WDPN31 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.5N 127.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 800 NM WEST-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 07W (MEKKHALA) WITH A FULLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC) AS THE UPPER LEVEL CONVECTION HAS BEEN
SHEARED AWAY TO THE SOUTHEAST. ENVIRONMENTAL CONDITIONS ARE
ASSESSED AS UNFAVORABLE WITH MODERATE TO HIGH (20-25 KTS) VERTICAL
WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT, OFFSET BY WARM (27-28 C)
SEA SURFACE TEMPERATURES (SSTS) AND MODERATE POLEWARD OUTFLOW ALOFT
DUE TO THE SYSTEMS POSITIONING NEAR AN UPPER LEVEL TROUGH. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE FULLY
EXPOSED LLCC IN SATELLITE IMAGERY LOOP, AND THE INITIAL INTENSITY
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SLIGHTLY WIDER
SPREAD OF AGENCY DVORAK FIXES AND CIMSS OBJECTIVE 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: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 32 KTS AT 260000Z
   CIMSS AIDT: 37 KTS AT 260000Z
   CIMSS D-MINT: 34 KTS AT 252157Z
   CIMSS D-PRINT: 33 KTS AT 260000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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: TS 07W IS FORECAST TO TRACK ALONG THE SOUTHERN
COAST OF MAINLAND JAPAN WITH INCREASING TRANSLATIONAL SPEED AS IT
CONTINUES TO BE STEERED BY THE SUBTROPICAL RIDGE (STR) CENTERED TO
THE EAST-SOUTHEAST OF THE SYSTEM. EXTRATROPICAL TRANSITION (ETT) IS
FORECAST TO BEGIN NO LATER THAN TAU 12 AS TS 07W BEGINS TO
ENCOUNTER HIGHER VWS DUE TO THE STRONG UPPER-LEVEL WESTERLIES,
EVENTUALLY EMBEDDING UNDERNEATH THE SUBTROPICAL JET AND COMPLETING
ETT NO LATER THAN TAU 48. IN REGARDS TO INTENSITY, THE WIND FIELD
IS EXPECTED TO BROADEN AS TS 07W WASHES OUT AND ELONGATES DURING
ETT, ACCOMPANIED BY A GENERAL WEAKENING TREND AS A RESULT OF
INCREASING VWS AND COOLING SSTS. DUE TO THE ASYMMETRICAL NATURE OF
SYSTEMS UNDERGOING ETT, THERE IS SOME UNCERTAINTY IN TS 07W
MAINTAINING GALE FORCE WINDS AS IT NEARS YOKOSUKA, JAPAN. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT FOR THE REMAINDER OF THE FORECAST PERIOD IN TERMS OF BOTH
ALONG AND CROSS TRACK SPREAD. THE OFFICIAL JTWC FORECAST TRACK IS
THUS LAID WITH HIGH CONFIDENCE, CLOSELY IN LINE WITH BOTH THE
MULTI-MODEL AND EXPERIMENTAL CONSENSUSES. FORECAST INTENSITY MODELS
HAVE DIVERGED SOME SINCE THE PAST FORECAST, WITH SEVERAL OF THE
MESOSCALE MODELS AND THE MULTI-MODEL CONSENSUS DEPICTING A SLIGHT
UPTICK IN INTENSITY AT TAU 24 FOLLOWED BY A SHARP DECLINE
THEREAFTER. HOWEVER, DUE TO THE EXPECTED WORSENING ENVIRONMENTAL
CONDITIONS FOR THE REMAINDER OF THE FORECAST PERIOD, THE OFFICIAL
JTWC INTENSITY DOES NOT INCLUDE THIS TEMPORARY SPIKE, BUT IS
THEREFORE ASSESSED WITH MEDIUM CONFIDENCE, OTHERWISE IN LINE WITH
THE MULTI-MODEL CONSENSUS.

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