On October 19, a trough of low pressure developed over the southwestern Caribbean, extending from north of Panama all the way toward the western tip of Cuba. There were some showers associated with the system, but they mostly lay to the east. The disturbance crawled westward for a day or two and then stalled. Meanwhile, upper-level winds were becoming a bit more favorable. Finally, a low pressure center formed early on October 23 west of Jamaica. Gradual consolidation continued, culminating in the designation of Tropical Depression Twenty-Eight the next day.
The depression was nearly stationary. The deepest convection and the mid-level center were southeast of the surface center and actually retreated a bit further south early on October 25. At the same time, the storm strengthened into Tropical Storm Zeta, the 27th named storm of the 2020 Atlantic hurricane season. The only previous season with a 27th storm was 2005, for which it was Epsilon (due to an unnamed storm), forming November 29th of that year. It was the second time "Zeta" was used, again after 2005. Zeta wasn't particularly well organized, but had some extremely strong storms in the southern semicircle. Winds in that region increased some during the day and Zeta strengthened. The outermost of these brought some rain to Honduras. That afternoon, the center of circulation reformed nearer to the mid-level center. All these structural changes notwithstanding, Zeta had scarcely moved since its formation.
By October 26, a ridge building in to the north finally got the storm moving toward the northwest. At first, the center outran the central dense overcast a little bit, but relaxing shear and high oceanic heat content allowed Zeta to come back with a vengeance later that day. It quickly strengthened into a hurricane, reaching an intensity of 80 mph winds and a pressure of 977 mb. That night, it made landfall in the northern Yucatan peninsula, in nearly the same location that Gamma and Delta had earlier in the month.
Zeta weakened over land to a tropical storm before emerging into the Gulf of Mexico during the morning of October 27. The storm had lost much of its central convection, but it redeveloped quickly that day. By the evening, a well-defined eyewall had appeared, beginning another period of intensification. Soon, Zeta was a hurricnae again. A powerful extratropical storm dipping into the Rocky Mountains began to influence the cyclone's track. It turned northward on October 28 as it approached the Gulf coast. Zeta's eye opened up a little that morning as well; rapid intensification brought it up to its peak intensity as a category 3 major hurricane with 115 mph winds and a minimum central pressure of 970 mb. It made landfall with these winds in southeastern Lousiana that afternoon. Note that, operationally, Zeta was classified as a category 2 hurricane, but it was upgraded to a category 3 in post-season analysis.
Remarkably, Zeta was the second major hurricane, third hurricane and fifth tropical cyclone of 2020 to make landfall in Louisiana. It also joined a list of six hurricane landfalls in the continental United States, tying a record set in 1985 for the most recorded in a season. Zeta's upgrade marked the first time three major hurricanes were ever recorded in October, and the latest in the year so far that a major hurricane had made landfall in the continental U.S. By that time, the storm was moving quickly northeast. Therefore, rains were limited, but water rose quickly and the New Orleans area experienced very strong winds and widespread power outages. Hurricane force winds also spread far inland due to Zeta's speed: the center moved crossed into Mississippi and then Alabama before it weakened to a tropical storm. It rocketed across the mid-Atlantic on the 29th and became extratropical that afternoon.
The above photo shows Zeta just before landfall in Lousiana.
Zeta's path through the Caribbean and Gulf of Mexico was extremely similar to that of several other cyclones of the 2020 season.
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