Following three straight active hurricane seasons, two tropical storm landfalls, millions of dollars in damage and a record-breaking summer in 2015, the Central Pacific Hurricane Center was yet again forecasting the possibility of another busy season.
But so far that hasn’t been the case. Nearly halfway through the June-through-November hurricane season, 2017 has frankly turned out to be a dud.
“Even in times of turmoil, there are periods of peace,” said Jeff Powell, lead forecaster with the National Weather Service in Honolulu.
And there’s no indication the season is going to pick up either, some experts said.
While the Central Pacific sees about four to five hurricanes in an average year, forecasters in May predicted five to eight hurricanes for the season, in part because of signals that El Nino might be developing.
But the global weather pattern triggered by warming water at the Pacific’s equator failed to materialize, leaving neutral conditions that generally don’t lean one way or the other as far as hurricane formation is concerned.
“If there is no El Nino, the frequency of tropical cyclones is not high,” Hawaii state climatologist Pao-Shin Chu said.
That’s true for the Pacific but generally the opposite for the Atlantic hurricane season, which is currently in the news with Hurricane Harvey ravaging Texas.
Technically, the Central Pacific — described as the area of our ocean from 140 degrees west longitude to the international dateline — has already experienced two tropical cyclones this year: Tropical Storm Fernanda and Tropical Depression Greg.
But both storms, which formed in the Eastern Pacific in July, were losing steam fast as they approached the Central Pacific and died quickly just after crossing 140 west and hundreds of miles from the islands.
August historically is the busiest month by far for hurricanes in the Central Pacific. But so far — with less than one week to go — there has been nothing.
“In August you expect to see at least one or two storms,” Chu said. “It’s pretty quiet.”
Colorado State University hurricane researcher Phil Klotzbach said early signs pointed to the likelihood of an El Nino, which typically enhances storm activity in the Central Pacific due to reductions in vertical wind shear and warmer sea surface temperatures.
“That El Nino didn’t materialize,” Klotzbach said in an email, “and consequently conditions have not been as conducive as thought.”
In general, he said, it appears the atmosphere in the Central Pacific has been too stable for storms this year.
For example, he said, cloud tops have been generally warmer than normal this year, according to measurements. Colder clouds mean deeper thunderstorms, which are the building blocks of hurricanes.
In addition, atmospheric pressure has been higher than normal, which is also indicative of a stable atmosphere.
Klotzbach said that over the past few weeks, tropical Pacific sea surface temperatures have cooled considerably. Warmer sea surface temperatures help fuel and intensify tropical cyclones.
Klotzbach said this year’s Central Pacific cyclone drop-off can be seen in the seasonal metric known as accumulated cyclone energy, or ACE, which takes into account the frequency, intensity and duration of all named storms.
Halfway through the season, the region has recorded a measly 2 ACE score.
By comparison, the 1981- through-2010 full season
average, he said, is about
In 2014, the year of destructive Tropical Storm Iselle, the Central Pacific scored 40 ACE, while the record-setting El Nino year of 2015 achieved a score of 115 ACE. Last year, when Tropical Storm Darby made landfall on the Big Island and then unleashed flash flooding in Honolulu, ended up with 39 ACE.
“Given that the tropical central Pacific has continued to cool in recent weeks, I don’t necessarily see a pickup coming,” Klotzbach said.
Chu agreed. With the lack of El Nino conditions and cooler sea surface temperatures, it is likely the second half of the season will not be active, he said.
“The season is not over, so we still have to pay attention,” Chu added, noting that Hurricane Iniki struck in September and Hurricane Iwa arrived in November. “We are not out of the woods yet.”
John Bravender, warning coordination meteorologist with the National Weather Service, said he could see downgrading the official forecast to normal (four to five). That leaves open for the possibility of two or three more storms for the year.
Bravender added that it only takes one big storm to make a bad hurricane season. He said residents should remain ready, alert and prepared.
Maria Lutz, regional disaster officer with the American Red Cross, said she would not advise anyone to let their guard down.
“We’re so fortunate that nothing has come too close to Hawaii,” Lutz said. “But as we all know, things can change in a moment.”