Two tropical waves over the central tropical Atlantic passed over the Windward islands in the last week of October, producing stormy conditions there. The second was moving faster than the first, and they merged into a single large disturbance over the eastern Caribbean. On October 30, this disturbance developed concentrated thunderstorm activity and consolidated pretty quickly. The next day, it attained tropical cyclone status as Tropical Depression Twenty-Nine. At the time, it was centered well south of Haiti.
Overnight, the storm strengthened into Tropical Storm Eta. This brought 2020 into a tie with 2005 for the most named storms ever recorded in a single Atlantic hurricane season, with 28. Eta formed much, much earlier than 2005's final named storm, Tropical Storm Zeta, which formed on December 30 of that year and lasted into the first week of 2006. Also, because of 2005's unnamed subtropical storm, this was the first use of the Greek letter "Eta" for any cyclone. The newly named Eta moved nearly due westward under the influence of a ridge to its north. Though late fall was closing down many other parts of the Atlantic basin, the southwestern Caribbean remained close to ideal for tropical cyclone development: high oceanic heat content still prevailed along with ample moisture and low wind shear. Eta took full advantage of these conditions beginning on November 1.
Eta's subsequent intensification event was among the most rapid ever recorded. It became a hurricane early on November 2 and the tropical storm force wind radius greatly expanded. The inner core of the system was still fairly small, supporting rapid intensity changes. Similar to in Hurricane Delta a few weeks previously, a tiny warm spot appeared on infrared imagery surrounded by incredibly cold cloud tops that afternoon. Around the same time, Eta became a category 2 and then, a few hours later, a major hurricane. It was now approaching Nicaragua, and it began to slow down and turn toward the southwest. Unlike Delta before it, it managed to clear out its eye that evening. The ring of cold cloud tops, some colder than -90° C, expanded further. Eta peaked that night as the strongest hurricane yet of the 2020 season, with maximum winds of 150 mph (tying Laura) and a minimum central pressure of 923 mb. At the time, this made Eta the second-most intense November Atlantic hurricane recorded, after only the unnamed Cuba hurricane of 1932. However, Eta would be surpassed in both these records by Hurricane Iota just weeks later.
By that time, some of the western half of the circulation was over Nicaragua. Unfortunately, the storm had slowed to a crawl, causing a prolonged period of flooding rains as Eta meandered just off the coast. An eyewall replacement cycle also took place, leaving the cyclone with slightly lower winds but a larger eyewall; in any case, it still made landfall as a category 4 late in the afteroon on November 3. Once inland, Eta pushed westward and weakened rapidly, especially once it reached mountainous terrain farther inland. Early on November 4, it was downgraded to a tropical storm, and that evening, a tropical depression. What was left of the low-level center crossed the inland border into Honduras.
After another day of traversing central America, the weak depression turned northward back toward the Caribbean. It was unclear whether the low-level center had truly survived, but without significant evidence to the contrary, it was maintained as a tropical depression. During the evening, Eta reemerged over water and convection began to increase again. An upper-level trough began to draw the system northeast at increasing speeds on November 6. Little changed with the storm that day since the circulation was ill-defined and beset by moderate southwesterly shear.
A great deal of upper-level divergence did support deep convection and warm Caribbean waters helped Eta to spin up once again on the 7th. The cyclone regained tropical storm strength while centered near the Cayman Islands, but its structure was quite different from before: it had the comma-shape of a storm with some subtropical characteristics. The center also reformed nearer to the mid-level spin and Eta strengthened as it moved northeast toward central Cuba. Early on November 8, Eta made landfall there as a strong tropical storm. This resulted in minor flooding and storm surge, especially on the east side. Later in the day, the storm reemerged over water in the extreme southwest Atlantic.
An upper-level trough over the northwestern Caribbean had been guiding the cyclone; it closed off into an upper-level low and Eta began to rotate counterclockwise around it, veering first north and then northwest toward south Florida. The storm lost most of its central convection by later in the day as very dry air was entrained from the west. The exception to this was Eta's northern semicircle, which was still very moist, and brought flooding rains with tropical storm conditions into the Florida peninsula. That night, the center made landfall in the Florida keys with maximum sustained winds an estimated 65 mph. Continuing its arc, the storm veered west and soon after southwest across the Gulf of Mexico.
Early in the day on November 9, Eta had little thunderstorm activity to speak of, but a compact core redeveloped as shear diminished and the circulation developed a moisture envelope helping to shield it from the dry air without. That evening, the storm was centered off the coast of far western Cuba, bringing some rainfall there. However, it soon reversed course and moved northward again as the subtropical ridge north of it eroded on November 10. Eta was vigorous, but shear displaced the mid-level center well east of the surface circulation by that evening. After recovering overnight, the storm briefly restrengthened into a category 1 hurricane during the morning of November 11. Dry air overwhelmed the circulation soon after and Eta weakened as it moved northward offshore of the west Florida coast. Nevertheless, there was still a significant storm surge in the Tampa Bay area.
Soon, Eta turned northeast. The storm made its final landfall in northwestern Florida early on November 12 as a weakening tropical storm. It crossed the peninsula quickly and emerged into the Atlantic near the Florida border that afternoon. Eta merged with a front early the next morning off the coast of the Carolinas and became extratropical. Persisting for nearly 13 days, the storm was unusually long-lived for a November tropical cyclone.
The above image shows an infrared image of Eta near its peak intensity on November 3. Notice the remarkably large and intense central dense overcast around the eye.
Eta took an unusual winding track through the Caribbean and Gulf of Mexico due to alternating influences from ridges and troughs.
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