PHILADELPHIA — After a season that produced a record number of tropical storms — including several that devastated the Gulf Coast and two that set off flooding and caused hundreds of thousands of power outages in the Philadelphia region — the Atlantic Basin might be in for another active, damaging, and costly season in 2021, forecasters are saying.
That’s the consensus of preseason outlooks issued so far that are again seeing significantly above-average numbers for named storms, those with peak winds of at least 39 mph; hurricanes, winds of 74 mph or more; and “major” hurricanes, winds 111 mph or higher, or a Category 3 on the Saffir-Simpson scale.
Bowing to the limits of science, meteorologists eschew too much in the way of specificity, but the likelihood of at least one Category 3 making landfall on the U.S. mainland is near 70%, according to the forecast released Thursday by Colorado State University, a pioneer in long-range hurricane outlooks.
The outlooks have been quite similar to those issued this time last year that correctly foresaw above-average numbers of storms — but not nearly above-average enough in a year in which the basin, which also includes the Caribbean Sea and Gulf Mexico, became reacquainted with the Greek alphabet after the National Hurricane Center ran out of names.
The 2021 forecasts
Colorado State foresees 17 named storms, with eight of those becoming hurricanes, during the June 1 to Nov. 30 season. The normals would be 11 tropical storms, six hurricanes, and two Category 3s, by the hurricane center’s calculations.
Colorado State’s is reasonably in line with the call by AccuWeather Inc. — 16 to 20 named storms, seven to 10 hurricanes, three to five majors. The WeatherBell Analytics’ forecast calls for 16 to 22 tropical storms, nine to 13 hurricanes, and three to six Category 3s, with an ominous addition: It predicts three to six of the hurricanes making landfall.
The government will weigh in next month, and it would be surprising if it, too, didn’t call for an active season.
Sea-surface temperatures in the subtropical North Atlantic, where hurricanes are spawned, have been above-normal, meteorologist Philip Klotzbach noted in the Colorado State forecast.
In addition, satellite imagery shows that the Gulf of Mexico also is warmer than normal, particularly southeast of Louisiana.
“Overall, the current SST anomaly pattern correlates relatively well with what is typically seen in active Atlantic hurricane seasons,” said Klotzbach.
Conditions in the tropical Pacific won’t be as cool as last season, when they were ideal for tropical storm development in the Atlantic.
But they won’t revert to El Nino, in which widespread warming results in more evaporation, thus more convection and strong west-to-east winds that can rip apart incipient tropical storms in the Atlantic.
About 2020
Hurricane Laura, blamed for at least 14 deaths in the Gulf region, was one of a record 12 tropical storms that made landfall on the United States last year.
Two of those, Fay and Isaias, had significant impacts in the Philadelphia region.
So many named storms formed — a record 30 — that the hurricane center ran through the naming alphabet. However that record might require an asterisk.
Several were “one-day wonders,” observed Frank D. Marks, director of Hurricane Research Division at NOAA’s Atlantic Oceanographic and Meteorological Laboratory.
Comparing 2020′s bounty with those of previous seasons would be “really problematical,” said Christopher Landsea, chief of the National Hurricane Center’s Tropical Analysis and Forecasting Branch. Monitoring and detection have improved since the cosmically destructive 2005 season, the previous record holder with 28 named storms.
That caveat notwithstanding, 2020 was an extraordinary tropical storm season, and about the last thing that coastal residents and property owners need is another active season.
Historically, hurricanes have been the No. 1 drain on disaster-emergency funds, and the government’s swamped National Flood Insurance Program. As of October it was $20.5 billion in debt, even though Congress had “canceled” $15 billion of its debt in 2018.
One forecast is safe: No storms will be named for Greek letters this year. By tradition, after the 21st storm — q, u, x, y, and z were omitted — the center would conscript the Greek alphabet, starting with Alpha. Last year it got all the way to Iota.
Starting this year, the center will use an alternate set of names, starting with Adria, in accord with World Meteorological Organization protocols.
