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Hurricane Delta Forecast Discussion Number 18
2020-10-09 04:37:20| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Thu Oct 08 2020 000 WTNT41 KNHC 090237 TCDAT1 Hurricane Delta Discussion Number 18 NWS National Hurricane Center Miami FL AL262020 1000 PM CDT Thu Oct 08 2020 Reports from Air Force and NOAA Hurricane Hunter aircraft investigating Delta indicate that the hurricane strengthened a little more this evening. Peak flight-level winds were 120 kt, and the highest SFMR-observed surface winds were 98 kt. Using a blend of adjusted flight-level and surface wind observations, the current intensity estimate is set at 105 kt. The eye became obscured on satellite images a couple of hours ago, but recently it has become apparent again. Delta could intensify a little more within the next 6 hours or so. Thereafter, sharply decreasing oceanic heat content, significantly increasing west-southwesterly shear, and drier mid-level air should cause weakening. The official intensity forecast through landfall is above most of the model guidance. However, even 24-hour tropical cyclone intensity forecasts are still subject to an uncertainty of 1 Saffir-Simpson category, so one should not focus on the exact official landfall intensity forecast. Moreover, even if Delta weakens some, it will still have serious storm surge impacts due to its large size. Aircraft and satellite center fixes show that the hurricane is gradually turning toward the right. The motion is now north-northwestward, or 340/10 kt. Delta should turn northward on Friday as it moves on the western side of a mid-tropospheric high pressure area. Later on Friday, a 500-mb shortwave trough over the southern United States is likely to cause the tropical cyclone to turn north-northeastward and cross the northern Gulf of Mexico coast. Delta should then move northeastward on the eastern side of the trough over the southeastern United States for the next day or two before dissipating near Kentucky. The official track forecast is very close to the previous NHC track, and in very good agreement with the various consensus track predictions. Key Messages: 1. Life-threatening storm surge is expected near and east of where Delta makes landfall Friday, and a Storm Surge Warning is in effect from High Island, Texas, to Ocean Springs, Mississippi. The highest inundation of 7 to 11 feet is expected somewhere between Rockefeller Wildlife Refuge and Morgan City, Louisiana. Residents in the warning area should promptly follow advice given by local officials. The storm surge risk remains high despite the forecast decrease in intensity before landfall since Delta is a relatively large hurricane. 2. Hurricane-force winds are expected Friday afternoon and evening somewhere within the Hurricane Warning area between High Island, Texas, and Morgan City, Louisiana. Hurricane force winds will also spread inland across portions of southern Louisiana near the path of Deltas center Friday evening and Friday night. 3. Heavy rainfall will lead to significant flash flooding and minor to major river flooding in parts of Louisiana Friday and Saturday. Additional flooding is expected across portions of the central Gulf Coast into the Lower Mississippi Valley. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 25.7N 93.6W 105 KT 120 MPH 12H 09/1200Z 27.4N 93.7W 105 KT 120 MPH 24H 10/0000Z 29.8N 93.0W 85 KT 100 MPH...INLAND 36H 10/1200Z 32.0N 91.9W 45 KT 50 MPH...INLAND 48H 11/0000Z 33.5N 90.2W 25 KT 30 MPH...INLAND 60H 11/1200Z 34.9N 88.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 12/0000Z 36.5N 87.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 13/0000Z...DISSIPATED $$ Forecaster Pasch/Berg
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