It comes following the devastating 2020 season, which featured 30 named storms, tied the record set in 2005 with seven major hurricanes, and featured back-to-back Category 4 monsters in Nicaragua that lashed the same communities just two weeks apart. A record 11 tropical storms and hurricanes made landfall in the United States.
The announcement coincides with the gradual development of a system over the open Atlantic that is likely to soon earn the name Ana.
“If you’re in an evacuation zone, now is the time to ensure … you have a plan,” Ben Friedman, acting NOAA administrator, said in a call with reporters on Thursday.
NOAA’s outlook calls for a 60 percent likelihood of an above-average season, with a 70 percent probability of 13 to 20 named storms. Six to 10 of them should be hurricanes.
“This includes three to five major hurricanes with winds of at least 111 miles per hour,” said Don Graves, deputy secretary of commerce. It’s almost identical to NOAA’s outlook from last year, which proved to be too conservative.
The NOAA outlook complements the forecast made by researchers at Colorado State University in early April, which called for an above-average season with 17 named storms. That contrasts against an average of a dozen per year. The United Kingdom Met Office, which oversees weather forecasts across the United Kingdom, anticipates a near to slightly above-average season.
Integral to this year’s forecast is the El Niño Southern Oscillation (ENSO), a large-scale driver of global weather patterns that stem from water temperatures in the east tropical Pacific.
Last year’s historic season was tied to the cool phase of this oscillation known as La Niña, during which ocean temperatures were below normal in the tropical Pacific Ocean. But La Niña events tend to promote more upward motion and calmer upper-level winds in the Atlantic favorable for increasing tropical storminess.
At present, La Niña conditions have dwindled, with an ENSO-neutral pattern likely to persist into the summer months. That metric alone would suggest closer to average hurricane conditions in the Atlantic during 2021.
“Should La Niña return later in the hurricane season, which appears possible … it could increase the likelihood we see … activity in the higher end of our outlooks,” said Matthew Rosencrans, NOAA’s lead hurricane forecaster at the Climate Prediction Center.
Water temperatures in the Atlantic are another important driver of the outlook as warmer oceans tend to favor more frequent and intense storms. Near- to below-average sea surface temperatures are present in the tropical Atlantic, while the subtropics exhibit positive temperature anomalies. Likewise, much of the Gulf of Mexico is atypically mild, although cooler water lurks near the coastline because of drainage from recent heavy rain.
Rosencrans noted that oceans last year were slightly warmer — about 1 degree above average basin-wide in the Atlantic vs. 0.68 degrees above average this year.
There are already signs that the Atlantic hurricane season could get a jump-start in the coming days, during which a strengthening swirl of low pressure north-northeast of Bermuda is likely to earn the name Ana. It will probably become a subtropical storm, meaning it holds both tropical and nontropical characteristics. The National Hurricane Center estimates a 90 percent likelihood of eventual development, but the system first needs more convection, or shower and thunderstorm activity, collocated with the center of circulation before it’s able to earn a name and title.
It would mark the seventh consecutive year to host a preseason storm in the Atlantic Basin, or a system that forms before the current advertised June 1 start date. NOAA has considered moving the ostensible start of hurricane season up to May 15. That’s already a practice in the Pacific.
In the meantime, forecasters with the National Hurricane Center are continuing to pore over data from last year in an effort to quality-control the season. The group has retroactively removed Marco’s landfall, upgraded Zeta’s landfall in Louisiana to major hurricane strength and knocked Iota back from a Category 5 to a high-end Category 4 hurricane. Scientists are still writing reports for each of the whopping 30 storms.
“People associated 2020 with the year we experienced the worst global pandemic in the country,” Graves said. “But it was the most active Atlantic hurricane season in at least 170 years.”
NOAA is also working to make improvements that will streamline hurricane forecasts this year, including rolling out a new storm surge model known as PSURGE. It’s also testing technological systems that will triple computing capacity and storage in the 2022 to 2023 time frame that should boost forecasting in the future.