From owner-wx-tropl@LISTSERV.ILLINOIS.EDU Tue Oct 19 10:25:50 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 o9J2PnlI005281 for ; Tue, 19 Oct 2010 10:25:50 +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 o9IMbc8D022864; Mon, 18 Oct 2010 21:25:20 -0500 (CDT) Received: by LISTSERV.ILLINOIS.EDU (LISTSERV-TCP/IP release 14.5) with spool id 3945167 for WX-TROPL@LISTSERV.ILLINOIS.EDU; Mon, 18 Oct 2010 21:25:19 -0500 Received: from relay01.cites.uiuc.edu (relay01.cites.uiuc.edu [128.174.4.23]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id o9J2PJTZ016757 for ; Mon, 18 Oct 2010 21:25:19 -0500 (CDT) Received: from weather3.admin.niu.edu (weather3.admin.niu.edu [131.156.8.48]) by relay01.cites.uiuc.edu (8.14.4/8.14.2) with ESMTP id o9J2PCal027670 for ; Mon, 18 Oct 2010 21:25:18 -0500 (CDT) Received: by weather3.admin.niu.edu (Postfix, from userid 501) id 1F757108B0002; Mon, 18 Oct 2010 21:25:11 -0500 (CDT) X-Proofpoint-Spam-Reason: safe Message-ID: <20101019022512.1F757108B0002@weather3.admin.niu.edu> Date: Mon, 18 Oct 2010 21:25:11 -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 Typhoon 15w (megi) Warning Nr 25// To: WX-TROPL@LISTSERV.ILLINOIS.EDU Precedence: list WDPN31 PGTW 190300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (MEGI) WARNING NR 25// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TYPHOON (TY) 15W (MEGI), LOCATED APPROXIMATELY 455 NM SOUTHEAST OF HONG KONG, CHINA, HAS TRACKED WESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY INDICATES THAT TY 15W HAS CONTINUED TO RE-CONSOLIDATE AND HAS DEVELOPED A 10-NM DIAMETER IRREGULAR EYE OVER THE PAST 06 HOURS. A 182321Z TRMM 37H IMAGE SHOWS A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH A MICROWAVE EYE FEATURE AND STRONG CORE CONVECTION OVER ALL QUADRANTS. ANIMATED WATER VAPOR IMAGERY DEPICTS EXCELLENT RADIAL OUTFLOW ESPECIALLY POLEWARD OUTFLOW, ENHANCED BY STRONG WESTERLY FLOW ACROSS CENTRAL CHINA. THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION BASED ON THE TRMM IMAGE AND EYE. THE CURRENT INTENSITY OF 90 KNOTS IS BASED ON DVORAK ESTIMATES OF 90 KNOTS FROM PGTW AND KNES. 3. FORECAST REASONING. A. NO CHANGE IN FORECAST PHILOSOPHY, HOWEVER, THE TRACK HAS BEEN ADJUSTED BETWEEN TAU 24 AND 72 TO ACCOUNT FOR A MORE POLEWARD TRACK. B. TY 15W IS TRACKING WESTWARD ALONG THE SOUTHWEST PERIPHERY OF THE MID-LEVEL SUBTROPICAL RIDGE (STR). THE FORECAST TRACK HAS BEEN ADJUSTED SLIGHTLY BETWEEN TAU 24-72 BASED ON OBSERVED WEAKENING OF THE WESTERN STR, WHICH HAS SHIFTED WEST OVER THE PAST 24 HOURS, AND EVIDENCE OF A DEEPENING SHORTWAVE TROUGH OVER SOUTHEAST CHINA. MODEL GUIDANCE (INCLUDING THE MAJORITY OF ENSEMBLE DATA) HAS SUBSEQUENTLY TRENDED TOWARD A STAIR-STEP PATTERN. ALL AVAILABLE DYNAMIC MODELS (ECMWF, UKMO, GFS, JGSM, NOGAPS, GFDN) PLUS WBAR NOW SUPPORT THIS TRACK AND ARE IN GOOD AGREEMENT WITH THE EXCEPTION OF THE GFS. THE GFS INDICATES A SHARP NORTH-NORTHEASTWARD TRACK THROUGH TAU 72 BEFORE TURNING NORTH-NORTHWESTWARD. ANALYSIS OF THE GFS SLP FIELDS INDICATES POSSIBLE EXCESSIVE INTERACTION WITH A WEAK SYSTEM FORMING NORTHEAST OF LUZON; A LOBE OF LOWER PRESSURES EXTENDING NORTHEASTWARD OUT OF TY 15W IS EVIDENT AS WELL AS THE INTERACTION. THIS TRACK IS DEEMED AS UNLIKELY CONSIDERING THE STRENGTH AND POSITION OF THE STEERING STR POSITIONED TO THE NORTH. TY 15W IS EXPECTED TO TURN WEST-NORTHWESTWARD TO NORTHWESTWARD IN THE NEXT 12-24 HOURS IN RESPONSE TO THE WEAKENING WESTERN STR ASSOCIATED WITH A SHORTWAVE TROUGH PROPAGATING THROUGH SOUTHEAST CHINA, AND SHOULD TRACK NORTHWESTWARD THROUGH TAU 72. TY 15W IS FORECAST TO INTENSIFY TO A PEAK INTENSITY OF 115 KNOTS BY TAU 48 DUE TO THE FAVORABLE ENVIRONMENT. C. THE SYSTEM IS FORECAST TO RESUME A WEST-NORTHWESTWARD TRACK AS THE STR RE-BUILDS NORTH NEAR TAU 72. TY 15W IS EXPECTED TO WEAKEN AFTER TAU 72 DUE TO INCREASING VWS AND LAND INTERACTION NEAR TAU 96.32// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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.