WDPN31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (MEKKHALA) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.9N 125.2E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 478 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 37 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CLOUD-FILLED EYE EMBEDDED WITHIN A CIRCULAR CENTRAL DENSE OVERCAST
(CDO). POLEWARD VENTILATION HAS BECOME LESS RESTRICTED, INDICATING
THAT THE MODERATE NORTHERLY VERTICAL WIND SHEAR (VWS) HAS EASED,
AND THE NORTHERN PERIPHERY OF THE CDO APPEARS TO BE RECOVERING.
TYPHOON 07W HAS SHIFTED NORTHWARD AT A SLIGHTLY FASTER PACE OF 7
KTS. A PARTIAL 222117Z WSF-M MWI PASS REVEALED A SLIGHT TILT IN THE
VORTEX. ENVIRONMENTAL ANALYSIS INDICATES UNFAVORABLE CONDITIONS
CHARACTERIZED BY MODERATE VWS AND UPWELLING OF COOLER SUB-SURFACE
WATERS. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED
ON THE EYE FEATURE OBSERVED IN THE MSI. THE INITIAL INTENSITY WAS
LOWERED TO 115 KTS BASED ON THE SUSTAINED DEGRADED APPEARANCE ON
ANIMATED SATELLITE IMAGERY COMPARED TO ITS PEAK STRUCTURE AT
221200Z, WHICH ALIGNS WITH THE SUBJECTIVE DVORAK FIXES RANGING FROM
T6.0 TO T6.5 AND IS SLIGHTLY HIGHER THAN THE OBJECTIVE ESTIMATES
FROM CIMSS.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 128 KTS AT 222000Z
   CIMSS ADT: 102 KTS AT 230100Z
   CIMSS AIDT: 99 KTS AT 230100Z
   CIMSS D-MINT: 121 KTS AT 221749Z
   CIMSS D-PRINT: 114 KTS AT 230030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: UPWELLING OF COOLER WATERS

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE OVERALL FORECAST TRACK HAS
SHIFTED EASTWARD.

FORECAST DISCUSSION: HAVING BEEN ON A WEST-NORTHWESTWARD
TRAJECTORY, TYPHOON 07W HAS MADE ITS LONG-AWAITED SHIFT TOWARDS THE
NORTHWEST. THE SYSTEM SITS IN A COMPETING STEERING ENVIRONMENT WITH
A RIDGE OVER THE SOUTH CHINA SEA RESPONSIBLE FOR THE LOW FORWARD
SPEED. THE FAR WESTERN EXTENSION OF A DEEP-LAYER STR CENTERED NEAR
THE DATELINE IS PRIMARILY STEERING THE SYSTEM POLEWARD AND TOWARDS
A WEAKNESS IN THE RIDGE. MEKKHALA WILL REACH THE RIDGE AXIS BY TAU
60, AFTER WHICH TIME IT WILL ACCELERATE NORTHEASTWARD AND UNDERGO
EXTRATROPICAL TRANSITION. THERE REMAINS SOME UNCERTAINTY ON THE
INITIAL TRACK AS THE TYPHOON APPROACHES OKINAWA, THOUGH CONFIDENCE
IS INCREASING FOR A VERY CLOSE APPROACH TO THE ISLAND. BECAUSE THE
SYSTEM RELATIVELY COMPACT, THE STRONGEST WINDS WILL BE CONFINED TO
A SMALL AREA NEAR THE CENTER, AND A SLIGHT DEVIATION IN THE CPA CAN
BRING ABOUT SIGNIFICANT DIFFERENCES IN POTENTIAL IMPACTS. MEKKHALA
LIKELY PEAKED AT 221200Z AT CLOSE TO SUPER TYPHOON INTENSITY. FROM
HERE ON OUT, THE ENVIRONMENT WILL NO LONGER BE CONDUCIVE FOR
INTENSIFICATION AS AN UPPER LEVEL RIDGE TO THE NORTH EXERTS
INCREASING VWS. THE FORECAST CALLS FOR STEADY WEAKENING DUE TO A
COMBINATION OF UNFAVORABLE VWS AND UPWELLING. AS THE SYSTEM
APPROACHES HONSHU, IT WILL BE IN PHASE WITH A JET STREAK OVER
NORTHERN HONSHU. STRONG UPPER LEVEL SUPPORT WILL MODERATE THE RATE
OF WEAKENING AT TAU 96 AND TAU 120 AS THE SYSTEM BROADENS OUT.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM AND HWRF, WHICH ARE
THE WESTERN OUTLIERS, THE MODELS ARE TIGHTLY GROUPED THROUGH TAU
72, TAKING THE SYSTEM POLEWARD AND VERY CLOSE TO OKINAWA. THE
LATEST MODEL SUITE HAS NOTABLY SHIFTED EASTWARD FOR THE ENTIRETY OF
THE FORECAST PERIOD, AND THE JTWC THUS HAS FOLLOWED SUIT BY NUDGING
EASTWARD. THE RESULT IS A REDUCED CPA FOR OKINAWA AND A SLIGHTLY
LARGER CPA FOR THE KANTO PLAIN. FUTURE FORECASTS MAY SHOW FURTHER
ADJUSTMENTS TO THE EAST IF TRENDS CONTINUE. THE FORECAST TRACK
LARGELY FOLLOWS THE CENTER OF THE TIGHT MODEL GROUPING THROUGH TAU
72 WITH HIGH CONFIDENCE AND THEN ALIGNS WITH THE MEAN OF THE ECMWF
AND GFS GLOBAL MODELS WITH MEDIUM CONFIDENCE. THE EXPERIMENTAL
GOOGLE DEEPMIND AND AI-IFS OCCUPY THE EASTERNMOST SIDE OF THE
GUIDANCE ENVELOPE. THE INTENSITY FORECAST IS CONSISTENT WITH THE
STEADY WEAKENING DEPICTED BY THE GFS AND GOOGLE DEEPMIND MODELS FOR
THE FIRST 60 HOURS. HWRF, WHICH SHOWS REINTENSIFICATION TO 125 KTS
FOLLOWED BY SLOW WEAKENING, WAS DEEMED UNREALISTIC. MOST OF THE
RELIABLE INTENSITY AIDS LEVEL OFF THE RATE OF WEAKENING AFTER TAU
60, AND THE INTENSITY FORECAST REFLECTS THE SLOWER RATE OUT TO TAU
120 WITH MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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