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Tropical Storm Elsa Forecast Discussion Number 19

2021-07-05 04:58:57| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Sun Jul 04 2021 000 WTNT45 KNHC 050258 TCDAT5 Tropical Storm Elsa Discussion Number 19 NWS National Hurricane Center Miami FL AL052021 1100 PM EDT Sun Jul 04 2021 Similar to this time last night, Elsa has undergone another convective bursting pattern, except that tonight this has translated into at least some slight strengthening. An Air Force Reserve reconnaissance aircraft investigating the cyclone this evening has found maximum 850-mb flight-level winds of 55 kt and reliable SFMR surface winds of about 55 kt. Although there have been SFMR winds of 60 kt or more reported northeast and north of the center, those values appear to be contaminated by shoaling and/or breaking waves owing to the shallow water flowing in and around the offshore Cayo Anclitas and Cayo Pingues archipelagos. The estimated center pressure of 1004 mb based on dropsonde data also does a higher intensity of 60 kt. Therefore, based on the most reliable data, the intensity has been increased to 55 kt. The initial motion estimate is 310/13 kt. There remains no significant change to the previous few track forecasts and synoptic reasonings. Elsa is expected to move northwestward and then northward around the western periphery of a mid-level subtropical ridge during the next 3 days, followed by acceleration toward the northeast on days 4 and 5 as the cyclone moves near the southeast U.S. coast and then over the northwestern Atlantic. The new NHC track forecast is basically just an update and extension of the previous advisory track, and lies close to a blend of the tightly packed corrected consensus model HCCA and the simple consensus models TVCA and GFEX. Cuban radar data from Pilan and Camaguey have occasionally revealed an eye-like feature in the low -and mid-levels of the cyclone where cloud top temperatures have been colder than -80C and also where significant lightning activity has been occurring. Given that the circulation centers have become better aligned and the upper-level outflow pattern is well-established and steadily improving, some additional strengthening during the next 12 h is forecast, which calls for Elsa to be near hurricane strength before landfall occurs along the south-central coast of Cuba tomorrow. Over the eastern Gulf of Mexico late Monday and Tuesday, some restrengthening is forecast after Elsa clears Cuba, but southwesterly vertical wind shear is expected to hinder the intensification process. The official intensity forecast remains on the high side of the numerical model guidance, and follows a blend of the HCCA intensity consensus model, and the LGEM and and Decay-SHIPS statistical-dynamical models. Key Messages: 1. Widespread heavy rain will continue to affect portions of Jamaica tonight where isolated to scattered flash flooding and mudslides will be possible. Heavy rain will then impact the Cayman Islands and Cuba tonight into Monday resulting in significant flooding and mudslides over Cuba. As Elsa approaches the Florida Keys, Florida Peninsula, and coastal Georgia Monday through Wednesday, heavy rainfall may result in isolated flash, urban, and minor river flooding. Mid to late week, heavy rains across coastal South Carolina may result in isolated flash flooding. 2. Tropical storm conditions and a dangerous storm surge are expected with hurricane conditions possible in portions of eastern Cuba tonight. Tropical storm conditions are expected in portions of central and western Cuba tonight and Monday, and will spread into portions of the Florida Keys by late Monday. 3. Tropical Storm and Surge Surge Watches are in effect for portions of the west coast of the Florida peninsula where tropical storm conditions and a dangerous storm surge are possible beginning as early as Monday night and continuing into Tuesday. 4. There is a risk of tropical storm conditions, storm surge, and rainfall impacts along the remainder of the Florida Peninsula Tuesday night through Wednesday and the coasts of Georgia and the Carolinas Wednesday and Thursday. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 20.6N 79.2W 55 KT 65 MPH 12H 05/1200Z 21.9N 80.7W 60 KT 70 MPH 24H 06/0000Z 23.5N 82.1W 50 KT 60 MPH 36H 06/1200Z 25.1N 82.9W 50 KT 60 MPH 48H 07/0000Z 27.1N 83.2W 50 KT 60 MPH 60H 07/1200Z 29.2N 82.8W 45 KT 50 MPH...INLAND 72H 08/0000Z 31.5N 81.6W 35 KT 40 MPH...INLAND 96H 09/0000Z 36.0N 76.0W 35 KT 40 MPH...INLAND 120H 10/0000Z 41.0N 66.8W 40 KT 45 MPH...OVER WATER $$ Forecaster Stewart

