Hurricane Ida (2021)

Storm Active: August 26-September 1

Around August 23, a tropical wave that had entered the Atlantic basin back in mid-August began to generate some concentrated thunderstorm activity as it crossed into the Caribbean Sea. Most of the vorticity associated with the system was quite far south, though, and still embedded in the intertropical convergence zone. On the 25th, a broad low formed along the wave axis. In part due to the influence of an upper-level trough over the northwest Caribbean, the system consolidated farther north, culminating in Tropical Depression Nine the next day. At that point, it was located just southwest of Jamiaca and was lifting to the north-northwest.

Initially, most of the rain was displaced north and east of the low-level circulation, causing considerable flooding in Jamaica. The storm was over very warm water and in an environment of high relative humidity, though, so it wasted no time in organizing. By that afternoon, it was upgraded to Tropical Storm Ida. Overnight, vigorous convection began a trend of rapid intensification, which continued through August 27. By the time its center was baring down on western Cuba that afternoon, Ida was already a hurricane. The system first crossed over Isla de la Juventud, before making landfall in mainland Cuba that evening as a category 1. Land interaction barely slowed down the storm, and before long it had continued northwest into the Gulf of Mexico.

Conditions in the Gulf were nearly ideal: wind shear died down even more, the atmosphere was moist, and Ida's path took it directly over a warm eddy that had some of the highest oceanic heat content in the Atlantic basin. Intensification was at first slow and steady as the cyclone cleared out an eye on the 28th and became a category 2 hurricane. During the final day of its approach to the Gulf coast, however, Ida exploded. The minimum central pressure was observed to drop from 985 mb to 929 mb in just 24 hours, bringing the hurricane to category 4 strength with top sustained winds of 150 mph. The storm had also grown significantly and carried an enormous storm surge into southeast Louisiana upon landfall during the early afternoon of August 29. These top winds matched those of Laura a year earlier, tying the record for the highest recorded in a Louisiana landfall.

The storm brought hurricane-force winds well inland as it turned north and weakened. Early on August 30, it was downgraded to a tropical storm and crossed into Mississippi. It became a tropical depression and turned northeastward that evening. Even after bringing 10+ inches of rain to a large swath of Louisiana and Mississippi, Ida caused more tremendous rainfall on its journey toward the Atlantic. An interaction between it and an approaching cold front led to the cyclone's post-tropical transition on September 1, but more importantly led to enhanced precipitation over parts of the mid-Atlantic and widespread flooding. The next day, Ida's remnants moved over Atlantic Canada before dissipating.

The above image shows Ida at peak intensity as a strong category 4 hurricane just before landfall in Louisiana.

Ida's track took it directly across areas of high oceanic heat content in the northern Gulf of Mexico; this contributed to the rapid intensification just before landfall.

Hurricane Henri (2021)

Storm Active: August 15-23

On August 14, a non-tropical low developed north-northeast of Bermuda in the subtropical Atlantic. It developed surprisingly quickly and had an impressive, if small, satellite signature by the next afternoon. The low was navigating around a high pressure ridge to its west, which was located over the U.S. east coast. This clockwise flow unusually pushed the system south, bringing it just east of Bermuda late on August 15. At that time, it was designated Tropical Depression Eight. Despite its proximity to the island, Eight was so small that Bermuda experience little more than showers.

Anomalously warm waters allowed the system to intensify and become Tropical Storm Henri by the afternoon of August 16. The storm continued its loop around Bermuda and turned west-southwest on the 17th. Curved bands near the center became better defined throughout that day and the storm steadily strengthened. Hints of an eye appeared on satellite imagery on August 18, bringing Henri to the verge of hurricane strength. However, wind shear out of the north increased that evening, squashing the cyclone's cloud shield and halting intensification. The storm proved resilient since it had access to warm ocean temperatures and ample moist air, and only weakened slightly over the next day in the face of 25 knots of shear.

