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Tropical Storm Eta Forecast Discussion Number 30
2020-11-07 21:54:30| National Hurricane Center (Atlantic)
Issued at 400 PM EST Sat Nov 07 2020 000 WTNT44 KNHC 072054 TCDAT4 Tropical Storm Eta Discussion Number 30 NWS National Hurricane Center Miami FL AL292020 400 PM EST Sat Nov 07 2020 An earlier Air Force Reserve Hurricane Hunter aircraft found that Eta had strengthened to 50 kt with a central pressure of 994 mb. Since that time, the storm organization is unchanged in satellite imagery, while the central convection looks a little more ragged in radar data from Grand Cayman Island and Cuba. Eta is currently being affected by 25-35 kt of southwesterly vertical wind shear, and water vapor imagery shows upper-level dry air approaching the inner core from the west. The initial motion now 050/14. There is little change to the forecast philosophy through the first 96 h of the forecast. A mid- to upper-level trough over the Gulf of Mexico should steer Eta northeastward for the next 12 h or so, which would bring the center near or over the coast of central Cuba. Then from 12-96 h, the trough should cut off into a closed low near western Cuba, with Eta turning northward and eventually westward near the Florida Keys and south Florida as it merges with the low. The track guidance has shifted a little to the west over Cuba and a little to the south near Florida, possibly in response to data from the G-IV jet mission earlier today, and the new track forecast does likewise. The track guidance becomes quite divergent after 96 h, and the 96-120 h motion is now slower than the previous forecast as a result. The intensity forecast is tricky. Strong upper-level divergence caused by the trough is allowing the cyclone to strengthen. However, at some time in the next 24-48 h the shear and dry air entrainment should prevent any further strengthening. The intensity guidance shows a little intensification during the next 24-36 h with the bulk of the guidance peaking near 60 kt. After that time, the dry air should cause at least some weakening. The new intensity forecast is increased a bit from the previous forecast to show a 60-kt intensity at 24 and 36 h. This requires issuing a hurricane watch for the Florida Keys and portions of south Florida. Key Messages: 1. Heavy rainfall will continue across the Cayman Islands, portions of Cuba, and Jamaica, and will spread north into the Bahamas and southern Florida. This rain may result in significant, life-threatening flash flooding and river flooding in Cuba. Flash and urban flooding will also be possible for the Cayman Islands, Jamaica, the Bahamas and southern Florida, along with potential minor river flooding in central Florida. 2. Tropical storm conditions will continue for a few more hours in portions of the Cayman Islands, and are expected tonight and Sunday in portions of Cuba and the northwestern Bahamas, where Tropical Storm Warnings are in effect. 3. Damaging tropical-storm-force winds are expected Sunday night, with hurricane-force winds possible, in the Florida Keys and portions of the southern Florida peninsula, where a Tropical Storm Warning and Hurricane Watch are in effect. Elsewhere across portions of the east and west coasts of the Florida peninsula, the risk of tropical-storm-force winds will extend well away from Eta's center, and Tropical Storm Watches and Warnings are in effect. 4. A life-threatening storm surge is possible along portions of the southern coast of the Florida peninsula and the Florida Keys, where a Storm Surge Watch is in effect. Residents in the Storm Surge Watch area should follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 20.4N 80.7W 50 KT 60 MPH 12H 08/0600Z 21.6N 79.4W 55 KT 65 MPH...INLAND 24H 08/1800Z 23.3N 79.0W 60 KT 70 MPH...OVER WATER 36H 09/0600Z 24.7N 79.9W 60 KT 70 MPH 48H 09/1800Z 25.2N 81.2W 55 KT 65 MPH 60H 10/0600Z 25.7N 82.8W 55 KT 65 MPH 72H 10/1800Z 26.1N 83.6W 50 KT 60 MPH 96H 11/1800Z 26.5N 84.0W 50 KT 60 MPH 120H 12/1800Z 27.0N 84.0W 45 KT 50 MPH $$ Forecaster Beven
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Tropical Storm Eta Forecast Discussion Number 29
2020-11-07 19:00:28| National Hurricane Center (Atlantic)
