TROPICAL STORM SIMON DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192014 800 PM PDT SUN OCT 05 2014 The cloud pattern associated with Simon continues to slowly degrade this evening. The cloud tops have gradually warmed and recent microwave data indicate that the low-level center is located to the southwest of the main convective mass due to moderate southwesterly shear. The latest Dvorak Data T-numbers from SAB and TAFB are 3.5, but current intensity numbers remain higher due to Dvorak weakening constraints. The initial wind speed has been lowered to 60 kt, closer to the data T-numbers and a little below what was supported by the earlier NOAA aircraft data. Increasing southwesterly shear, cooler sea surface temperatures, and drier air should cause continued weakening during the next couple of days. Simon is forecast to become a tropical depression within 36 hours and should degenerate to a remnant low by Tuesday, before the center reaches the Baja California peninsula. The updated NHC intensity forecast is in good agreement with the SHIPS/LGEM guidance and is close to the model consensus. Simon is moving north-northwestward or 345 degrees at about 6 kt. The cyclone should turn northward, then north-northeastward during the next 24 hours around the western side of a mid-level high located near the coast of southwestern Mexico. Although the track guidance generally agrees on this scenario, there continues to be differences in how soon Simon or its remnants will reach the Baja peninsula. The GFS takes the cyclone across the Baja peninsula in about 48 hours, while the ECMWF and UKMET shows this occurring about a day later. The NHC track forecast remains in between these solutions and is close to the multi-model consensus. Even if Simon or its remnant circulation does not make it across the rugged terrain of the Baja California peninsula, moisture associated with this system is expected to spread across the northern Baja California peninsula, northwestern Mexico, and into the U.S. Desert Southwest, which could trigger heavy rains in those regions during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 23.8N 117.6W 60 KT 70 MPH 12H 06/1200Z 24.6N 117.6W 45 KT 50 MPH 24H 07/0000Z 25.7N 117.3W 35 KT 40 MPH 36H 07/1200Z 26.9N 116.8W 30 KT 35 MPH 48H 08/0000Z 28.1N 115.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 09/0000Z 30.0N 114.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 10/0000Z...DISSIPATED
Posted on: Mon, 06 Oct 2014 02:48:42 +0000
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