS AT 250630Z
   CIMSS AIDT: 47 KTS AT 250630Z
   CIMSS D-MINT: 45 KTS AT 250510Z
   CIMSS D-PRINT: 56 KTS AT 250630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: MODERATE DRY AIR ENTRAINMENT OCCURRING ALONG THE
   NORTHERN SEMICIRCLE

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 07W IS FORECAST TO CONTINUE ROUNDING THE
STEERING STR CENTERED TO THE EAST AND ACCELERATE NORTHEASTWARD.
AROUND TAU 12, MEKKHALA IS EXPECTED TO BE NEAR ITS CLOSEST POINT OF
APPROACH TO OKINAWA, BEFORE TRACKING ALONG THE SOUTHERN COAST OF
MAINLAND JAPAN. AT TAU 36, 07W WILL ENCOUNTER HIGH (30-35 KTS) VWS
ASSOCIATED WITH THE UPPER-LEVEL WESTERLIES AND SIGNIFICANT DRY AIR
ENTRAINMENT, SHALLOWING THE VORTEX AND INDUCING EXTRATROPICAL
TRANSITION (ETT). MEKKHALA IS FORECAST TO COMPLETE TRANSITION
BETWEEN TAU 48-60 AS THE STORM PASSES SOUTH OF TOKYO. REGARDING
INTENSITY, 07W IS FORECAST TO GRADUALLY WEAKEN FROM TAU 0 THROUGH
THE END OF THE FORECAST PERIOD AT TAU 60. DESPITE THE HOSTILE
ENVIRONMENT, 07W WILL LIKELY MAINTAIN ITS INTENSITY FAIRLY WELL AS
IT UNDERGOES AND COMPLETES ETT, MAINTAINING GALE FORCE WINDS
THROUGH TAU 60.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE REMAINS IN
GOOD AGREEMENT THROUGHOUT THE DURATION OF THE FORECAST PERIOD.
THERE IS SLIGHT DISAGREEMENT AMONG MODELS AS 07W IS FORECAST TO
ACCELERATE NORTHEASTWARD, CAUSING ALONG-TRACK DISCREPANCIES.
NOTABLY, THE AI-BASED AND PHYSICS-BASED ECMWF DETERMINISTIC AND
ENSEMBLE TRACKERS ARE SIGNIFICANTLY FASTER THAN OTHER MODELS.
DISREGARDING ECMWF AS THE ONLY MODEL OUTLIER, THE JTWC TRACK
FORECAST IS PLACED WITH OVERALL HIGH CONFIDENCE. RELIABLE INTENSITY
AIDS ARE IN GENERALLY DECENT AGREEMENT THAT 07W WILL GRADUALLY
WEAKEN THROUGH TAU 60. THE JTWC INTENSITY FORECAST LIES VERY CLOSE
TO THE MULTI-MODEL CONSENSUS AND THE HAFS-A SOLUTION WITH HIGH
CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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