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Tropical Storm Zeta Forecast Discussion Number 13

2020-10-27 21:41:18| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Tue Oct 27 2020 000 WTNT43 KNHC 272041 TCDAT3 Tropical Storm Zeta Discussion Number 13 NWS National Hurricane Center Miami FL AL282020 400 PM CDT Tue Oct 27 2020 Visible satellite images show that the low-level center of the storm is slightly displaced to the north of the main area of deep convection. Since the organization of the tropical cyclone has not yet improved, the current intensity is held at 55 kt, which is a blend of subjective and objective Dvorak estimates. Zeta should move over warm waters and through a moist, low-shear environment through tomorrow morning, so strengthening is anticipated, and the cyclone is likely to regain hurricane intensity within the next 6-12 hours. The NHC intensity forecast is on the high side of the model guidance suite. Zeta is expected to interact with a frontal zone and become an extratropical cyclone as it approaches the eastern United States in a couple of days. After moving off the U.S. east coast, the system is forecast to become absorbed by the same frontal system. Zeta continues to move northwestward, or at about 310/12 kt. The expected large-scale steering flow evolution remains about the same as before. Zeta is expected to turn northward and move along the western side of a mid-level anticyclone centered east of Florida through Wednesday morning. Then, a vigorous 500-mb shortwave trough approaching from the west should cause Zeta to accelerate north- northeastward and move inland along the central Gulf Coast by late Wednesday. The cyclone should continue to accelerate ahead of the trough and move over the southeastern and eastern U.S. through Thursday. The official track forecast was nudged just slightly westward in 24 to 36 hours to be in better agreement with the latest GFS and ECMWF explicit model fields. Given Zeta's acceleration near landfall, strong winds are likely to spread well inland along the northern Gulf coast Wednesday night. KEY MESSAGES: 1. A life-threatening storm surge is expected along portions of the northern Gulf Coast by late Wednesday, with the highest inundation occurring somewhere between the Mouth of the Pearl River and Dauphin Island, Alabama. Residents in the Storm Surge Warning area should follow any advice given by local officials. 2. Hurricane conditions are expected by late Wednesday within portions of the Hurricane Warning area between Morgan City, Louisiana, and the Mississippi/Alabama border. Damaging winds, especially in gusts, will spread well inland across portions of southeast Mississippi and southern Alabama Wednesday night due to Zeta's fast forward speed. 3. Localized heavy rainfall from Zeta will continue tonight in portions of the Yucatan Peninsula of Mexico and western Cuba where additional flash flooding is possible in urban areas. Tonight through Thursday heavy rainfall is expected from portions of the central U.S. Gulf Coast into the Ohio Valley and Mid-Atlantic States. This rainfall will lead to flash, urban, small stream, and minor river flooding. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 22.7N 90.3W 55 KT 65 MPH 12H 28/0600Z 24.5N 91.3W 70 KT 80 MPH 24H 28/1800Z 27.9N 91.0W 70 KT 80 MPH 36H 29/0600Z 32.4N 87.8W 45 KT 50 MPH...INLAND 48H 29/1800Z 37.2N 81.3W 30 KT 35 MPH...POST-TROP/EXTRATROP 60H 30/0600Z 40.0N 70.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 30/1800Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Zeta Forecast Discussion Number 12

