Tropical Storm DANAS Advisory lun, 07.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (DANAS) WARNING NR 15//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 23W (DANAS), LOCATED APPROXIMATELY 139 NM EAST-
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT
20 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS THE SYSTEM HAS FURTHER DEEPENED, MAINTAINED A HIGHLY
SYMMETRICAL SIGNATURE WITH TIGHTLY CURVED DEEP CONVECTIVE FEEDER
BANDS WRAPPING INTO A WELL-DEFINED 25-NM EYE. TY 23W SUSTAINED A
MESOSCALE ANTICYCLONE ALOFT THAT IS PROVIDING A HIGHLY EFFICIENT
RADIAL VENTING MECHANISM. ADDITIONALLY, ANIMATED WATER VAPOR IMAGERY
SHOWS THAT EVEN AS THE EASTWARD OUTFLOW HAS DIMINISHED, A POLEWARD
OUTFLOW CHANNEL INTO THE WESTERLIES HAS OPENED UP IN THE LAST SIX
HOURS. THE ROBUST ALL-AROUND OUTFLOW HAS BEEN THE PRIMARY FACTOR TO
THE RAPID INTENSIFICATION OF 23W OVER THE PAST 24 HOURS. THE INITIAL
POSITION IS BASED ON THE EYE FEATURE IN THE MSI WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY IS BASED ON THE CONGRUENT DVORAK ESTIMATES FROM
PGTW AND KNES. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS JUST TO
THE SOUTH OF AND FAST APPROACHING THE RIDGE AXIS IN AN AREA OF LOW TO
MODERATE (10-20 KNOT) VERTICAL WIND SHEAR (VWS). THE CYCLONE IS
TRACKING ALONG THE OUTER PERIPHERY OF A DEEP-LAYERED SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TYPHOON DANAS IS FORECAST TO REMAIN ON ITS CURRENT TRACK
THROUGH TAU 12 UNDER THE STEERING INFLUENCE OF THE STR. AFTER TAU 12,
THE SYSTEM WILL CREST THE RIDGE AXIS AND BEGIN TO RECURVE POLEWARD.
THE GRADUAL INCREASE IN VWS, COINCIDENT WITH THE POLEWARD MOTION, AND
THE SYSTEM BECOMING EMBEDDED IN THE STRONG MID-LATITUDE WESTERLIES,
WILL SLOWLY DEGRADE THE SYSTEM. AFTER TAU 24, TY 23W WILL ACCELERATE
NORTHEASTWARD TOWARDS SASEBO, JAPAN, AND BEGIN EXTRATROPICAL
TRANSITION (ETT). THE SYSTEM WILL COMPLETE ETT BY TAU 48. AFTER TAU
48, THE NOW STORM-FORCE COLD-CORE LOW WILL CONTINUE TO ACCELERATE BUT
ON A MORE EAST-NORTHEASTWARD TRAJECTORY AND CROSS THE SEA OF JAPAN
AND THE NORTHERN TIP OF HONSHU BEFORE EXITING BACK INTO THE PACIFIC
OCEAN. INCREASING VWS AND COOLING SEA SURFACE TEMPERATURES WILL CAUSE
ITS RAPID DETERIORATION. NUMERICAL MODEL GUIDANCE IS IN TIGHT
AGREEMENT WITH SLIGHT VARIATIONS AT THE RECURVE POINT. THE JTWC
FORECAST IS LAID SLIGHTLY FASTER THAN AND JUST TO THE RIGHT OF CONW -
AND BIASED TOWARDS ECMWF - WITH HIGH CONFIDENCE.   //
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