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Hurricane Delta Forecast Discussion Number 8
2020-10-06 16:54:19| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Tue Oct 06 2020 000 WTNT41 KNHC 061454 TCDAT1 Hurricane Delta Discussion Number 8 NWS National Hurricane Center Miami FL AL262020 1100 AM EDT Tue Oct 06 2020 Satellite imagery and recent NOAA Hurricane Hunter aircraft data show that Delta is a very symmetric and compact hurricane. The aircraft reported a tiny 5-nmi-wide eye, which has also been seen in radar imagery from the Cayman Islands, and there is a hint of a pinhole eye in infrared satellite data. The central pressure has continued to fall, with the lastest center dropwindsonde data supporting a pressure of 955 mb. The plane has reported a peak flight-level winds of 109 kt, and believable SFMR winds of 102 kt. Therefore, the initial intensity is set at 100 kt, making Delta the third major hurricane of the 2020 Atlantic hurricane season. Delta has continued to rapidly strengthen over the past 24 hours, with an estimated 55-kt increase in wind speed between 1200 UTC Monday and 1200 UTC today. Environmental conditions of low vertical wind shear, deep warm waters, and sufficient mid-level moisture are expected to support additional rapid intensification through today, and the only reason that the strengthening could slow is if a difficult-to-predict eyewall replace cycle begins. The SHIPS Rapid intensification index continues to indicate a high likelihood of at least an additional 25-30 kt of intensity increase before the system reaches the northeastern portion of the Yucatan Peninsula. Given that, the NHC intensity forecast is above the various intensity aids and call for Delta to be an extremely dangerous category 4 hurricane when it nears the Yucatan. It could be stronger than indicated below since landfall is predicted to occur between the 12 and 24 h forecast points. Some reduction in intensity is likely when Delta moves over land, but the environmental conditions over the southern Gulf of Mexico are expected to support re-strengthening, and the NHC intensity forecast shows a second peak in 48-72 hours. As mentioned before, increasing southwesterly shear and cooler shelf waters near the northern Gulf coast are expected to cause some reduction in wind speed, but Delta is still expected to be a dangerous hurricane when it nears the northern Gulf coast. Delta is moving west-northwestward at about 14 kt. A mid-level ridge that extends westward across Florida and the northeastern Gulf of Mexico should continue to steer Delta west-northwestward to northwestward during the next couple of days. As the hurricane nears the western portion of the ridge it should slow down. By day three a developing trough over the south-central United States is expected to cause Delta to turn northward toward the northern Gulf coast. The track guidance is tightly clustered through 48 hours, but there is still a fair amount of spread thereafter regarding the timing and details of the northward turn. The ECMWF and its ensemble mean are well west of the bulk of the remainder of the guidance. The NHC track lies near the TVCA multi-model consensus which is close to a blend of the GFS, HWRF, UKMET ensemble mean. Key Messages: 1. Extremely dangerous storm surge and hurricane conditions are expected within portions of the northern Yucatan Peninsula of Mexico beginning tonight, and a Hurricane Warning is in effect. 2. Heavy rainfall will affect portions of the Cayman Islands, western Cuba and the northern Yucatan Peninsula through midweek. This rainfall could lead to significant flash flooding and mudslides. The potential for heavy rain and flash flooding will increase across portions of the central Gulf Coast, Tennessee Valley, and southeastern United States as Delta moves inland later this week. 3. There is an increasing likelihood of life-threatening storm surge and dangerous hurricane-force winds, especially along the coasts of Louisiana and Mississippi, beginning on Friday. Residents in these areas should ensure they have their hurricane plan in place and monitor updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 18.2N 82.6W 100 KT 115 MPH 12H 07/0000Z 19.4N 84.5W 120 KT 140 MPH 24H 07/1200Z 21.0N 87.2W 120 KT 140 MPH 36H 08/0000Z 22.3N 89.6W 105 KT 120 MPH 48H 08/1200Z 23.4N 91.3W 110 KT 125 MPH 60H 09/0000Z 24.6N 92.3W 115 KT 130 MPH 72H 09/1200Z 26.3N 92.5W 110 KT 125 MPH 96H 10/1200Z 30.5N 91.2W 70 KT 80 MPH...INLAND 120H 11/1200Z 34.5N 87.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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