The 2019 hurricane season was the fourth consecutive season with above normal storm activity. With early signs pointing to no El Niņo this year, we may see the trend continue.
Early climate signals are raising red flags that El Niņo will be a no-show this hurricane season, a bad sign for storm-weary states that have suffered four consecutive years of above normal activity.
Hurricanes are a low priority with coronavirus turning the world upside down, but June 1 will come regardless of what the virus is doing.
Meteorologists acknowledge March is a tricky time for predictions with Earth in the throes of seasonal metamorphosis, but the clues almost all point to a neutral or La Niņa pattern come summer.
The two patterns, both recurring phases of the El Niņo -Southern Oscillation cycle, are more accommodating to Atlantic tropical cyclones than the cutting western gales that shred hurricanes during an El Niņo event.
NOAA hurricane forecast update: With death of El Niņo, expect a more active storm season
February forecast models were leaning against an El Niņo for the 2020 hurricane season. That was reinforced Mar. 5 with updates in the Euro (ECMWF) and the American Global Forecast System (GFS) showing a cooling over the next several months in the equatorial Pacific more consistent with a neutral or La Niņa pattern.
“I think we have a pretty high confidence that we are not going to have an El Niņo,” said Todd Crawford, chief meteorologist for IBM’s The Weather Company. “We’ve had slight El Niņo conditions a couple of years now so it’s time to slosh back here toward La Niņa given the natural oscillation. It’s kind of due.”
El Niņo occurs in tandem with the relaxation of the trade winds - those Earth-skimming easterlies that have guided sailing ships across the world's oceans for centuries.
With the trade winds reduced, warm water that has piled up in the western Pacific Ocean and around Indonesia rushes back toward the east. That movement of warm water shifts rainfall patterns and the formation of deep tropical thunderstorms. The exploding storms whose cloud tops can touch the jet stream disrupt upper air patterns so winds come more out of the west
The west winds create shear in the Atlantic, which can be deadly to budding hurricanes.
La Niņa is marked by strong winds from the east that push warm Atlantic waters toward the U.S., while weaker winds from the west are less able to disrupt storms. The eastern Pacific Ocean is cooler than normal as east winds push surface water toward Asia.
During neutral years - between La Niņa and El Niņo - ocean temperatures, tropical rainfall patterns and wind patterns are closer to long term averages.
“I find it striking that only two out of 20 models are predicting El Niņo for the August through October peak of hurricane season, and barely so,” said Jeff Masters, co-founder of Weather Underground and a writer for Scientific American. “Thus, the odds favor an above-average Atlantic hurricane season based on the likely absence of a significant El Niņo.”
Last year, a weak El Niņo abruptly called it quits in August – an unexpected twist to an explosive hurricane season that ended with 18 named storms, including six hurricanes, three of which were major hurricanes of Category 3 or higher.
That's compared to an average season of 12 named storms. The 2019 season was also marked by Category 5 Dorian’s brutal assault on the northern Bahamas and was the first time since 2012's Hurricane Sandy that a season spawned an "S" storm.
The last strong El Niņo was 2015 into early 2016. Since then, an overactive Atlantic has spawned six Category 5 cyclones – Matthew in 2016, Irma and Maria in 2017, Michael in 2018, and 2019’s Dorian and Lorenzo.
“In recent years, water temperatures have been so warm, that even neutral years have been busy,” said Bob Henson, a meteorologist and writer for Weather Underground. “It’s too early to make a confident forecast of how the upcoming hurricane season will evolve, but the tea leaves now on the table suggest that 2020 could be the Atlantic’s fifth season in a row with above average activity.”
Seas are warmer than average over nearly all of the tropical and subtropical Atlantic with the Caribbean and Bahamas waters running a degree warmer than normal for this time of year.
Crawford said he believes Atlantic water temperature is more strongly tied to hurricane activity than the El Nino phase, with warmer waters spawning more storms. Still, having an El Niņo or La Niņa can skew the season to be under or overachieving.
“What’s unsettling is that 2018 and 2019 overperformed even though La Nina was absent,” Henson said. “One factor making these last two season so active was consistently and unusually warm sea-surface temperatures in the Atlantic basin.”
Henson called the abnormal ocean heat a “flashing red indicator of human-produced climate change.”
Most of the earliest hurricane forecasts are made in April, including Colorado State University’s prediction, which is scheduled for release April 2. The National Oceanic and Atmospheric Administration doesn’t typically release its forecast until May.