Meanwhile, it continued westward along the 30°N parallel. As the shear abated during the afternoon of August 19, Henri's structure began to improve again. The next morning, it began a long-anticipated turn toward the north as the ridge steering it collapsed and was replaced by a trough along the eastern seaboard. The next morning, Henri strengthened into a hurricane as it accelerated north-northeastward. An eye even opened up briefly on August 21, though it was a bit ragged, and most deep convection was south and east of the center.

Normally, a cyclone in Henri's position would have recurved out to sea, but the setup in this case was quite different. A ridge was building to the system's east, while simultaneously an elongated upper-level low over the mid-Atlantic exerted a pull toward the west. This allowed Henri to defy climatology and continue northward toward land. While located over the Gulf stream, the storm deepened a little more, reaching its peak intensity of 75 mph winds and a minimum pressure of 986 mb early on August 22. The storm began to slow down upon nearing the coast, yet another unusual feature of its track: tropical cyclones that do manage to hit the northeast are typically accelerated to forward speeds of over 30 mph by mid-latitude jet streams. Henri, in contrast, was hemmed in by the ridge and continued to swirl around the upper-level low, turning left around landfall.

Colder waters weakened the storm down to a strong tropical storm before the center made landfall along the coast of Rhode Island that afternoon. Along with some minor storm surge, Henri was primarily a rainmaker. It looped slowly west, weakened to a tropical depression, and stalled over New York state before turning east on August 23. The storm finally became post-tropical that afternoon. What was left of Henri accelerated eastward and moved out to sea the next day.

The above image shows Henri as a minimal hurricane moving north toward New England on August 22.

It's hard to overstate how odd Henri's track was: the cyclone even originated in the subtropics east of Bermuda. For a storm with such an origin to loop back west and hit North America was unprecedented.

Hurricane Grace (2021)

Storm Active: August 13-21

On August 9, a tropical wave entered the Atlantic and moved quickly westward. From the start, the system produced an impressive area of thunderstorms, but its quick motion slowed down development. Four days later, it became organized enough to be designated Tropical Depression Seven well east of the Lesser Antilles. The storm covered ground rapidly, and was approaching the Windward Islands by the next day when it was upgraded to Tropical Storm Grace. Despite the upgrade, aircraft reconaissance indicated that the cyclone had serious structural issues: the low-level center was very ill-defined and difficult to even identify. In fact, sometime around August 14, Grace might have opened up into a trough of low pressure.

Nevertheless, the system was maintained as a tropical cyclone through the 14th, though it did weaken to a depression south of Puerto Rico. Disorganized thunderstorms extended from north of Puerto Rico to well south of the Dominican Republic by the next day along the former tropical wave axis. There were several areas of vorticity, but Grace consolidated some toward the southern end that evening. On August 16, the center was better defined and Grace clipped the souternmost point of the Dominican Republic, still as a tropical depression. Heavy rainfall in Hispaniola led to the risk of mudslides and flooding.

Land interaction lessened from that point and Grace slowly became a bit better organized as the strong subtropical ridge continued to push it just north of west. The center passed just south of Haiti that night, thankfully sparing the country the heaviest rainfall. Early on August 17, the storm regained tropical storm strength just in time for a direct hit on the island of Jamaica. The small country was not enough to significantly disrupt the cyclone, and in fact it strengthened gradually and grew in size that day. By the time it emerged off the west coast of Jamaica, Grace was a strong tropical storm.

Now over open water, the storm could tap into the highest oceanic heat content anywhere in the Atlantic. Relative humidity levels near Grace were only moderate (in the 50-60% range), which slowed the storm's intensification with occasional dry air intrusions. Otherwise, there was little to stop its strengthening and the cyclone was upgraded to a hurricane on August 18. The storm reached its first peak intensity of 80 mph winds and a pressure of 986 mb overnight before making landfall in the northern Yucatan peninsula before sunrise on August 19. The storm weakened over land and became a tropical storm late that morning, but maintained a vigorous circulation and emerged as a still strong tropical storm into the Bay of Campeche that evening.

