Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 11w Warning Nr 07//

From: SIU Weather Processor <[email-masked]>
Date: Thu, 9 Sep 2010 09:37:05 -0500

WDPN31 PGTW 091500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 11W (MERANTI), LOCATED APPROXIMATELY 180 NM
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTH-NORTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED (IR) SATELLITE
IMAGERY SHOWS A MIDGET SYSTEM WITH A WELL-DEFINED LOW LEVEL
CIRCULATION CENTER (LLCC) AND A 091128Z SSMIS DEPICTS A DEEP
CONVECTIVE MICROWAVE EYE. THE INITIAL POSITION IS BASED ON A RADAR
FIX FROM TAIWAN AND THE AFOREMENTIONED SSMIS IMAGE WITH HIGH
CONFIDENCE. THE INITIAL INTENSITY IS BASED ON THE CONVECTIVE
SIGNATURE AND NOT ON DVORAK ESTIMATES BECAUSE THEY ARE
UNDERESTIMATING THIS MIDGET SYSTEM. UPPER LEVEL ANALYSIS INDICATES
A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL HAS CONTINUED TO
MOVE FARTHER NORTHWESTWARD, WHICH HAS ALLOWED IMPROVED POLEWARD
OUTFLOW AND DECREASED VERTICAL WIND SHEAR (VWS). ADDITIONALLY, TY
11W CONTINUES TO MAINTAIN A GOOD EQUATORWARD OUTFLOW CHANNEL,
ALLOWING IT TO RAPIDLY INTENSIFY.
3. FORECAST REASONING.
   A. THE CURRENT INTENSITY HAS INCREASED SIGNIFICANTLY SINCE THE
PREVIOUS FORECAST BECAUSE OF THE DECREASED VWS AND DUAL OUTFLOW
CHANNELS. THE FORECAST TRACK PHILOSOPHY HAS GENERALLY REMAINED THE
SAME EXCEPT FOR AN INCREASE IN TRACK SPEED DUE TO A STRAIGHTER TRACK.
   B. TY 11W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A
SUBTROPICAL STEERING RIDGE AND IS EXPECTED TO MAKE LANDFALL IN
APPROXIMATELY 12 HOURS OVER SOUTHEASTERN CHINA. TY 11W SHOULD BEGIN
TO FEEL THE AFFECTS OF LAND AND BEGIN TO WEAKEN BY TAU 12. BY TAU
36, TY MERANTI IS EXPECTED TO DISSIPATE AS A SIGNIFICANT TROPICAL
CYCLONE OVER THE MOUNTAINOUS TERRAIN OF CHINA. NUMERICAL MODEL
GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF THE UKMO MODEL
WHICH ERRONEOUSLY TRACKS THE SYSTEM NORTHEASTWARD TOWARDS TAIWAN
BEFORE TURNING IT NORTHWARD. THIS FORECAST IS SLIGHTLY WEST OF
CONSENSUS TO ACCOUNT FOR THE UKMO MODEL AND IS WITHIN THE TIGHT
MODEL PACKING OF WBAR, ECMWF, NOGAPS, JGSM, AND GFS.//

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message. For help with WX-TROPL
write to [email-masked]. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.