WDPN31 PGTW 252100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.8N 126.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 67 NM WEST-NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE INITIAL POSITION OF TROPICAL STORM (TS) 07W (MEKKHALA) IS
PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY SHOWING AN ALMOST ENTIRELY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC) OFF THE WEST COAST OF OKINAWA,
WHILE THE UPPER LEVEL CONVECTION CONTINUES TO DECOUPLE AND BE
SHEARED TO THE SOUTHEAST. THE INITIAL INTENSITY IS ASSESSED WITH
HIGH CONFIDENCE BASED ON SEVERAL SURFACE OBSERVATIONS FROM SOUTHERN
OKINAWA AND MIYAKOJIMA RANGING FROM 35 TO 40 KTS, AS WELL AS THE
AGENCY DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES LISTED BELOW.
ENVIRONMENTAL ANALYSIS REVEALS AN UNFAVORABLE ENVIRONMENT WITH LOW
TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS), MODERATE
EQUATORWARD OUTFLOW ALOFT, AND DRY AIR ENTRAINMENT TO THE NORTH,
OFFSET ONLY BY WARM (27-28 C) SEA SURFACE TEMPERATURES (SSTS).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 44 KTS AT 251800Z
   CIMSS ADT: 37 KTS AT 251800Z
   CIMSS AIDT: 37 KTS AT 251800Z
   CIMSS D-MINT: 34 KTS AT 251736Z
   CIMSS D-PRINT: 39 KTS AT 251800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 07W IS EXPECTED TO CPA OKINAWA WITHIN THE
NEXT FEW HOURS AND CONTINUE TRACKING NORTHEASTWARD ALONG THE
SOUTHERN COAST OF MAINLAND JAPAN THEREAFTER, SHIFTING SLIGHTLY
NORTH OF THE PREVIOUS FORECAST AS TS 07W CONTINUES TO TRACK MORE
NORTH-NORTHEASTWARD. THE SYSTEM IS FORECAST TO CONTINUE INCREASING
IN TRANSLATIONAL SPEED AS IT HAS NOW ROUNDED THE AXIS OF THE
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. TS 07W IS EXPECTED TO
ENCOUNTER VWS OF 25-30 KTS BEYOND TAU 12, WHILE IT BECOMES EMBEDDED
WITHIN THE UPPER LEVEL WESTERLIES AND BEGINS ITS EXTRATROPICAL
TRANSITION (ETT) NO LATER THAN TAU 36. THESE FACTORS, ACCOMPANIED
WITH THE COOLER (26-27 C) SSTS BY TAU 24 AS THE STORM FOLLOWS ALONG
THE KUROSHIO CURRENT WILL DEPRIVE TS 07W OF ANY REDEEMING
ENVIRONMENTAL CONDITIONS. THEREFORE, INTENSITY IS EXPECTED TO
CONTINUE STEADILY DECREASE THROUGHOUT THE FORECAST, ALTHOUGH TS 07W
IS FORECAST TO MAINTAIN GALE FORCE WINDS THROUGHOUT THE REMAINDER
OF THE FORECAST. 

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT, WITH
THE EXCEPTION OF GALWEM AND ECMWF TRACKERS WHICH CONTINUE TO BE
OUTLIERS IN TRACK SPEED. THEREFORE, AN ADJUSTED MULTI-MODEL
CONSENSUS WAS RAN TO EXCLUDE THESE TRACKERS. THE OFFICIAL JTWC
TRACK FORECAST IS LAID WITH HIGH CONFIDENCE, CLOSELY IN LINE WITH
THE ADJUSTED MULTI-MODEL CONSENSUS AND SLIGHTLY SLOWER THAN THE
EXPERIMENTAL AI MODELS. INTENSITY MODEL GUIDANCE IS IN GOOD
AGREEMENT ON THE WEAKENING TREND OF TS 07W FOR THE REMAINDER OF THE
FORECAST PERIOD, BUT RETAIN A 15-20 KT SPREAD. THUS, THE OFFICIAL
JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE, JUST
ABOVE THE MULTI-MODEL CONSENSUS, WITH THE MOST UNCERTAINTY
ASSOCIATED WITH THE FINAL INTENSITY OF THE STORM AND HOW LONG IT
WILL MAINTAIN GALE FORCE WINDS.

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