Tropical Storm JELAWAT Advisory Sun Sep 30

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (JELAWAT) WARNING NR 39//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 18W (JELAWAT) LOCATED APPROXIMATELY 350 NM SOUTHWEST
YOKOSUKA, JAPAN, HAS ACCELERATED NORTHEASTWARD AT 25 KNOTS OVER THE
PAST SIX HOURS.  ANIMATED WATER VAPOR IMAGERY SHOWS TY 18W CONTINUES
TO WEAKEN AS INDICATED BY WARMING CONVECTIVE TOPS. ADDITIONALLY, A
SERIES OF MICROWAVE IMAGERY INCLUDING THE 292307Z SSMI-S PASS SHOWS
CONVECTIVE BANDING HAS BEGUN TO UNRAVEL. THE INITIAL POSITION IS
BASED ON A RADAR REFLECTIVITY LOOP FROM JAPAN METEOROLOGICAL AGENCY
AND EXTRAPOLATED FROM THE SSMI-S IMAGE WITH FAIR CONFIDENCE. THE
INITIAL INTENSITY IS BASED ON CONGRUENT DVORAK ESTIMATES FROM PGTW
AND KNES. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS NOW EMBEDDED
DEEP IN BAROCLINIC ZONE AND HAS BEGUN EXTRA-TROPICAL TRANSITION. THIS
IS EVIDENCED BY THE ADVECTION OF COLD AIR STRATOCUMULUS INTO THE LOW
LEVEL CIRCULATION, AS SEEN ON ANIMATED MULTISPECTRAL SATELLITE
IMAGERY. VERTICAL WIND SHEAR, ALREADY AT 30-50 KNOTS, CONTINUES TO
INCREASE EVEN AS THE STORM MOTION IS IN-PHASE WITH UPPER LEVEL WIND
FLOW. THE CYCLONE IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF AN
EXTENSION OF THE SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 18W WILL MAKE LANDFALL OVER SOUTHERN HONSHU IN JUST OVER SIX
HOURS, DRAG ACROSS THE KANTO PLAIN, AND RE-EMERGE IN THE SEA OF JAPAN
BEFORE BECOMING A COLD CORE LOW BY TAU 24. INCREASING VWS, DECREASING
SSTS, AND INTERACTION WITH LAND WILL CAUSE THE STEADY EROSION OF THE
SYSTEM. MODEL GUIDANCE REMAINS TIGHT AND CONSISTENT WITH THE MAJORITY
OF THE AIDS TRACKING THE VORTEX OVER THE MOUNTAINOUS REGION OF
HONSHU. THE CURRENT FORECAST KEEPS THE TRACK RIGHT OF AND SLIGHTLY
FASTER THAN CONSENSUS. CONFIDENCE IN THE FORECAST TRACK REMAINS HIGH.
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