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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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Post-Tropical Cyclone Epsilon Forecast Discussion Number 29

2020-10-26 03:36:14| National Hurricane Center (Atlantic)

Issued at 300 AM GMT Mon Oct 26 2020 000 WTNT42 KNHC 260236 TCDAT2 Post-Tropical Cyclone Epsilon Discussion Number 29 NWS National Hurricane Center Miami FL AL272020 300 AM GMT Mon Oct 26 2020 Recent satellite-derived wind data indicate that Epsilon no longer has the structure of a tropical cyclone. The low-level circulation is stretched out along a north-south axis, with an area of lighter winds noted near and north of the ill-defined center. Furthermore, infrared cloud tops have warmed over the past several hours as convection wanes near the center. Therefore, Epsilon has been declared a post-tropical cyclone, and this will be the last NHC advisory for the system. A partial 22Z ASCAT-A overpass showed at least 55-kt winds in the southern semicircle of the cyclone, which supports keeping the initial intensity at 60 kt. Post-tropical Epsilon is firmly embedded in the mid-latitude westerlies, and the cyclone will continue racing northeastward at around 35-40 kt for the next day or so. The cyclone will remain a very powerful and dangerous storm until it is absorbed by another large extratropical low pressure system over the northeastern Atlantic. The global models remain in very good agreement with this scenario, and no notable changes were made to the official NHC forecast. Additional information on this system can be found in High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 48.6N 38.8W 60 KT 70 MPH...POST-TROPICAL 12H 26/1200Z 52.1N 30.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 24H 27/0000Z 57.0N 24.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 27/1200Z...ABSORBED $$ Forecaster Reinhart/Zelinsky

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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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Tropical Storm Epsilon Forecast Discussion Number 28

2020-10-25 21:36:45| National Hurricane Center (Atlantic)

Issued at 900 PM GMT Sun Oct 25 2020 000 WTNT42 KNHC 252036 TCDAT2 Tropical Storm Epsilon Discussion Number 28 NWS National Hurricane Center Miami FL AL272020 900 PM GMT Sun Oct 25 2020 Epsilon is nearly extratropical, with late morning scatterometer data showing that the circulation has become stretched out as the cyclone interacts with a high-latitude low pressure system and an associated mid- upper-level trough to its north. The main reason that the cyclone is still classifiable as a tropical cyclone is persistent deep convection very near the center of circulation. Based on the scatterometer data showing an area of peak winds of 56 kt, the initial intensity is being lowered to 60 kt. What remains of the trapped tropical airmass near the center of the cyclone supporting the deep convection should mix out over the next few hours, as Epsilon moves over cold waters of about 15 degrees C and continues to wrap cooler and stable air into its circulation. The post-tropical cyclone will remain large and powerful until it is absorbed by another large extratropical low over the north Atlantic in about 24-36 h. Epsilon is racing east-northeastward at around 40 kt, embedded within the mid-latitude westerlies. A fast east-northeastward or northeastward motion is expected to continue until the system gets absorbed by the aforementioned high-latitude low pressure system. The latest NHC forecast track is essentially an update of the previous one and remains in the middle of the tightly clustered consensus guidance. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 46.2N 44.3W 60 KT 70 MPH 12H 26/0600Z 49.4N 35.8W 55 KT 65 MPH...POST-TROP/EXTRATROP 24H 26/1800Z 54.4N 26.2W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 27/0600Z...ABSORBED $$ Forecaster Latto

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Hurricane Epsilon Forecast Discussion Number 27

2020-10-25 15:59:08| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Sun Oct 25 2020 000 WTNT42 KNHC 251458 TCDAT2 Hurricane Epsilon Discussion Number 27 NWS National Hurricane Center Miami FL AL272020 1100 AM AST Sun Oct 25 2020 Epsilon continues its extratropical transition, as the cloud tops near the center of circulation are warming while the cloud pattern continues to expand over the northern portion of the circulation. The initial intensity is being held at 65 kt for this advisory based on early morning ASCAT data. Partial data from a more recent scatterometer pass also suggested this intensity. The cyclone is now moving over waters of only 17 degrees C and the waters ahead of the system are even cooler than that. Epsilon is also interacting with a baroclinic zone as evidenced by a large area of cool and stable air stratocumulus wrapping around the southwestern portion of the circulation. These factors should cause what remains of the inner-core convection to weaken over the next several hours, and the system should complete its extratropical transition by tonight. The post-tropical cyclone will remain large and powerful for the next day or so until it is absorbed by another large extratropical low over the north Atlantic in about 36-48 h. Epsilon is moving quickly east-northeastward at around 30 kt. The cyclone is expected to accelerate even more today, with a fast east-northeastward or northeastward motion expected until the system is absorbed by the other low. The latest NHC forecast track is little changed from the previous one and lies in the middle of the tightly clustered consensus guidance. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 44.3N 49.4W 65 KT 75 MPH 12H 26/0000Z 47.0N 41.8W 65 KT 75 MPH...POST-TROP/EXTRATROP 24H 26/1200Z 51.5N 31.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 27/0000Z 56.4N 23.1W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 27/1200Z...DISSIPATED $$ Forecaster Latto

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