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.

Subtropical Storm Alpha (2020)

Storm Active: September 18

Around September 14, a non-tropical low formed in the northeastern Atlantic, at around 45 ° N latitude. Unusually, it moved slowly south-southeastward over the following couple of days and then took a turn toward the east. This brought it over at least somewhat warmer water, and some more cloud cover developed near the center. By September 18, based on information from satellite imagery and Portugal-based radar, the system had developed a warm-core and a small, but well-organized convective pattern. As with some northeastern Atlantic cyclones from previous years, the tiny warm-core was still contained in a larger extratropical cyclone. A combination of these factors led to the naming of Subtropical Storm Alpha*, with maximum sustained winds estimated at 50 mph.

With Alpha's formation, 2020's parade of storms continued at a ridiculous pace. Alpha was the 22nd named storm, the earliest, and only second, 22nd storm ever recorded, after Wilma of 2005 which formed on October 17 of that year. After completing the hurricane names list for a given year, the Greek alphabet is used to name cyclones. 2020 was only the second year this was ever required, again after 2005. This wasn't the only strange thing about Alpha. Just a few hours after classification, the storm made landfall in central Portugal, with winds of 50 mph and a minimum pressure of 996 mb. Only Vince of 2005 had made landfall in Europe as a tropical or subtropical cyclone before in recent history, though many cyclones reach Europe after becoming extratropical.

After landfall, the low-level circulation was quickly weakened by its encounter with mountainous terrain, though this did not prevent heavy downpours from occurring in Portugal and western Spain. Less than 12 hours after operationally being classified a subtropical storm, Alpha became extratropical. Its remnants dissipated over northern Spain the next day.

*Note: Though operationally classified on September 18, the post-season analysis in 2021 indicated that Alpha in fact had become a subtropical storm the previous day.

The above images shows Subtropical Storm Alpha just before landfall in Portugal.

The precursor to Alpha spent several days in the northeast Atlantic as an extratropical cyclone (triange points above) and only became subtropical briefly (square points).

Tropical Storm Wilfred (2020)

Storm Active: September 18-20

On September 14, a low-latitude tropical wave moved across the coastline of the nation of Guinea into the eastern Atlantic ocean. The system tracked a bit north of west over the next several days at 10-15 mph and displayed some organized thunderstorm activity. By late on September 17, there was a low-pressure center, and satellite estimates indicated that gale-force winds were occurring. The next morning, a closed circulation developed, so the disturbance was upgraded directly to Tropical Storm Wilfred. Wilfred was the 21st named storm of the 2020 season, surpassing the known storm total for 1933, which had previously had the second-most storms on record with 20 (though totals before the satellite era were likely undercounted). Only 2005 had a 21st named storm previously, Vince, which formed on October 9 of that year, so Wilfred handily beat this record. 2005's 21st storm was a "V" not a "W" due to an unnamed tropical storm identified in post-season analysis. By the same token, Wilfred was only the second time the letter "W" was even used, after 2005's Wilma.

Ocean waters were pretty warm under Wilfred, but the ouflow of massive Hurricane Teddy far to the northwest was already causing increasing shear over the cyclone. Convection became rather disorganized overnight and an uncoved low-level swirl appeared on visible satellite imagery on September 19. Nevertheless, Wilfred maintained minimal tropical storm intensity through the day. Soon after, weakening began and it became a tropical depression. Late that night, it dissipated.

The above image shows Wilfred shortly after formation.

Wilfred spent only a few days as a tropical storm before it succumbed to unfavorable conditions.

Tropical Storm Beta (2020)

Storm Active: September 17-22

During the second week of September, a trough of low pressure formed over the eastern Gulf of Mexico. It produced some showers, but otherwise did not show signs of development. Fortunately for the disturbance, it moved extraordinarily slowly, drfiting generally westward for five days until it was off the coast of Texas. Meanwhile, Tropical Depression Nineteen moved into the Gulf and strengthened into Hurricane Sally, which made conditions near the trough unfavorable for cyclonogenesis. As before, though, it wasn't going anywhere. It next dipped south toward the Bay of Campeche, and was vigorous enough to produce heavy rain near the coastline of southern Texas and Mexico as it went. Around the 15th, a surface low-pressure center formed and gradually deepened. It moved little, but thunderstorm activity became concentrated, culminating in the formation of Tropical Depression Twenty-Two during the evening of September 17.

