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Hurricane Delta Forecast Discussion Number 13
2020-10-07 22:48:20| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Wed Oct 07 2020 000 WTNT41 KNHC 072048 TCDAT1 Hurricane Delta Discussion Number 13 NWS National Hurricane Center Miami FL AL262020 400 PM CDT Wed Oct 07 2020 The center of Delta has moved off the northern coast of the Yucatan peninsula and is now located over the southern Gulf of Mexico. The hurricane remains well organized in satellite imagery with a large curved band wrapping around the center and a fairly symmetric CDO. An Air Force Reserve reconnaissance aircraft has provided a few center fixes this afternoon, and found that Delta's passage over land has resulted in weakening, and the initial wind speed is set at 75 kt, which is based on a peak flight-level wind of 81 kt. The aircraft also reported a minimum pressure of 977 mb on its final center penetration, and data from the plane indicate that there has been some increase in the radius of maximum winds. Re-strengthening is anticipated over the next 24-36 hours while Delta moves within a favorable upper-level environment and over the relatively deep warm waters of the southern and central Gulf of Mexico. Most of the intensity guidance brings Delta back up to major hurricane status, and so does the official forecast. The global models also significantly deepen Delta during the next 36 hours, lending confidence to re-intensification. After 36 hours, increasing shear and cooler waters over the northern Gulf of Mexico are likely to cause some decrease in intensity before Delta makes landfall, however the hurricane's wind field is forecast to expand, which will increase the storm surge and wind threats. Regardless of Delta's landfall intensity, life-threatening storm surge and strong winds are likely over a large portion of the northwestern and northern Gulf coast. Delta has been moving on a consistent northwestward heading of 305 degrees at about 15 kt. Delta should continue on this general heading with some reduction in forward speed tonight and early Thursday as it approaches the western extent of the subtropical ridge. A mid- to upper-level trough over Texas is forecast to slide eastward over the next couple of days, which is expected to cause Delta to turn north-northwestward on Thursday, and northward toward the northern Gulf coast by Friday. A faster northward to north-northeastward motion in 48-60 hours will bring the center onshore along the northern Gulf coast late Friday. The cross track spread in the dynamical models has decreased this cycle, with the model predictions converging on the previous NHC track forecast. Therefore, little change has been made to the previous official forecast, and it lies near the center of the now tightly clustered guidance envelope. Key Messages: 1. Winds and water levels along the northern coast of the Yucatan Peninsula will gradually subside this evening. Heavy rainfall, which could lead to significant flash flooding, will affect the northern Yucatan Peninsula through early Thursday. 2. Delta is expected to grow in size as it approaches the northern Gulf Coast, where life-threatening storm surge and dangerous hurricane-force winds are likely beginning Friday, particularly for portions of the Louisiana coast. Storm Surge and Hurricane Watches are in effect, and residents in these areas should follow advice given by local officials. 3. Flash, urban, small stream and minor to isolated moderate river flooding is likely Friday and Saturday from portions of the central Gulf Coast into portions of the Lower to Middle Mississippi Valley. As Delta moves farther inland, additional heavy rainfall is expected in the Ohio Valley and Mid Atlantic this weekend. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 22.1N 89.5W 75 KT 85 MPH 12H 08/0600Z 23.2N 91.2W 85 KT 100 MPH 24H 08/1800Z 24.8N 92.9W 95 KT 110 MPH 36H 09/0600Z 26.7N 93.4W 100 KT 115 MPH 48H 09/1800Z 29.1N 92.9W 90 KT 105 MPH 60H 10/0600Z 31.6N 91.9W 45 KT 50 MPH...INLAND 72H 10/1800Z 33.7N 90.5W 30 KT 35 MPH...INLAND 96H 11/1800Z 37.0N 85.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 12/1800Z...DISSIPATED $$ Forecaster Brown
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