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| #1105871 (Received by flhurricane at: 11:09 AM 05.Sep.2022) TCDAT1 Tropical Storm Earl Discussion Number 11 NWS National Hurricane Center Miami FL AL062022 1100 AM AST Mon Sep 05 2022 Earl is attempting to restructure again this morning. Convection, which had been primarily located east of the center, due to persistent moderate westerly vertical wind shear, has begun to pivot up-shear into the northern quadrant of the storm. A NOAA-P3 mission that was in the storm this morning indicated the low-level wind field in the northern semicircle of the storm had also intensified, with several dropsondes indicating boundary layer mean winds in the 55-65 kt range and one reported a surface wind gust of 57 kt. These values match the twin Doppler radar (TDR) onboard of the aircraft, with peak 0.5 km winds above 64 kt. The peak SFMR winds from the mission were 58 kt, with 700-mb flight-level winds at 63 kt. The satellite presentation this morning though remains somewhat ragged, with the low-level circulation partially exposed, though TDR analysis suggest the vertical tilt between the low- and mid-level centers has decreased compared to yesterday. Based partially on the these aircraft observations, the intensity has been set at 55 kt for this advisory, which also agrees with the latest TAFB intensity estimate. The center of the cyclone may have relocated a bit northeast of the previous position, but the mean general motion appears to still be to the north-northwest at 340/4 kt. The track model guidance is generally in good agreement in the short-term that this slow northward motion should continue, as the cyclone moves poleward through a weakness in the deep-layer ridging to its north. This mid-level ridge is then forecast to continue breaking down as a deep-layer trough approaches from the eastern United States. This synoptic pattern change should be enough for Earl to begin a somewhat faster north-northeastward motion after 72 hours. However, after this time, uncertainty in the along-track direction between both deterministic and ensemble guidance starts to increase dramatically, with the GFS and its ensemble mean faster, and the ECWMF and its ensemble mean slower. The latest NHC track forecast is a bit further to the east early on, due to the adjustment in the initial position, but ends up near, if a bit slower, than the previous forecast track by the end of the forecast period. This track is close to an average of the latest GFS and ECMWF forecasts. Given the large uncertainty observed in the guidance at day 5, forecast track confidence in that time frame is lower than normal. While Earl was found to be a bit stronger by the NOAA-P3 aircraft this morning, westerly vertical wind shear is still quite evident, and both the GFS- and ECMWF-based SHIPS guidance suggests this shear could actually increase a bit more over the next 24-36 hours. Thus, only a slight additional amount of intensification is forecast today, followed by Earl remaining steady over the 24-36 hour period. After the cyclone moves poleward of the shear zone induced by a nearby tropical upper-tropospheric trough, the shear is expected to decrease significantly, allowing more robust intensification. The tropical storm wind field is also forecast to increase dramatically during this period as a result of the system also undergoing a positive upper-level trough interaction. The latest NHC intensity forecast still shows a peak intensity of 105 kt by day 5, though some regional hurricane models (HWRF, COAMPS-TC) are a bit higher than this forecast. KEY MESSAGES: 1. Heavy rainfall from Earl is expected to lead to limited flash, urban, and small stream flooding impacts over the Leeward Islands, U.S. and British Virgin Islands, and Puerto Rico today. Rapid rises on rivers and mudslides in areas of steep terrain are possible in Puerto Rico. Considerable flood impacts cannot be ruled out in areas that receive heavier rainfall totals. 2. Currently Earl is forecast to track to the southeast of Bermuda. However, the wind field of the tropical cyclone is expected to increase significantly, and interests on the island should continue to monitor the progress of the storm closely. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 21.5N 65.3W 55 KT 65 MPH 12H 06/0000Z 22.5N 65.3W 60 KT 70 MPH 24H 06/1200Z 23.7N 65.5W 60 KT 70 MPH 36H 07/0000Z 24.7N 65.6W 60 KT 70 MPH 48H 07/1200Z 25.9N 65.6W 65 KT 75 MPH 60H 08/0000Z 27.0N 65.3W 70 KT 80 MPH 72H 08/1200Z 28.3N 64.8W 80 KT 90 MPH 96H 09/1200Z 31.3N 62.8W 95 KT 110 MPH 120H 10/1200Z 34.4N 59.1W 105 KT 120 MPH $$ Forecaster Papin |
