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Tropical Storm Eta Forecast Discussion Number 35
2020-11-09 03:54:56| National Hurricane Center (Atlantic)
Issued at 1000 PM EST Sun Nov 08 2020 000 WTNT44 KNHC 090254 TCDAT4 Tropical Storm Eta Discussion Number 35 NWS National Hurricane Center Miami FL AL292020 1000 PM EST Sun Nov 08 2020 Although deep convection has waned near the center of Eta since this afternoon, radar imagery continues to show a ring of low-topped convection around the center, with some deep convection returning over the northeastern portion of the circulation. Doppler radar velocities of 64-68 kt around 5000 ft, and recent NOAA reconnaissance aircraft observations support maintaining the 55 kt initial intensity. The aircraft reported a minimum pressure of around 993 mb. Since Eta has a fairly large radius of maximum winds and a dry slot that has wrapped into the inner core, it appears that any short-term strengthening should be slow to occur. As a result, the new NHC intensity forecast calls for a little less strengthening until Eta moves into the southeastern Gulf of Mexico in about 24 hours. Regardless of whether Eta becomes a hurricane near the Florida Keys, there is little difference in impacts between a 55-to-60-kt tropical storm and a 65-kt hurricane. After 24 hours, Eta is forecast to move over warmer sea surface temperatures in the southeastern Gulf of Mexico and the vertical shear is forecast to decrease. This is expected to allow for some strengthening and Eta is forecast re-gain hurricane strengthen by Tuesday. Gradual weakening is predicted between 72-120 hours due to increasing southwesterly shear and the entrainment of dry mid-level air. The updated NHC intensity forecast is near the SHIPS/LGEM models during the first couple of days, and in good agreement with the HFIP corrected consensus model thereafter. Eta has turned northwestward this evening around the north side of a cut-off low located just south of western Cuba. The tropical cyclone should turn west-northwestward to westward overnight, and a southwestward motion is expected on Tuesday as Eta pivots around the upper-low. In 36-48 h, Eta is expected to slow down and possibly stall over the southeastern Gulf of Mexico as the steering currents weakening. In about 3 days, Eta should begin moving northward between a mid-level ridge over the western Atlantic and a broad trough over the central United States. The models that maintain Eta has a deeper system show a faster northeastward motion late in the period, whereas models that weaken Eta slow its northward progression by day 5. The NHC track forecast lies near the model consensus at 96 and 120 h, and is similar to the previous advisory. Key Messages: 1. Heavy rainfall from Eta will continue across portions of Cuba, Jamaica, the Bahamas, and southern Florida and spread north into central Florida. Life-threatening flash flooding is possible across the urban areas of southeast Florida. Significant, life-threatening flash flooding and river flooding is possible in Cuba, and significant flash and urban flooding are possible for Jamaica, the Bahamas and the remainder of southern Florida, along with potential minor river flooding in central Florida. 2. Hurricane conditions are expected tonight and early Monday across portions of the Florida Keys, and are possible across portions of southern Florida. Tropical storm conditions will extend well away from Eta's center across the southern and central portions of the Florida peninsula. 3. There is a danger of life-threatening storm surge in portions of the Florida Keys. Life-threatening storm surge is possible along portions of the southern coast of the Florida peninsula. Residents in these areas should follow any advice given by local officials. 4. Eta is forecast to approach the Florida Gulf Coast later this week as a tropical storm, and could bring impacts from rain, wind, and storm surge. Interests in this area should monitor the progress of Eta and updates to the forecast this week. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 24.6N 80.5W 55 KT 65 MPH 12H 09/1200Z 24.9N 82.6W 60 KT 70 MPH 24H 10/0000Z 24.2N 84.3W 60 KT 70 MPH 36H 10/1200Z 23.6N 85.1W 65 KT 75 MPH 48H 11/0000Z 24.2N 85.1W 65 KT 75 MPH 60H 11/1200Z 25.5N 84.9W 65 KT 75 MPH 72H 12/0000Z 26.6N 84.6W 60 KT 70 MPH 96H 13/0000Z 28.2N 83.6W 55 KT 65 MPH 120H 14/0000Z 30.0N 82.0W 45 KT 50 MPH...INLAND $$ Forecaster Brown