2020-10-27 15:51:06| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Tue Oct 27 2020 811 WTNT43 KNHC 271451 TCDAT3 Tropical Storm Zeta Discussion Number 12 NWS National Hurricane Center Miami FL AL282020 1000 AM CDT Tue Oct 27 2020 High-resolution GOES-16 visible satellite images indicate that the center of Zeta has moved just offshore of the northern coast of Yucatan. Based on Air Force and NOAA aircraft observations a little while ago, after the cyclone's interaction with the Yucatan, the maximum winds had decreased to near 55 kt. The cloud pattern of the storm is well organized, with a small Central Dense Overcast and numerous banding features. Given this, Zeta is likely to restrengthen as it moves over the warm waters of the southern Gulf of Mexico and in a low-shear environment today through tomorrow morning. When the cyclone nears the northern Gulf Coast in 30-36 hours, decreasing oceanic heat content and possibly stronger shear will likely halt the intensification process. The official intensity forecast shows slight weakening near landfall, but Zeta is likely to be at or near hurricane strength when it crosses the coastline. The NHC intensity forecast is close to the model consensus and a blend of the LGEM and Decay-SHIPS guidance. The storm continues its generally northwestward motion, or at around 305/12 kt. Zeta will move northwestward to northward around the southwestern and western periphery of a mid-level high pressure area centered east of Florida for the next 24 hours or so. Then, a strong 500-mb shortwave trough approaching from the west should cause Zeta to accelerate north-northeastward to northeastward by late Wednesday and Thursday. This will bring Zeta across the north-central Gulf coast late Wednesday and over the southeastern United States on Thursday. Aside from some speed differences, the track models are in good agreement and have shown good run-to-run consistency. The official track forecast is about the same as the previous one and close to the model consensus. Given Zeta's acceleration near landfall, strong winds are likely to spread well inland along the northern Gulf coast Wednesday night. KEY MESSAGES: 1. A life-threatening storm surge is expected along portions of the northern Gulf Coast by late Wednesday, with the highest inundation occurring somewhere between the Mouth of the Pearl River and Dauphin Island, Alabama. Residents in the Storm Surge Warning area should follow any advice given by local officials. 2. Hurricane conditions are expected by late Wednesday within portions of the Hurricane Warning area between Morgan City, Louisiana, and the Mississippi/Alabama border. Damaging winds, especially in gusts, will spread well inland across portions of southeast Mississippi and southern Alabama Wednesday night due to Zetas fast forward speed. 3. Between tonight and Thursday, heavy rainfall is expected from portions of the central U.S. Gulf Coast into the Ohio Valley and Mid-Atlantic States near and in advance of Zeta. This rainfall will lead to flash, urban, small stream, and minor river flooding. 4. Tropical storm conditions will continue in portions of the northern Yucatan Peninsula of Mexico during the next few hours. Heavy rainfall is expected across the Yucatan Peninsula, the Cayman Islands, and western Cuba today, which will lead to flash flooding in urban areas. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 21.6N 89.5W 55 KT 65 MPH 12H 28/0000Z 23.1N 90.9W 70 KT 80 MPH 24H 28/1200Z 25.7N 91.6W 75 KT 85 MPH 36H 29/0000Z 29.3N 89.9W 70 KT 80 MPH 48H 29/1200Z 34.2N 85.2W 30 KT 35 MPH...INLAND 60H 30/0000Z 38.5N 76.5W 30 KT 35 MPH...INLAND 72H 30/1200Z 41.0N 66.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 31/1200Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Zeta Forecast Discussion Number 10

2020-10-27 03:47:30| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Mon Oct 26 2020 000 WTNT43 KNHC 270247 TCDAT3 Hurricane Zeta Discussion Number 10 NWS National Hurricane Center Miami FL AL282020 1000 PM CDT Mon Oct 26 2020 Satellite images are showing that convection has been increasing near Zeta tonight, with cold cold tops to at least -93C, and occasional hints of a warm spot related to the early-stages of an eye beneath the clouds. Yet, the NOAA Hurricane Hunter aircraft mission found that Zeta has basically been steady state in terms of maximum winds and pressures, with peak SFMR values hovering between 65-70 kt and dropsonde data showing central pressures of about 982 mb. The data did show that the area of hurricane-force winds has grown, about 40 n mi in the eastern semicircle, and it is possible that the worst of this hurricane will be after the center makes landfall. The initial wind speed is kept at 70 kt on this advisory. The hurricane is running out of time to get much stronger before landfall during the next couple of hours, but some increase in intensity is possible. Zeta should spend less than 12 hours over land as it crosses Yucatan, but that's enough time to probably drop it below hurricane strength early tomorrow. However, environmental conditions are unseasonably conducive for intensification so late in the year in the southern and central Gulf of Mexico, with fairly light shear and warm waters during the next 24 to 36 hours. The peak intensity forecast is raised slightly after considering those factors, and some models like the HWRF or ECMWF even suggest it could get a little stronger. As the hurricane nears the northern Gulf Coast, it is likely to encounter stronger shear and cooler waters, so some weakening is anticipated, but Zeta is still expected to be at or near hurricane intensity at landfall. The NHC intensity forecast is generally similar to the previous one, lying above the model consensus. Zeta continues to move on a generally northwestward track, or about 305/11 kt. The hurricane should move around the southwestern and western periphery of a mid-level subtropical high centered just east of Florida. Thereafter, a potent shortwave trough approaching from the Desert Southwest and Texas is likely to cause the cyclone to accelerate north-northeastward to northeastward on Wednesday and move over the southeastern and eastern United States. Model guidance is in very good agreement, with only some minor differences, and the new forecast is close to the previous one and the models consensus. The system should move off the Mid-Atlantic U.S. coast and become an extratropical cyclone within 3 days, and dissipate soon thereafter. KEY MESSAGES: 1. Hurricane conditions and dangerous storm surge are expected to continue in portions of the northern Yucatan Peninsula of Mexico through early Tuesday. Heavy rainfall is expected across the Yucatan Peninsula, the Cayman Islands, and western Cuba through Tuesday, which could lead to flash flooding in urban areas. 2. Hurricane conditions and life-threatening storm surge are possible along portions of the northern Gulf Coast on Wednesday, and Storm Surge and Hurricane Watches are in effect. Residents in the watch areas should follow any advice given by local officials. 3. Between Tuesday night and Thursday, heavy rainfall is expected from portions of the central Gulf Coast into the southern Appalachians and Mid-Atlantic States near and in advance of Zeta. This rainfall will lead to flash, urban, small stream, and minor river flooding. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 20.2N 87.1W 70 KT 80 MPH 12H 27/1200Z 21.3N 88.8W 60 KT 70 MPH...INLAND 24H 28/0000Z 23.1N 90.7W 65 KT 75 MPH...OVER WATER 36H 28/1200Z 25.6N 91.6W 75 KT 85 MPH 48H 29/0000Z 29.1N 90.1W 65 KT 75 MPH 60H 29/1200Z 33.8N 85.7W 35 KT 40 MPH...INLAND 72H 30/0000Z 38.5N 76.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 31/0000Z...DISSIPATED $$ Forecaster Blake