A trough over the United States tugged the depression slowly toward the northeast or north-northeast over the next day toward the central Gulf of Mexico. Convection increased some, but the center was a bit elongated. Nevertheless, measurements indicated the presence of tropical storm force winds on the 18th, so the depression strengthened into Tropical Storm Beta. Oddly, two additional storms had been named in the time between Tropical Depression Twenty-Two formed and when it strengthened to a tropical storm; these two took the names Wilfred and Alpha, leaving Beta for our depression. Beta was the 23rd named storm of 2020, only the second time this occurred after 2005's Alpha, which was named on October 22 of that year (note that 2005 had an unnamed subtropical cyclone identified after the season's conclusion, explaining why Alpha was the 23rd storm).

Beta strengthened some that evening and its minimum pressure dropped a fair bit. It was still being affected by shear from the steering trough, which exposed the center of circulation overnight. The displaced moisture brought steady rain to southern Lousiana for a day or so. On the 19th, the trough lifted out to the northeast and Beta missed its escape route. Instead, it turned westward and slowed to a crawl as a new ridge built in to the north. Wind shear decreased some too, allowing convection to recover the center that afternoon. The storm had a new threat to deal with: a dry continental airmass approaching from the west. It did a decent job combating this and maintained a central dense overcast. On the 20th, Beta reformed a bit farther west and picked up some speed in that general direction, maintaining its intensity as a moderately strong tropical storm.

By September 21, the system neared the central Texas coastline. Steering currents were collapsing again and Beta slowed down, bringing an extended period of frequent rainfall to some parts of southeast Texas. The storm weakened a bit too due to land interaction. It officially made landfall that night and weakened to a tropical depression during the morning of September 22. Dry continental air eliminated nearly all deep convection, but Beta still was a wet storm at the surface: the Houston area received over a foot of rain from the storm. There wasn't much to steer the cyclone, but it started moving east-northeast over land that afternoon, tracing a weak upper-level trough. The cyclone was far enough from the coast that weakening continued, and it degenerated into a remnant low late on September 22. This low brought moderate rainfall across the south, Ohio valley, and ultimately mid-Atlantic as it moved northeastward for the next several days before dissipating.

Beta was a well-organized tropical storm in the satellite image above, taken on September 20.

The storm took a slow, meandering track through the Gulf of Mexico before making landfall in Texas.

Tropical Storm Vicky (2020)

Storm Active: September 14-17

On September 11, a system emerged off of Africa that was partially associated with a tropical wave that became Teddy in a few days time. An area of vorticity split off and tracked more northward. The next day, it moved over the Cape Verde islands, bringing isolated heavy rainfall. Soon after that, a low pressure center appeared and on September 14, the system managed to develop into Tropical Depression Twenty-One northwest of the Cape Verde islands. A linear outflow boundary approaching from the northwest signaled the arrival of less favorable atmospheric conditions, but the depression nonetheless strengthened into Tropical Storm Vicky later that day. Vicky was the earliest twentieth named storm, or "V" storm, after Tropical Storm Tammy of 2005, which formed on October 5 of that year. Tammy was the twentieth storm of 2005 due to an unnamed storm that was identified in post-season analysis. The 2005 season was also the first to use the letter "V", making 2020 the second such occurrence.

Shear came roaring in out of the west and exposed the center of circulation soon after, but Vicky strengthened a bit more to reach peak winds of 50 mph late that evening. The next day, the system turned toward the west-northwest but persisted as a tropical storm. It seemed that other aspects of the upper-air environment (as well as warm ocean temperatures) were enough to offset the shear a little. Nevertheless, weakening eventually commenced on September 16. The outflow of the nearby and powerful Hurricane Teddy hastened Vicky's demise and it became a remnant low on September 17. Moving south of west now, the low continued on a little further until dissipation occurred.

The image above shows Vicky over the eastern Atlantic, with the Cape Verde islands in the bottom right.

Vicky moved into a highly unfavorable environment after forming and hence was a short-lived tropical storm.

Hurricane Teddy (2020)

Storm Active: September 12-22

On September 10, a fairly well-organized tropical wave entered the Atlantic from the east. It had an ample amount of moisture associated with it and moved steadily westward south of the Cape Verde islands. But as with several previous systems in the 2020 season, there was another tropical wave right on its heels, which had an influence on the first's ultimate development and track. That second wave ultimately became Tropical Storm Vicky. By the next day, the system had a low-pressure center associated with it. Convection wrapped halfway around the center in a curved band over the western semicircle; on the 12th, further organization led to the designation of Tropical Depression Twenty.