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Tropical Storm Eta Forecast Discussion Number 34
2020-11-08 21:57:52| National Hurricane Center (Atlantic)
Issued at 400 PM EST Sun Nov 08 2020 000 WTNT44 KNHC 082057 TCDAT4 Tropical Storm Eta Discussion Number 34 NWS National Hurricane Center Miami FL AL292020 400 PM EST Sun Nov 08 2020 Eta's appearance in radar and satellite imagery has changed little since the previous advisory and the last reconnaissance mission a few hours ago, with a ragged mid-level eye-like feature briefly wrapping up for less than an hour before quickly decaying. Average velocity values from the Miami, Florida, NOAA WSR-88D Doppler weather radar have occasionally been as high as 60 kt between 10,000-12,000 ft ASL to the north and northeast of the center. Therefore, the initial intensity is being maintained at 55 kt for this advisory. A NOAA reconnaissance aircraft is scheduled to investigate Eta around 0000Z this evening. The initial motion estimate is 325/12 kt. There is no significant change to the previous track forecast reasoning from the last 36 hours. Eta is now moving northwestward around the northeastern side of an upper-level low that has formed over the extreme northwestern Caribbean Sea near the Isle of Youth. The combined easterly flow between the upper-low and a deep-layer ridge located near the U.S. mid-Atlantic coast is expected to force Eta westward overnight and then turn the cyclone slowly southwestward in the 24-48 hour period, with the cyclone possibly stalling just west of the lower Florida Keys when steering currents collapse around 48 hours. By 72 hours and beyond, a broad mid-latitude trough is forecast to move from the U.S. west coast eastward over the central U.S. by 96 hours, and then over the eastern U.S. by 120 hours, which will erode the western portion of the ridge and act to gradually lift Eta northeastward toward northern Florida. The latest NHC model guidance has shifted slightly northward, possibly due to the NOAA G-IV jet aircraft synoptic track dropsonde observations from earlier this morning, and now shows the center of Eta making landfall in the middle or lower Florida Keys late tonight and early Monday. The new NHC official track forecast has been nudged northward close to the consensus models HCCA and TCVA. It should be noted that although the latest model guidance and track forecast shows landfall in the Florida Keys, the strongest winds are occurring, and are expected to occur, well to the north and east of the center. Satellite imagery indicates that a pronounced dry slot has wrapped into the eastern portion of Eta's circulation, with radar data suggesting that it has occasionally penetrated into the inner core region as well, eroding the thunderstorm activity in the southern portion of the aforementioned eye-like feature. However, with the vertical shear forecast to steadily decrease from the current 25 kt down to less than 10 kt by 24 hours while Eta is moving over 28.5 deg C SSTs, strengthening is expected late tonight during the convective maximum period and continuing into Monday, resulting in Eta intensifying into a hurricane during that time. Environmental conditions are expected to remain somewhat favorable for Eta to maintain hurricane status through 60 hours, followed by gradual weakening from 72-120 hours due to increasing southwesterly shear of 20-25 kt and entrainment of very dry mid-level air. The latest official intensity forecast is similar to the previous NHC advisory, and remains above the model guidance through 36 hours and is a little below the guidance thereafter. Based on ASCAT data and surface observations, the wind radii were expanded in the northwest and northeast quadrants. Key Messages: 1. Hurricane conditions are expected tonight and early Monday across portions of the Florida Keys, and are possible across portions of southern Florida. Tropical storm conditions will extend well away from Eta's center across the southern and central portions of the Florida peninsula. 2. There is a danger of life-threatening storm surge in portions of the Florida Keys. Life-threatening storm surge is possible along portions of the southern coast of the Florida peninsula. Residents in these areas should follow any advice given by local officials. 3. Heavy rainfall from Eta will continue across portions of Cuba, Jamaica, the Bahamas, and southern Florida and will spread north into central Florida. This rain may result in significant, life- threatening flash flooding and river flooding in Cuba. Significant flash and urban flooding are also possible for Jamaica, the Bahamas and southern Florida, along with potential minor river flooding in central Florida. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 23.9N 79.5W 55 KT 65 MPH 12H 09/0600Z 24.7N 81.1W 60 KT 70 MPH 24H 09/1800Z 24.6N 83.4W 65 KT 75 MPH 36H 10/0600Z 23.6N 84.8W 65 KT 75 MPH 48H 10/1800Z 24.0N 85.1W 65 KT 75 MPH 60H 11/0600Z 25.1N 85.0W 65 KT 75 MPH 72H 11/1800Z 25.8N 84.8W 60 KT 70 MPH 96H 12/1800Z 27.1N 84.0W 55 KT 65 MPH 120H 13/1800Z 29.0N 82.8W 50 KT 60 MPH $$ Forecaster Stewart
