WDPN31 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (MEKKHALA) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 124.8E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 311 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SLIGHT
IMPROVEMENT IN DEEP CONVECTION WRAPPING AROUND THE INNER CORE OF
TYPHOON 07W OVER THE PAST 6 HOURS, DESPITE THE PERSISTENT
NORTHEASTERLY VERTICAL WIND SHEAR (VWS). EVEN SO, THE MAJORITY OF
DEEP CONVECTION REMAINS IN THE SOUTHWEST QUADRANT. ANIMATED WATER
VAPOR IMAGERY SHOWS HEALTHY EQUATORWARD OUTFLOW AND SIGNS OF WEAK
RADIAL OUTFLOW IN THE NORTHERN SEMICIRCLE THANKS TO THE DEEP
CONVECTION THAT HAS MANAGED TO FIGHT ITS WAY THROUGH THE STRONG
SHEAR. A 240948Z WSFM 37 GHZ MICROWAVE IMAGE REVEALED FAIRLY
SYMMETRIC LOW-MID LEVEL CLOUD BANDS WRAPPING INTO THE CORE AND
CONFIRMS THE ASYMMETRY OF DEEP CONVECTION. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE CENTER OF ROTATION
OBSERVED IN ANIMATED RADAR IMAGERY FROM TAIWAN, SUPPORTED BY THE
MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 65 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON A CONSENSUS OF THE AGENCY DVORAK FIXES,
HOWEVER THERE HAS BEEN A LACK OF RELIABLE WIND SPEED MEASUREMENTS
OVER THE PAST 6 HOURS. THE ENVIRONMENT IS CHARACTERIZED AS
UNFAVORABLE, WITH STILL-WARM SEA SURFACE TEMPERATURES BEING
OVERCOME PRIMARILY BY HIGH (30-35 KTS) VWS.

INITIAL WIND RADII BASIS: COMBINATION OF SAR DATA AND OBJECTIVE
BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 53 KTS AT 241200Z
   CIMSS AIDT: 54 KTS AT 241200Z
   CIMSS D-MINT: 45 KTS AT 241034Z
   CIMSS D-PRINT: 52 KTS AT 241200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30-35 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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 CONTINUED ON A
NORTHWARD TRAJECTORY AS IT ROUNDS THE WESTERN PERIPHERY OF A
DEEP-LAYER STR CENTERED TO THE EAST. THE FORECAST TRACK WILL PASS
PARALLEL TO THE NORTHWEST COAST OF OKINAWA, WITH A CPA TO KADENA AB
EXPECTED AT 252100Z. AFTER TAU 36 THE TRACK SPEED CONTINUES TO
ACCELERATE AT A HIGHER RATE AS THE NORTHEASTWARD MOTION TAKES 07W
ON A TRACK THAT PARALLELS THE SOUTHEASTERN COAST OF HONSHU, JUST
OFFSHORE. OF NOTE, THE KANTO PLAIN REMAINS WITHIN THE UNCERTAINTY
ENVELOPE OF TRACK GUIDANCE AS THE SYSTEM APPROACHES THE TOKYO BAY
REGION JUST BEFORE TAU 72. THE INTENSITY IS FORECAST TO CONTINUE
ITS STEADY DECLINE THROUGHOUT THE FORECAST PERIOD IN AN ENVIRONMENT
OF GRADUALLY COOLING SEA SURFACE TEMPERATURES AND HIGH VWS. THE VWS
IS EXPECTED TO BRIEFLY DROP TO LESS HOSTILE VALUES WHILE POLEWARD
OUTFLOW GETS A BOOST FROM A JET STREAK TO THE NORTH BETWEEN TAU
24-48 AS MEKKHALA APPROACHES THE MIDLATITUDE WESTERLIES. THE SYSTEM
WILL BEGIN EXTRATROPICAL TRANSITION AFTER TAU 60 AS IT MOVES
POLEWARD AND THE ASSOCIATED BAROCLINIC FORCING ALLOWS THE SYSTEM TO
MAINTAIN TROPICAL STORM FORCE WINDS. EXTRATROPICAL TRANSITION
SHOULD BE COMPLETE WELL BEFORE TAU 72.

MODEL DISCUSSION: MODEL TRACK GUIDANCE FROM THE ECMWF DETERMINISTIC
AND ENSEMBLE SOLUTIONS REMAIN AS ANOMALOUSLY FASTER WESTERN
OUTLIERS FOR THE SECOND MODEL RUN IN A ROW. A MODIFIED MULTI-MODEL
CONSENSUS THAT EXCLUDES THE ECMWF SOLUTIONS HAS BEEN USED FOR THIS
FORECAST. THE REMAINDER OF TRACK GUIDANCE IS IN TIGHT AGREEMENT
ABOUT THE RECURVING TRACK WITH A CROSS-TRACK SPREAD OF 115 NM AT
TAU 72 AND IMPROVED ALONG-TRACK SPREAD OVER THE PREVIOUS MODEL RUN.
AFTER TAU 72 THE ALONG-TRACK SPREAD INCREASES AS UNCERTAINTY ABOUT
THE EXTRATROPICAL TRANSITION SCENARIO BECOMES EVIDENT. THE JTWC
TRACK FORECAST IS PLACED CLOSE TO THE MODIFIED CONSENSUS WITH HIGH
CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. THE
INTENSITY GUIDANCE IS IN GOOD AGREEMENT ABOUT THE OVERALL WEAKENING
TREND THROUGHOUT THE FORECAST PERIOD BUT WITHIN AN ENVELOPE OF
10-15 KTS. THEREFORE, THE JTWC INTENSITY FORECAST IS PLACED
SLIGHTLY ABOVE THE CONSENSUS WITH MEDIUM CONFIDENCE THROUGHOUT.

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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