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Tropical Storm Elsa Forecast Discussion Number 18

2021-07-04 22:43:48| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Sun Jul 04 2021 000 WTNT45 KNHC 042043 TCDAT5 Tropical Storm Elsa Discussion Number 18 NWS National Hurricane Center Miami FL AL052021 500 PM EDT Sun Jul 04 2021 Elsa continues to exhibit some well-defined convective banding features over the northern and eastern portions of the circulation. Dvorak current intensity estimates from TAFB and SAB are 45 and 55 kt respectively,so the advisory intensity remains at 50 kt. Although the cirrus-level outflow over the area looks fairly impressive, the SHIPS output diagnoses about 20 kt of vertical shear over the cyclone, which may be inhibiting strengthening. Another negative factor could be blockage of the low-level inflow by the land masses surrounding the cyclone. The storm has turned toward the northwest, and the initial motion estimate is now 310/12 kt. There is little change to the track forecast reasoning from the previous advisory package. Elsa should move around the western periphery of a mid-level subtropical high pressure area during the next 3 days or so. Thereafter, the system should accelerate northward to northeastward over the eastern United States and the northwest Atlantic. No significant changes have been made to the NHC track forecast, which remains close to the simple and correct model consensus solutions. Some strengthening could occur as the storm approaches the south coast of Cuba and although not explicitly shown in the official forecast, Elsa could strengthen to near 60 kt before landfall in that country. Over the eastern Gulf of Mexico, southwesterly shear is expected to limit strengthening. The official intensity forecast remains on the high side of the numerical model guidance. Key Messages: 1. Widespread heavy rain will continue to affect portions of Jamaica tonight where isolated to scattered flash flooding and mudslides will be possible. Heavy rain will then impact the Cayman Islands and Cuba through Monday resulting in significant flooding and mudslides over Cuba. As Elsa approaches the Florida Keys, Florida Peninsula, and coastal Georgia Monday through Wednesday, heavy rainfall may result in isolated flash, urban, and minor river flooding. 2. Tropical storm conditions and a dangerous storm surge are expected with hurricane conditions possible in portions of eastern Cuba tonight. Tropical storm conditions are expected in portions of central and western Cuba tonight and Monday, and will spread into portions of the Florida Keys by late Monday. 3. Tropical Storm and Surge Surge Watches are in effect for portions of the west coast of the Florida peninsula where tropical storm conditions and a dangerous storm surge are possible beginning as early as Monday night and continuing into Tuesday. 4. There is a risk of tropical storm conditions, storm surge, and rainfall impacts along the remainder of the Florida Peninsula Tuesday night through Wednesday and the coasts of Georgia and the Carolinas Wednesday and Thursday. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 19.8N 77.9W 50 KT 60 MPH 12H 05/0600Z 21.1N 79.4W 55 KT 65 MPH 24H 05/1800Z 22.7N 81.2W 50 KT 60 MPH...INLAND 36H 06/0600Z 24.2N 82.4W 50 KT 60 MPH...OVER WATER 48H 06/1800Z 25.8N 83.0W 50 KT 60 MPH 60H 07/0600Z 27.9N 83.0W 50 KT 60 MPH 72H 07/1800Z 30.5N 82.3W 30 KT 35 MPH...INLAND 96H 08/1800Z 34.9N 78.0W 30 KT 35 MPH...INLAND 120H 09/1800Z 40.0N 69.0W 35 KT 40 MPH...OVER WATER $$ Forecaster Pasch

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Tropical Storm Elsa Forecast Discussion Number 17

