Hurricane Delta was the record-tying fourth named storm of 2020 to make landfall in Louisiana, as well as the record-breaking tenth named storm to strike the United States in that year. The twenty-sixth tropical cyclone, twenty-fifth named storm, tenth hurricane, and third major hurricane of the record-breaking 2020 Atlantic hurricane season, Delta formed from a tropical wave which was first monitored by the National Hurricane Center (NHC) on October 1. Moving westward, the tropical wave began to quickly organize. A well-defined center of circulation formed with sufficiently organized deep convection on October 4, and was designated as Tropical Depression Twenty-six and soon thereafter, Tropical Storm Delta. Extremely rapid intensification ensued throughout October 5 into October 6, with Delta becoming a Category 4 hurricane within 28 hours of attaining tropical storm status. The rate of intensification was the fastest in the Atlantic basin since Hurricane Wilma in 2005. After peaking in intensity however, an unexpected increase in wind shear and dry air quickly weakened the small storm before it made landfall in Puerto Morelos, Mexico as a Category 2 hurricane with winds. It weakened some more over land before emerging into the Gulf of Mexico, where it was downgraded to a Category 1 hurricane. After that, it began to restrengthen, regaining Category 3 status late on October 8. It then turned northward and reached a secondary peak intensity of and winds of 120 mph early on October 9. Delta then began to turn more north-northeastward into an area of cooler waters, higher wind shear, and dry air, causing it to weaken back to Category 2 status. Delta then made landfall at 23:00 UTC near Creole, Louisiana with winds of and a pressure of . The storm began to weaken more rapidly after landfall, becoming post-tropical just 22 hours later.
Widespread tropical cyclone watches and warnings were issued throughout the Western Caribbean and the Mexican states of Yucatán and Quintana Roo, which had just been hit by Hurricane Gamma, in preparation for the storm. As Delta moved out of the Gulf of Mexico, more watches were issued for the U.S. Gulf Coast, an area that had already seen multiple strong hurricanes such as Laura and Sally earlier in the season. States of emergency were also declared in the U.S. states of Louisiana, Mississippi, and Alabama and several coastal and low-lying areas were ordered to evacuate. In Mexico, trees and power lines were blown down, and roofs were ripped off homes and other buildings. Louisiana and Southeast Texas were again by heavy rain, high winds, and storm surge, and 14 weak tornadoes were confirmed in Mississippi, Alabama, Georgia and the Carolinas. Total insured losses resulting from the storm amounted to $3.09 billion, with $2.9 billion in the US and US$186 million in Mexico.
Meteorological history
At 00:00 UTC on October 1, the National Hurricane Center (NHC) began to monitor a tropical wave moving into the Eastern Caribbean for potential development. It moved steadily westward at and began to organize late on October 3. A well-defined center of circulation formed with sufficiently organized deep convection around 18:00 UTC on October 4, marking the formation of Tropical Depression Twenty-Six. Thunderstorm activity continued to increase after formation, but was initially confined to the southern portion of the circulation due to northerly wind shear. Once the shear lessened on October 5, convection became more symmetric around the center, and the system strengthened to become Tropical Storm Delta by 12:00 UTC that day about south-southwest of Montego Bay, Jamaica.
Continuing westward in defiance of forecasts that repeatedly predicted a northwestward turn, Delta began a period of rapid intensification, becoming a Category 1 hurricane 12 hours after being named. As it finally began to turn northwestward early on October 6, Delta continued to rapidly intensify, reaching Category 2 status just nine hours later at 09:00 UTC. Delta's intensification was described as the fastest in a 24-hour period since Hurricane Wilma of 2005. By 12:30 UTC, Delta began to develop a small pinhole eye only 4 nautical miles (4.6 miles) in diameter, although it was not visible in satellite imagery. Rapid intensification continued and at 15:00 UTC, Delta was upgraded to Category 3 major hurricane status, before reaching Category 4 status just 20 minutes later, after an NOAA hurricane Hunter aircraft indicated that the storm's 1-minute sustained wind speed was at . Delta intensified from a tropical depression to Category 4 hurricane in just over 36 hours, breaking the record of 42 hours that Hurricane Keith set in 2000.