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Tropical Storm Eta Forecast Discussion Number 33
2020-11-08 16:00:41| National Hurricane Center (Atlantic)
Issued at 1000 AM EST Sun Nov 08 2020 000 WTNT44 KNHC 081500 TCDAT4 Tropical Storm Eta Discussion Number 33 NWS National Hurricane Center Miami FL AL292020 1000 AM EST Sun Nov 08 2020 Eta remains a sheared tropical storm, although the low-level center has become embedded a little farther into the convective cloud mass. Cuban radar data from Camaguey indicate that Eta's center has moved back over water and is now located just offshore the east-central coast of Cuba. Radar imagery also indicates that a fairly impressive band of deep convection wraps more than half way around the center, especially in the western semicircle. Cirrus outflow has expanded in the southern semicircle, and indication that the shear may be decreasing somewhat. However, water vapor satellite imagery still shows a fair amount of dry mid-/upper-level air impinging on the cyclone from the southwest. The initial intensity of 55 kt is based on a report of 850-mb flight-level winds of 70 kt and reliable SFMR winds of 55-57 kt. The initial motion estimate is now 355/10 kt. Eta is interacting with a sharp mid-/upper-level, negatively tilted trough that extends east-southeastward across the Gulf of Mexico and into the northwestern Caribbean Sea. The eastern end of the trough is forecast to develop into a cutoff low alter today, which will act to turn Eta northwestward by this afternoon, and westward later tonight. The complex interaction between these two features is forecast to continue through 72 hours, resulting in the development of weak steering currents and Eta slowing down and possibly stalling near or just west of the Florida Keys by day 3. Thereafter, the global and regional models show widely varying solutions ranging from a motion toward the south or southwest (UKMET) toward Yucatan, to slow northward (ECMWF) or northeastward motion (GFS/HWRF) over the eastern Gulf of Mexico. The new NHC track forecast lies to the north, or to the right, of the 12Z interpolated models and consensus models (due to the interpolater possibly having some problems handling the sharp westward turn that Eta is forecast to make), and lies close to the previous advisory track and a blend of the operational 00Z ECMWF, and 06Z GFS and UKMET model tracks. Now that Eta's center is back over water, gradual re-strengthening is expected to begin later this afternoon. The global models are forecasting to vertical wind shear to steadily decrease across the center for the next next 48 hours as Eta moves north of the cutoff low and into a col small region region between the low and an upper-level trough moving eastward across northern Florida. The GFS- and ECMWF-based SHIPS intensity guidance indicate that the shear will decrease to less than 10 kt by 36 hours, but the shear will likely decrease sooner since SHIPS model uses winds that extend out 500 km (270 nmi) from the center, which are not always representative of the wind flow near the center. With favorable low-shear conditions and sea-surface temperatures warmer than 28 deg C, the only hindering factor appears to be proximity to dry mid-level air, which could get entrained into the inner core and inhibit development of deep convection in that part of the cyclone. For now, the new NHC intensity forecast remains similar to the previous advisory, which is above the model guidance up to 36 hours and a little below the guidance thereafter, and shows Eta at 65 kt or Category 1 hurricane intensity in the 24-72 hour period. However, it is certainly possibly that if dry air does not penetrate into Eta's inner core later today, then the cyclone could become a hurricane before it reaches the Florida Keys tonight. For this reason, a Hurricane Warning has been issued for portions of the Florida Keys. Key Messages: 1. Heavy rainfall from Eta will continue across portions of Cuba, Jamaica, the Bahamas, and southern Florida and spread north into central 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 Jamaica, the Bahamas and southern Florida, along with potential minor river flooding in central Florida. 