Atmospheric conditions were better in the southern Gulf of Mexico than they had been over the Caribbean, with ample moisture in the air. It didn't take long for Grace to take advantage. By the morning of August 20, it had regained hurricane strength and extremely deep convection began firing north and east of the center. This managed to wrap all the way around by the afternoon and the cyclone rapidly intensified. Remarkably, it went from a category 1 to a high-end category 3 by late that night, becoming the first major hurricane of the 2021 season. An eye feature began to clear out just before Grace made its final landfall in Mexico very early in the morning on August 21. At landfall, Grace had an estimated peak intensity of 125 mph sustained winds and a minimum central pressure of 962 mb. This was the highest windspeed in a recorded landfall along the Mexican Gulf coast south of Tampico, surpassing Karl of 2010.

After moving inland, the mountainous terrain of Mexico quickly weakened the cyclone, bringing it to a tropical storm by that afternoon. Grace dissipated entirely by that evening after bringing heavy precipitation even as far as Mexico City. The remnants continued into the eastern Pacific ocean and ultimately reformed into a tropical storm early on August 23. Since the circulation had dissipated and reformed, however, the cyclone received a new name: Tropical Storm Marty. Marty persisted for only a few days before becoming post-tropical.

The above image is an infrared satellite view of Grace on the night of its final landfall in Mexico as a major hurricane.

A strong subtropical ridge kept Grace moving on a steady trajectory just north of west for almost its entire existence.

Tropical Storm Fred (2021)

Storm Active: August 10-14, 15-18

Around August 1, a tropical wave left Africa and entered the Atlantic. The wave did not develop much over the following 6 days, as conditions were not favorable and there was another wave closeby to the east. A few hundred miles east of the Windward Islands, the disturbance won out over its neighbor and developed a broad low-pressure center. By August 9, the system was located just north of Barbados. It moved west-northwestward into the Caribbean soon after. The circulation was quite impressive on satellite imagery: it had well-defined banding features and a clear spin. Nevertheless, it wasn't until that night that a center of circulation formed and it was upgraded to Tropical Storm Fred south of Puerto Rico.

Fred was dealing with dry air to its west, but its immediate problem was land interaction. After missing Puerto Rico to the south, the storm hit Hispaniola directly on the 11th, passing directly over the center of the island by that evening. The circulation was significantly disrupted and Fred weakened to a tropical depression. Though the cyclone was back over water overnight, there was some wind shear out of the west and it left most of its thunderstorm activity behind. It took most of the day on August 12 for Fred to slowly recover as it paralleled the northern coast of Cuba.

More land soon interrupted this reorganization, as Fred moved over central Cuba the next day. In fact, the low-level circulation became impossible to locate by that evening. Sometime soon after, Fred degenerated into a trough of low pressure and ceased to be a tropical cyclone temprorarily. However, heavy rains were still widespread across the region, so this changed the overall imapcts little. The system's remnants moved west-northwestward into the Gulf of Mexico on August 14 and began to organize again. The wind shear was a bit more favorable and ocean temperatures were warm as ex-Fred rounded the edge of the subtropical ridge and moved north-northwestward well west of Florida. On August 15, the circulation closed off and the system regained tropical storm status.

At first, the center was exposed on the western edge of the convection, but a semicircular core blossomed that evening and Fred began to strengthen. This trend continued through the morning of August 16 and Fred turned just east of north. By that time, the storm had a classic "comma" appearance, with a large curved band on the east side and a dry slot just southeast of the center. Some dry air intrusion via this slot capped Fred's intensity, but it still managed to become a strong tropical storm with top sustained winds of 65 mph before its final landfall in the Florida panhandle that afternoon. After landfall, the cyclone weakened steadily but brought a wide swath of heavy rain to the U.S. southeast and up the Appalachians. On August 17, Fred weakened to a tropical depression as it accelerated north-northeastward.

