ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM Tropical Storm Zeta Discussion Number 4 NWS National Hurricane Center Miami FL AL282020 1100 AM EDT Sun Oct 25 2020 Although the cloud pattern of the storm is not well-organized and somewhat elongated zonally, the system is producing very vigorous deep convection, particularly over the southern portion of the circulation. Cirrus cloud motions show that the upper-level outflow is well-defined. The current intensity estimate remains at 35 kt in agreement with Dvorak values from both TAFB and SAB, and pending another Hurricane Hunter mission into the system this afternoon. The center is difficult to locate at this time, and the best estimate for motion is quasi-stationary. A high pressure area developing near Florida should induce a general northwestward motion over the next couple of days. Later, a shortwave trough approaching from the west is likely to cause Zeta to turn northward and north-northeastward while it nears the northern Gulf Coast in 72-84 hours. The official track forecast lies between the GFS solution which is farther east and the ECMWF prediction which lies farther south and west. Given the favorable upper-level outflow pattern and very high oceanic heat content over the northwestern Caribbean, strengthening is likely until the center moves near or over the Yucatan Peninsula late tomorrow. Zeta should be near or at hurricane strength when it approaches the Yucatan. The official intensity forecast for the next 36 hours is close to the model consensus. After Zeta moves into the central Gulf of Mexico, increasing southwesterly shear and diminishing oceanic heat content are expected to prevent strengthening. The NHC intensity forecast over the Gulf is above the latest model consensus. Although not explicitly shown in the official forecast, the unfavorable atmospheric and oceanic conditions over the northern Gulf of Mexico could cause Zeta to weaken by the time the center nears the northern Gulf coast. However, users are reminded that these intensity forecasts are subject to uncertainty. KEY MESSAGES: 1. Tropical storm conditions are expected in portions of the northern Yucatan Peninsula of Mexico Monday night and early Tuesday, with hurricane conditions possible. 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 could be at or just below hurricane strength when it approaches the northern Gulf Coast on Wednesday, and could bring storm surge, rainfall, and wind impacts to areas 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 25/1500Z 17.8N 83.8W 35 KT 40 MPH 12H 26/0000Z 18.4N 84.1W 40 KT 45 MPH 24H 26/1200Z 19.2N 85.1W 50 KT 60 MPH 36H 27/0000Z 20.3N 86.7W 60 KT 70 MPH 48H 27/1200Z 21.9N 88.7W 65 KT 75 MPH 60H 28/0000Z 24.0N 90.3W 65 KT 75 MPH 72H 28/1200Z 27.0N 90.5W 65 KT 75 MPH 96H 29/1200Z 35.0N 85.5W 25 KT 30 MPH...INLAND 120H 30/1200Z...DISSIPATED $$ Forecaster Pasch NNNN