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Tropical Storm Elsa Forecast Discussion Number 35

2021-07-08 22:56:50| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Thu Jul 08 2021 000 WTNT45 KNHC 082056 TCDAT5 Tropical Storm Elsa Discussion Number 35 NWS National Hurricane Center Miami FL AL052021 500 PM EDT Thu Jul 08 2021 A NOAA NOS observing site at Wrightsville Beach, North Carolina, recently reported a sustained wind of 41 kt, so Elsa's maximum winds are now estimated to be 45 kt. A number of other observing sites in the vicinity have also reported sustained tropical-storm-force winds. Elsa's slight strengthening may be the result of baroclinic forcing associated with an approaching short-wave trough. The system's cloud tops have warmed somewhat during the day, but it is still producing some very heavy rains. Elsa's low-level center is a bit elongated from southwest to northeast, but surface synoptic data indicate that it has moved into northern North Carolina. The storm continues to gradually accelerate toward the northeast, and the initial motion estimate is 040/18 kt. A faster northeastward motion is expected over the next 1-2 days as the cyclone moves along with the mid-latitude southwesterly flow ahead of a broad mid-tropospheric trough over the eastern United States and Canada. Elsa should move near or over southeastern New England and Atlantic Canada within the next 24-48 hours. The official track forecast remains close to the previous one and similar to the multi-model consensus, TVCA. The global models suggest that not much additional strengthening is likely. Simulated satellite imagery from these models show an extratropical appearance in 24-36 hours so the official forecast shows an extratropical transition by late Friday. This is also supported by cyclone phase analyses of the model fields from Florida State University. Key Messages: 1.As Elsa moves from North Carolina to Virginia today and this evening, heavy rainfall may result in limited flash and urban flooding. Heavy rainfall from the Mid-Atlantic into New England through Friday could lead to considerable flash and urban flooding. 2. Tropical storm conditions should continue along portions of the North Carolina coast this afternoon and spread over the mid-Atlantic coast later today or tonight. Tropical storm conditions are expected in portions of the southern New England states and New York by Friday. Gusty winds are expected over portions of Atlantic Canada Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 36.3N 78.3W 45 KT 50 MPH...INLAND 12H 09/0600Z 38.7N 75.1W 45 KT 50 MPH...INLAND 24H 09/1800Z 42.5N 70.0W 45 KT 50 MPH...OVER WATER 36H 10/0600Z 47.0N 63.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 10/1800Z 51.5N 54.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 60H 11/0600Z 56.0N 45.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 11/1800Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Elsa Forecast Discussion Number 34

2021-07-08 16:58:42| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Thu Jul 08 2021 000 WTNT45 KNHC 081458 TCDAT5 Tropical Storm Elsa Discussion Number 34 NWS National Hurricane Center Miami FL AL052021 1100 AM EDT Thu Jul 08 2021 Surface synoptic observations and high-resolution satellite images indicate that the center of the storm has moved into North Carolina. WSR 88-D Doppler radar data and surface reports indicate that the maximum winds are near 40 kt. These highest winds are likely occurring in some of the stronger convective bands near the coast. Elsa is gradually accelerating toward the northeast, and the initial motion is about 040/17 kt. A faster northeastward motion is expected over the next couple of days as the cyclone becomes entrained into the mid-latitude southwesterly flow ahead of a broad mid-tropospheric trough over the eastern United States and Canada. Elsa should move near or over southeastern New England and Atlantic Canada during the next 24-48 hours. The official track forecast is basically an update of the previous one and continues to follow the multi-model consensus. Some slight intensification is possible within the next 24-36 hours due to baroclinic forcing from a mid-latitude short wave trough. Around 36 hours, the simulated satellite imagery from the global models depicts a cloud pattern resembling that of a frontal cyclone. Moreover, the FSU phase analyses of the GFS fields shows the system becoming extratropical at that time. This is also reflected in the official forecast. Key Messages: 1. As Elsa moves across North Carolina and Virginia today, heavy rainfall may result in limited flash and urban flooding. Heavy rainfall from the Mid-Atlantic into New England through Friday could lead to considerable flash and urban flooding. 2. Tropical storm conditions are expected along portions of the North Carolina coast today and the mid-Atlantic coast by this afternoon or tonight. Tropical storm conditions are expected in portions of the southern New England states and New York by Friday. Gusty winds are expected over portions of Atlantic Canada Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 35.0N 79.7W 40 KT 45 MPH 12H 09/0000Z 37.3N 77.0W 40 KT 45 MPH...INLAND 24H 09/1200Z 40.6N 72.5W 45 KT 50 MPH...OVER WATER 36H 10/0000Z 44.5N 67.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 10/1200Z 49.0N 59.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 11/0000Z 53.5N 50.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 11/1200Z 59.0N 40.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 12/1200Z...DISSIPATED $$ Forecaster Pasch