The storm continued to bring severe weather northward and eventually transitioned into a post-tropical storm over West Virginia the next day. Even after becoming post-tropical, ex-Fred brought severe weather into New England. It finally dissipated around August 19.

The above image shows Fred at peak intensity just before landfall in the Florida panhandle.

Fred's intensity was kept in check by land interaction for most of its lifetime.

Hurricane Elsa (2021)

Storm Active: June 30-July 9

On June 27, a vigorous tropical wave left the African coastline. It stuck to the low-latitudes away from any Saharan dry air and quickly moved westward. By the 29th, it had developed a broad low pressure center and was showing signs of organization. Things really ramped up the next day when spiral banding features became evident, though satellite data indicated that there was still only a sharp trough at surface level (winds flowed around a line oriented north to south, rather than around a center of circulation). Moist equatorial inflow from the southwest generated some more spin and helped the system reach tropical depression status that night.

By the morning of July 1, the cyclone was producing gale force winds and was upgraded to Tropical Storm Elsa. Remarkably, Elsa broke the record for earliest fifth named storm (or "E" storm) that had been set just one year previously by 2020's Tropical Storm Edouard on July 6 of that year. It was still early in the summer and the tropical trade winds that blow east to west were very strong: Elsa reached a remarkable forward speed of 29 mph toward the west-northwest that afternoon. Such forward speeds are rare in the tropics, as opposed to the mid-latitudes where they are more common. Typically, this speed would make it hard for thunderstorm activity to "keep up" with the system's center, but otherwise favorable conditions allowed Elsa to intensify (albeit gradually) throughout the day.

Overnight, a circular central dense overcast blossomed and the storm's core became much better defined. This allowed a faster burst of strengthening that continued into July 2 and brought Elsa to hurricane strength that morning. The center passed just south of the island of Barbados and crossed the Windwards into the Caribbean sea later that morning. Elsa became a hurricane farther east in the tropics than any other recorded storm so early in the calendar year since 1933. It also was the fastest moving hurricane ever recorded in the tropics, at one point reaching 31 mph. However, after reaching a peak intensity of 85 mph winds and a pressure of 991 mb that afternoon, the storm's rapid forward speed finally caught up with it: the center of circulation outrun the associated thunderstorm activity and convection collapsed.

As a result, some weakening occurred overnight and into the morning of July 3, putting Elsa at high-end tropical storm strength. It passed well south of Puerto Rico and the Dominican Republic, and paralleled the southern coast of Haiti that afternoon. Though it stayed offshore, torrential rainfall impacted the southeastern peninsula. The cyclone approached the western edge of the steering ridge that evening and finally slowed down, allowing new deep convection to develop over the center of circulation. And yet, Elsa continued to baffle: even as the satellite presentation improved, aircraft reconnaissance indicated that central pressure continued to increase, rising to 1009 mb on July 4. Such a pressure is more typical of a tropical depression than a strong tropical storm!

Regardless, more rain was in store as the storm passed just north of Jamaica that day. Elsa then slowed even more and turned northwest toward central Cuba. The system remained fairly disorganized but held nearly steady in intensity up to landfall in Cuba on July 5. Fortunately, impacts in the country were not that severe. That evening, the center emerged into the Gulf of Mexico. Being back over water allowed the cyclone to again build a core, but it was slow going; wind shear out of the southwest kept the low-level circulation exposed and the thunderstorm activity primarily to the northeast. Nevertheless, slow strengthening occurred as Elsa moved north toward Florida on the 6th.

Satellite imagery during that afternoon indicated that the shear vector was now from the south - a bit more favorable for intensification as the center was moving northward. Hints of an eye appeared on radar and Elsa regained hurricane strength that evening. By that time, the outer bands were affecting western Florida, but the compact core meant that most impacts stayed offshore. Overnight, dry air invaded the core and the system weakened again to a tropical storm. It still had maximum sustained winds of 65 mph, however, when it made landfall in northwestern Florida late in the morning of July 7.

