From owner-wx-tropl@LISTSERV.ILLINOIS.EDU Fri Oct 15 22:29:06 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 o9FET4aE006991 for ; Fri, 15 Oct 2010 22:29:05 +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 o9ELxwsf022943; Fri, 15 Oct 2010 09:28:19 -0500 (CDT) Received: by LISTSERV.ILLINOIS.EDU (LISTSERV-TCP/IP release 14.5) with spool id 3901575 for WX-TROPL@LISTSERV.ILLINOIS.EDU; Fri, 15 Oct 2010 09:28:19 -0500 Received: from relay10.cites.uiuc.edu (relay10.cites.uiuc.edu [128.174.196.10]) by vacuum.cso.uiuc.edu (8.14.2/8.14.2) with ESMTP id o9FESJjj017802 for ; Fri, 15 Oct 2010 09:28:19 -0500 (CDT) Received: from weather3.admin.niu.edu (weather3.admin.niu.edu [131.156.8.48]) by relay10.cites.uiuc.edu (8.14.4/8.14.2) with ESMTP id o9FESCMp028889 for ; Fri, 15 Oct 2010 09:28:19 -0500 (CDT) Received: by weather3.admin.niu.edu (Postfix, from userid 501) id D3F9040501A6; Fri, 15 Oct 2010 09:28:12 -0500 (CDT) X-Proofpoint-Spam-Reason: safe Message-ID: <20101015142812.D3F9040501A6@weather3.admin.niu.edu> Date: Fri, 15 Oct 2010 09:28:12 -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 11// To: WX-TROPL@LISTSERV.ILLINOIS.EDU Precedence: list WDPN31 PGTW 151500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (MEGI) WARNING NR 11// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TYPHOON 15W (MEGI), LOCATED APPROXIMATELY 850 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY AND A 151059Z SSMIS 37H IMAGE DEPICT A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH TIGHTLY-CURVED BANDING (TCB). ANIMATED WATER VAPOR IMAGERY INDICATES GOOD OVERALL OUTFLOW WITH THE EXCEPTION OF THE NORTHWEST QUADRANT, WHERE OUTFLOW IS HINDERED BY A TUTT LOW NEAR 20N 130E AND UPPER-LEVEL TROUGHING EXTENDING SOUTHWESTWARD. THERE IS HIGH CONFIDENCE IN THE CURRENT POSITION BASED ON THE TCB AND AFOREMENTIONED SSMIS IMAGE. THE CURRENT INTENSITY OF 90 KNOTS IS BASED ON DVORAK ESTIMATES OF 90 KNOTS FROM BOTH KNES AND PGTW. RJTD IS CURRENTLY AT 70 KNOTS. 3. FORECAST REASONING. A. NO CHANGE IN FORECAST PHILOSOPHY. B. TY 15W HAS CONTINUED TO TRACK NORTHWESTWARD ALONG THE SOUTHWEST PERIPHERY OF THE MID-LEVEL SUBTROPICAL RIDGE (STR) TOWARD A WEAKNESS POSITIONED JUST SOUTH OF OKINAWA. THE 15/00Z UPPER AIR ANALYSES SHOW A MAJOR MIDLATITUDE SHORTWAVE TROUGH OVER NORTHEASTERN ASIA WITH THE AXIS ALONG 128E. THE STR HAS REMAINED STRONG AND EXTENDS FROM A HIGH CENTERED NEAR 24N 133E WESTWARD TO 130E. THIS STR IS EXPECTED TO STRENGTHEN AS THE TROUGH PROPAGATES NORTHEASTWARD IN THE NEXT 24 HOURS. THIS WILL ALLOW TY 15W TO TURN MORE WESTWARD TOWARD NORTHERN LUZON. TY 15W SHOULD CONTINUE TO INTENSIFY UNDER FAVORABLE (INCLUDING IMPROVING OUTFLOW AS THE TUTT LOW WEAKENS) CONDITIONS THROUGH TAU 72, AND IS EXPECTED TO REACH SUPER TYPHOON STRENGTH BEFORE MAKING LANDFALL OVER LUZON. MODEL GUIDANCE, INCLUDING UKMO, JGSM, ECMWF AND GFS (AS WELL AS ALMOST ALL ENSEMBLE SOLUTIONS), IS TIGHTLY CLUSTERED AND SHOWS A GENERALLY WESTWARD TRACK. THE ONLY OUTLIERS ARE NOGAPS, WBAR AND GFDN. GFDN HAS CONSISTENTLY INDICATED A WEST-NORTHWESTWARD TRACK TOWARD TAIWAN WHILE NOGAPS HAS BEEN HIGHLY ERRATIC OVER THE PAST 5 RUNS AND NOW INDICATES A RE-CURVE TRACK TOWARD OKINAWA. THE CURRENT NOGAPS TRACK MAKES LITTLE SENSE AS THE SYSTEM IS TRACKING INTO A STRONG, BROAD LOW-LEVEL HIGH SITUATED OVER NORTHEAST ASIA (INTO LOW-LEVEL NORTHEASTERLY FLOW) AND ALSO TRACKS THE SYSTEM THROUGH AN UPPER-LEVEL RIDGE. THEREFORE, THE NOGAPS SOLUTION IS DISCOUNTED. THE GFDN SOLUTION IS ALSO PROBLEMATIC WITH A TRACK INTO THE WESTERN STEERING RIDGE. BASED ON THIS ANALYSIS, THE CURRENT FORECAST IS POSITIONED SOUTH AND FASTER THAN THE CONSENSUS TO OFFSET THESE OUTLIERS AND FAVORS THE TIGHT CLUSTER OF UKMO, ECMWF, GFS AND JGSM. C. AFTER TAU 72, TY 15W IS FORECAST TO MAKE LANDFALL OVER LUZON AT OR NEAR SUPER TYPHOON STRENGTH. THE SYSTEM SHOULD WEAKEN CONSIDERABLY WHILE CROSSING THE MOUNTAINOUS TERRAIN OF LUZON BUT IS EXPECTED TO RE-EMERGE INTO THE SOUTH CHINA SEA AT TYPHOON STRENGTH. THIS FORECAST CONTINUES TO FAVOR THE SOUTHERN CLUSTER OF MODELS.// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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.