From owner-wx-tropl@LISTSERV.ILLINOIS.EDU Sat Nov 13 11:01:30 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 oAD31S4r014871 for ; Sat, 13 Nov 2010 11:01:29 +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 oACG5cDI006383; Fri, 12 Nov 2010 21:01:12 -0600 (CST) Received: by LISTSERV.ILLINOIS.EDU (LISTSERV-TCP/IP release 14.5) with spool id 4342928 for WX-TROPL@LISTSERV.ILLINOIS.EDU; Fri, 12 Nov 2010 21:01:12 -0600 Received: from relay05.cites.uiuc.edu (relay05.cites.uiuc.edu [128.174.4.40]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id oAD31Ctp008874 for ; Fri, 12 Nov 2010 21:01:12 -0600 (CST) Received: from weather3.admin.niu.edu (weather3.admin.niu.edu [131.156.8.48]) by relay05.cites.uiuc.edu (8.14.4/8.14.2) with ESMTP id oAD315Yl024813 for ; Fri, 12 Nov 2010 21:01:12 -0600 (CST) Received: by weather3.admin.niu.edu (Postfix, from userid 501) id E4882405001E; Fri, 12 Nov 2010 21:01:05 -0600 (CST) X-Proofpoint-Spam-Reason: safe Message-ID: <20101113030105.E4882405001E@weather3.admin.niu.edu> Date: Fri, 12 Nov 2010 21:01:05 -0600 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 Depression 18w Warning Nr 02// To: WX-TROPL@LISTSERV.ILLINOIS.EDU Precedence: list WDPN31 PGTW 130300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL DEPRESSION (TD) 18W (EIGHTEEN), LOCATED APPROXIMATELY 280 NM SOUTHEAST OF HUE, VIETNAM, HAS TRACKED NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A 122330Z PGTW SATELLITE FIX AND A 122359Z SSMIS MICROWAVE IMAGE. THE CURRENT INTENSITY ESTIMATE OF 25 KNOTS IS BASED ON DVORAK T-NUMBER VALUES OF 1.5 FROM PGTW AS WELL AS STRUCTURE EVIDENT IN MICROWAVE SATELLITE IMAGERY. RECENT ANIMATED MULTISPECTRAL SATELLITE IMAGERY INDICATES THAT SOUTH-SOUTHWESTERLY VERTICAL WIND SHEAR IS DISPLACING THE DEEPEST CONVECTION ASSOCIATED WITH TD 18W TO THE NORTHEAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). 3. FORECAST REASONING A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE FOR TD 18W. B. TD 18W IS TRACKING NORTHWESTWARD UNDER THE INFLUENCE OF LOW TO MID-LEVEL SUBTROPICAL RIDGING TO THE NORTH. GENERALLY NORTHWESTWARD MOTION IS EXPECTED TO CONTINUE THROUGH THE FORECAST PERIOD AS THE SUBTROPICAL RIDGE TO THE NORTH REMAINS THE DOMINANT STEERING INFLUENCE. THIS TRACK SCENARIO IS SUPPORTED BY THE AVAILABLE NUMERICAL GUIDANCE. TD 18W LIES NORTHWEST OF AN UPPER LEVEL ANTICYCLONE CENTER IN AN AREA OF MODERATE SOUTHWESTERLY VERTICAL WIND SHEAR, WHICH IS INCREASING IN MAGNITUDE AHEAD OF AN APPROACHING UPPER LEVEL TROUGH TO THE NORTHWEST. THE CYCLONE IS EXPECTED TO MAINTAIN INTENSITY OR WEAKEN UNDER THE COMPETING INFLUENCES OF INCREASING VERTICAL WIND SHEAR AND FAVORABLE POLEWARD OUTFLOW AHEAD OF THE APPROACHING TROUGH. BY TAU 24, THE CYCLONE WILL MOVE INLAND AND DISSIPATE BELOW THE WARNING THRESHOLD INTENSITY OF 25 KNOTS. HOWEVER, DUE TO EFFECTS OF SUSTAINED VERTICAL WIND SHEAR, DISSIPATION MAY OCCUR PRIOR TO LANDFALL.// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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.