The Atlantic was roiled with a remarkable number of storms on Wednesday, September 16, 2020: a landfalling category 2 hurricane in the U.S. (Sally), two other category 2 hurricanes in the central Atlantic (Teddy and Paulette), Tropical Storm Vicky in the eastern Atlantic, a subtropical storm in the Mediterranean (called a “medicane”) named Ianos, and three “Invests” scattered across the Atlantic with the potential to develop into named storms by this weekend.

Teddy strengthens in central Atlantic; potential déjà vu encounter for Bermuda

Sprawling Hurricane Teddy could become the second major Atlantic hurricane of the 2020 season as it plows northwest across the open waters of the tropical central Atlantic. Teddy vaulted to hurricane status on Tuesday night and by 11 a.m. Wednesday was a Category 2 storm with top sustained winds of 100 mph, located about 800 miles east of the Lesser Antilles. The first hurricane hunter mission into Teddy is scheduled for Thursday afternoon.

Even as it strengthens, Teddy has struggled to gain an organized inner core and carve out a clear eye. More challenges lie ahead over the next couple of days, as Teddy faces moderate wind shear (10-20 knots) and a gradually drying atmosphere (mid-level relative humidity dropping from around 60% to around 40%). In Teddy’s favor, sea surface temperatures along its path will rise from around 28°C (82°F) to around 29°C (84°F), providing ample oceanic energy.

Moreover, Teddy is a large hurricane, with an expansive field of thunderstorms (convection). That broad structure should help keep it resilient. Already, tropical storm-force winds extend more than 170 miles to the northwest, northeast, and southeast of Teddy. As Teddy matures and gains latitude, its wind field is likely to expand even further, leading to a vast expanse of high surf and swells. All told, there is a chance Teddy could reach category 3 or even 4 strength in the next several days, as predicted by NHC on Wednesday morning, but Teddy could also stay mainly in the high cat-2 range, as predicted by the 12Z Wednesday runs of the HWRF and HMON intensity models.

Teddy is being steered by a strong ridge over the central Atlantic. As Teddy approaches the west side of the ridge, it’s expected to gradually angle northward and recurve out to sea. However, long-range track models have trended toward a more westward-oriented ridge, which makes it more plausible that Teddy could pass over or near Bermuda early next week, only a few days after the direct strike from Hurricane Paulette. The westward trend also raises the possibility that Teddy might continue northwestward toward North America. The crucial factor is the evolution of a strong upper low swinging through southeast Canada this weekend. If that upper low happens to leave behind a small remnant over the eastern U.S., then Teddy could conceivably rotate around that small low and reach Atlantic Canada. This scenario emerged in the 0Z and 12Z Wednesday runs of the European model, which brought Teddy onshore near the Maine/New Brunswick border around Tuesday of next week. The Euro is among the best-performing long-range track models, but its 0Z and 12Z Wednesday forecasts were not reflected in the 0Z or 12Z GFS or UKMET models, or in the 0Z GFS ensembles. There’s ample time to see if other models converge around the Euro scenario. History suggests a track like this is unlikely but not impossible.

Although the 2020 Atlantic season has spun off named storms at a blistering record pace, there has been just one major hurricane (Category 3 or stronger) – Laura – as of Wednesday morning. By comparison, 2005 produced five major Atlantic hurricanes by the time it got to Rita, and 1933 – the Atlantic’s second most prolific season on record prior to this year – also generated five majors among its first seventeen tropical storms and hurricanes.

A powerful ‘medicane’ taking aim on Greece this week

A strong low-pressure center with subtropical characteristics over the Mediterranean Sea – the type of storm nicknamed a “medicane” – could bring high winds and torrential rains to Greece late this week. The system has an asymmetric warm-core structure much like that of a named subtropical storm, according to analysis from Florida State University based on the 06Z Wednesday run of the GFS model. The structure is predicted to shift by Thursday toward symmetric warm-core, more like a tropical storm.

Reanalysis of data going back to the 1940s suggests that about one or two medicanes typically form each year, although the phenomenon was not recognized until the satellite era. Because medicanes are a neither-fish-nor-fowl creature, they do not fall under any naming scheme overseen by the World Meteorological Organization. Since 2017, the National Observatory of Athens has been naming medicanes that affect Greece, and they have dubbed this week’s system Ianos. (Several other European countries and unofficial groups have come up with their own naming systems.)

Medicane Ianos showed clear banding and a central core of convection on visible satellite imagery, with hints of an eye developing late Wednesday. Ianos has ample opportunity to strengthen further as it passes over SSTs of 27-28°C (81-82°F), around 1°C warmer than average.

Ianos is predicted to approach the Peloponnese Peninsula of southern Greece, including the Ionian Islands just to the west, on Friday. It may briefly move onshore before angling southward, perhaps making another landfall in northeast Libya around Sunday. The 12Z Wednesday run of the GFS model predicted that the surface pressure of Ianos may drop as low as 986 mb early Friday, with sustained surface winds near 50 mph. Considerably stronger gusts may develop as Ianos nears the Greek coast. The storm will push extremely high levels of atmospheric moisture (precipitable water 4+ standard deviations above normal) across the rugged terrain of southern Greece; widespread 2″ – 4″ rainfall amounts are possible, with higher localized totals.

