From owner-wx-tropl@LISTSERV.ILLINOIS.EDU Fri Oct 22 11:12:40 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 o9M3Cdle029118 for ; Fri, 22 Oct 2010 11:12:39 +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 o9LJQBWe014749; Thu, 21 Oct 2010 22:12:11 -0500 (CDT) Received: by LISTSERV.ILLINOIS.EDU (LISTSERV-TCP/IP release 14.5) with spool id 3991515 for WX-TROPL@LISTSERV.ILLINOIS.EDU; Thu, 21 Oct 2010 22:12:11 -0500 Received: from relay07.cites.uiuc.edu (relay07.cites.uiuc.edu [128.174.4.73]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id o9M3CBuq018160 for ; Thu, 21 Oct 2010 22:12:11 -0500 (CDT) Received: from weather3.admin.niu.edu (weather3.admin.niu.edu [131.156.8.48]) by relay07.cites.uiuc.edu (8.14.4/8.14.2) with ESMTP id o9M3C4ZC029716 for ; Thu, 21 Oct 2010 22:12:10 -0500 (CDT) Received: by weather3.admin.niu.edu (Postfix, from userid 501) id 34766108B0002; Thu, 21 Oct 2010 22:12:04 -0500 (CDT) X-Proofpoint-Spam-Reason: safe Message-ID: <20101022031204.34766108B0002@weather3.admin.niu.edu> Date: Thu, 21 Oct 2010 22:12:04 -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 Depression 17w (seventeen) To: WX-TROPL@LISTSERV.ILLINOIS.EDU Precedence: list WDPN32 PGTW 220300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED APPROXIMATELY 760 NM NORTHEAST OF HAGATNA, GUAM, HAS TRACKED WEST- NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A 212221Z SSMI PASS AND A 212330Z PGTW SATELLITE FIX. THE CURRENT INTENSITY ESTIMATE OF 30 KNOTS IS CONSISTENT WITH A DVORAK ESTIMATE OF 30 KNOTS FROM KNES AT 212057Z AND STRUCTURE EVIDENT IN THE SSMI IMAGE. DEEP CONVECTION IS CONFINED TO THE SOUTH AND WESTERN PORTIONS OF THE PARTIALLY-EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DUE TO MODERATE NORTHEASTERLY VERTICAL WIND SHEAR INDUCED BY THE FLOW BETWEEN AN UPPER LEVEL RIDGE TO THE NORTH AND A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE SOUTH. THE LLCC IS TRACKING WEST-NORTHWESTWARD UNDER THE INFLUENCE OF A DEEP SUBTROPICAL STEERING RIDGE TO THE NORTH. 3. FORECAST REASONING. A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE FOR THIS SYSTEM. B. TD 17W WILL CONTINUE TO TRACK NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF A DEEP SUBTROPICAL RIDGE TO THE NORTH FOR THE NEXT 12 HOURS. THEREAFTER, A DEVELOPING MIDLATITUDE TROUGH TO THE NORTH IS EXPECTED TO WEAKEN THE STEERING RIDGE AND INDUCE A POLEWARD TURN INTO A WEAK STEERING ENVIRONMENT. THE AVAILABLE NUMERICAL GUIDANCE IS IN GOOD GENERAL AGREEMENT WITH THIS SCENARIO, ALTHOUGH THERE IS SOME UNCERTAINTY IN THE EXACT TRACK GIVEN THE ANTICIPATED WEAK STEERING SETUP. UNFAVORABLE ENVIRONMENTAL FACTORS, INCLUDING PERSISTENT UPPER LEVEL CONVERGENCE, EASTERLY VERTICAL WIND SHEAR, AND THE INTRODUCTION OF DRIER AIR TOWARD THE CENTER OF TD 17W FROM THE SOUTHEAST, SHOULD PREVENT THE SYSTEM FROM INTENSIFYING SIGNIFICANTLY AND RESULT IN DISSIPATION BELOW THE 25 KNOT WARNING THRESHOLD INTENSITY BY TAU 36.// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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.