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Hurricane Zeta Forecast Discussion Number 9

2020-10-26 21:49:27| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Mon Oct 26 2020 000 WTNT43 KNHC 262049 TCDAT3 Hurricane Zeta Discussion Number 9 NWS National Hurricane Center Miami FL AL282020 400 PM CDT Mon Oct 26 2020 The cloud pattern of Zeta became better organized today, with deep convection forming over and around the center and some banding features developing. The Air Force Reserve Hurricane Hunters recently found surface winds to near 70 kt over the inner northeastern quadrant of the circulation and a central pressure of around 981 mb, signifying that the system had become a hurricane. Given the increased organization over very warm waters, some additional strengthening is possible before the center crosses the east coast of the Yucatan Peninsula this evening. Some weakening should occur while Zeta interacts with land tonight and early Tuesday. Once the center moves into the southern Gulf of Mexico tomorrow, atmospheric and oceanic conditions are conducive for some re-strengthening. When Zeta moves over the northern Gulf of Mexico later on Wednesday, cooler shelf waters and some increase in southwesterly shear should halt the intensification process, with some weakening possible by the time the center reaches the northern Gulf Coast, but Zeta is still expected to be at or near hurricane intensity at landfall. The NHC intensity forecast is similar to the previous one and is near or above the model consensus. The hurricane continues to move on a generally northwestward track, or at about 305/10 kt. There are basically no changes to the track forecast reasoning, or to the forecast itself. For the next couple of days, Zeta should move around the southwestern and western periphery of a mid-level high pressure area centered just east of Florida. Thereafter, a shortwave trough approaching from the west is likely to cause the cyclone to accelerate north-northeastward to northeastward and move over the southeastern and eastern United States. The system should move off the northeast U.S. coast and become an extratropical cyclone within the next 4 days. The guidance has come into better agreement since yesterday, and the official track forecast is very close to the corrected model consensus, HCCA. Storm Surge, Hurricane, and Tropical Storm Watches have been issued for a portion of the northern U.S. Gulf Coast. KEY MESSAGES: 1. Hurricane conditions and dangerous storm surge are expected in portions of the northern Yucatan Peninsula of Mexico this evening through early Tuesday. Through Tuesday, heavy rainfall is expected across the Yucatan Peninsula, the Cayman Islands, and central to western Cuba, which could lead to flash flooding in urban areas. 2. Hurricane conditions and life-threatening storm surge are possible along portions of the northern Gulf Coast on Wednesday, and Storm Surge and Hurricane Watches are in effect. Residents in the watch areas should follow any advice given by local officials. 3. Between Tuesday night and Thursday, heavy rainfall is expected from portions of the central Gulf Coast into the southern Appalachians and Mid-Atlantic States near and in advance of Zeta. This rainfall will lead to flash, urban, small stream, and minor river flooding. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 19.5N 86.0W 70 KT 80 MPH 12H 27/0600Z 20.5N 87.7W 75 KT 85 MPH 24H 27/1800Z 22.1N 89.9W 65 KT 75 MPH 36H 28/0600Z 24.2N 91.4W 70 KT 80 MPH 48H 28/1800Z 26.8N 91.4W 70 KT 80 MPH 60H 29/0600Z 30.8N 88.9W 60 KT 70 MPH...INLAND 72H 29/1800Z 35.0N 83.5W 30 KT 35 MPH...INLAND 96H 30/1800Z 42.0N 68.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 31/1800Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Zeta Forecast Discussion Number 8

