NOAA's updated hurricane outlook calls for even more storms in 2021

The National Oceanic and Atmospheric Administration on Wednesday updated its 2021 Atlantic hurricane seasonal forecast, slightly increasing expectations for the number of named storms and powerful hurricanes.

Why it matters: With the U.S. already reeling from extreme heat and wildfires, disaster response agencies are overstretched. A particularly destructive and active hurricane season could overwhelm some of its response capacity.

Details: The updated forecast is based on conditions observed across the North Atlantic Ocean basin, including sea surface temperatures, upper-level winds, rainfall in West Africa, and the potential development of another La Niña event in the tropical Pacific, among other factors.

• This hurricane season comes in the wake of the North Atlantic basin's most active season on record, with 30 named storms occurring in 2020, 11 of which struck the U.S., setting a benchmark.

By the numbers: NOAA is forecasting a 65% chance of an above-average season, with a 70% probability of 15–21 named storms. Of these named storms, NOAA is predicting that 7–10 will be hurricanes and 3–5 will be major hurricanes of Category 3, 4 or 5 strength.

• These numbers reflect the five named storms that have already formed this season, including the earliest fifth-named storm on record for the Atlantic basin (Hurricane Elsa).
• While the season has slowed its pace since the early storms, NOAA meteorologist Matthew Rosecrans said that quiet is not likely to remain.
• "NOAA forecasters do anticipate that a busy hurricane season lies ahead," Rosecrans said.
• NOAA typically updates its outlook as the peak of the hurricane season during August, September and October begins.

Flashback: Of the 30 named storms last year, 13 were hurricanes, and seven were "major" hurricanes of at least Category 3 intensity.

• The hardest-hit region last year was the Gulf Coast, particularly central and western Louisiana, where two hurricanes struck land within 25 miles of each other at different points in the season.

Yes, but: NOAA did not cite climate change in this outlook.

• However, climate change's influence on tropical cyclones, which is the general term for tropical storms, hurricanes and typhoons, is increasingly detectable, according to scientific studies. Nearly a dozen of the storms in the Atlantic Ocean last year underwent a process known as rapid intensification, leaping across several intensity categories in a matter of hours.
• In a warming world, more frequent bouts of rapid intensification are expected.
• In addition, hurricanes are now moving more slowly, and they may be weakening more slowly once they cross over land. They're also dropping more rainfall than they used to, thanks to the added moisture from warmer ocean and air temperatures.
• Other forecasting groups that issue seasonal outlooks have unanimously called for an above-average season, though not as busy as 2020 was. These include Colorado State University, AccuWeather and Penn State University.