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Hurricane SEYMOUR Forecast Discussion Number 14
2016-10-26 16:39:11| National Hurricane Center (East Pacific)
Issued at 800 AM PDT WED OCT 26 2016 000 WTPZ45 KNHC 261439 TCDEP5 HURRICANE SEYMOUR DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL EP202016 800 AM PDT WED OCT 26 2016 Seymour continues to maintain an impressive central dense overcast, consisting of very deep convection around a 15 n mi well-defined eye. However, the distribution of convection has become slightly asymmetric since the last advisory, with the greatest coverage to the north and east of the center. The convective asymmetry is likely indicative of some increase in southwesterly shear. A blend of the latest Dvorak T- and CI-numbers, including UW-CIMSS ADT values, is used to lower the initial intensity estimate of 120 kt. Seymour is living on borrowed time. A large mid- to upper-level trough seen in water vapor imagery upstream of the cyclone should cause a considerable increase in southwesterly shear within 24 hours. By that time, Seymour will already have reached much cooler waters. This should result in weakening, with the rate of filling only increasing with time. By 36 hours, the shear should become extremely strong and cause the vortex to shear apart, with the middle and upper portions of the circulation moving well to the north or northeast of the low-level center. The official forecast shows Seymour becoming a post-tropical remnant low in 48 hours in general agreement with global models that depict this decoupling as soon as 36 to 42 hours. The NHC intensity forecast shows about the same rate of weakening as the previous one and is close to the multi-model consensus. The initial motion estimate is 290/13. Seymour has begun to gain a little more latitude recently as it nears the western periphery of a mid-level ridge west of the Baja California peninsula. The cyclone's motion should slow and become northwesterly soon and then shift north-northwestward and northward in 24 to 36 hours as Seymour becomes embedded in the flow between the high to the northeast and the trough to the northwest. Once Seymour becomes a shallow system in 48 hours, the remnant low will slow further and turn north-northeastward until dissipation. The NHC track forecast is only slightly to the left of the previous one after 24 hours and a little faster during the remnant low phase. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 16.9N 120.2W 120 KT 140 MPH 12H 27/0000Z 18.0N 121.5W 105 KT 120 MPH 24H 27/1200Z 19.7N 122.6W 80 KT 90 MPH 36H 28/0000Z 21.1N 122.9W 60 KT 70 MPH 48H 28/1200Z 22.2N 122.4W 35 KT 40 MPH...POST-TROP/REMNT LOW 72H 29/1200Z 23.7N 121.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 30/1200Z...DISSIPATED $$ Forecaster Kimberlain
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