2020-10-26 15:50:51| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Mon Oct 26 2020 000 WTNT43 KNHC 261450 TCDAT3 Tropical Storm Zeta Discussion Number 8 NWS National Hurricane Center Miami FL AL282020 1000 AM CDT Mon Oct 26 2020 After a significant strengthening episode early this morning, Zeta appears to have changed little in intensity recently. High spatial and temporal resolution GOES-16 visible satellite images indicate that the low-level center of the storm is located near the northwestern edge of the main area of vigorous deep convection. The current intensity estimate is held at 60 kt which is the average of recent Dvorak estimates from TAFB and SAB. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate Zeta in a few hours, and should provide a better estimate of the strength of the storm. Zeta is moving northwestward, or about 305/9 kt. A mid-level high pressure area centered just east of Florida should steer the tropical cyclone on a continued northwestward heading for the next day or so, taking center over the northern part of the Yucatan Peninsula. By around 48 hours, Zeta is expected to turn northward over the Gulf along the western side of the high. Afterward, a shortwave trough moving into the southern Plains should induce a turn toward the north-northeast and take the center inland over the southern United States. The system should then move fairly quickly northeastward across the eastern U.S. and emerge into the Atlantic by day 4. The official track forecast has been adjusted a bit to the west of the previous one but not quite as far west as the corrected model consensus. Zeta is apparently experiencing some north-northwesterly shear given the displacement of the low-level center from the convection. However, this shear is expected to abate very soon, and the cyclone is likely to strengthen into a hurricane before reaching the northeastern Yucatan Peninsula. Some weakening should occur while Zeta interacts with land during the next 12 to 24 hours. The atmospheric and oceanic environment should be somewhat conducive while the system moves over the southern Gulf of Mexico in a day or two, and the official forecast shows some re-strengthening in 24-36 hours. Later in the forecast period, when Zeta approaches the northern Gulf Coast, cooler shelf waters and some increase in southwesterly shear could cause some weakening. The official intensity forecast is similar to the previous ones and shows Zeta still near hurricane strength at landfall along the northern Gulf of Mexico coast, which is near or above most of the model guidance. Zeta is likely to become an extratropical cyclone when it emerges into the Atlantic, and be absorbed by a frontal system around the end of the forecast period. Given the timing of the track and the forecast wind radii, watches will likely be required for a portion of the northern Gulf Coast later today. KEY MESSAGES: 1. Hurricane conditions and dangerous storm surge are expected in portions of the northern Yucatan Peninsula of Mexico tonight and early Tuesday. Tropical storm conditions could occur over extreme western Cuba beginning later today. 2. Through Tuesday, heavy rainfall is expected from Zeta across the Yucatan Peninsula of Mexico, the Cayman Islands, and central to western Cuba. This rainfall may lead to flash flooding in urban areas. Between Tuesday night and Thursday, heavy rainfall is expected from portions of the central U.S. Gulf Coast into the southern Appalachians, and Mid-Atlantic States near and in advance of Zeta. This rainfall will lead to flash, urban, small stream, and minor river flooding. 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 dangerous storm surge, wind, and rainfall impacts from Louisiana to the Florida Panhandle. Residents in these areas should monitor the progress of Zeta, as Hurricane and Storm Surge watches will likely be issued later today. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 19.1N 85.3W 60 KT 70 MPH 12H 27/0000Z 20.1N 86.7W 75 KT 85 MPH 24H 27/1200Z 21.5N 88.8W 65 KT 75 MPH 36H 28/0000Z 23.3N 90.8W 70 KT 80 MPH 48H 28/1200Z 25.7N 91.8W 70 KT 80 MPH 60H 29/0000Z 28.9N 90.7W 65 KT 75 MPH 72H 29/1200Z 33.0N 87.0W 35 KT 40 MPH...INLAND 96H 30/1200Z 40.0N 73.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 31/1200Z...DISSIPATED $$ Forecaster Pasch

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