The predicted track and evolution of Ianos are roughly similar to that of Medicane Zorbas, which produced wind damage in Greece and flash flooding in Tunisia and Libya in September 2018.

Paulette becomes a smoke-icane

A huge quantity of smoke from this month’s catastrophic wildfires in the western U.S. poured into the circulation of Hurricane Paulette on Wednesday morning, creating a surreal scene on satellite imagery (Figure 4). This tweet from the University of Wisconsin CIMSS group shows the smoke extending clear back to the western U.S.

At 11 a.m. EDT Wednesday, the National Hurricane Center issued its final advisory for Paulette, which had transitioned to a powerful extratropical storm with 85 mph winds, speeding to the east-northeast at 30 mph towards the Azores Islands.

Paulette scored a direct hit on the island of Bermuda on Monday as a category 1 hurricane with 85 mph winds. Paulette intensified to a category 2 storm with 100 mph winds while the rear eyewall was pounding the island, and the storm knocked out power to 25,000 of the 36,000 customers on Bermuda and blocked many roads with debris. Fortunately, the island was “back up and running in record time,” said the national security minister, as reported by The Royal Gazette. No deaths or serious injuries were reported from Paulette.

Tropical Storm Vicky in the Eastern Atlantic expected to dissipate

At 11 a.m. EDT Wednesday, Tropical Storm Vicky was located in the eastern Atlantic, about 800 miles west-northwest of the Cabo Verde Islands. Vicky was headed west at 9 mph, with top sustained winds of 40 mph. The storm had managed to survive extremely high wind shear of 50 – 60 knots, but is expected to succumb to the wind shear and become a remnant low by Friday. Vicky is not a threat to any land areas.

Prior to formation, the tropical wave that spawned Vicky brought deadly flooding to Praia, capital of the Cabo Verde Islands, where three inches of rain fell on September 12. The floods killed one person and caused substantial damage to infrastructure and agriculture.

Gulf of Mexico disturbance 90L expected to develop

An area of disturbed weather in the southwestern Gulf of Mexico, about 200 miles off the coast of Mexico, was designated 90L by NHC on Wednesday morning. The system was growing more organized on Wednesday afternoon, with satellite imagery showing an increase in 90L’s size, accompanied by rotation at mid-levels of the atmosphere.

Conditions for development are expected to be favorable this week, with moderate wind shear of 10 – 20 knots, warm ocean temperatures of 30 Celsius (86°F), and a moist atmosphere. The system is predicted to meander at speeds of less than 5 mph over the next five days, and could potentially drift northwards and be a threat to the U.S. Gulf Coast by early next week. There is increasing model support for development of 90L, and in its 2 p.m. EDT Wednesday Tropical Weather Outlook, NHC gave 90L two-day and five-day odds of development of 50% and 70%, respectively. A hurricane hunter aircraft is scheduled to investigate 90L on Thursday afternoon. The next name on the Atlantic list of storms is Wilfred, which is the last name on the list.

Eastern Atlantic tropical wave 98L expected to develop

A tropical wave in the eastern Atlantic, designated 98L by NHC, has favorable conditions for development this week, with moderate wind shear of 10 – 20 knots predicted, along with warm ocean temperatures of 27.5 – 28 Celsius (81.5 – 83.4°F) and a moist atmosphere. The system has modest model support for development, and is predicted to move west to west-northwest at 10 to 15 mph, reaching the Lesser Antilles Islands around Wednesday, September 22. It is too early to tell if 98L will affect the islands yet, though the models are increasingly predicting that 98L will turn more to the northwest early next week and miss the islands.

In its 2 p.m. EDT Wednesday Tropical Weather Outlook, NHC gave 98L two-day and five-day odds of development of 50% and 70%, respectively.

If 90L and 98L both become tropical storms, they will be named Wilfred and Alpha (or vice versa), as the regular 2020 list of names would be exhausted and NHC would turn to the Greek alphabet. It’s done so only once before, in 2005. There are 24 names on the Greek alphabet list, so barring a cataclysmic amount of activity, that list would not be exhausted by year’s end. There is no protocol in place for what would happen if a Greek-named storm were to be destructive enough to merit retirement.

Northeast Atlantic’s 99L headed towards Portugal, but not likely to develop

A non-tropical low-pressure system was located on Wednesday afternoon over the far northeastern Atlantic, about 500 miles west of Portugal. This low, which NHC designated 99L, is forecast to move southeast and then east over the next three days, approaching Portugal on Friday.

How climate change is making hurricanes more dangerous

The system has marginal conditions for development into a subtropical cyclone, with high wind shear of 25 – 40 knots predicted this week, along with cold ocean temperatures of 21 – 22 Celsius (70 – 72°F). In its 2 p.m. EDT Wednesday Tropical Weather Outlook, NHC gave 99L two-day and five-day odds of development of 20%.

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Posted on September 16, 2020 (5:05pm EDT)