From owner-wx-tropl@LISTSERV.ILLINOIS.EDU Wed Sep 22 10:19:31 2010 Received: from vacuum.cso.uiuc.edu (vacuum.cso.uiuc.edu [128.174.5.113]) by cozumel.ust.hk (8.13.8/8.13.8) with ESMTP id o8M2JUNF003876 for ; Wed, 22 Sep 2010 10:19:31 +0800 Received: from vacuum.cso.uiuc.edu (vacuum.cso.uiuc.edu [128.174.5.113]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id o8LITEwN028356; Tue, 21 Sep 2010 21:19:20 -0500 (CDT) Received: by LISTSERV.ILLINOIS.EDU (LISTSERV-TCP/IP release 14.5) with spool id 3521068 for WX-TROPL@LISTSERV.ILLINOIS.EDU; Tue, 21 Sep 2010 21:19:20 -0500 Received: from relay06.cites.uiuc.edu (relay06.cites.uiuc.edu [128.174.196.8]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id o8M2JKT1013388 for ; Tue, 21 Sep 2010 21:19:20 -0500 (CDT) Received: from weather3.admin.niu.edu (weather3.admin.niu.edu [131.156.8.48]) by relay06.cites.uiuc.edu (8.14.4/8.14.2) with ESMTP id o8M2JDCS007657 for ; Tue, 21 Sep 2010 21:19:19 -0500 (CDT) Received: by weather3.admin.niu.edu (Postfix, from userid 501) id 65A1D405002B; Tue, 21 Sep 2010 21:19:13 -0500 (CDT) X-Spam-Score: 0 X-Spam-Details: rule=no-quarantine_notspam policy=no-quarantine score=0 spamscore=0 ipscore=0 phishscore=0 bulkscore=98 adultscore=0 classifier=spam adjust=0 reason=mlx engine=5.0.0-1005130000 definitions=main-1009210233 X-Spam-OrigSender: ldm@weather3.admin.niu.edu X-Spam-Bar: Message-ID: <20100922021913.65A1D405002B@weather3.admin.niu.edu> Date: Tue, 21 Sep 2010 21:19:13 -0500 Reply-To: wxmaster@COX.NET Sender: WX-TROPL Tropical Storm and Hurricane WX products From: SIU Weather Processor Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 13w Warning Nr 08// To: WX-TROPL@LISTSERV.ILLINOIS.EDU Precedence: list WDPN32 PGTW 220300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W WARNING NR 08// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL STORM (TS) 13W (MALAKAS), LOCATED APPROXIMATELY 325 NM SOUTH-SOUTHEAST OF IWO TO, JAPAN HAS TRACKED WEST- NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY, A 211629Z AMSR-E 89GHZ IMAGE, AND A 212321Z VISUAL IMAGE ALL COMBINE TO SIGNIFICANTLY INCREASE POSITION CONFIDENCE. THE SYSTEM HAS A FULLY-EXPOSED, WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH TIGHTLY-WRAPPED SHALLOW CONVECTIVE BANDING WRAPPING INTO A WELL-DEFINED CENTER. THE BULK OF THE DEEP CONVECTION IS BEING DISPLACED EQUATORWARD FROM THE LLCC. ANIMATED WATER VAPOR IMAGERY SHOWS OUTFLOW OVER THE POLEWARD QUADRANTS IS BEING SUPPRESSED BY CONFLUENT FLOW ALOFT, RESULTING IN THE STORM DEVELOPING AT A LOWER-THAN-CLIMATOLOGICAL RATE. THE SYSTEM IS TRACKING STEADILY WEST-NORTHWESTWARD ALONG THE SOUTHERN FLANK OF THE SUB-TROPICAL RIDGE, WHICH IS BEGINNING TO WEAKEN AS A DEEPENING MID- LATITUDE TROUGH MOVES INTO THE YELLOW SEA. THE CURRENT INTENSITY IS BASED ON AN AVERAGE OF DVORAK ESTIMATES OF 35 AND 45 KNOTS FROM PGTW AND RJTD. 3. FORECAST REASONING. A. THE FORECAST REASONING HAS NOT CHANGED SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TS 13W IS EXPECTED TO INTENSIFY SLOWLY OVER THE NEXT 24-36 HOURS AS IT TRACKS ALONG THE SOUTHERN PERIPHERY OF THE STEERING RIDGE. ALTHOUGH THE SYSTEM IS BEING SUPPRESSED BY UPPER LEVEL CONVERGENCE ON ITS NORTHERN FLANK, IT IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT, WITH HIGH OCEAN HEAT CONTENT AND LOW VERTICAL WIND SHEAR. THE APPROACH OF AN UPSTREAM MID-LATITUDE TROUGH WILL ACT TO WEAKEN THE RIDGE ALONG THE 140TH MERIDIAN, GIVING THE SYSTEM AN ALLEY TO RECURVE INTO THE MID-LATITUDES. AS TS 13W APPROACHES THE AXIS OF THE RIDGE AND SLOWS BEFORE RECURVATURE, POLEWARD OUTFLOW WILL INCREASE AND THE SYSTEM WILL INTENSIFY SIGNIFICANTLY, REACHING TYPHOON STRENGTH BY 23/12Z. NUMERICAL MODEL GUIDANCE IS IN STRONG AGREEMENT WITH THE TRACK INCLUDING THE AREA OF RECURVATURE, WITH SOME VARIATION IN TIMING. ECMWF, TYPICALLY A STRONG PERFORMER, PROJECTS THE SLOWEST AND LATEST TURN AROUND THE RIDGE. THE FORECAST ADJUSTS CONSENSUS SLIGHTLY SLOWER IN COGNIZANCE OF THIS TENDENCY BUT OTHERWISE ADHERES CLOSELY TO CONSENSUS DUE TO STRONG AGREEMENT AND COHERENT SCENARIO PRESENTED BY THE DYNAMIC AIDS. C. EXTRA-TROPICAL TRANSITION WILL BEGIN AS THE SYSTEM CROSSES 30 DEGREES NORTH LATITUDE AND BEGINS COUPLING WITH THE MID-LATITUDE WESTERLIES. SURFACE AND GRADIENT-LEVEL WINDFIELDS AROUND THE STORM WILL EXPAND AS IT INTERACTS WITH A STRONGLY BAROCLINIC ZONE AND COMES UNDER THE INFLUENCE OF A DEEP, NEGATIVELY TILTED TROUGH. THE SYSTEM WILL REMAIN VIGOROUS IN ITS WARM SECTOR AS SEA SURFACE TEMPERATURES REMAIN HIGH THROUGH 35 DEGREES NORTH. THE SYSTEM WILL OCCLUDE AND COMPLETE TRANSITION TO A STORM FORCE EXTRA-TROPICAL LOW BEFORE CROSSING 40 DEGREES NORTH. // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from WX-TROPL send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with "unsub wx-tropl" in the body of your message. For help with WX-TROPL write to cnovy@cox.net. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.