2021-07-04 16:57:46| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Sun Jul 04 2021 000 WTNT45 KNHC 041457 TCDAT5 Tropical Storm Elsa Discussion Number 17 NWS National Hurricane Center Miami FL AL052021 1100 AM EDT Sun Jul 04 2021 A NOAA P-3 Hurricane Hunter aircraft has been investigating Elsa this morning. Flight-level and SFMR surface observations from the aircraft indicate that the maximum winds are near 50 kt and the estimated central pressure, about 1009 mb, is rather high for a system of this intensity. Also, tail Doppler radar data from the aircraft show an eastward tilt of the center with height. Nonetheless, the storm still looks fairly impressive on satellite images with a well-defined convective banding feature over the northern through eastern portions of the circulation. Also, the highest cloud tops are quite cold and near -70C. Elsa's forward speed has slowed a little more, and the current motion is around 290/11 kt. There hasn't been much change to the track forecast or reasoning since the previous advisory. Over the next few days, the tropical cyclone should move around the western periphery of the subtropical ridge. The NHC forecast track is similar to the previous official forecast, and close to the model consensus. The latest GFS and HWRF solutions are to the west of this forecast. Elsa should remain in a low-shear environment through Monday, and some strengthening is likely before the storm reaches Cuba, assuming the circulation becomes better aligned vertically. The storm should weaken somewhat due to its passage over Cuba. After the cyclone emerges into the southeastern Gulf of Mexico, only slight restrengthening is forecast due to moderate southwesterly shear. The official intensity forecast is on the high end of the numerical intensity guidance suite. Key Messages: 1. Widespread heavy rain will continue to affect portions of southern Haiti and Jamaica today where isolated to scattered flash flooding and mudslides will be possible. Heavy rain will then impact the Cayman Islands and Cuba today into Monday resulting in significant flooding and mudslides over Cuba. As Elsa approaches the Florida Keys and Florida Peninsula Monday through Wednesday, heavy rainfall may result in isolated flash, urban, and minor river flooding. 2. Tropical storm conditions and dangerous storm surge are expected with hurricane conditions possible in portions of eastern Cuba later today and tonight. Tropical storm conditions are expected in portions of central and western Cuba tonight and Monday. 3. Tropical storm conditions, storm surge, and rainfall impacts are expected beginning late Monday in the Florida Keys, and are possible along the coast of southwestern Florida beginning Monday night. Tropical Storm Warnings and Watches are in effect in those areas. 4. There is a risk of tropical storm conditions, storm surge, and rainfall impacts along the remainder of the Florida Peninsula Monday night through Wednesday and the coasts of Georgia and the Carolinas Wednesday and Thursday. However, uncertainty in the forecast remains larger than usual due to Elsa's potential interaction with Cuba. FORECAST POSITIONS AND MAX WINDS INIT 04/1500Z 18.7N 76.8W 50 KT 60 MPH 12H 05/0000Z 20.2N 78.2W 55 KT 65 MPH 24H 05/1200Z 21.9N 80.0W 60 KT 70 MPH...INLAND 36H 06/0000Z 23.4N 81.5W 50 KT 60 MPH...OVER WATER 48H 06/1200Z 24.7N 82.5W 50 KT 60 MPH 60H 07/0000Z 26.5N 83.0W 50 KT 60 MPH 72H 07/1200Z 28.6N 82.8W 50 KT 60 MPH 96H 08/1200Z 33.5N 79.5W 40 KT 45 MPH...INLAND 120H 09/1200Z 38.5N 71.0W 35 KT 40 MPH...OVER WATER $$ Forecaster Pasch

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Tropical Storm Elsa Forecast Discussion Number 16