Issued at 100 PM EST Sat Nov 07 2020 000 WTNT44 KNHC 071800 TCDAT4 Tropical Storm Eta Special Discussion Number 29 NWS National Hurricane Center Miami FL AL292020 100 PM EST Sat Nov 07 2020 This special advisory is being issued to update the first 36 h of the intensity forecast of Eta. An Air Force Reserve Hurricane Hunter aircraft found a better defined center north of the Cayman Islands with flight-level and SFMR winds supporting an initial intensity of 50 kt, along with a central pressure of 994 mb. The updated intensity forecast shows a little more intensification during the first 12 h, although it is unclear how much intensification may occur due to strong vertical shear and interaction with a developing upper-level low nearby. No changes were made to the forecast track. The first 36 h of the wind radii were adjusted for the new intensity forecast. Note that this special advisory is being issued in lieu of the 100 PM EST (1800 UTC) intermediate advisory. Key Messages: 1. Heavy rainfall will continue across the Cayman Islands, portions of Cuba and Jamaica, and will spread north into the Bahamas and southern Florida. This rain may result in significant, life- threatening flash flooding and river flooding in Cuba. Flash and urban flooding will also be possible for the Cayman Islands, Jamaica, the Bahamas and southern Florida. 2. Tropical storm conditions are expected today and Sunday in portions of the Cayman Islands, Cuba, and the northwestern Bahamas, where a Tropical Storm Warning is in effect. 3. Tropical storm conditions are expected by late Sunday in the Florida Keys and along portions of the southeast Florida coast, where a Tropical Storm Warning is in effect. Tropical storm conditions are possible elsewhere in portions of southern and central Florida beginning Sunday night, where a Tropical Storm Watch is in effect. Additional Tropical Storm Warnings will likely be needed later today. FORECAST POSITIONS AND MAX WINDS INIT 07/1800Z 20.0N 81.1W 50 KT 60 MPH 12H 08/0000Z 20.8N 80.6W 55 KT 65 MPH 24H 08/1200Z 22.5N 79.5W 55 KT 65 MPH...INLAND 36H 09/0000Z 23.8N 79.3W 55 KT 65 MPH...OVER WATER 48H 09/1200Z 25.0N 80.1W 55 KT 65 MPH 60H 10/0000Z 25.8N 81.9W 55 KT 65 MPH 72H 10/1200Z 26.2N 83.2W 50 KT 60 MPH 96H 11/1200Z 26.5N 84.0W 45 KT 50 MPH 120H 12/1200Z 28.5N 84.0W 40 KT 45 MPH $$ Forecaster Beven
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Tropical Storm Eta Forecast Discussion Number 28
2020-11-07 16:01:19| National Hurricane Center (Atlantic)
Issued at 1000 AM EST Sat Nov 07 2020 000 WTNT44 KNHC 071501 TCDAT4 Tropical Storm Eta Discussion Number 28 NWS National Hurricane Center Miami FL AL292020 1000 AM EST Sat Nov 07 2020 Satellite imagery and surface data indicate that Eta has become a little better organized this morning, with the center re-forming to the northeast near an area of deep convection. Surface observations from Grand Cayman Island show that the system has regained tropical-storm strength, and the initial intensity is increased to 35 kt. The initial motion is uncertain dur to the reformation, with the best estimate of 055/15. This general motion should continue for the next 24 h or so as Eta is steered by a mid- to upper-level trough over the Gulf of Mexico. From 24-96 h, the trough is forecast to become a cut-off low, and Eta is expected to turn northward, northeastward, and eventually westward as it merges with the low. There remains some spread in the guidance in just where these turns will occur and how close the center will come to south Florida and the Florida Keys. This part of the new track is nudged just a little north of the previous track. After 96 h, Eta should move slowly across the eastern Gulf of Mexico, with the forecast track showing a northward motion as a compromise of the poorly-agreeing guidance. Although the storm is experiencing moderate to strong southwesterly shear, strong upper-level divergence caused by the trough should allow strengthening through about 48 h, although the cyclone may acquire some subtropical characteristics as it merges with the baroclinic system. After that time, dry air entrainment is likely to cause Eta to slowly weaken through the remainder of the forecast period. The new intensity forecast is unchanged from the old forecast. The new forecast track requires a Tropical Storm Warning for south Florida and the Florida Keys at this time. Key Messages: 1. Heavy rainfall will continue across the Cayman Islands, portions of Cuba and Jamaica, and will spread north into the Bahamas and southern Florida. This rain may result in significant, life-threatening flash flooding and river flooding in Cuba. Flash and urban flooding will also be possible for the Cayman Islands, Jamaica, the Bahamas and southern Florida. 2. Tropical storm conditions are expected today and Sunday in portions of the Cayman Islands, Cuba, and the northwestern Bahamas, where a Tropical Storm Warning is in effect. 3. Tropical storm conditions are expected by late Sunday in the Florida Keys and along portions of the southeast Florida coast, where a Tropical Storm Warning is in effect. Tropical storm conditions are possible elsewhere in portions of southern and central Florida beginning Sunday night, where a Tropical Storm Watch is in effect. Additional Tropical Storm Warnings will likely be needed later today. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 19.6N 81.8W 35 KT 40 MPH 12H 08/0000Z 20.8N 80.6W 40 KT 45 MPH 24H 08/1200Z 22.5N 79.5W 45 KT 50 MPH...INLAND 36H 09/0000Z 23.8N 79.3W 50 KT 60 MPH...OVER WATER 48H 09/1200Z 25.0N 80.1W 55 KT 65 MPH 60H 10/0000Z 25.8N 81.9W 55 KT 65 MPH 72H 10/1200Z 26.2N 83.2W 50 KT 60 MPH 96H 11/1200Z 26.5N 84.0W 45 KT 50 MPH 120H 12/1200Z 28.5N 84.0W 40 KT 45 MPH $$ Forecaster Beven
