Hurricane Sally was downgraded to a post-tropical depression on Thursday morning, but the weakened storm continued its inexorable onslaught of heavy rains over the southeastern U.S., bringing torrential rains and flash flood warnings across five states – Alabama, Florida, Georgia, North Carolina, and South Carolina. At least two deaths are being blamed on the storm, one in Alabama and one in Georgia.
Sally made landfall near Gulf Shores, Alabama, at 5:45 a.m. EDT September 16 as a category 2 hurricane with maximum sustained winds of 105 mph and a central pressure of 965 mb. Sally was moving forward at 2 – 3 mph at landfall, and the storm dumped catastrophic amounts of rain.
Sally’s rains brought destructive flash flooding and major river flooding, with 10 rivers in Alabama and Florida at major flood stage on Wednesday or Thursday. More than 24 inches of rain had been recorded at Pensacola Naval Air Station, and radar-estimated rainfall amounts in excess of 20 inches fell on approximately a 100-mile stretch of coast along the Alabama/Florida border. Sally will undoubtedly be a multi-billion-dollar storm, and will likely have its name retired at the end of the season.
According to poweroutage.us, over 510,000 customers in Alabama, Florida, and Georgia were without power on Thursday morning as a result of Sally.
Some wind reports during Sally’s landfall:
– a sustained wind of 81 mph and a gust to 99 mph at Dauphin Island, Alabama;
– a sustained wind of 61 mph and a gust to 86 mph at the Pensacola Naval Air Station, Florida;
– a sustained wind of 98 mph and a gust to 116 mph at an elevated National Ocean Service CO-OP station in Fort Morgan, Alabama;
– a sustained wind of 75 mph and a gust to 93 mph at a University of Florida weather tower at Gulf Shores, Alabama; and
– a sustained wind of 71 mph and a pressure of 970.9 mb inside the eastern portion of Sally’s eye at NOAA buoy 42012, about 50 miles southeast of Mobile, Alabama.
Storm surge flooding from Sally has abated
Sally’s powerful winds and very slow motion resulted in the hurricane’s piling up a large and damaging storm surge near the Florida/Alabama border, to the right of where the eye made landfall. A peak storm tide of 5.6 feet occurred Wednesday morning at Pensacola, Florida – its third highest water level on record. At 11 a.m. EDT Thursday, storm surge flooding at all coastal locations close to where the center had moved ashore had fallen below 1.5 feet.
At 11 a.m. EDT Thursday, September 17, Sally, by then no longer a tropical cyclone, was centered 115 miles southwest of Athens, Georgia, headed northeast at 21 mph with top sustained winds of 30 mph and a central pressure of 1004 mb. Sally was predicted to dump additional rains of four to six inches over portions of the Carolinas and Virginia.
Teddy becomes the Atlantic’s second major hurricane of the year
Powerful Hurricane Teddy intensified into the Atlantic’s second major hurricane of the 2020 season in the open waters of the tropical central Atlantic on Thursday morning, September 17. The average formation date for the season’s second major hurricane is October 3.
At 11 a.m. EDT Thursday, Teddy was a category 3 storm with top sustained winds of 120 mph and a central pressure of 957 mb. Teddy was headed northwest at 12 mph, and was located about 1,155 miles southeast of Bermuda. The first hurricane hunter missions into Teddy, under way on Thursday afternoon, confirmed it as a major hurricane.
Teddy was a large hurricane, with tropical-storm-force winds that extended out up to 255 miles from the center. This large wind field has created big swells that are creating dangerous surf conditions along the north coast of South America and the north-facing shores of the Caribbean islands. Swells from Teddy will begin to affect most of the U.S. East Coast by this weekend, and the Canadian Maritime Provinces by early next week.
Forecast for Teddy
Teddy has favorable conditions for intensification through Saturday, with moderate wind shear (10-20 knots) and ocean temperatures of 28 – 29 degrees Celsius (82 – 84°F). Over the weekend, Teddy will encounter the cool water wake left behind by Hurricane Paulette, which should limit intensification. The National Hurricane Center forecast calls for Teddy to peak as a category 4 hurricane on Friday, then gradually weaken to category 2 strength by the time it makes its closest approach to Bermuda on Monday.
Teddy is being steered by a strong ridge over the central Atlantic. As Teddy approaches the west side of the ridge, a trough of low pressure to the north is expected to turn the hurricane northwards when it is near Bermuda on Monday morning – only a few days after the island’s direct strike from Hurricane Paulette.
Beyond Teddy’s encounter with Bermuda, the crucial factor in determining the storm’s track 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 “cutoff” low along the U.S. East Coast, then Teddy could rotate around that low and make landfall in Nova Scotia or New England on Tuesday or Wednesday. This is the scenario the European model has been suggesting during its past several runs. However, it is tricky to get a correct forecast of the timing and strength of such a cutoff low so far in advance, and a more likely track for Teddy would have it move more to the north-northeast over Newfoundland, or northeast out to sea.