Elsa brought moderate flooding to the southeast as it began to curve northeastward, passing inland into Georgia. At first, it weakened over land, but it maintained an impressive circulation. It remained a tropical storm and even restrengthened some as it passed over the Carolinas on July 8. By the evening, flooding rains had spread northward into the mid-Atlantic states. The cyclone's center exited the coast briefly overnight before making further landfalls in New England during the morning of July 9. By that time, it was losing tropical characteristics as it continued to accelerate northeastward. At last, Elsa completed its long journey and became post-tropical that afternoon. Its remnants passed through Atlantic Canada and ultimately dissipated over the north Atlantic.

The above image shows Elsa near peak intensity passing over the Windward Islands.

Elsa had impacts all the way across the Caribbean and all the way up the eastern coastline of North America.

Tropical Storm Danny (2021)

Storm Active: June 28-29

Around June 26, a surface trough well southeast of Bermuda was producing some scattered thunderstorm activity as it moved rather quickly west-northwestward. Ocean waters beneath the disturbance weren't especially warm, nor the atmosphere too moist, but some gradual organization occurred nevertheless. Early on the 28th, it was apparent that a well-defined center of circulation had developed, and the system was classified Tropical Depression Four. At the time, it was a very small, sheared system off the South Carolina coastline.

The depression's track was a little unusual: a strong high was situated over the eastern seaboard, which kept Four moving quickly west-northwestward toward land. The system had a rather high pressure reading of 1013 mb due to ambient high pressures in the surrounding area and this shallowness also contributed to its fast forward motion in the strong low-level flow. In any case, warm waters near the coast allowed the storm to strengthen a bit around landfall and it became Tropical Storm Danny. It made landfall during the evening of the 28th a little north of the Georgia-South Carolina border. Because the cyclone was small, heavy rain and tropical storm force winds were confined to a small region.

After landfall, the storm deterioriated rapidly. It weakened to a tropical depression overnight and dissipated the next morning over central Georgia.

The above image shows the tiny Tropical Storm Danny just before landfall in South Carolina.

Danny was another short-lived tropical cyclone because it formed so close to land.

Tropical Storm Claudette (2021)

Storm Active: June 19-21

Around June 12, a broad area of low pressure associated loosely with the central American gyre (CAG) to the south formed in the southern Bay of Campeche. It was producing occasional bursts of thunderstorm activity and some spin was evident on satellite imagery, but the size of the system and its proximity to land inhibited tropical cyclone development. The low barely moved for the next several days. It finally made some northward progress starting on June 17 toward a weakness in the subtropical ridge. It was quite disorganized though, with the only convection a band northeast of the ill-defined center.

The disturbance changed little the next day as it approached the northern coastline of the Gulf of Mexico, though aircraft and satellite measurements indicated that it possessed sustained wind speeds to gale force. Heavy rain swept across southeastern Louisiana as the system approached. It was only early on the 19th, as the center was moving over land, that it finally became organized enough to be named Tropical Storm Claudette, with peak winds of 45 mph. However, the classification of the system changed its impacts little; flooding was the primary concern as it moved inland and turned northeast, crossing into Mississippi. Claudette weakened to a tropical depression later on June 19.

An approaching cold front steered the system east-northeast across the southeast United States, bringing scattered downpours and gusty winds with it. The next day, as Claudette approached the Atlantic, the proximity to water fueled some convective redevelopment and the cyclone began to strengthen again. It became a tropical storm again on June 21 near the coast. Forunately, it was fast-moving, and was swept out along the mid-latitude westerlies in short order. After passing over the Gulf stream, it encountered cooler waters. The center was still not well-defined, and Claudette lost its identity as it sped away from land that evening.

