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Hurricane Willa Forecast Discussion Number 5
2018-10-21 10:44:39| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Sun Oct 21 2018 000 WTPZ44 KNHC 210844 TCDEP4 Hurricane Willa Discussion Number 5 NWS National Hurricane Center Miami FL EP242018 300 AM MDT Sun Oct 21 2018 Willa has continued to rapidly intensify based on a well-defined CDO with an intermittent pinhole eye evident in high-resolution GOES-16 infrared (IR) satellite imagery. Upper-level outflow has become well established in all quadrants. The intensity is difficult to ascertain since satellite intensity estimates vary widely based on the scene type used and also the small size of the hurricane. TAFB and SAB both provided an estimate of T4.0/65 kt, whereas UW-CIMSS ADT and SATCON were 67 kt and 56 kt, respectively. In contrast, NHC objective T-numbers are T5.0/90 kt using an embedded center and as high as T6.0/115 kt using a pinhole eye. Given that the eye has not been maintained in IR imagery, the advisory intensity of 75 kt lies between the subjective TAFB/SAB estimate and lower NHC objective estimate. Willa is moving at 315/06 kt. There is no significant change to the previous forecast track reasoning. Willa is forecast to continue moving northwestward for the next 24 h or so, followed by a turn toward the north on Monday, with a motion toward the northeast expected on Tuesday as the hurricane gradually rounds the western periphery of the deep-layer ridge. By late Tuesday, Willa is forecast to accelerate northeastward ahead of a deep-layer trough that will be approaching Baja California, resulting in landfall along the west-central coast of Mexico on Wednesday. The latest 00Z model guidance is tightly packed about the previous forecast track, and only minor forward speed adjustments were required. A 96-h position has been provided only for continuity purposes, and Willa will likely have dissipated over the Mexican mountains by then. Willa's small inner-core wind field along with ideal environmental conditions consisting of low shear, high mid-level moisture, and warm SSTs of 28 deg C should allow the hurricane to continue to rapidly intensify for the next 24-36 hours, followed by a leveling off in the intensity by early Tuesday due to expected cold upwelling beneath the slow-moving hurricane. In 60-72 hours, increasing southwesterly shear ahead of the aforementioned deep-layer trough is expected to induce steady weakening until landfall occurs. Rapid dissipation over the mountainous terrain of mainland Mexico will occur after landfall. The official intensity forecast is a tad above the consensus models HCCA and FSSE, and is little below the robust Navy COAMPS-TC model forecast. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 16.2N 106.5W 75 KT 85 MPH 12H 21/1800Z 16.8N 107.0W 85 KT 100 MPH 24H 22/0600Z 17.6N 107.4W 100 KT 115 MPH 36H 22/1800Z 18.7N 107.7W 115 KT 130 MPH 48H 23/0600Z 19.8N 107.7W 120 KT 140 MPH 72H 24/0600Z 22.3N 106.1W 90 KT 105 MPH...NEAR WNCTRL MEXICO 96H 25/0600Z 26.9N 101.2W 25 KT 30 MPH...INLAND NCNTRL MEXICO 120H 26/0600Z...DISSIPATED INLAND $$ Forecaster Stewart
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