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Hurricane Delta Forecast Discussion Number 21
2020-10-09 22:56:14| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Fri Oct 09 2020 000 WTNT41 KNHC 092056 TCDAT1 Hurricane Delta Discussion Number 21 NWS National Hurricane Center Miami FL AL262020 400 PM CDT Fri Oct 09 2020 Reports from an Air Force Reserve Hurricane Hunter aircraft and WSR-88D Doppler radar data indicate that Delta has weakened some more since the last advisory. The eye structure on the radar has become less organized, with about 50 percent of the eyewall remaining in the northern semicircle. The aircraft reported maximum 700-mb flight-level winds have decreased to the 100-105 kt range, along with maximum SFMR surface wind estimates in the 80-85 kt range. In addition, the central pressure has risen to near 966 mb. Based on these data, the initial intensity is lowered to 90 kt. The initial motion is now north-northeastward or 015/12 kt, with the hurricane moving between a deep-layer ridge over the eastern Gulf of Mexico and a mid- to upper-level trough over the U.S. Southern Plains. This motion should continue through the next 24 h or so, followed by a turn toward the northeast as Delta or its remnants move along the southern edge of the mid-latitude westerlies. While the track guidance remains tightly clustered, the guidance is a little faster than the previous run. So, the new track forecast is similar in direction, but slightly faster than the previous one. The forecast track has the center of Delta making landfall in southwestern Louisiana in the next few hours and then moving across central and northeastern Louisiana tonight and Saturday morning. After that, the system should move across northern Mississippi into the Tennessee Valley before it dissipates. Increasing vertical shear and decreasing oceanic heat content along the forecast track could cause a little more weakening in the last few hours before landfall. However, there will still be significant impacts from winds and storm surge (see Key Messages below). After landfall, rapid weakening is anticipated, with Delta expected to weaken to a tropical storm tonight and to a tropical depression by Saturday afternoon. As in the last advisory, the cyclone is forecast to dissipate between 60-72 h based on the consensus of the global models. Key Messages: 1. Life-threatening storm surge is occurring and will continue near and east of where Delta makes landfall this evening, and a Storm Surge Warning is in effect from High Island, Texas, to the Mouth of the Pearl River, Louisiana. The highest inundation of 7 to 11 feet is expected somewhere between Rockefeller Wildlife Refuge and Morgan City, Louisiana. 2. Hurricane-force winds are expected this afternoon and evening within portions of the Hurricane Warning area, especially along the coast of southwest Louisiana. Hurricane-force winds will also spread inland across portions of southern Louisiana near the path of Deltas center this evening and tonight. 3. Heavy rainfall will lead to significant flash flooding and minor to major river flooding in parts of Louisiana today and Saturday. Additional flooding is expected across portions of the central Gulf Coast into the Lower Mississippi Valley. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 29.3N 93.2W 90 KT 105 MPH 12H 10/0600Z 31.1N 92.5W 60 KT 70 MPH...INLAND 24H 10/1800Z 33.1N 91.0W 35 KT 40 MPH...INLAND 36H 11/0600Z 34.4N 89.2W 30 KT 35 MPH...INLAND 48H 11/1800Z 35.9N 87.1W 25 KT 30 MPH...INLAND 60H 12/0600Z 37.6N 84.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 12/1800Z...DISSIPATED $$ Forecaster Beven
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