Tokyo under the gun
Posted by JAC on 10/4/2009, 9:22 am


SGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MELOR) WARNING NR 20//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
  A. SUPER TYPHOON (STY) 20W (MELOR), LOCATED APPROXIMATELY 210 NM
WEST-NORTHWEST OF SAIPAN, HAS TRACKED WESTWARD AT 14 KNOTS OVER THE
PAST SIX HOURS. RECENT ANIMATED MULTISPECTRAL IMAGERY SHOWS A 30 NM
WIDE, CLOUD-FREE, VERY WELL-DEFINED EYE ALONG WITH EXCELLENT RADIAL
OUTFLOW TO ALL QUADRANTS. STY 20W HAS CONTINUED TO TRACK ALONG THE
SOUTHWESTERN PERIPHERY OF THE MID- TO UPPER-LEVEL SUBTROPICAL RIDGE
(STR) LOCATED TO THE NORTH. THE INITIAL FORECAST INTENSITY OF 145
KNOTS IS BASED ON DVORAK SATELLITE INTENSITY ESTIMATES OF 7.0 FROM
RJTD AND KNES (140 KNOTS) AND 7.5 (155 KNOTS) FROM PGTW.
3. FORECAST REASONING
  A. THE FORECAST REASONING HAS NOT CHANGED SIGNIFICANTLY SINCE THE
PREVIOUS PROGNOSTIC REASONING BULLETIN.
  B. STY 20W WILL GRADUALLY TURN POLEWARD AFTER TAU 36 AS AN UPPER
LEVEL MID-LATITUDE TROUGH WILL SIGNIFICANTLY WEAKEN THE STR AND
ALLOW FOR RECURVATURE. STY 20W WILL TURN SHARPLY NORTHEASTWARD AFTER
TAU 48 AS THE SYSTEM ENCOUNTERS A STRONG BAROCLINIC BOUNDARY OVER
JAPAN. THE STRONG BAROCLINIC BOUNDARY IS ASSOCIATED WITH THE JET
STREAM AND HAS VERTICAL WIND SHEAR (VWS) VALUES IN EXCESS OF 80
KNOTS. THE UNFAVORABLE INTRODUCTION OF THE SOUTHWESTERLIES AHEAD OF
THE MID-LATITUDE TROUGH, THE STRONG VWS AND BAROCLINIC INTERACTION
WILL ALL ACT IN CONCERT TO WEAKEN THE TY 20W AS IT BEGINS TO
ACCELERATE RAPIDLY NORTHEASTWARD AFTER TAU 48.
  C. AFTER TAU 72, EXTRA-TROPICAL TRANSITION (ET) WILL BEGIN AS THE
SYSTEM MOVES INTO THE MID-LATITUDE WESTERLIES. THE SYSTEM WILL
CONTINUE TO ACCELERATE NORTHEASTWARD TOWARDS THE MID-LATITUDES. STY
20W WILL BE COMPLETELY EXTRA-TROPICAL BY TAU 120. ALL THE AVAILABLE
CONSENSUS MEMBERS EXCEPT JGSM FORECAST A RECURVATURE SCENARIO AROUND
TAU 48. MOST OF THESE THE MODELS KEEP THE SYSTEM OVER OPEN WATER AND
SOUTH OF THE KANTO PLAIN. THE EXCEPTIONS ARE THE GFDN, ECMWF AND THE
NOGAPS MODELS THAT TAKE STY 20W INLAND JUST WEST OF THE KANTO PLAIN.
THIS FORECAST IS BASED ON THE MODELS THAT KEEP THE STORM SOUTH OVER
WATER AS THEY ACCURATELY INITIALIZE THE STRENGTH AND SHAPE OF THE
STR.//
NNNN
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Melor the Monster - a solid Cat5, 914mb and dropping - JAC, 10/3/2009, 9:25 pm
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