Fish Storms

The 2020 parade of record-early named storms in the Atlantic continued on Monday, September 7, with the formation of Tropical Storm Paulette in the central Atlantic and Tropical Storm Rene in the eastern Atlantic.  Neither storm is on a track that poses a long-range threat to the Caribbean or USA.

FISH STORMS:  
A west-northwest to northwest track into the central Atlantic

Steering currents will carry both Paulette and Rene to the west-northwest or northwest during the week. This will put them into the central Atlantic in a location where few tropical cyclones ever go on to make a landfall in the Caribbean or the U.S., making them excellent candidates to be “fish” storms – tropical cyclones primarily of concern to shipping, with no impact on any land areas. There are two exceptions: Rene could bring tropical storm conditions to the Cabo Verde islands on Monday evening through Tuesday, and Paulette could affect Bermuda by the middle of next week.

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It is likely that as Paulette gets stronger, it will move farther north, where strong winds of an upper-level trough expected to form north of Puerto Rico later this week will have a greater influence on a stronger storm. This trough is also likely to bring higher wind shear, weakening Paulette.

Spaghetti plot of potential paths for Tropical Storm Paulette. 
None of the potential paths currently bring Paulette near the USA

Rene is less likely to experience high wind shear from this trough, and more likely to become a hurricane. Rene may move slightly faster than Paulette, allowing the two storms to grow close enough late this week to affect each other’s track and intensity.

A parade of storms fill the Atlantic as the peak of hurricane season 2020 approaches.  While these are mostly "fish" storms, one might be able to slip into the Caribbean sometime next week.

2020 parade of record-early named storms continues

With two days to go until the typical September 10 frequency peak of the Atlantic hurricane season, we’ve already had 17 named storms, five hurricanes, and one intense hurricane. According to Colorado State University hurricane scientist Phil Klotzbach, the averages for this point in the season are six named storms, three hurricanes, and one intense hurricane.

The European model forecast for September 14 shows a consolidated Tropical Cyclone Teddy approaching the Caribbean.  Forecasts 7 days in advance are unreliable but it is interesting to follow how the forecasts evolve.

Paulette’s arrival on September 7 marks the earliest date, in records going back to 1851, that any Atlantic season has produced its sixteenth tropical storm, topping the record held by Philippe from September 17, 2005. Only four more names remain on the 2020 Atlantic list: Sally, Teddy, Vicky, and Wilfred. Tropical Storm Rene formed on on Monday, September 7 as well; the record for earliest-forming “R” storm in the Atlantic was September 18, 2005 (Rita).

It is looking increasingly likely that the National Hurricane Center will have to turn to the Greek alphabet, a last resort that’s been used only in 2005. That unforgettable year produced tropical storms Alpha, Beta, Gamma, Delta, Epsilon, and – on December 30 – Zeta.

This GFS forecast for September 21, 2020 shows a potential Hurricane Teddy and Hurricane Vicky with one in the central Atlantic and one in the Gulf of Mexico.  Forecasts 14 days in advance are notoriously unreliable, but it is interesting to watch how these forecasts evolve.

A potential more concerning storm: the next African tropical wave

This time of year tropical storm and hurricane activity is typically very prominent over the Atlantic Ocean's main development region, roughly from the west coast of Africa to the Caribbean, within which the majority of intense hurricanes form.

Top models for forecasting tropical cyclone genesis are giving strong support for development to a new tropical wave predicted to emerge from the coast of Africa on Thursday, September 10, 2020.  Meanwhile a small low pressure area near Bermuda is also given some chance of developing and moving toward the mid-Atlantic of the USA.

Currently satellites show rippling with thunderstorms over Mali and Burkina Faso.  Its unclear how quickly the disturbance (potential TS Teddy or TS Sally) will consolidate and strengthen when it moves offshore.

The wave is predicted to move mostly westward at low latitude at roughly 15 mph next week. Given its lower-latitude position compared to Paulette and Rene, this new tropical wave (potential TS Sally or TS Teddy) may be a threat to the Caribbean and North America. In a 2 p.m. EDT September 8, 2020 Tropical Weather Outlook, NHC gave the new wave two-day and five-day odds of development of 0% and 50%, respectively.

A robust tropical wave prepares to exit Africa, September 9, 2020

Unlike Paulette and Rene, however, this upcoming storm probably will not recurve, or swing out to sea so soon. That means that while Paulette and Rene were quickly written off as fish storms, the next storm, which could be named Sally or Teddy, is one to keep an eye on.

Systems exiting Africa in the coming days may have a slightly increased chance to affect land or even the mainland USA, thanks to anomalous high pressure building over northeast North America and the northwest Atlantic.  That high pressure couple help suppress storms further south and delay their turn to the north longer than would be typically expected in September.

The pattern also favors a dip in the jet stream, known as a trough, over the central and eastern continental USA during mid-late September.  This trought could scoop up any storms that make it into the Caribbean as they turn north.  However, uncertainty in the long-range tracks of storms that haven't even formed is exceptionally high.

Potential Tropical Cyclone Teddy forecast to emerge from Africa on Thursday, September 10, 2020 and move generally west across the Atlantic.

