WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (MEKKHALA) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.1N 124.8E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 474 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CLOUD-FILLED EYE SURROUNDED BY CONVECTIVE BANDING WRAPPING INTO THE
CORE. THE CONVECTION IS NOTABLY SHALLOWER IN THE NORTHERN
SEMICIRCLE WHERE NORTH-NORTHEASTERLY SHEAR IS APPLYING PRESSURE TO
THE SYSTEM. ANIMATED WATER VAPOR IMAGERY REVEALS THAT POLEWARD
OUTFLOW REMAINS WEAK WHILE THE EQUATORWARD CHANNEL HAS PERSISTED
WITH MODERATE OUTFLOW. A 230453Z AMSR-2 36 GHZ MICROWAVE IMAGE
SHOWS A WELL-DEFINED MICROWAVE EYE AND FURTHER DEMONSTRATES THE
ASYMMETRY OF CONVECTIVE BANDING SEEN IN THE MSI. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED MSI
AND THE AMSR-2 MICROWAVE IMAGE. THE INITIAL INTENSITY OF 110 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES,
SLIGHTLY ABOVE THE CIMSS INTENSITY ESTIMATES LISTED BELOW. THE
ENVIRONMENT IS CHARACTERIZED AS UNFAVORABLE AS THE SLOW SPEED OF
ADVANCE HAS ENHANCED UPWELLING OF COOLER WATER, COMBINED WITH
MODERATE (20-25 KTS) NORTH-NORTHEASTERLY VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 109 KTS AT 230600Z
   CIMSS ADT: 99 KTS AT 230600Z
   CIMSS AIDT: 98 KTS AT 230600Z
   CIMSS D-MINT: 102 KTS AT 230500Z
   CIMSS D-PRINT: 97 KTS AT 230600Z

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: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON (TY) 07W (MEKKHALA) HAS SLOWED IN ITS
GENERALLY NORTHWESTWARD TRACK OVER THE PAST 6 HOURS AS IT TRACKS
AROUND THE AXIS OF THE STEERING STR CENTERED TO THE NORTHEAST. THE
TRACK IS FORECAST TO MAINTAIN A PRIMARILY NORTHWARD COMPONENT OVER
THE NEXT 36 HOURS AS THE SYSTEM CONTINUES AROUND THE RIDGE AXIS,
THEN TURN NORTHEASTWARD WITH A SLIGHTLY FASTER TRACK SPEED AS IT
APPROACHES OKINAWA. THE CPA TO KADENA AB IS EXPECTED AT 260100Z AS
THE CENTER OF TY MEKKHALA TRACKS ALONG THE NORTHWEST COAST OF
OKINAWA. AFTER TAU 72, THE SYSTEM IS FORECAST TO ACCELERATE RAPIDLY
ON A NORTHEASTWARD TRACK AND SKIRT ALONG THE SOUTHEASTERN COAST OF
HONSHU, PASSING JUST SOUTH OF TOKYO AFTER TAU 96. THE ALREADY
UNFAVORABLE ENVIRONMENTAL CONDITIONS, WITH COOLER SST AND
INCREASING VWS, WILL CONTINUE TO PROMOTE STEADY WEAKENING THROUGH
TAU 96. AFTER TAU 96, BAROCLINIC FORCING WILL INITIATE
EXTRATROPICAL TRANSITION AND SHOULD ALLOW 07W TO MAINTAIN 50-55 KT
INTENSITY THROUGH THE END OF THE FORECAST PERIOD, WITH
EXTRATROPICAL TRANSITION EXPECTED TO BE COMPLETE BY TAU 120.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT
WITH THE RECURVING TRACK OF 07W THROUGH TAU 72, WITH A CROSS-TRACK
SPREAD OF 100 NM. AFTER TAU 72, SOME UNCERTAINTY ABOUT THE
ACCELERATING TRACK SPEED AND THE EXTRATROPICAL TRANSITION SCENARIO
RESULT IN A SIGNIFICANT ALONG-TRACK SPREAD OF 990 NM. JGSM AND
NAVGEM COMPRISE THE SLOWEST OUTLIERS OF THE GROUP, SUCH THAT
EXCEPTING THEM RESULTS IN A MORE MODEST 550 NM ALONG-TRACK SPREAD.
THE JTWC TRACK FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS 
WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE
THEREAFTER. THE INTENSITY GUIDANCE CONFORMS TO A TIGHT ENVELOPE
WITH THE EXCEPTION OF HAFS-A AS A MUCH WEAKER OUTLIER, AND HWRF AS
A MUCH HIGHER OUTLIER. THE REMAINDER OF GUIDANCE SUGGESTS A STEADY
WEAKENING TREND THROUGH TAU 72 THAT LEVELS OFF FOR THE REMAINDER OF
THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO
THE CONSENSUS WITH HIGH CONFIDENCE THROUGH TAU 72, AND MEDIUM
CONFIDENCE THEREAFTER.

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