WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (MEKKHALA) WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0N 124.6E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 374 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
RAPID WEAKENING CONTINUES WITH TYPHOON 07W SHAVING OFF 40 KTS OF
INTENSITY IN 24 HOURS WHILE GAINING SOME FORWARD SPEED. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTION CONFINED TO THE
SOUTHERN SEMICIRCLE. THE HIGH RESOLUTION MSI ALSO DEPICTS MULTIPLE
VORTICES CLEARLY ROTATING WITHIN AN EXPOSED, LOW- TO MID-LEVEL
INNER CORE, OR WHAT USED TO BE THE EYEWALL. A 232320Z SSMIS PASS
SHOWCASED WELL THE EXPOSED LOWER LEVEL CORE AND CONVECTION SOUTH OF
THE CENTER. POLEWARD OUTFLOW ALOFT REMAINS VIRTUALLY NONEXISTENT
DUE TO STRONG NORTHEASTERLY VERTICAL WIND SHEAR (VWS). THE
ENVIRONMENT IS HOSTILE, CHARACTERIZED BY WARM SEA SURFACE
TEMPERATURE (SST) STRONGLY OFFSET BY HIGH VWS. THE INITIAL POSITION
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED CENTER. THE
INITIAL INTENSITY IS LOWERED TO 75 KTS WITH MEDIUM CONFIDENCE,
WHICH IS ON THE LOWER END OF THE SUBJECTIVE DVORAK FIXES RANGING
FROM T4.5 TO T5.0 AND ABOVE MOST OF THE OBJECTIVE ESTIMATES FOR
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: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 80 KTS AT 232000Z
   CIMSS ADT: 55 KTS AT 240100Z
   CIMSS AIDT: 48 KTS AT 240100Z
   CIMSS D-MINT: 50 KTS AT 232321Z
   CIMSS D-PRINT: 49 KTS AT 240100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30+ KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK THROUGH TAU 48 HAS
SHIFTED WESTWARD AND FASTER.

FORECAST DISCUSSION: TYPHOON MEKKHALA WILL CONTINUE TO TRACK
POLEWARD AS IT ROUNDS THE WESTERN PERIPHERY OF A DEEP-LAYER STR. THE
EXTENSION OF THE RIDGE WILL ERODE AWAY, ALLOWING FOR THE TYPHOON TO
TURN TOWARDS THE NORTHEAST BY TAU 24. THE SYSTEM WILL BEGIN TO
ACCELERATE AND UNDERGO EXTRATROPICAL TRANSITION AS THE MID-LATITUDE
WESTERLY FLOW BECOMES MORE DOMINANT AT THE HIGHER LATITUDES.
EXTRATROPICAL TRANSITION TO A COLD-CORE BAROCLINIC LOW WILL
COMPLETE BY TAU 96. RAPID WEAKENING WILL CONTINUE WHILE THE TYPHOON
MOVES THROUGH AN ENVIRONMENT OF HIGH VWS FOR THE FIRST 24 HOURS.
WHILE THE VWS WILL SUBSIDE AFTER TAU 24, THE SYSTEM WILL MOVE OVER
PROGRESSIVELY COOLER WATERS. THESE COMPETING FACTORS WILL ENABLE
07W TO MAINTAIN ITS STRENGTH TO TAU 60. BEYOND TAU 60, MEKKHALA
WILL TRAVERSE SUB-26 DEGREE CELSIUS WATERS BUT TAP INTO THE
DIVERGENT REGION OF A POTENT JET STREAK OVER NORTHERN HONSHU. THE
INTENSITY WILL HOVER AT NEAR STORM-FORCE AS THE SYSTEM SKIRTS THE
SOUTHERN COAST OF HONSHU.

MODEL DISCUSSION: THE MAJORITY OF THE MODEL GUIDANCE HAS ONCE AGAIN
SHIFTED WESTWARD AND FAST THROUGH TAU 48, NECESSITATING A FURTHER
ADJUSTMENT IN THE JTWC FORECAST TRACK TO THE WEST AND TO INCREASE
THE FORWARD MOTION. THE EFFECT ON OKINAWA IS A HIGHER CPA DISTANCE
BUT AN EARLIER TIME. THE ALONG-TRACK SPREAD HAS DRASTICALLY REDUCED
FOR TAU 72, ALLOWING FOR AN ASSESSMENT OF MEDIUM CONFIDENCE IN THE
TRACK FORECAST. WHILE MODELS GENERALLY AGREE ON THE OVERALL TRACK,
THE CROSS-SPREAD AS 07W APPROACHES THE KANTO PLAIN INCREASES TO 150
NM, WITH JGSM AND ECMWF BRINGING THE SYSTEM ONSHORE. WHILE THE JTWC
FORECAST PRESENTLY DEPICTS AN OFFSHORE TRACK, THE KANTO PLAIN IS
WELL WITHIN THE UNCERTAINTY ENVELOPE, AND FUTURE FORECASTS MAY SHOW
AN EVEN CLOSER APPROACH AS THE MODELS CONVERGE ON A SOLUTION. THE
JTWC INTENSITY FORECAST IS ALIGNED WITH THE RAPID WEAKENING
DEPICTED BY HAFS-A AND THE EXPERIMENTAL GOOGLE DEEPMIND. THE GFS
AND COAMPS-TC SOLUTIONS HAVE BEEN DEEMED UNRELIABLE, SHOWING SLOW
WEAKENING THROUGH TAU 60-72. THE FORECAST LEVELS OFF THE INTENSITY
AT 50 KTS WITH MEDIUM CONFIDENCE, WHICH IS BETWEEN THE GFS AND
DEEPMIND SOLUTIONS.

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