From owner-wx-tropl@LISTSERV.ILLINOIS.EDU Thu Oct 21 23:57:29 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 o9LFvRQv024286 for ; Thu, 21 Oct 2010 23:57:28 +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 o9KBrl0l001368; Thu, 21 Oct 2010 10:57:15 -0500 (CDT) Received: by LISTSERV.ILLINOIS.EDU (LISTSERV-TCP/IP release 14.5) with spool id 3983153 for WX-TROPL@LISTSERV.ILLINOIS.EDU; Thu, 21 Oct 2010 10:57:15 -0500 Received: from relay04.cites.uiuc.edu (relay04.cites.uiuc.edu [128.174.196.5]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id o9LFvEZW020939 for ; Thu, 21 Oct 2010 10:57:14 -0500 (CDT) Received: from weather3.admin.niu.edu (weather3.admin.niu.edu [131.156.8.48]) by relay04.cites.uiuc.edu (8.14.4/8.14.2) with ESMTP id o9LFv8GT005571 for ; Thu, 21 Oct 2010 10:57:14 -0500 (CDT) Received: by weather3.admin.niu.edu (Postfix, from userid 501) id 6086B405042A; Thu, 21 Oct 2010 10:57:06 -0500 (CDT) X-Proofpoint-Spam-Reason: safe Message-ID: <20101021155708.6086B405042A@weather3.admin.niu.edu> Date: Thu, 21 Oct 2010 10:57:06 -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 16w (sixteen) To: WX-TROPL@LISTSERV.ILLINOIS.EDU Precedence: list WDPN32 PGTW 211500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL DEPRESSION (TD) 16W (SIXTEEN), LOCATED APPROXIMATELY 460 NM SOUTH OF IWO TO, HAS TRACKED NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. THE DISTURBANCE HAS MIGRATED BENEATH AN UPPER LEVEL RIDGE EXTENSION OVER THE PAST SIX HOURS, BUFFERING IT FROM MODERATE NORTHERLY VERTICAL WIND SHEAR AND ALLOWING DEEP CONVECTION TO BUILD IN OVER THE LOW LEVEL CIRCULATION CENTER (LLCC). PREVIOUSLY CONVECTION HAD BEEN INHIBITED BY AN ENCROACHING TROPICAL UPPER LEVEL TROPOSPHERIC TROUGH THAT HAD DUG TO THE NORTH OF THE SYSTEM. CURRENTLY THE SYSTEM IS ASSESSED AT 25 KNOTS, MEETING JTWC WARNING CRITERIA FOR SYSTEMS IN THE NORTHWESTERN PACIFIC. DVORAKS FROM PGTW AND RJTD RANGE FROM 1.5 TO 2.0 OR 25 TO 30 KNOTS. A 210814Z WINDSAT IMAGE SHOWS A WELL-DEFINED CIRCULATION CENTER WITH WINDS AS HIGH AS 20 KNOTS. SINCE THEN DEEP CONVECTION HAS BUILT OVER THE CENTER, WHICH HAS LIKELY INCREASED THE INTENSITY OF THE LLCC TO 25 KNOTS. BANDING FEATURES ARE STILL RELATIVELY IMMATURE AND BEST DEFINED IN THE LOWER LEVELS AS HIGHLIGHTED IN A 211228Z TMI 37H MICROWAVE IMAGE. THE HIGHER FREQUENCY IMAGE SHOWS THAT THE LLCC IS STILL BIASED TOWARDS THE NORTH OF THE BUILDING CONVECTION. 3. FORECAST REASONING. A. THIS MESSAGE ESTABLISHES THE FORECAST REASONING FOR THIS SYSTEM. B. TD 16W WILL TRACK UNDER THE INFLUENCE OF STRONG LOW TO MID- LEVEL RIDGING TO THE NORTH. THE SYSTEM WILL SLOWLY INTENSIFY UNDER THE PROTECTION OF THE UPPER LEVEL RIDGE AXIS, BENEFITING FROM LOW VERTICAL WIND SHEAR AND FAVORABLE WESTWARD VENTING INTO AN UPPER LEVEL INVERTED TROUGH OVER THE PHILIPPINE SEA. IT IS POSSIBLE FOR THE SYSTEM TO INTENSIFY FASTER THAN FORECAST IF THIS TROUGH PULLS NORTH, WHICH WOULD IMPROVE OUTFLOW. C. AROUND TAU 72 A MID TO DEEP LAYER TROUGH WILL ERODE THE STEERING RIDGE TO THE NORTH AND DRAW THE SYSTEM POLEWARD. MODEL GUIDANCE ALL SUGGEST OR HINT AT A BREAK IN THE STEERING RIDGE WITH NOGAPS OVERDEEPENING A LONGWAVE TROUGH, WHICH IS RESPONSIBLE FOR THE EROSION OF THE STEERING RIDGE, AND PULLS THE SYSTEM NORTH DAYS AHEAD OF THE OTHER TRACKERS. ECMWF RESOLVES A WEAKER SYSTEM AND CONTINUES TO TRACK THE SYSTEM WEST UNDER THE INFLUENCE OF THE LOW LEVEL EASTERLY FLOW. THE OFFICIAL FORECAST LIES CLOSE TO THE MODEL CONSENSUS, WHICH ACCOUNTS FOR THE PREMATURE RECURVATURE OF NOGAPS AND THE NEAR WESTWARD STRAIGHT-RUNNING ECMWF SOLUTION. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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.