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Tropical Storm Elsa Forecast Discussion Number 33

2021-07-08 11:01:06| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Thu Jul 08 2021 000 WTNT45 KNHC 080901 TCDAT5 Tropical Storm Elsa Discussion Number 33 NWS National Hurricane Center Miami FL AL052021 500 AM EDT Thu Jul 08 2021 Doppler radar and surface observation indicate that the center of Elsa is moving into southern South Carolina at this time. The organization of the storm has changed little during the past several hours, with a complex of bands in the eastern semicircle. The initial intensity is 35 kt, and these winds are occurring along an area of the coast and coastal waters well southeast of the center. The initial motion is now 035/16. The track guidance is in good agreement that Elsa should accelerate northeastward during the next few days as it becomes entrained into the mid-latitude southwesterly flow, with the track carrying the system across the Carolinas and the mid-Atlantic states during the next 24 hours, then near or over southeastern New England and Atlantic Canada. The new forecast track is basically an update of the previous track, and it is very close to the consensus models. Rawinsonde data and GOES-16 RGB airmass imagery show an upper-level shortwave trough over the southeastern United States to the west of Elsa, and the global models forecast this system to follow the cyclone northeastward and take on a negative tilt. This should result in increasing upper-level divergence over Elsa, which in turn should lead to some strengthening as the storm moves near or over the east coast of the United States. The 00Z ECMWF model is not as bullish on intensification as its previous run, but it and the 00Z UKMET still call for strengthening, and even the weaker GFS forecasts the favorable upper-air pattern. Based on this, the new intensity forecast shows a little more strengthening than the previous forecast. Based on the new forecast track, the tropical storm warning has been extended northward along the United States east coast to Massachusetts. Non-tropical gale warnings are in effect for the coastal areas to the north of the tropical storm warning due to the likelihood that Elsa will become extratropical as it reaches that area. Key Messages: 1. As Elsa moves across the Carolinas Thursday, heavy rainfall may result in limited flash and urban flooding. Heavy rainfall from the Mid-Atlantic into New England Thursday and Friday could lead to considerable flash and urban flooding. 2. Tropical storm conditions are expected along portions of the coasts of Georgia and South Carolina this morning. Tropical storm conditions are also expected along the coasts of North Carolina starting later today and the mid-Atlantic by this afternoon or tonight. Tropical storm conditions are expected in portions of the southern New England states and New York by Friday. Gale winds are expected over the portions of the New Hampshire and Maine coasts by late Friday or Friday night, and those conditions are possible over portions of Atlantic Canada Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 33.4N 81.3W 35 KT 40 MPH...INLAND 12H 08/1800Z 35.5N 79.3W 35 KT 40 MPH...INLAND 24H 09/0600Z 38.8N 75.2W 40 KT 45 MPH...INLAND 36H 09/1800Z 42.5N 70.1W 45 KT 50 MPH...OVER WATER 48H 10/0600Z 46.9N 63.6W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 10/1800Z 51.9N 54.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 11/0600Z 56.6N 44.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 12/0600Z...DISSIPATED $$ Forecaster Beven

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Tropical Storm Elsa Forecast Discussion Number 32

