WDPN31 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.0N 128.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 740 NM WEST-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 07W (MEKKHALA) AS A FULLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) COMPLETELY DEVOID OF ANY CONVECTION AND IS A SHELL OF
ITS FORMER SELF. THE 20-25KT WESTERLY VERTICAL WIND SHEAR (SHEAR)
IS ALSO PRESENT IN ANIMATED IMAGERY, EVIDENCED BY THE MIDDLE AND
HIGH ETAGE CLOUDS STREAKING EFFORTLESSLY ACROSS THE STORM.
ADDITIONALLY, A SURFACE OBSERVATION FROM OKINOERABU, LOCATED
APPROXIMATELY 45NM FROM THE CENTER, REPORTED 27 KTS AT 0500Z.
ENVIRONMENTAL ANALYSIS REVEALS A HIGHLY UNFAVORABLE ENVIRONMENT,
CHARACTERIZED BY HIGH (20-25 KTS) VWS, POOR OUTFLOW, AND A RELATIVELY 
DRIER ENVIRONMENT THAT IS BEGINNING TO ENTRAIN INTO THE
CORE. THE SEA SURFACE TEMPERATURES ARE STILL FAVORABLE (26-27 C);
HOWEVER, 07W IS EXPECTED TO CROSS THE 26C ISOTHERM WITHIN 12 HOURS. 
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE FULLY
EXPOSED NATURE OF THE LLCC. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 260740Z
   CIMSS ADT: 25 KTS AT 260740Z
   CIMSS AIDT: 32 KTS AT 260740Z
   CIMSS D-MINT: 31 KTS AT 260452Z
   CIMSS D-PRINT: 28 KTS AT 260740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: MEKKHALA WILL MAINTAIN A NORTHEASTWARD TRACK
FOR THE DURATION OF THE FORECAST AS IT COMPLETES ROUNDING THE STR
CENTERED TO ITS EAST AND ACCELERATES POLEWARD. 07W IS FORECAST TO
BEGIN EXTRATROPICAL TRANSITION (ETT) NO LATER THAN TAU 12 AS IT
TRACKS ALONG THE SOUTHERN COAST OF MAINLAND JAPAN, AND IS EXPECTED
TO BE INTERACTING WITH THE POLAR FRONT JET BY THAT POINT. ETT IS
FORECAST TO COMPLETE NO LATER THAN TAU 36 AS 07W BECOMES FURTHER
EMBEDDED AND EXHIBITS BAROCLINIC CHARACTERISTICS. REGARDING
INTENSITY, MEKKHALA IS FORECAST TO GRADUALLY WEAKEN THROUGH THE
FORECAST PERIOD WHILE IT TRANSITIONS; HOWEVER, THE POSSIBILITY FOR
GREATER WEAKENING IS POSSIBLE AS THE FAST-MOVING SYSTEM TRACKS
DEEPER INTO THE HOSTILE ENVIRONMENT. 


MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 12, WITH NEGLIGIBLE DIFFERENCES BETWEEN
MEMBERS. AS A RESULT, THE JTWC TRACK FORECAST IS LAID WITH HIGH
CONFIDENCE. THE JTWC INTENSITY FORECAST DEVIATES SLIGHTLY FROM
INTENSITY AIDS, WHICH DEPICT 07W INTENSIFYING FOR 24 HOURS BEFORE
DRASTICALLY WEAKENING. GIVEN THE INCREASINGLY HOSTILE ENVIRONMENT,
THIS OUTCOME WAS DEEMED UNLIKELY, THOUGH THE POSSIBILITY CANNOT BE
ENTIRELY RULED OUT. THE JTWC INTENSITY FORECAST IS ASSESSED WITH
MEDIUM CONFIDENCE.

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