2021-07-04 10:36:39| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Sun Jul 04 2021 000 WTNT45 KNHC 040836 TCDAT5 Tropical Storm Elsa Discussion Number 16 NWS National Hurricane Center Miami FL AL052021 500 AM EDT Sun Jul 04 2021 The last pass from the Air Force Hurricane Hunters provided interesting and somewhat confusing data on Elsa. The flight-level winds and SFMR data indicate that Elsa's intensity remains around 55 kt, but the wind center is located well to the east of the previous fixes. However, the minimum pressure observed with this new wind center is a few millibars higher than the fixes that were made further west last night. The new center is now beneath the strongest convection, so it seems likely that the mid-level circulation has built downward to the surface and led to this center reformation. Elsa does appear a little better organized in geostationary satellite and microwave images, and it now has a central dense overcast that is fairly symmetric around the center. The NOAA Hurricane Hunters will be investigating Elsa shortly, and the data the aircraft collects will be very helpful in understanding these structural changes and the new intensity information. Elsa appears to have slowed down, and smoothing through the latest center reformation yields an initial motion of 285/12 kt. Despite the changes to the initial motion and position, the overall track forecast reasoning has not changed much. Elsa is expected to move west-northwestward and track near or over Jamaica and eastern Cuba later this morning and then across or just south of the central and western portions of Cuba later today through early Monday. By early Monday, however, Elsa should be making a turn to the north as it moves between the subtropical ridge over the western Atlantic and a trough over the Gulf of Mexico. This motion should take the storm near the Florida Keys by late Monday and near or over the west coast of Florida on Tuesday. After that time, the storm is forecast to turn northeastward and increase its forward speed as it tracks across the southeast U.S. and over the western Atlantic on the northwest side of the ridge. The NHC track forecast is a little slower than the previous one, due in part to the initial motion and position. The short term intensity forecast is very dependent on Elsa's exact track. If the core of the storm moves directly over Jamaica or Cuba, the small vortex would likely be very disrupted due to the mountainous islands. However, if the storm manages to pass between those islands today, some strengthening seems possible given the improved appearance in satellite images. Weakening is forecast to occur on Monday due to a combination of land interaction with Cuba and an increase in vertical wind shear. After the storm moves over the Florida Straits and the eastern Gulf of Mexico, only a small amount of restrengthening is expected due to continued moderate wind shear. The NHC intensity forecast is largely an update of the previous one and in line with the majority of the typically skillful intensity aids. Key Messages: 1. Widespread heavy rain will move across southern Haiti and Jamaica tonight into Sunday where isolated to scattered flash flooding and mudslides will be possible. Heavy rain will then impact the Cayman Islands and Cuba Sunday into Monday resulting in significant flooding and mudslides over Cuba. As Elsa approaches the Florida Keys and Florida Peninsula early next week, isolated flash flooding and minor river flooding will be possible. 2. Tropical storm conditions and dangerous storm surge are expected with hurricane conditions possible in portions of eastern Cuba later this morning. Tropical storm conditions are possible in central and western Cuba tonight and Monday. 3. There is an increasing risk of tropical storm conditions, storm surge, and rainfall impacts beginning late Monday in the Florida Keys, and a Tropical Storm Watch is in effect for portions of the Florida Keys. 4. There is a risk of tropical storm conditions, storm surge, and rainfall impacts along the Florida Peninsula Monday night through Wednesday and the coasts of Georgia and the Carolinas Wednesday and Thursday. However, uncertainty in the forecast remains larger than usual due to Elsa's potential interaction with Cuba. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 18.1N 75.5W 55 KT 65 MPH 12H 04/1800Z 19.5N 77.4W 60 KT 70 MPH...NEAR CUBA 24H 05/0600Z 21.5N 79.4W 60 KT 70 MPH...NEAR CUBA 36H 05/1800Z 23.0N 81.0W 50 KT 60 MPH...INLAND 48H 06/0600Z 24.6N 82.2W 45 KT 50 MPH...OVER WATER 60H 06/1800Z 25.9N 82.8W 50 KT 60 MPH 72H 07/0600Z 27.8N 82.9W 50 KT 60 MPH...NEAR FLORIDA COAST 96H 08/0600Z 33.2N 80.0W 40 KT 45 MPH...INLAND 120H 09/0600Z 38.4N 72.7W 35 KT 40 MPH...OVER WATER $$ Forecaster Cangialosi/Reinhart

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Tropical Storm Elsa Forecast Discussion Number 15