2. Tropical storm conditions are expected to continue today in portions of Cuba and the northwestern Bahamas, where Tropical Storm Warnings are in effect. 3. Hurricane conditions are expected in portions of the Florida Keys by early Monday where a Hurricane Warning is now in effect. Damaging tropical-storm-force winds are expected to begin in the Florida Keys by this afternoon. Tropical Storm conditions are also expected and hurricane conditions are possible for 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 dangerous storm surge is expected in portions of the Florida Keys where a Storm Surge Warning is in effect. A Storm Surge Watch is also in effect for portions of the southern coast of the Florida peninsula. Residents in the Storm Surge Warning and Watch areas should follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 22.5N 79.2W 55 KT 65 MPH 12H 09/0000Z 24.1N 79.8W 60 KT 70 MPH 24H 09/1200Z 24.5N 82.4W 65 KT 75 MPH 36H 10/0000Z 23.9N 84.1W 65 KT 75 MPH 48H 10/1200Z 23.8N 85.0W 65 KT 75 MPH 60H 11/0000Z 24.0N 85.5W 65 KT 75 MPH 72H 11/1200Z 24.9N 85.2W 65 KT 75 MPH 96H 12/1200Z 26.2N 84.5W 55 KT 65 MPH 120H 13/1200Z 26.9N 83.9W 50 KT 60 MPH $$ Forecaster Stewart
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Tropical Storm Eta Forecast Discussion Number 32
2020-11-08 09:49:09| National Hurricane Center (Atlantic)
Issued at 400 AM EST Sun Nov 08 2020 000 WTNT44 KNHC 080849 TCDAT4 Tropical Storm Eta Discussion Number 32 NWS National Hurricane Center Miami FL AL292020 400 AM EST Sun Nov 08 2020 Although Eta has a ragged and asymmetric appearance in satellite and radar images, the cloud tops are quite cold with a lot of embedded lightning strikes being detected in the northeastern quadrant. The center is estimated to be very near the south coast of central Cuba, with much of the thunderstorms over the island. Since the storm has not changed much since last evening, the initial intensity is held at 55 kt. The NOAA Hurricane Hunters are scheduled to investigate Eta again later this morning once it emerges off the north coast of Cuba. Eta continues to move northeastward, but at a slightly slower pace of 10 kt. The cyclone is now located just to the east or southeast of a mid- to upper-level low. This feature and a broader trough over the Gulf of Mexico should cause Eta to turn northward later this morning and then northwestward this afternoon and evening. This track should take the core of Eta across central Cuba during the next couple of hours and then into the Straits of Florida. Eta is forecast to pass over the Florida Keys tonight. After that time, a slow westward motion is expected as the cyclone merges with the trough over the eastern Gulf of Mexico on Monday and Tuesday. Later in the week, the steering currents weaken and Eta will likely be drifting around over the Gulf of Mexico. The new NHC track forecast is a little to the south, or left, of the previous one to come into better agreement with the latest models. The tropical storm is feeling some effects of southwesterly wind shear and water vapor satellite images show a swath of dry air entraining into the western side of the circulation. These factors along with the interaction with the landmass of Cuba later this morning should cause Eta to hold steady in strength or weaken a little in the short term. The shear is expected to lessen when the storm moves over the Straits of Florida, and that could allow Eta to become more symmetric and strengthen, and it could become a hurricane as it approaches the Florida Keys tonight. After the cyclone passes the Keys and enters the Gulf of Mexico, there are mixed signals in the models. Although the shear is expected to be moderate while Eta passes over the warm waters of the Gulf of Mexico Loop current, there will likely be drier air surrounding the storm. As a compromise, the NHC intensity forecast shows Eta holding relatively steady in strength for much of the forecast period. Key Messages: 1. Heavy rainfall from Eta will continue across portions of Cuba, Jamaica, the Bahamas, and southern Florida and spread north into central 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 Jamaica, the Bahamas and southern Florida, along with potential minor river flooding in central Florida. 