Michael Lowry in Yale Climate Connections:
Waters across the Atlantic’s tropical belt — extending from the coast of Africa through the Caribbean — are hotter now than in any other late May on record, with over 90% of the area’s sea surface engulfed in record or near-record warmth. The extent of marine heat has never been greater heading into a hurricane season, outpacing by wide margins the previous late May record-holder in 2005, a year remembered for one of the most active and destructive hurricane seasons in modern history.
Although record-setting sea surface temperatures alone don’t guarantee a busy hurricane season, they do strongly influence it, especially when the abnormal warmth coincides with the tropical belt known as the Main Development Region, or MDR, the area where 85% of Category 3, 4, and 5 hurricanes form. When considered alongside a developing La Niña — the periodic cooling of the equatorial Pacific that reduces storm-busting Atlantic wind shear — the unprecedented ocean heat is driving up seasonal hurricane outlooks higher than ever before.
Colorado State University — the group that pioneered seasonal hurricane forecasts in the 1980s — issued its most aggressive April forecast last month in almost 30 years of doing such preseason outlooks. NOAA, the parent agency of the National Weather Service, will release its first 2024 hurricane season outlook May 23, and expectations are for similarly bullish numbers.
The exceptional warm-up of the North Atlantic began in earnest last spring and continued through the 2023 hurricane season. Despite one of the strongest El Niño events on record, which would typically deter hurricane activity, the Atlantic churned out 20 named storms last season, the fourth-highest number since 1950, according to NOAA. Forecasters largely credited the record-warm tropical Atlantic for counteracting the heavy hand of El Niño.
Get ready for what nearly all the experts think will be one of the busiest Atlantic hurricane seasons on record, thanks to unprecedented ocean heat and a brewing La Nina.
There’s an 85% chance that the Atlantic hurricane season that starts in June will be above average in storm activity, the National Oceanic and Atmospheric Administration announced Thursday in its annual outlook. The weather agency predicted between 17 and 25 named storms will brew up this summer and fall, with 8 to 13 achieving hurricane status (at least 75 mph sustained winds) and four to seven of them becoming major hurricanes, with at least 111 mph winds.
An average Atlantic hurricane season produces 14 named storms, seven of them hurricanes and three major hurricanes.
“This season is looking to be an extraordinary one in a number of ways,” NOAA Administrator Rick Spinrad said. He said this forecast is the busiest in the 25 years that NOAA has been issuing in May. The agency updates its forecasts each August.
About 20 other groups — universities, other governments, private weather companies — also have made seasonal forecasts. All but two expect a busier, nastier summer and fall for hurricanes. The average of those other forecasts is about 11 hurricanes, or about 50% more than in a normal year.
La Nina usually reduces high-altitude winds that can decapitate hurricanes, and generally during a La Nina there’s more instability or storminess in the atmosphere, which can seed hurricane development. Storms get their energy from hot water. Ocean waters have been record warm for 13 months in a row and a La Nina is forecast to arrive by mid to late summer. The current El Nino is dwindling and is expected to be gone within a month or so.
“We’ve never had a La Nina combined with ocean temperatures this warm in recorded history so that’s a little ominous,” said University of Miami tropical meteorology researcher Brian McNoldy.
This May, ocean heat in the main area where hurricanes develop has been as high as it usually is in mid-August. “That’s crazy,” McNoldy said. It’s both record warm on the ocean surface and at depths, which “is looking a little scary.”
In yet another dire warning about the coming Atlantic hurricane season, the National Oceanic and Atmospheric Administration on Thursday predicted that this year could see between 17 to 25 named tropical cyclones, the most it has ever forecast in May for the Atlantic Ocean.
The NOAA forecast joins more than a dozen other recent projections from experts at universities, private companies and other government agencies that have predicted a likelihood of 14 or more named storms this season; many were calling for well over 20.
Rick Spinrad, the NOAA administrator, said at a news conference on Thursday morning that the agency’s forecasters believed eight to 13 of the named storms could become hurricanes, meaning they would include winds of at least 74 miles per hour. Those could include four to seven major hurricanes — Category 3 or higher — with winds of at least 111 m.p.h.