WDPN31 PGTW 152100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR 
033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 37.0N 134.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 263 NM WEST-NORTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 07W (LAN) EMERGED BACK OVER THE SOUTHERN SEA OF
JAPAN NEAR THE TOYOOKA, AROUND THE 151100Z HOUR, HAVING
SIGNIFICANTLY BROADENED AND WEAKENED. A 150908Z RCM-1 SYNTHETIC
APERTURE RADAR (SAR) PASS CAPTURED THE NORTHERN HEMISPHERE OF THE
WIND FIELD WHILE THE CENTER WAS STILL OVER LAND AND SHOWED A BROAD
EXPANSE OF 40-45 KNOT WINDS. A NEARLY COINCIDENT SMAP PASS SHOWED
MAXIMUM WINDS OF 41 KNOTS (10MIN), SUPPORTING A 45 KNOT INTENSITY
AS THE SYSTEM WENT FEET WET. NOT MUCH HAS CHANGED SINCE THE 1200Z
ASSESSMENT OTHER THAN THE SYSTEM HAS MOVED FURTHER INTO THE SEA OF
JAPAN AND THE ENTIRE EXPANSE OF THE CIRCULATION IS NOW OVER THE WARM
(28-29C) WATERS. ANIMATED SHORTWAVE INFRARED (SWIR) AND PROXYVIS
SATELLITE IMAGERY DEPICTS A BROAD ROTATION WITH SHALLOW CONVECTIVE
BANDS WRAPPING INTO A PARTIALLY OBSCURED LOW LEVEL CIRCULATION
CENTER (LLCC). A 151606Z GPM 89GHZ MICROWAVE IMAGE SHOWED
FRAGMENTARY DEEP CONVECTIVE CELLS TO THE NORTH, AND WEAK BANDING
FEATURES ELSEWHERE. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE PROXYVIS. THE
INITIAL INTENSITY IS HELD STEADY AT 45 KNOTS, ABOVE THE
DVORAK-BASED INTENSITY ESTIMATES (WHICH ARE STRUGGLING DUE TO THE
LACK OF ORGANIZED DEEP CONVECTION), BUT IN LINE WITH BOTH THE
DRPINT AND DMINT ESTIMATES AND EARLIER SAR DATA. THE ENVIRONMENT
REMAINS MARGINALLY FAVORABLE, WITH ROBUST POLEWARD OUTFLOW AND LOW
(5-10 KNOTS) SOUTHWESTERLY SHEAR OFFSET BY THE FACT THAT THE SYSTEM
HAS BROADENED OUT SIGNIFICANTLY AND IS STILL RECOVERING FROM ITS
PASSAGE OVER JAPAN. OF NOTE, THE LATEST CIMSS SHEAR ANALYSIS
INDICATES SHEAR IS MUCH LOWER (APPROXIMATELY 15 KNOTS) THAN THE
MODELS WOULD OTHERWISE SUGGEST, WHICH WILL HAVE POSITIVE DOWNSTREAM
EFFECTS.

INITIAL WIND RADII BASIS: PERSISTENCE WITH EARLIER SAR DATA. 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 32 KTS AT 151730Z
   DPRINT: 44 KTS AT 151800Z
   DMINT:  45 KTS AT 151606Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: NO SIGNIFICANT CHANGES IN THE FORECAST TRACK
ARE EXPECTED, AS THE SYSTEM CONTINUES TO TRACK AROUND THE STEERING
RIDGE TO THE EAST, AND TRACE A GRACEFUL ARC NORTH-NORTHEASTWARD
TOWARDS SAKHALIN ISLAND. THE LATEST SUPER-ENSEMBLE MEAN CONTINUES
TO WALK WESTWARD WITH EACH SUCCESSIVE RUN, AND HENCE THERE REMAINS
A POSSIBILITY THE SYSTEM WILL TRACK CLOSER TO THE RUSSIAN COAST
THROUGH TAU 48. BUT FOR NOW THE TRACK REMAINS WELL OFFSHORE IN LINE
WITH THE BULK OF THE DETERMINISTIC GUIDANCE. IN THE NEXT 12 HOURS,
SOME SLIGHT WEAKENING IS ANTICIPATED, AS THE SYSTEM SLOWLY RECOVERS
FROM ITS TRAVERSE OVER THE JAPANESE ISLANDS. BUT NOW THAT THE FULL
WIDTH OF THE CIRCULATION IS OVER OPEN WATERS AND MOVING AWAY FROM
THE NEGATIVE INFLUENCE OF LAND, THE PROCESS OF VORTEX RECOVERY
SHOULD BE RELATIVELY QUICK. ASSUMING THE CIMSS ANALYSIS IS CORRECT
AND SHEAR IS MUCH LOWER THAN EXPECTED BY THE MODELS, AND CARRYING
THIS FORWARD, THE SYSTEM IS LIKELY TO MAKE AN ATTEMPT AT
REINTENSIFICATION AFTER TAU 12. HOWEVER, SSTS WILL RAPIDLY DECREASE
AS THE SYSTEM GAINS LATITUDE, ROBBING IT OF ENERGY TO SUPPORT
INTENSIFICATION AND THE BEST THAT IT WILL BE ABLE TO DO IS MAINTAIN
40-45 KNOT INTENSITY THROUGH TAU 24. THEREAFTER, INCREASED SHEAR
AND MORE IMPORTANTLY, A DRASTIC REDUCTION IN SST AND AN INFLUX OF
VERY DRY CONTINENTAL AIR FROM THE WEST, WILL BEGIN TO RAPID ERODE
AND WEAKEN TS 07W AS IT MOVES INTO THE FAR NORTHERN PORTION OF THE
SEA OF JAPAN. AROUND TAU 24, THE SYSTEM ALSO BEGINS EXTRATROPICAL
TRANSITION (ETT), AS IT MOVES INTO THE BASE OF A 500MB TROUGH AND
WEAK BAROCLINIC ZONE. FULL ETT IS EXPECTED NO LATER THAN TAU 48 AS
THE SYSTEM ENTERS THE SEA OF OKHOTSK. IF THE SYSTEM DOES ULTIMATELY
MOVE FURTHER WEST AND OVER THE COAST OF EASTERN RUSSIA, IT WILL
WEAKEN AND DISSIPATE PRIOR TO ETT. AT PRESENT THIS IS CONSIDERED A
LOW, BUT NON-ZERO, PROBABILITY ALTERNATE SCENARIO. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN VERY TIGHT
CROSS AND ALONG-TRACK AGREEMENT, MAYBE TOO GOOD. THE ENTIRE
ENVELOPE, ALONG WITH THE ENSEMBLE AND SUPER-ENSEMBLE MEANS, IS
WALKING WESTWARD WITH EACH SUCCESSIVE MODEL RUN, INTRODUCING HIGHER
UNCERTAINTY THAN WOULD BE EXPECTED BY JUST LOOKING AT THE TRACK
GUIDANCE ENVELOPE. THE JTWC FORECAST IS PLACED ON THE FAR WESTERN EDGE 
OF THE GUIDANCE PACKAGE WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS
MIXED, WITH THE GFS AND CMC HOLDING ONTO THE SYSTEM ABOVE 35 KNOTS
ALL THE WAY THROUGH THE END OF THE MODEL RUN, WHILE THE REMAINING
CONSENSUS MEMBERS AND THE MEAN, ARE CLOSE TO THE JTWC FORECAST. BUT
THE UNCERTAINTY IN THE TRACK AND THE RESULTANT ALTERNATE SCENARIO,
ALSO GENERATES INCREASED UNCERTAINTY IN THE INTENSITY FORECAST. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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