2021-07-08 04:59:35| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Wed Jul 07 2021 000 WTNT45 KNHC 080259 TCDAT5 Tropical Storm Elsa Discussion Number 32 NWS National Hurricane Center Miami FL AL052021 1100 PM EDT Wed Jul 07 2021 Doppler radar and surface observations indicate that Elsa is maintaining its intensity. However, these winds aren't close to the center but, rather, in a strong band of convection in the eastern semicircle of the storm. The current wind speed is set to 40 kt in accordance with an earlier sustained wind report of 38 kt, and radar velocities reduced to the surface that would support at least 40 kt. Some weakening is expected overnight while a significant portion of Elsa's circulation remains over land. However by late Thursday, more of the storm will be moving over water, and a fair number of the models suggest re-intensification could take place. It is a little puzzling why the ECMWF and UKMET models, however, are showing a strengthening tropical storm close to the mid-Atlantic states, especially without a significant trough interaction or warm waters. I'm getting some deja vu in this case after working Claudette from a few weeks ago, with those same models also over-intensifying that storm. The GFS has been relatively consistent in showing only a small intensification of Elsa, and the NHC forecast will continue to be closer to that model's relatively weaker solution. The storm has turned north-northeastward tonight and is moving a little faster, about 14 kt. Elsa should move northeastward at an increasing forward speed during the next few days as it becomes embedded within fast southwesterly flow ahead of a mid-latitude trough. No significant changes were made to the previous track forecast since guidance remains in good agreement. Elsa is likely to become absorbed north of Newfoundland by another extratropical low by day 4. There is greater confidence tonight that some portion of North Carolina and the mid-Atlantic coast will receive tropical-storm force-winds, so the Tropical Storm Watch has been upgraded to a Tropical Storm Warning in those areas. Areas to the north remain less certain, and remain under a Tropical Storm Watch. Key Messages: 1. As Elsa moves across southeastern Georgia into the Lowcountry of South Carolina tonight, heavy rainfall may result in considerable flash, urban, and minor river flooding. Heavy rainfall, from North Carolina across the mid-Atlantic and into New England Thursday and Friday, could lead to isolated flash and urban flooding. 2. Tropical storm conditions are expected along portions of the coasts of Georgia and South Carolina tonight. Tropical storm conditions are also expected along the coasts of North Carolina on Thursday and the mid-Atlantic by Thursday night. Tropical storm conditions are possible in the southern New England states and New York by Friday. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 32.1N 82.3W 40 KT 45 MPH...INLAND 12H 08/1200Z 34.1N 80.7W 35 KT 40 MPH...INLAND 24H 09/0000Z 37.1N 77.3W 35 KT 40 MPH...INLAND 36H 09/1200Z 40.4N 72.9W 40 KT 45 MPH...OVER WATER 48H 10/0000Z 44.5N 67.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 60H 10/1200Z 49.0N 60.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 11/0000Z 54.0N 50.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 12/0000Z...DISSIPATED $$ Forecaster Blake

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Tropical Storm Elsa Forecast Discussion Number 31

2021-07-07 22:57:27| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Wed Jul 07 2021 000 WTNT45 KNHC 072057 TCDAT5 Tropical Storm Elsa Discussion Number 31 NWS National Hurricane Center Miami FL AL052021 500 PM EDT Wed Jul 07 2021 Surface synoptic data indicate that the center of Elsa has moved into extreme southern Georgia and, assuming continued weakening since earlier today, the maximum winds are estimated to be 40 kt. This may be a generous estimate of the current intensity since no surface observations of sustained tropical-storm-force winds have been recently received. Elsa should weaken into a tropical depression on Thursday. By early Friday, the dynamical models show some restrengthening of the cyclone as it moves along the Mid-Atlantic coastline. However, the simulated satellite imagery from the global models at that time depict the system resembling a frontal cyclone, so it is dubious as to whether Elsa will be completely tropical in 48 hours. Due to the uncertainty as to when extratropical transition will occur, tropical storm watches have been issued for Long Island and portions of southern New England at this time. The initial motion is northward, or 010/12 kt. Elsa is forecast to turn north-northeastward overnight as it moves around the northwestern periphery of an Atlantic subtropical ridge while accelerating northeastward ahead of a broad mid-level trough over the eastern United States and Canada on Thursday. The official forecast is about the same as the previous one and closely follows the multi-model consensus. Key Messages: 1. Heavy rainfall may result in considerable flash, urban, and isolated moderate river flooding over northern Florida. Heavy rainfall across southeast Georgia, South Carolina, North Carolina, and southeastern Virginia may result inconsiderable flash and urban flooding across southeast Georgia and the Lowcountry of South Carolina. Heavy rainfall across the Northeast and New England Thursday and Friday could lead to isolated flash and urban flooding. 2. Although the center of Elsa is expected to remain inland of the coastline from Georgia through the Carolinas during the next day or two, tropical storm conditions are expected along portions of the coasts of Georgia and South Carolina tonight. Tropical storm conditions are also possible along the coast of the mid-Atlantic and southern New England states by Thursday night or Friday. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 30.8N 83.4W 40 KT 45 MPH...INLAND 12H 08/0600Z 32.8N 82.1W 35 KT 40 MPH...INLAND 24H 08/1800Z 35.6N 79.4W 30 KT 35 MPH...INLAND 36H 09/0600Z 38.8N 75.4W 35 KT 40 MPH...INLAND 48H 09/1800Z 42.0N 70.5W 35 KT 40 MPH...INLAND 60H 10/0600Z 46.0N 64.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 10/1800Z 50.0N 57.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 11/1800Z...DISSIPATED $$ Forecaster Pasch

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