NHC was also watching an area of low pressure, located just southwest of Bermuda, producing sparse and disorganized heavy thunderstorm activity and moving slowly westward toward the southeastern U.S. In a 2 p.m. EDT Monday Tropical Weather Outlook, NHC gave this disturbance two-day and five-day odds of development of 10% and 70%, respectively.

Hurricane Sally by the numbers:
Gusts to 123 mph, 30 inches of rain and a 6-foot storm surge: Hurricane Sally by the numbers

Hurricane Sally was no Fish Storm!  The slow-moving Sally dumped 20 to 30 inches of rain, while piling up ocean water along the shore, inundating coastal communities.

While the storm is still dumping rain on the Carolinas, we can examine some of its key figures:

123 mph: The peak gust observed during the storm in Orange Beach, Ala. Most of the strongest gusts on land were seen in coastal Alabama. Several locations clocked gusts over 100 mph, with a few gusts over 120 mph.

These readings almost all have caveats, and it is typically difficult to get the strongest winds of a hurricane to hit a calibrated weather station. The damage, and there’s lots of it, leaves little doubt as to the storm’s severity, however. Numerous structures were damaged, and trees were mowed down — some uprooted, others splintered in half.

Hurricane ‘maximum sustained’ winds are seldom felt on land and may not mean what you think

The Center for Severe Weather Research mobile radar unit, known as Doppler on Wheels, detected a 123-mph gust in Orange Beach, Ala., which is probably reliable.

965 millibars: The storm’s minimum central pressure when it made landfall. Sally was a strengthening Category 2 when it came ashore. Its pressure had cratered 18 millibars in the previous 24 hours, an indication of speedy strengthening.

2-mph forward speed: Sally was an extremely slow-moving hurricane. In the hours leading up to and after landfall, it crawled along at a snail’s pace.

On Monday, while over the eastern Gulf of Mexico, the storm traveled an average of 6 mph. By Tuesday, as it sat menacingly just offshore, it slowed to a mere 2 mph, a near-record-slow pace in the region. Sally made landfall moving at 3 mph before mercifully speeding up, if slowly, thereafter.

Its slow forward progress enabled it to unload tremendous rainfall along the coast while prolonging the storm surge. It finally started to gain some speed Wednesday afternoon as it passed through interior eastern Alabama.

Six feet: The approximate peak surge, or storm-driven rise in ocean water above normally dry land. This surge resulted in serious coastal flooding in Pensacola, Fla., where heights reached 5.6 feet, the third-highest level on record, trailing just Hurricane Ivan in 2004 and the Great Miami Hurricane of 1926.

In addition to the storm surge pushing into the coast, there was the somewhat rare phenomenon of “reverse surge,” where water sloshed out of Mobile Bay and into the Gulf of Mexico as the center passed and winds pushed water off the bay.

Water levels in the bay dropped by about six feet, and it took almost a day for conditions to return to normal.

30 inches: The maximum amount of rain observed in Bellview, Fla. When Sally slowed to a crawl, its eyewall — the zone of extreme winds and torrential rain surrounding the storm center — relentlessly hammered the Alabama coast and Florida Panhandle.

The National Weather Service declared a relatively unusual “high risk” for flooding rains in this zone, and 20 to 30 inches of rain descended.

In the predawn hours Wednesday, the Weather Service declared several flash-flood emergencies, the most urgent and severe flash-flood alert. Beyond that, flood watches and warnings have extended from the Gulf Coast to the lower Mid-Atlantic with the storm lifting northeastward.

By warming ocean waters, climate change is thought to be intensifying rainfall in tropical storms and hurricanes and increasing the amount of water they generate.

500,000 in the dark: As of Thursday morning, more than half a million customers in Alabama and Florida remained without power. In southwest Louisiana, an additional 55,000 customers remained without power as repairs continued in the aftermath of Hurricane Laura three weeks ago.

16 years: The number of years since Alabama’s previous direct hurricane strike — Hurricane Ivan in 2004. Coincidentally, Ivan hit at the exact same location as Sally — Gulf Shores, Ala. — on the same date, Sept. 16.

Eight landfalls: Sally is the eighth tropical cyclone to come ashore in the United States this year. The term tropical cyclone broadly refers to tropical depressions, storms and hurricanes. According to Colorado State University hurricane researcher Phil Klotzbach, that number is a record season-to-date, surpassing seven to date in 1916. The most in one year is nine, which certainly seems as if it could be threatened in 2020.

Four hurricanes: With Sally in the books, there have been four hurricane strikes in the United States in 2020. Hanna hit Texas, Isaias ran into North Carolina, Laura blasted Louisiana and Sally struck Alabama. Sally is also one of six hurricanes to have made landfall this year in the Atlantic Ocean basin, all while strengthening.

Eight storms left?: With Sally one of 20 named storms in 2020, just eight more are needed to tie the most on record: 28 in 2005. Sally was the 18th named storm of the year, and there have been two more since. Assuming Tropical Storm Wilfred forms, forecasters will need to draw from the Greek alphabet for referencing storms.

Running out of hurricane names, we’ll soon switch to the Greek alphabet. That could present a problem.

10 weeks: The amount of time left in hurricane season, which runs through Nov. 30. We’re barely past peak.