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Tropical Depression Eta Forecast Discussion Number 27
2020-11-07 09:56:14| National Hurricane Center (Atlantic)
Issued at 400 AM EST Sat Nov 07 2020 593 WTNT44 KNHC 070856 TCDAT4 Tropical Depression Eta Discussion Number 27 NWS National Hurricane Center Miami FL AL292020 400 AM EST Sat Nov 07 2020 Satellite images show a large area of deep convection associated with Eta, but there is not much organization to the thunderstorm activity. An ASCAT-A pass from several hours ago showed that the circulation of Eta has become a little better defined, and the center was located a fair distance to the west-southwest of what was previously analyzed. The pass also showed that Eta has not strengthened to a tropical storm yet, with the maximum winds in the 25-30 kt range. Based on that data, and a blend of the latest Dvorak classifications, the initial intensity is held at 30 kt. After adjusting the initial position, the estimated motion is a little slower to the east-northeast than before, 060/9 kt. It should be noted that some of the models show the center re-forming to the northeast later today, which is possible given the depression's convective asymmetry. Regardless of these details, the large scale track forecast reasoning is unchanged. A continued east-northeast to northeast motion is expected during the next day or two as Eta moves in the flow on the east side of a mid- to upper-level trough over the Gulf of Mexico. This motion should take Eta near or to the west of the Cayman Islands later today and over central Cuba tonight and Sunday. After that time, the mid- to upper-level low is expected to cut off over the eastern Gulf of Mexico or the Florida Straits. As a result, Eta will pivot around the low, which should cause a slow down and a turn to the north and then the northwest toward the Florida Keys and south Florida Sunday night and Monday. As Eta merges with the upper low, a slower motion to the northwest or north is forecast across the eastern Gulf of Mexico by the middle of next week. The NHC track forecast lies between the GFS and ECMWF models, and is quite similar to the previous one. Eta is expected to gradually strengthen on its approach to Cuba as it remains over warm waters and in an region of upper-level diffluence. However, by the time Eta reaches Cuba, the models show an increase in southwesterly wind shear and drier air being drawn into the circulation. These factors should cause Eta to level off in strength, and likely become asymmetric. When Eta interacts and merges with the upper low, it will likely take on a subtropical appearance and develop a large wind field near southern Florida. The storm is forecast to slowly weaken when it passes to the west of Florida as it moves in a drier environment. The NHC intensity forecast is largely an update of the previous one and lies near the high end of the model guidance. Based on the new forecast, the government of the Bahamas has issued a Tropical Storm Warning for the northwestern Bahamas. In addition, the Tropical Storm Watch along the east coast of Florida has been extended northward. Key Messages: 1. Heavy rainfall is diminishing across portions of Central America, although the threat of life-threatening flooding may continue, along with landslides in areas of higher terrain. Heavy rainfall from Eta will continue across the Cayman Islands and portions of Cuba, resulting in significant, life-threatening flash flooding and river flooding in Cuba. Flash and urban flooding will also be possible for the Cayman Islands, Jamaica, the Bahamas and southern Florida. 2. Tropical storm conditions are expected later today and Sunday in portions of the Cayman Islands, Cuba, and the northwestern Bahamas, where a Tropical Storm Warning is in effect. 3. Tropical storm conditions are possible in the Florida Keys and portions of south and central Florida beginning late Sunday, where a Tropical Storm Watch is in effect. Tropical Storm Warnings could be required for these areas later today. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 18.3N 84.9W 30 KT 35 MPH 12H 07/1800Z 19.3N 82.9W 40 KT 45 MPH 24H 08/0600Z 20.7N 80.9W 45 KT 50 MPH 36H 08/1800Z 22.6N 80.2W 50 KT 60 MPH...INLAND 48H 09/0600Z 23.8N 80.2W 55 KT 65 MPH...OVER WATER 60H 09/1800Z 24.9N 81.2W 55 KT 65 MPH 72H 10/0600Z 25.5N 83.7W 50 KT 60 MPH 96H 11/0600Z 26.0N 84.7W 45 KT 50 MPH 120H 12/0600Z 27.3N 85.0W 40 KT 45 MPH $$ Forecaster Cangialosi
