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Hurricane SIMON Forecast Discussion Number 16
2014-10-05 16:49:09| National Hurricane Center (East Pacific)
Issued at 800 AM PDT SUN OCT 05 2014 000 WTPZ44 KNHC 051449 TCDEP4 HURRICANE SIMON DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192014 800 AM PDT SUN OCT 05 2014 Simon continues to weaken. The distribution of deep convection has become more asymmetric during the last 12 hours, and there has been a general warming of cloud top temperatures. The cyclone's cloud canopy has also been expanding over the northern semicircle while eroding some to the south. This transformation of the cloud pattern is primarily related to an increase in southwesterly shear over the hurricane, as diagnosed by UW-CIMSS shear analyses and SHIPS model output. A blend of Dvorak Final-T and CI-numbers from TAFB and SAB is used to reduce the initial intensity to 85 kt. As Simon gains latitude during the next couple of days, a further increase in shear is expected in association with a mid- to upper-level shortwave trough several hundred miles west of the coast of southern California. The abrupt and substantial increase in shear, combined with water temperatures around 25 deg C and other considerably less conducive thermodynamic conditions, should result in a rapid decay of the cyclone. Global models show the low- to mid-level centers of Simon decoupling around 48 hours, and Simon should become a remnant low in 72 hours, if not sooner. The NHC intensity forecast, like the previous one, shows rapid weakening over the next 48 hours and is in excellent agreement with the latest multi-model consensus. The initial motion estimate is 325/09. Simon is moving into a region of weak steering on the western periphery of a subtropical ridge centered near western Mexico. This synoptic pattern should result in the cyclone's gradual turning toward the north with a decrease in forward speed over the next day or so. The previously mentioned shortwave trough should cause Simon to turn northeastward within 48 hours, with Simon or its remnants likely moving over the north-central portion of the Baja California peninsula later in the forecast period. The NHC forecast has not changed much relative to the previous one and remains close to the multi-model consensus, substantially slower than the GFS solution which brings Simon inland over northwestern Mexico in 72 hours. Even if Simon or its remnant circulation does not make it across the rugged terrain of the Baja California peninsula, deep moisture associated with the cyclone 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 in a few days. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 22.9N 117.1W 85 KT 100 MPH 12H 06/0000Z 23.6N 117.4W 70 KT 80 MPH 24H 06/1200Z 24.5N 117.5W 55 KT 65 MPH 36H 07/0000Z 25.4N 117.2W 40 KT 45 MPH 48H 07/1200Z 26.2N 116.8W 30 KT 35 MPH 72H 08/1200Z 28.2N 115.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 09/1200Z 29.7N 113.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 10/1200Z...DISSIPATED $$ Forecaster Kimberlain
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