Hurricane Eta (2020)

Storm Active: October 31-November 13

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.

Hurricane Zeta (2020)

Storm Active: October 24-29

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.

Hurricane Epsilon (2020)

Storm Active: October 19-25

Early on October 16, a non-tropical low pressure system formed over the central tropical Atlantic, well to the east-southeast of Bermuda. The system moved little over the next few days, but gradually deepened. By October 19, thunderstorm activity had increased near the center. Advisories were initiated on Tropical Depression Twenty-Seven that morning. Initially, the center was exposed due to westerly shear, but conditions soon improved and the system strengthened. It was named Tropical Storm Epsilon a few hours later. Epsilon was the 26th named storm of 2020. 2005 was the only other year to see a 26th named storm (Delta, which formed on November 22 of that year). The name "Epsilon" was also used that year, for a cyclone which was named on November 29th.

Initially, the cyclone moved little, but early on October 20 a ridge built in and began pushing Epsilon northwest. The storm sat in a decidedly mixed environment: water temperatures where warm and there was plentiful atmospheric instability, but wind shear was still affecting the storm, and there were pockets of dry air in the circulation. Nevertheless, it fared well; a central dense overcast developed that morning, and an eye feature appeared intermittently later in the day. Accompanying these structural improvements was a corresponding increase in winds, and Epsilon rapidly intensified into a hurricane that evening.

The storm turned toward the west overnight and continued its intensification trend. The eye cleared out further and cloud tops in the small eyewall cooled. Aircraft reconaissance arriving during the afternoon of October 21 found that Epsilon was remarkably on the verge of major hurricane strength. A few hours later, it reached category 3 intensity, with peak winds of 115 mph and a central pressure of 951 mb. After a wobble, the center then assumed a north-northwest heading. The hurricane was running out of warm waters to traverse as it gained latitude, and, inevitably, began to decay. On October 22 it dropped back to category 1 intensity, though its satellite presentation was still impressive. Epsilon made its closest approach to Bermuda that afternoon, but was almost 200 miles east; gale force winds impacted the island, but little rain.

The hurricane followed a typical trajectory as it moved further into the mid-latitudes, recurving north and east and accelerating as it went. It underwent some normal structural changes too: the windfield broadened, the core became less compact, and the cyclone as a whole became asymmetric. Nevertheless, Epsilon maintained category 1 hurricane status through for the next few days. High surf and rip currents affected the northeast United States and Atlantic Canada. On October 25, the storm reached a forward speed of over 40 mph; by that time, it was north of 45 ° N, and the circulation was elongating. Satellite estimates indicated that Epsilon weakened to a tropical storm. Nevertheless, it maintained enough deep convection to be classified as tropical through the evening, when it finally completed extratropical transition. The next day, the remnants were absorbed by another powerful low.

The above image shows Epsilon near peak intensity over the open Atlantic. The storm exhibited a relatively small core inside a large mesoscale circulation; this structure is common for hurricanes in the subtropics.

Epsilon's path took it past the island of Bermuda well to the east, so it caused only minor land imapcts.

Hurricane Delta (2020)

Storm Active: October 4-10

Around October 1, a tropical wave entered the Caribbean. Associated thunderstorms were vigorous, but unorganized, and the disturbance continued west-northwestward. Within a few days, a low pressure center developed in association with the wave and it steadily consolidated. Late on October 4, Tropical Depression Twenty-Six was designated a little south of Jamaica. The depression was entering the western Caribbean, where it found nearly ideal conditions for development: the highest oceanic heat content in the Atlantic basin, low shear, and high humidity. It became Tropical Storm Delta, the 25th named storm of 2020, on October 5. This handily beat Gamma of 2005, the 25th storm of that season, which was named on November 15 of that year (a storm identified in post-season analysis in 2005 accounts for the 25th being Gamma, not Delta). It was also the second time the Delta named was used, after 2005.

Vigorous convection wrapped around the cyclone's center soon after it was named and rapid strengthening began; even a few dry slots did not slow it down for long. Delta became a hurricane that very evening. The cyclone was very compact, with a small central dense overcast. Quick deepening continued on October 6: the storm incredibly became a category 4 by midday, reaching its peak intensity of 145 mph winds and a pressure of 956 mb. The core was so compact that no eye was apparent on visible satellite imagery; nevertheless, analysis indicated there was a pinhole eye, only a few miles in diameter. Meanwhile, Delta sped up a bit toward the west-northwest.

