- By Kimberly Miller Palm Beach Post Staff Writer
An El Niño watch issued Thursday put the world on alert that the capricious climate pattern with a global sway on weather is likely to make an appearance this fall or winter.
For Florida, the periodic warming of the equatorial Pacific Ocean can mean a less active hurricane season with fewer powerhouse Cat 5 tropical cyclones. But it also leans toward stormier days during the darkest part of the year when the Sunshine State typically enjoys its dry season.
Scientists said this week not to count either scenario as certain, but the evidence of an awakening El Niño was enough for the Climate Prediction Center to trigger the watch.
“The issue for the hurricanes is does El Niño develop in time and with sufficient strength to suppress the later part of the season,” said Gerry Bell, the lead seasonal hurricane forecaster for the National Oceanic and Atmospheric Administration. “Conditions are evolving more toward an El Niño right now, but there is sill a long way to go.”
Climate Prediction Center forecasters are giving El Niño a 50 percent chance of arriving in the fall, with a 65 percent chance of appearing during the winter. Hurricane seasonal predictions are largely dependent on El Niño because of its wide-scale influence in the tropics.
NOAA’s May 24 hurricane forecast for this season called for between 10 and 16 named storms, five to nine hurricanes and up to four major hurricanes of Category 3 or higher.
An average hurricane season has 12 named storms, six hurricanes and two major hurricanes.
Bell said the low end of the NOAA forecast reflects the idea that El Niño was a possibility, but that the clues weren’t strong enough in May to base the prediction on it.
“Last month, there was too much uncertainty,” said Bell, noting that NOAA will issue an updated forecast in August. “Things have continued to evolve so the chance of El Niño increased.”
The onset of El Niño 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.
“The takeaway for Florida is this might provide some relief for the late-season hurricanes so they aren’t as vicious as last season,” said Jeff Weber, an atmospheric scientist with the University Corporation for Atmospheric Research. “The big Cape Verde storms that travel across the Atlantic, they’re the ones that will more likely be torn apart by a sheared environment.”
Traditionally, storms that form off the coast of Africa have been called Cape Verde hurricanes. In 2013, the government of Cape Verde changed the official name of the 10-island nation to the Republic of Cabo Verde.
Hurricane Irma, which maintained Category 5 winds for 60 hours, was a Cabo Verde hurricane.
A La Niña was bubbling during the height of the 2017 hurricane season and was officially declared in October. The opposite of El Niño, La Niña tends to encourage hurricanes. In 2017, there were 17 named storms, including 10 hurricanes and six major hurricanes.
“There were already conducive conditions, but La Niña helped strengthen them and increased those very long-lived major hurricanes last year,” Bell said.
Bell said El Niño is officially declared when ocean temperatures in the equatorial Pacific are more than 1 degree above normal and are expected to maintain that temperature for six months.
Between 2015 and 2016, one of the strongest El Niño events on record occurred, and the atmosphere responded in spades. That hurricane season spawned just 11 named storms with only four becoming hurricanes.
South Florida was under an El Niño influence in January 2016 when record rains pushed Lake Okeechobee levels to more than 16 feet in February and forced discharges to the St. Lucie and Caloosahatchee estuaries that lasted for months.
“It’s amazing how everything works,” Bell said. “These changes in rainfall patterns affect the atmospheric winds that span more than half the globe, and therefore, affecting wind patterns around the world.”