There was a little bit of northerly shear affecting the depression, which kept the convection confined to the southern semicircle throughout the next day. Further, the large circulation was still partially embedded in a monsoon trough located in the Intertropical Convergence Zone, which slowed intensification in the short term. Eventually, thunderstorm activity became more concentrated and began to wrap around the circulation. The depression was upgraded to Tropical Storm Teddy early on September 14. This was the earliest nineteenth, or "T" storm, surpassing the record set by the unnamed Azores subtropical storm of 2005, which formed on October 4 of that year.

Teddy had a lot going for it: light shear, warming waters, and plenty of humidity. It began to intensify quickly later that day as it continued just north of west, bringing it to a high-end tropical storm. The increase in winds paused on September 15 as the system took some time to build an eyewall and fight off incursions of dry air. Teddy turned northwest and strengthened again overnight to category 2 hurricane strength. It was a large system, with excellent outflow in all directions but the west. The storm passed well to the northeast of the Lesser Antilles on the 16th, sparing them of any impacts save large waves. Starting that evening, more deep convection developed and wrapped around the eye, which itself warmed and cleared out by early on September 17. Teddy became a very powerful hurricane, rocketing up to category 4 strength by the afternoon and reaching its peak intensity of 140 mph winds and a pressure of 945 mb.

The cyclone underwent some structural changes overnight and became a bit less defined, leading to a bit of weakening. Aircraft and satellite measurements indicated the next day that an eyewall replacement cycle (EWRC) began, in which a new outer eyewall formed, contracted, and eventually replaced the old. These EWRC's are typical for strong hurricanes. They usually lower its top winds, but expand its windfield, and indeed Teddy's wind radii had increased by that afternoon, even though it was down to a category 3. The new outer eyewall became more complete over the next day as the cyclone fluctuated in intensity, but Teddy's EWRC was quite slow. By the afternoon of September 19, the inner eyewall had finally collapsed for the most part, leaving the outer one surrounding a much larger, ragged eye.

Teddy had taken a turn back toward the west-northwest that day, but it soon resumed its northwest course. Environmental factors were becoming less conducive for a hurricane: the storm was tracking over the cold wake left by Hurricane Paulette about a week prior, the air was becoming drier, and wind shear was increasing. As a result, Teddy's eye filled in and it weakened to a category 2. The storm rounded the edge of the retreating subtropical ridge that evening, turning north and then east of north. On September 21, this fortunately brought the center well east of Bermuda, which had just had a direct hit from Paulette. Even so, Teddy was large enough to bring tropical storm conditions to the island from 150 miles away.

The storm began a rather complex interaction with an frontal low approaching from the northwest that day. The lows rotated a bit around one another, accelerating Teddy northward and bending its track back to the left. At the same time, warm Gulf stream waters and a baroclinic energy boost deepened the hurricane even as it began to dsiplay extratropical characteristics. The minimum central pressure dropped back to 950 mb at its lowest during the morning of September 22. By that time, Teddy was a few hundred miles south of Nova Scotia, but was slowing down. The cyclone was certainly a hybrid of tropical and extratropical, though it had enough of a warm core to still be considered a hurricane. Maximum winds decreased to category 1 strength, but Teddy was now extremely massive: rain extended as far west as eastern Maine and tropical storm force winds reached over 300 miles in every direction from the center, including over 500 (!) miles in the northeast quadrant. The entire island of Nova Scotia was within the wind field.

Luckily, Teddy soon lost its baroclinic energy source and also moved over much colder waters, bringing about a steady decay of the cyclone, as well as extratropical transition late that night. The low that had been Teddy made landfall in central Nova Scotia with maximum winds of around 65 mph on September 23 and continued into the Gulf of St. Lawrence later that day. The low was absorbed by a larger system on the 24th.

The image above shows Teddy as a major hurricane over the open Atlantic.

This image is Teddy on September 22 shortly before completing extratropical transition. It was a large, hybrid cyclone, ranking among the largest recorded by gale force wind diameter. The U.S. northeast is visible at top left, along with some smoke in the upper atmosphere from the 2020 California wildfires.

Teddy hit Nova Scotia as an extratropical cyclone, but by then it was weakening significantly, so imapacts were limited.