As with many storms forming from CAG's, Claudette was a rather messy cyclone; it never looked completely tropical. 2020's Tropical Storm Cristobal was similar in this regard, and was another June CAG storm. Such systems develop most often in June or October/November.

Unusually, Claudette spent more time over land as a tropical cyclone than it did over water!

Tropical Storm Bill (2021)

Storm Active: June 14-15

On June 13, a non-tropical low pressure center developed just off the coast of the southeastern United States in association with a stalled warm front. It moved northeastward a little farther from land and encountered the hot waters of the Gulf stream; sea surface temperature anomalies were extremely high just off of the North Carolina. By the morning of June 14, a burst of convection had covered the low. It was designated Tropical Depression Two shortly after.

The system strengthened steadily during the next day despite moderate wind shear. As a result it was upgraded to Tropical Storm Bill. It also accelerated significantly on its northeastward path. By the afternoon of the 15th, Bill had reached its peak intensity of 60 mph winds, but was already beginning extratropical transition. The central thundestorm activity was displaced from the center by strong upper-level winds and the cyclone became extratropical that evening.

The above image shows Bill as a tropical storm on June 15.

Bill formed near land, but rapidly moved out to sea during its brief stint as a tropical cyclone.

Tropical Storm Ana (2021)

Storm Active: May 22-23

Around May 20, a low pressure system developed east of Bermuda. At first, it was non-tropical, an elongated low with an attached frontal boundary on the southeastern side. However, it acquired some tropical characteristics as it moved generally in a counterclockwise loop over the next day or two. Ocean temperatures were below the usual threshold for supporting tropical development, but some cool air aloft drove enough instability for thundestorm activity to pop up near the low's center by early on May 22. The system was already producing gale force winds by this point. It had a small radius of maximum winds, a characteristic indicative of a tropical cyclone, but it was embedded in an upper-level low. Because of the latter, it was named Subtropical Storm Ana that morning, the first named storm of the 2021 Atlantic hurricane season. With Ana's formation, 2021 marked the seventh consecutive season with a storm forming before the traditional start date of June 1.

Later that day, Ana's center came within 175 miles (280 km) of Bermuda to the northeast, but the central area of thunderstorms was so small that the island received little more than showers and gusty winds. That evening, Ana began a more definite movement toward the northeast as it felt the flow of an upper-level trough exiting Atlantic Canada. This took the small storm away from the safe haven of low wind shear under its upper-level low. Related to this, Ana transitioned to a fully tropical storm by early on the 23rd. This didn't do much to alter the storm's fate; moving northeast over even colder waters and harsh shear, it weakened to a tropical depression and then degenerated to a remnant low that evening.

The image above shows Ana as a subtropical storm shortly after naming.

Ana was a small and short-lived cyclone with no land impacts.

Professor Quibb's Picks – 2021

My personal prediction for the 2021 North Atlantic Hurricane season (written May 16, 2021) is as follows:

17 cyclones attaining tropical depression status,
16 cyclones attaining tropical storm status,
8 cyclones attaining hurricane status,
5 cyclones attaining major hurricane status.

I predict that the 2021 season will feature above-average activity, though not at the pace of the record-breaking 2020 season. Every decade, the NOAA revises the 30-year averages for number of cyclones to reflect new data and better track climate change; the 1991-2020 averages were 14.4 tropical storms, 7.2 hurricanes, and 3.2 major hurricanes, up from 12.1 tropical storms, 6.4 hurricanes, and 2.7 major hurricanes in the 1981-2010 period. My forecast therefore exceeds this new average, but not by a great deal.

In making this prediction, I first consider the El Niño Southern Oscillation (ENSO) index, which measures sea surface temperature anomalies in the equitorial Pacific ocean. Warmer than normal temperatures (El Niño) correlate to decreased Atlantic activity (and increased Pacific activity) and cooler than normal temperatures (La Niña) the opposite. A La Niña event, the strongest in nearly a decade, is currently ongoing and began in the latter half of 2020, contributing to the frenzy of activity of that season.