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Tropical Depression Eta Forecast Discussion Number 26
2020-11-07 03:53:42| National Hurricane Center (Atlantic)
Issued at 900 PM CST Fri Nov 06 2020 000 WTNT44 KNHC 070253 TCDAT4 Tropical Depression Eta Discussion Number 26 NWS National Hurricane Center Miami FL AL292020 900 PM CST Fri Nov 06 2020 A NOAA Hurricane Hunter aircraft that flew a tail-Doppler radar mission earlier this evening reported that Eta's circulation remained elongated, and that there had not been any significant increase in winds since this afternoon. There has been some increase in deep convection near and to the east of the estimated center, but there has been little overall change in organization. Therefore, the initial intensity remains 30 kt for this advisory. Eta is expected to strengthen over the next 24 to 48 hours while it moves over warm waters and within an area of strong upper-level divergence to the southeast of a mid- to upper-level trough over the Gulf of Mexico. Eta's structure is likely to take on characteristics of a subtropical cyclone as it merges with the cutoff low late Sunday and Monday. As this occurs, Eta's wind field is expected to increase in size. By 72 hours and beyond, dry air entrainment is likely to cause some weakening. The new NHC intensity forecast is close to the previous one. Eta is moving toward northeastward at a faster forward speed of around 10 kt. An additional increase in forward speed should occur overnight as Eta moves northeastward around the southeastern portion of a developing mid- to upper-level trough over the Gulf of Mexico. This feature should continue to steer Eta northeastward during the next 24 hours, but after that time the trough is forecast to cut-off, with Eta turning northward, and then northwestward around and into the mid- to upper-level closed low. The merged system is likely to move northwestward or northward later in the period. The latest runs of the dynamical models have trended toward a more northward track on Sunday and Monday with some of them showing a track near or over the southern portion of the Florida peninsula in 48 to 60 hours. The new NHC track forecast has been adjusted slightly northward during that time and lies between the TVCA multi-model consensus and the HFIP corrected consensus aid. Since Eta's wind field is forecast to expand when it moves north of Cuba, tropical-storm-force winds are expected to cover a large area to the north and northeast of the center regardless of the exact track of the center. The new forecast track requires a Tropical Storm Watch for the northwestern Bahamas, the southern Florida peninsula, and the Florida Keys. Additional watches for the Florida peninsula may be required overnight or on Saturday morning. Key Messages: 1. Heavy rainfall is diminishing across portions of Central America, although the threat of life-threatening flooding may continue, along with landslides in areas of higher terrain. Heavy rainfall from Eta will move into the Cayman islands and portions of Cuba, resulting in significant, life-threatening flash flooding and river flooding in Cuba. Flash and urban flooding will also be possible for the Cayman Islands, Jamaica, southeast Mexico, the Bahamas and Southern Florida. 2. Tropical storm conditions are expected this weekend in portions of the Cayman Islands and Cuba, where a Tropical Storm Warning is in effect. 3. There is an increasing risk of impacts from wind and flash and urban flooding due to heavy rainfall in portions of southern Florida, the Florida Keys, and portions of the Bahamas this weekend and early next week. Tropical Storm Watches have been issued for portions of these areas and additional watches may be required overnight or on Saturday morning. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 18.0N 85.2W 30 KT 35 MPH 12H 07/1200Z 19.0N 83.2W 40 KT 45 MPH 24H 08/0000Z 20.3N 81.1W 45 KT 50 MPH 36H 08/1200Z 21.9N 79.9W 50 KT 60 MPH...INLAND 48H 09/0000Z 24.0N 79.9W 55 KT 65 MPH...OVER WATER 60H 09/1200Z 25.0N 81.3W 55 KT 65 MPH 72H 10/0000Z 25.2N 82.6W 50 KT 60 MPH 96H 11/0000Z 26.0N 84.3W 45 KT 50 MPH 120H 12/0000Z 27.0N 84.7W 45 KT 50 MPH $$ Forecaster Brown
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