Central Pacific hurricane season draws to a close
Hurricane Douglas, TD Boris only big storms in otherwise quiet year
A hurricane that came within “razor-thin” distance of the islands and a tropical depression that fizzled out before reaching Hawaii were the only two tropical cyclones in a quiet Central Pacific hurricane season that started June 1 and ended Monday.
The two storms on record for the Central Pacific this year were below the seasonal average of four to five tropical cyclones, said John Bravender, warning coordination meteorologist for the National Oceanic and Atmospheric Administration and the National Weather Service in Honolulu.
“One of the things we were looking at going into hurricane season was thinking that La Nina conditions might develop, which means cooler water along the equator, and it turns out that it did,” Bravender said Monday. “Water cooled off through the summer and we were La Nina by August, and La Nina usually equates with below-normal Pacific hurricanes and an above-normal Atlantic hurricane season.”
El Nino and La Nina are complex weather patterns resulting from changes in ocean temperatures, and the hurricane seasons generally reflect those patterns.
NOAA had predicted that the 2020 hurricane season would bring two to six tropical cyclones in the Central Pacific basin based on La Nina events, with a 75 percent chance of “near-to-below-normal tropical cyclone activity” and a 25 percent chance of above-normal activity.
Under La Nina, early climate models predicted that a drier October would eventually give way to wetter-thanaverage conditions across the state through at least April.
The strength of La Nina events can affect trade wind frequency, too, Bravender said. Cooler waters along the equator means more wind shear across the Central Pacific, which has been known to protect Hawaii from near-cyclones and hurricanes.
“They can help weaken them as they come here, but that’s not always the case as we have seen in the past,” he said. “We don’t always have wind shear over us, so we can have things like Hurricane Iniki come up and not weaken as it approaches.”
Iniki was the most powerful hurricane to strike the state in recorded history in 1992.
Last year, there were four tropical cyclones and six in 2018. There were 16 recorded tropical cyclones in the Central Pacific in 2015, the highest ever due to a strong El Nino that season, he said.
NOAA data shows that the Central Pacific was very inactive in the 2010 to 2013 seasons, which yielded one cyclone each.
This year, Tropical Depression Boris was the first tropical cyclone in the Central Pacific, moving in from the east on June 27 and weakening a day later. Boris was only the second tropical cyclone in June in the Central Pacific since 1950, and the first since Tropical Storm Barbara in 2001, NOAA said in a news release last week.
Hurricane Douglas, which prompted hurricane warnings for Maui County, Oahu and Kauai, and a tropical storm warning for Hawaii island, entered the basin on July 24 as a Category 4 major hurricane. The storm brought heavy rain, swells and high surf across east-facing shores.
Douglas quickly moved west-northwest toward Hawaii and gradually weakened before eventually passing within 30 miles north of the state July 26 as a Category 1 hurricane, “keeping the most damaging wind and rain impacts away from land,” NOAA said.
“Just because there aren’t a lot in the basin as a whole, it doesn’t really give you an idea of what the threat is for Hawaii itself,” Bravender said. “Because even with just two tropical cyclones this year, we were extremely lucky with a nearmiss from Douglas.”
Had Hurricane Douglas hit Maui, it would have been the first hurricane-strength system to strike the island in nearly 150 years, according to weather service records and historical accounts of an 1871 cyclone.
On the other hand, when the Pacific is quiet, the Atlantic is usually busy, and vice versa. Bravender said the Atlantic had an extremely active season, racking up a record-breaking 30 named storms and 12 that made landfall in the United States.
“For the second time, the Atlantic basin ran out of names in their annual hurricane list and started using Greek letters again,” he said. “It’s an incredibly active period for them.”
After speaking to one of the Atlantic hurricane specialists recently, Bravender relayed that they had issued twice as many advisories this year.
This is the fifth consecutive year with an above-normal Atlantic hurricane season, according to NOAA, due to the effects of La Nina and the warm phase of the Atlantic Multi-Decadal Oscillation, which is described by the organization as an ongoing series of “long-duration changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 20-40 years at a time.”
The phenonemon began in 1995 and has caused an increase in stronger and longerlasting storms since in the Atlantic, according to a NOAA news release on the Atlantic hurricane season last week.
“Throughout this relentless hurricane season, NOAA worked around-the-clock to provide critical data and reliable forecasts to our nation’s communities in the path of devastating storms,” U.S. Secretary of Commerce Wilbur Ross said in the news release. “The services provided by
NOAA, alongside our emergency management partners, undoubtedly helped save many lives and protect property.”
So what does this mean for the next hurricane season in the Central Pacific?
Bravender said it’s too soon to tell, but for now “La Nina conditions are expected to continue well through the winter time.”
“It’s something we will be keeping an eye on and see how it all evolves.”