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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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