Once Teddy moves north of Bermuda, upper-level winds from the trough of low pressure steering the hurricane will accelerate the storm to a forward speed of 15 – 20 mph, likely creating a high 30 – 40 knots of wind shear. This wind shear is likely to weaken Teddy, as will the cooler waters it will traverse once it moves north of the Gulf Stream, at the latitude of New Jersey. Any potential landfall in Canada or New England would likely be at category 1 or category 2 strength, with storm surge, heavy rain, and high winds all likely to be significant threats.
Vicky weakens to a tropical depression
At 11 a.m. EDT Thursday, Tropical Depression Vicky was located in the central Atlantic, about 1,000 miles west of the Cabo Verde Islands. Vicky was headed west at 14 mph, with top sustained winds of 35 mph. The storm is expected to succumb to high wind shear of 30 – 40 knots and become a remnant low by Thursday night. Vicky is not a threat to any land areas.
90L in Gulf of Mexico nearing tropical depression status
An area of disturbed weather in the southwestern Gulf of Mexico, about 200 miles off the coast of Mexico (90L) was growing more organized on Thursday afternoon, with satellite imagery showing an increase in heavy thunderstorm activity. A pass by the ASCAT satellite overnight showed 90L had developed a fairly well-defined surface circulation, and an Air Force hurricane-hunter aircraft is to investigate 90L Thursday afternoon to determine if it has become Tropical Depression 22.
Conditions for development are expected to be favorable through the weekend, with light to moderate wind shear of 5 – 15 knots, warm ocean temperatures of 30 – 30.5 Celsius (86 – 87°F), and a moist atmosphere. The system is predicted to move at speeds of less than 5 mph over the next five days, with the most likely motion being to the north towards the U.S. Gulf Coast. There is high model support for development of 90L, and in its 2 p.m. EDT Thursday Tropical Weather Outlook, NHC gave 90L two-day and five-day odds of development of 90%. The next name on the Atlantic list of storms is Wilfred, which is the last name on the list.
Reduced chances of development for eastern Atlantic tropical wave 98L
A tropical wave in the eastern Atlantic, designated 98L by NHC, was located several hundred miles southwest of the Cabo Verde Islands on Thursday afternoon. Satellite images showed that 98L had an elongated surface circulation and a modest amount of poorly organized heavy thunderstorm activity. The system has favorable conditions for development through Saturday, with moderate wind shear of 10 – 20 knots predicted, along with warm ocean temperatures of 27.5 – 28 Celsius (81.5 – 82.4°F) and a moist atmosphere. Models support modest intensification through Saturday.
Into next week, 98L is predicted to move west-northwest at 10 to 15 mph, reaching the Lesser Antilles Islands around Thursday, September 24. However, 98L is predicted to encounter very hostile wind shear of 25 – 55 knots on Sunday through Wednesday, which is likely to weaken or destroy the system. The models continue to forecast that 98L will progress far enough to the north next week to miss the Lesser Antilles Islands.
In its 2 p.m. EDT Thursday Tropical Weather Outlook, NHC gave 98L two-day and five-day odds of development of 40% and 50%, 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 toward Portugal
Heavy thunderstorm activity has increased in association with a non-tropical low-pressure system that was located on Thursday afternoon over the far northeastern Atlantic, about 400 miles west of Portugal. This low, which NHC designated 99L, is forecast to move east-southeast and then northeast over the next two days at about 10 mph, approaching Portugal late Friday.
The system has marginal conditions for development into a subtropical cyclone, with high wind shear of 30 – 40 knots predicted this week, along with cold ocean temperatures of 22 Celsius (72°F). In its 2 p.m. EDT Thursday Tropical Weather Outlook, NHC gave 99L two-day and five-day odds of development of 30%.
Medicane Ianos churns toward Greece
An unusually strong “medicane” (a cyclone with tropical or subtropical features over the Mediterranean Sea) was heading toward the southwest coast of Greece on Thursday, September 17. Dubbed Medicane Ianos by the National University of Athens, the intensifying storm featured an eye on satellite imagery Thursday. Ianos had a central pressure of around 990 mb, with top sustained winds estimated at 60-65 mph, according to Severe Weather Europe. Based on analysis from Florida State University, Ianos had a symmetric warm core similar to that of a tropical storm.
The European and GFS global models and Germany’s regional ICON model agree that Ianos will continue along an east-northeast path that will take it near Greece’s Ionian Islands and then into the Peloponnese Peninsula of southern Greece by Friday. Ianos has ample opportunity to strengthen further amid light wind shear as it passes over SSTs of 27-28°C (81-82°F), around 1°C warmer than average. The storm may move some distance inland across the peninsula before turning sharply southward, heading toward Libya this weekend as a weaker system.
According to Severe Weather Europe, wind gusts from Ianos could exceed 100 mph, particularly on the Ionian Islands and across the adjacent Gulf of Patras. Ianos’s strong winds will push ample moisture against rugged terrain, squeezing out torrential rains that could top 10 inches in favored areas of southwest Greece. Flash flooding will be a distinct risk, and tornadoes and waterspouts are not out of the question.
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. 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.
Posted on September 17, 2020 (2:51pm EDT).