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Hurricane SIMON Forecast Discussion Number 11
2014-10-04 10:56:34| National Hurricane Center (East Pacific)
Issued at 200 AM PDT SAT OCT 04 2014 000 WTPZ44 KNHC 040856 TCDEP4 HURRICANE SIMON DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192014 200 AM PDT SAT OCT 04 2014 Microwave satellite imagery between 0000 UTC and 0500 UTC indicate that the inner-core convection had been unable to consolidate around the center and maintain a closed eye feature. A 0442 UTC AMSU overpass revealed that the eye of Simon was open in the northwest quadrant. Since that time, however, infrared satellite imagery indicates that a warm spot has developed near the center of a more symmetrical and growing CDO feature, suggesting that Simon might finally be getting more vertically coherent. The initial intensity has been increased to 75 kt based on a Dvorak intensity estimate of T4.5/77 kt from TAFB and the recent appearance of a warm spot in the CDO cloud canopy. The initial motion is 290/10 kt, which is based on several microwave satellite positions. There is basically no significant change to the previous track forecast or reasoning. The 00 UTC model guidance shows less divergence than previous runs, especially through 36 hours. After that time, the models show some noticeable difference on when and where Simon is expected to gradually recurve to the northeast when the cyclone nears the subtropical ridge axis that is situated along 23N-24N latitude. The GFS, GFS-ensemble mean, and HWRF models show a sharper and earlier turn to the northeast by about 48 hours due to a weaker ridge, whereas the ECMWF, UKMET, GFDL and NAVGEM models have Simon moving farther west and making a wider and slower turn. Given the high amplitude nature of the large mid-latitude ridge over the western U.S. and eastern Pacific and the deepening trough over the eastern United States, which should help to sustain the current steering flow pattern, the official forecast leans more toward the farther west and slower recurvature model solutions. The NHC forecast track is similar to but a little to the west of the previous forecast track and the consensus model TVCN. The global models indicate that the current impressive outflow and low vertical wind shear patterns surrounding Simon are expected to persist for at least the next 36 hours or so. However, the most significant strengthening, possibly even rapid intensification, is most likely to occur during the next 24 hours while the hurricane remains over sea-surface temperatures of 27-28C and where the depth of the warm water is sufficient to prevent any significant cold upwelling beneath Simon. By 36 hours, passage over cooler SSTs should induce gradual weakening, followed by more rapid weakening on Days 4 and 5 when southwesterly vertical wind shear is expected to increase to 25-40 kt. Simon is forecast to become a remnant low by 120 hours, but this could occur sooner if the cyclone moves farther west than the official forecast track is indicating, which would bring the cyclone over colder water. A NOAA Hurricane Hunter aircraft is scheduled to conduct a research flight into Simon around 1800 UTC today, at which time a better estimate of the strength of the hurricane will be obtained. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 19.5N 112.7W 75 KT 85 MPH 12H 04/1800Z 20.2N 114.4W 85 KT 100 MPH 24H 05/0600Z 21.4N 116.2W 95 KT 110 MPH 36H 05/1800Z 22.3N 117.2W 80 KT 90 MPH 48H 06/0600Z 23.3N 117.6W 70 KT 80 MPH 72H 07/0600Z 24.4N 117.4W 55 KT 65 MPH 96H 08/0600Z 25.2N 117.0W 35 KT 40 MPH 120H 09/0600Z 26.3N 116.1W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart
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