The cyclone continued to exhibit curious behavior the next morning: convection was extraordinarily deep near the center, but the eyewall appeared to collapse, weakening the storm. As a result, Delta lost some steam before making landfall in the Yucatan Peninsula as a category 3 hurricane that night. The storm weakened further over land, but emerged back into the Gulf of Mexico by that afternoon. By this time, the hurricane was rounding the edge of a subtropical ridge, and turned more toward the north. The southern Gulf of Mexico was still quite favorable for development and the core reorganized. After bottoming out at category 1, Delta was on the rise again by late on the 7th.

An eye finally cleared out on October 8 as the storm vaulted back up to major hurricane intensity. Delta reached a secondary peak of 120 mph winds and a pressure of 953 mb (its lowest yet) that night, but it soon entered a region of smaller oceanic heat content in the northern Gulf. Simultaneously, a fall frontal system increased southwesterly shear drastically. This fortunately weakened the storm on October 9th. It turned north-northeast and then made landfall in western Lousiana that afternoon as a category 2. Though top winds were down, Delta brought strong winds, storm surge, and flooding rains to the same region that Hurricane Laura had devastated just months earlier. In addition, the storm was the 10th of the season to make landfall in the United States, the most on record.

Rapid weakening ensued once the storm moved inland, toward the northeast. It weakened to a remnant low by the morning of October 10 over western Mississippi. The remnants moved across the eastern U.S., eventually bringing downpours across the mid-Atlantic region a few days later.

The image above shows Delta as it regained major hurricane strength in the Gulf of Mexico on October 8.

Delta was yet another hurricane in the Gulf of Mexico, and a second hurricane landfall for western Lousiana alone.

Hurricane Gamma (2020)

Storm Active: October 2-5

During the last week of September, a tropical wave entered the Caribbean sea and moved westward, bringing precipitation to the Windward Islands as it passed by. A few days later, a broad low-pressure formed in association with the system over the western Caribbean. The nascent circulation received some help from a Central American gyre (CAG), a seasonal monsoonal broad low that tends to persist over the region, especially in May-June and October-November. By October 1, a large-scale swirl was evident, but there wasn't much convection near the center. However, on October 2, the system became well-defined enough to be classified Tropical Depression Twenty-Five well north of the coastline of Honduras.

The depression moved slowly northwest and strengthened into Tropical Storm Gamma that night. Gamma was only the second instance of a 24th named storm in recorded history after Beta of 2005, which was named on October 27 of that year (an unnamed subtropical storm in 2005 was the reason the 24th named storm was Beta, not Gamma). Conditions were very favorable for intensification and the system strengthened quickly as it approached the Yucatan peninsula. The next morning, Gamma was reported as reaching its peak intensity of 70 mph winds and a minimum pressure of 980 mb before making landfall in the northeastern Yucatan around noon local time.

Though the above intensity was the operational peak observed for Gamma, a more careful post-season analysis found that the storm in fact achieved category 1 hurricane status just before landfall, around 16:45 UTC October 3. The revised intensity was 75 mph winds and a pressure of 978 mb.

Land did not weaken the storm much; in particular, flooding rains continued as the center moved slowly north-northwestward. Overnight, Gamma emerged into the Gulf of Mexico. Waters were still warm, but shear increased, halting any reintensification by later on October 4. At the same tame, the trough that had been lifting the cyclone north moved on, leaving Gamma trapped under a weak developing ridge. As a result, the cyclone began meandering. Overnight, shear and dry air removed nearly all thunderstorm activity from the circulation and the storm quickly weakened. It also retreated southwest, back toward land, and weakened to a tropical depression on October 5. Soon, it became a remnant low. Before long, the low was absorbed by the approaching Hurricane Delta.

The above image shows Gamma at peak intensity on October 3, just before making landfall in the Yucatan Peninsula.

Unfavorable conditions prevented Gamma from strengthening further in the Gulf of Mexico; it instead took an unusual path and made a second landfall in the Yucatan.