2021-07-04 05:00:03| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Sat Jul 03 2021 000 WTNT45 KNHC 040259 TCDAT5 Tropical Storm Elsa Discussion Number 15 NWS National Hurricane Center Miami FL AL052021 1100 PM EDT Sat Jul 03 2021 Elsa is undergoing a convective bursting pattern the past few hours, with some cold overshooting tops of -90 deg C east and northeast of the center. However, data from an Air Force Reserve reconnaissance aircraft indicate that this convective increase has not translated into an intensity increase. To the contrary, 5000-ft flight-level and SFMR surface winds have decreased while the central pressure has increased to 1004 mb. Based on the latest recon data, the intensity has been lowered to 55 kt. The aircraft has now climbed to 10,000 ft for safety reasons and will be penetrating the area of intense convection to check for stronger winds there. The initial motion estimate is now 295/15 kt. Elsa is forecast to gradually move around the western periphery of a deep-layer subtropical ridge over the next 96 hours, accompanied by an additional decrease in forward speed. The latest model guidance has continued to converge along the previous advisory track, with the corrected-consensus models HCCA and FSSE nearly on top of each other. The TCVA simple consensus model is also similar to the HCCA and FSSE models. However, out of respect for the slightly more westward GFS and GFS-ensemble models, which have performed admirably thus far with Elsa, the new official forecast lies a tad west of the aforementioned consensus models and lies nearly on top of the previous advisory track. After interacting with the mountainous terrain of southwestern Haiti, which could have caused some disruption in the low-level field despite the center remaining offshore, little change in intensity is expected tonight. However, some slight restrengthening could occur by Sunday afternoon as Elsa approaches the south-central coast of Cuba where the sea-surface temperatures are quite warm at more than 30 deg C and the water is deep. Weakening is expected after the cyclone moves across west-central Cuba, followed again by some slight restrengthening after Elsa emerges over the warm Gulf Stream in the Straits of Florida. Westerly vertical wind shear increasing to near 20 kt by 96 hours should prevent any significant strengthening from occurring. Elsa should become a very asymmetrical tropical cyclone late on day 3 and on day 4 with most of the heavy rain and strongest winds displaced along and to the east of the forecast track. The initial intensity is similar to the previous advisory and closely follows the simple and corrected consensus models. Given the remaining uncertainty in the track forecast and the degree of land interaction with Hispaniola and Cuba, users are urged to factor in some of this uncertainty. For reference, average NHC track errors at days 3 and 4 are 125 miles and 150 miles, respectively. The average NHC intensity errors are around 15 mph for both days 3 and 4. Key Messages: 1. Widespread heavy rain will move across southern Haiti and Jamaica tonight into Sunday where isolated to scattered flash flooding and mudslides will be possible. Heavy rain will then impact the Cayman Islands and Cuba Sunday into Monday resulting in significant flooding and mudslides over Cuba. As Elsa approaches the Florida Keys and Florida Peninsula early next week, isolated flash flooding and minor river flooding will be possible. 2. Tropical storm conditions and dangerous storm surge are expected with hurricane conditions possible in portions of eastern Cuba beginning early Sunday, with tropical storm conditions possible in central and western Cuba Sunday night and Monday. 3. There is an increasing risk of tropical storm conditions, storm surge, and rainfall impacts beginning Monday in the Florida Keys and the southern Florida Peninsula, and a Tropical Storm Watch is now in effect for portions of the Florida Keys. This risk will spread northward along the Florida Peninsula through Wednesday and reach the coasts of Georgia and the Carolinas Wednesday and Thursday, however uncertainty in the forecast remains larger than usual due to Elsa's potential interaction with the islands of Hispaniola and Cuba. Interests elsewhere in Florida and along the southeast U.S. coast should monitor Elsa's progress and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 17.9N 75.3W 55 KT 65 MPH 12H 04/1200Z 19.2N 77.3W 55 KT 65 MPH 24H 05/0000Z 20.9N 79.4W 60 KT 70 MPH 36H 05/1200Z 22.5N 81.0W 50 KT 60 MPH...INLAND 48H 06/0000Z 24.1N 82.2W 45 KT 50 MPH...OVER WATER 60H 06/1200Z 26.0N 82.8W 50 KT 60 MPH 72H 07/0000Z 28.0N 83.0W 50 KT 60 MPH 96H 08/0000Z 32.7N 81.0W 45 KT 50 MPH...INLAND 120H 09/0000Z 37.7N 74.9W 35 KT 40 MPH...OVER WATER $$ Forecaster Stewart/Papin

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