2. Tropical storm conditions are expected to continue today in portions of Cuba and the northwestern Bahamas, where Tropical Storm Warnings are in effect. 3. Damaging tropical-storm-force winds are expected to begin this afternoon, 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 dangerous 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 08/0900Z 21.5N 79.3W 55 KT 65 MPH 12H 08/1800Z 23.0N 79.4W 55 KT 65 MPH 24H 09/0600Z 24.5N 81.1W 60 KT 70 MPH 36H 09/1800Z 24.3N 83.0W 60 KT 70 MPH 48H 10/0600Z 24.2N 84.2W 60 KT 70 MPH 60H 10/1800Z 24.2N 85.0W 60 KT 70 MPH 72H 11/0600Z 24.6N 85.3W 60 KT 70 MPH 96H 12/0600Z 25.8N 85.0W 55 KT 65 MPH 120H 13/0600Z 26.7N 84.4W 50 KT 60 MPH $$ Forecaster Cangialosi
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Tropical Storm Eta Forecast Discussion Number 31
2020-11-08 03:57:06| National Hurricane Center (Atlantic)
Issued at 1000 PM EST Sat Nov 07 2020 000 WTNT44 KNHC 080256 TCDAT4 Tropical Storm Eta Discussion Number 31 NWS National Hurricane Center Miami FL AL292020 1000 PM EST Sat Nov 07 2020 A NOAA Hurricane Hunter aircraft found that Eta has continued to strengthen. An abbreviated mission found that the pressure had dropped to 991 mb, with believable SFMR winds of 55 kt. Since the plane left, the cloud pattern has not become better organized, and perhaps some shear is affecting the cyclone. Thus, the initial wind speed is kept at 55 kt. The storm continues to move to the northeast tonight. While the overall synoptic pattern remains the same, there has been a big change to note with the track forecast, with a notable south and west trend with almost all of the guidance on Sunday and beyond. It appears that the system becomes more involved with a closed low forming near western Cuba tomorrow, which causes a sharper and faster left turn near the Florida Straits or Keys. The new NHC forecast is shifted in that direction, but is well north of the bulk of the guidance due to continuity concerns, and future southward and faster shifts are possible. I should mention that even if the forecast does shift farther south, tropical-storm-force winds will likely cover much of the southern and central Florida peninsula due to the expected growth of Eta. Beyond Florida, this one of those times where the track uncertainty is much larger than normal, so check back tomorrow for further updates as big long-range changes are possible. Eta is likely to maintain its intensity before landfall in Cuba, then weaken somewhat due to the rugged terrain there. The storm should re-intensify over the Florida Straits in moderate shear conditions but with favorable forcing from the upper-level low. No change has been made to the intensity forecast near Florida, and Eta is likely to be near or at hurricane-strength there. Over the southeastern Gulf of Mexico, some dry air entrainment could briefly cause some weakening, but the system is forecast to move very slowly over the warm waters. In fact, a large portion of the guidance actually show it re-gaining hurricane strength as it moves farther away from any cooler shelf waters near Florida and sits over the Loop Current. While it seems pre-mature to raise the forecast much due to the large track uncertainty, the forecast is bumped up on days 3-4, but is below the model consensus. Key Messages: 1. Heavy rainfall will continue across 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 Jamaica, the Bahamas and southern Florida, along with potential minor to isolated moderate river flooding in Central Florida. 2. Tropical storm conditions 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 to begin Sunday afternoon, 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 dangerous 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 08/0300Z 20.7N 79.9W 55 KT 65 MPH 12H 08/1200Z 22.1N 79.3W 50 KT 60 MPH...INLAND 24H 09/0000Z 23.8N 79.8W 60 KT 70 MPH...OVER WATER 36H 09/1200Z 24.9N 81.4W 60 KT 70 MPH 48H 10/0000Z 25.0N 83.0W 55 KT 65 MPH 60H 10/1200Z 25.0N 84.0W 60 KT 70 MPH 72H 11/0000Z 25.5N 84.5W 60 KT 70 MPH 96H 12/0000Z 26.0N 84.5W 55 KT 65 MPH 120H 13/0000Z 27.0N 84.0W 45 KT 50 MPH $$ Forecaster Blake
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