Nevertheless, recent data indicate that the La Niña is waning and models generally show this should continue into the summer (see the above graph - the vertical axis indicates the relevant temperature anomaly). However, the ensemble average still indicates ENSO neutral to negative conditions. Overall, I predict lingering La Niña effects will still boost activity this year.

In the same vein, most of the 21st century has been in the positive phase of the theorized Atlantic Multidecadal Oscillation, which has led to elevated sea surface temperatures, and, generally, more hurricanes. It's hard to disentangle such long-term climate cycles from modern anthropogenic global warming, and the headline regarding ocean temperatures is largely the same as the last few years: the Atlantic, Caribbean, and Gulf of Mexico will be warm, even by recent standards. The largest anomalies are likely once again to be in the subtropical Atlantic.

A few other factors that influence tropical cyclone formation are relative humidity of the atmosphere and wind shear. A moist atmosphere allows nascent tropical disturbances to develop thunderstorm activity and grow. Wind shear refers to a change in wind direction and speed between the lower levels and upper levels of the atmosphere; higher values of wind shear hamper tropical cyclones because they prevent them from becoming or remaining vertically stacked. Long-term models can give at least some sense of what average conditions to expect during peak hurricane season (see above: the top figure shows expected precipitation anomalies for August-October 2021 and the bottom zonal wind shear anomalies for the same period). Using these and a few other factors, I'll give a finer analysis of the risks by region. My estimates are on a scale from 1 (least risk) to 5 (most risk).

U.S. East Coast: 3
A mixed bag of conditions leaves the U.S. east coast with middling risk. Indications are that the summer will be wet in this region, with ample heat and moisture for tropical cyclones to form and strengthen. On the other hand, the Bermuda high looks a bit weaker than usual given the neutral to negative ENSO index, suggesting that hurricane tracks might veer east out to sea. With neutral ENSO more likely late in the year, expect fall fronts to reduce east coast risk by the end of September; if there are landfalls here, it will be in the front end of the season.

Yucatan Peninsula and Central America: 2
After a devastating 2020, these areas will (hopefully) experience much less hurricane activity this year. Preciptation forecasts (see above) anticipate a drier west Caribbean, and while wind shear will be lower than average in most of the basin, the same is not true for the eastern Caribbean, where threats to the Yucatan and Central America could form. If hurricanes do affect this region, I'd expect it to be in October and November; rapid intensification episodes close to land are the primary risk.

Caribbean Islands: 5
Even in the most active season in history last year, tropical cyclone activity in the main development region in the tropics between the Windwards and Africa was lackluster. Things will probably be different this year. The dusty Saharan Air Layer (SAL), and its suffocating effect on east Atlantic tropical waves, looks to be less prominent than usual. Furthermore, shear is low, temperatures are warm, and precipitation anomalies are at least around neutral over the tropical Atlantic. This could open the door for some long-track hurricanes à la 2017. The biggest question mark is whether these will avoid land or not, but everywhere from the Lesser Antilles to the Bahamas should be on high alert.

Gulf of Mexico: 4
Though maybe a little dry, the Gulf may have the highest sea surface temperature anomalies outside the subtropical Atlantic this summer. Storms forming near the Bahamas and homegrown hurricanes in the Gulf are both likely to occur at sometime in the year, putting this region at above-average risk.

Overall, I expect the 2021 Atlantic hurricane season to be above-average, though not exceptionally so. Nevertheless, this is just an amateur forecast. Individuals in hurricane-prone areas should always have emergency measures in place. For more on hurricane safety sources, see here. Remember, devastating storms can occur even in otherwise quiet seasons.



Sources: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf, https://www.tropicaltidbits.com, https://www.trackthetropics.com/saharan-air-layer-sal-tracking/, https://www.wunderground.com/hurricane/articles/wind-shear-explainerhttp://www.webberweather.com