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Tropical Storm Zeta Forecast Discussion Number 5
2020-10-25 21:55:11| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Sun Oct 25 2020 000 WTNT43 KNHC 252055 TCDAT3 Tropical Storm Zeta Discussion Number 5 NWS National Hurricane Center Miami FL AL282020 500 PM EDT Sun Oct 25 2020 Although the overall cloud pattern of Zeta is still not very well organized, with a lack of distinct banding features, it continues to generate very intense deep convection mainly over the southeastern portion of the circulation. Moreover, in spite of its ragged appearance, the storm has strengthened today. Reports from a NOAA Hurricane Hunter aircraft investigating the system this afternoon indicate that, based on adjusted flight-level and SFMR-observed surface winds, the intensity has increased to near 45 kt and the central pressure has fallen to 999 mb. Since the storm will be moving over the high oceanic heat content of the northwestern Caribbean Sea and in a moist environment with low vertical shear through Monday, strengthening is forecast and Zeta will likely become a hurricane before it nears the Yucatan Peninsula in a day or so. After Zeta moves into the Gulf of Mexico, southwesterly shear is likely to increase and oceanic heat content below the cyclone will diminish, especially when the system approaches the northern Gulf coast on Wednesday. Therefore, no strengthening is forecast in 2-3 days and Zeta could be weakening by the time it reaches the northern Gulf coast. However, the intensity forecast is still subject to significant uncertainty. The center has been meandering this afternoon, and apparently has reformed nearer to the deep convection over the southeastern quadrant. Since this is not considered representative of larger-scale motion, the system is still considered to be quasi-stationary at this time. However, the track guidance is in agreement that Zeta will move northwestward over the next 1-2 days, passing near or over the Yucatan Peninsula. Thereafter, the cyclone is likely to turn north-northwestward to northward while it moves on the western side of a mid-tropospheric anticyclone near Florida. A turn toward the north-northeast is expected when Zeta nears the northern Gulf coast, due to an approaching shortwave trough. The track guidance has more than the usual amount of spread at the 72-hour time frame, with the ECMWF and the GFS predictions being about 300 miles apart near the northern Gulf coast. The official forecast track lies between these 2 solutions, and is similar to the previous NHC track. However, given the inherent uncertainties, one should not focus on the exact forecast track. Based on the new intensity forecast, the government of Mexico has issued a Hurricane Warning for a portion of the Yucatan peninsula. KEY MESSAGES: 1. Hurricane conditions and storm surge are expected in portions of the northern Yucatan Peninsula of Mexico Monday night and early Tuesday. Tropical storm conditions could occur over extreme western Cuba on Monday. 2. Through Wednesday, heavy rainfall is expected from Zeta across portions of central and western Cuba, the Cayman Islands, Jamaica, the northeast Yucatan peninsula of Mexico, southern Florida and the Keys. This rainfall may lead to flash flooding in urban areas. 3. Zeta is forecast to be at or just below hurricane strength when it approaches the northern Gulf Coast on Wednesday, and there is an increasing risk of storm surge, rainfall, and wind impacts from Louisiana to the Florida Panhandle. Residents in these areas should monitor the progress of Zeta and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 17.7N 83.4W 45 KT 50 MPH 12H 26/0600Z 18.7N 84.3W 55 KT 65 MPH 24H 26/1800Z 19.7N 85.7W 65 KT 75 MPH 36H 27/0600Z 21.1N 87.6W 65 KT 75 MPH...INLAND 48H 27/1800Z 23.2N 89.6W 65 KT 75 MPH 60H 28/0600Z 25.7N 90.8W 65 KT 75 MPH 72H 28/1800Z 29.4N 90.3W 60 KT 70 MPH...INLAND 96H 29/1800Z 37.0N 83.0W 25 KT 30 MPH...INLAND 120H 30/1800Z...DISSIPATED $$ Forecaster Pasch
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