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Tropical Storm Zeta Forecast Discussion Number 6
2020-10-26 03:44:45| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Sun Oct 25 2020 000 WTNT43 KNHC 260244 TCDAT3 Tropical Storm Zeta Discussion Number 6 NWS National Hurricane Center Miami FL AL282020 1100 PM EDT Sun Oct 25 2020 The tropical storm continues to produce deep convection on its south side, with the low-level center estimated to be near the northern edge of the thunderstorms. The last pass from the NOAA Hurricane Hunters a few hours ago indicated that the minimum pressure had fallen to 997 mb, and since the storm appears better organized than before the initial intensity is nudged up to 50 kt. This intensity estimate is slightly above the latest Dvorak numbers. The NOAA Hurricane Hunters are planning to be in Zeta again overnight and that data will be helpful in assessing the storm's intensity and structure. Zeta has not moved much during the past several hours, and the initial motion is a very slow north-northwest drift. As ridging begins to build over and near Florida, Zeta is forecast to move faster to the northwest overnight and Monday, and that should take the center of the cyclone near or over the northeastern portion of the Yucatan Peninsula in about 24 hours. The ridge is then expected to shift eastward over the western Atlantic on Tuesday and Wednesday as a large and quite powerful mid- to upper-level low moves eastward across the southwest and south-central United States. This change in the steering pattern should cause Zeta to accelerate northward toward the northern Gulf Coast, and likely make landfall there on Wednesday. The models remain in poor agreement on the details of the evolution of the steering pattern and consequently, there is about a 300 n mi spread in the landfall locations from the various models, which currently spans the region from the far western Florida panhandle to western Louisiana. The NHC track forecast is a little west of the previous one trending toward the middle of the guidance envelope. Based on the poor model agreement, the confidence in the track forecast is lower than normal. It is hoped that data being collected by the NOAA Gulfstream jet flying around Zeta and special NWS weather balloon launches will help the models come into better agreement on the future track of Zeta soon. Given the low wind shear conditions, moist air mass, and high oceanic heat content over the northwestern Caribbean, steady strengthening seems likely until Zeta reaches the Yucatan Peninsula by late Monday. The cyclone is expected to be a hurricane at landfall in Mexico, and the new forecast shows a slightly higher intensity there based on the new models and favorable conditions. The models differ on how long the core of Zeta will be inland over the Yucatan, but in general, it seems likely that significant weakening won't occur given the storm's expected increasing forward speed. The overall environmental conditions are anticipated to remain generally favorable while Zeta moves across the southern Gulf of Mexico, but there should be an increase in shear when it reaches the central Gulf and the cyclone will then be moving over the cooler shelf waters over the northern Gulf. The combination of the stronger shear and cooler waters should cause Zeta to level off in strength and perhaps weaken slightly before the U.S. landfall. The intensity models are in fair agreement, and the NHC forecast lies near the HCCA and IVCN consensus models. 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 could lead to flash flooding in urban areas. 3. Zeta is forecast to be at or near 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 26/0300Z 18.1N 83.8W 50 KT 60 MPH 12H 26/1200Z 18.9N 84.7W 60 KT 70 MPH 24H 27/0000Z 20.2N 86.5W 75 KT 85 MPH 36H 27/1200Z 21.8N 88.6W 65 KT 75 MPH 48H 28/0000Z 24.0N 90.4W 65 KT 75 MPH 60H 28/1200Z 27.1N 91.1W 65 KT 75 MPH 72H 29/0000Z 31.1N 89.6W 50 KT 60 MPH...INLAND 96H 30/0000Z 38.7N 78.8W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 31/0000Z...DISSIPATED $$ Forecaster Cangialosi
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