The Altantic should see more hurricanes this season, while the Pacific sees fewer – both subtly influenced by the ocean phenomenon known as La Niña.
The latest forecast from the nations’ climate agency calls for an above-normal number of hurricanes in the Atlantic basin: 12 to 18 storms strong enough to get a name, six to 10 that become hurricanes, and three to six that grow into major hurricanes with wind speeds of 111 mph or higher.
It adds up to a 70 percent likelihood of a busier-than-average season.
And U.S. residents should take heed, the National Oceanic and Atmospheric Administration says. Despite a busy hurricane season last year, none made landfall in the United States.
That pushes the odds, and our luck is not likely to hold out, said Gerry Bell, lead seasonal hurricane forecaster for NOAA’s Climate Prediction Center.
“We got lucky, absolutely,” Bell said. “There’s no reason to think we’re going to get lucky again.”
For the Pacific side, NOAA makes the opposite prediction: a 70 percent chance of a below-normal number of hurricanes.
That means 9 to 15 named storms and five to eight hurricanes, with one to three of those becoming major.
The main drivers of hurricanes include warmer ocean temperatures in the Atlantic and wind patterns in the Pacific.
But both can be influenced by La Niña, the periodic cooling of equatorial Pacific waters that can affect large-scale weather patterns.
When La Niña is active, wind shear, which can tear apart hurricanes before they get started, is decreased in the Atlantic and the Caribbean, potentially allowing more hurricanes to develop.
But the fading La Niña is unlikely to have much effect in the Atlantic this year, Bell said. The NOAA forecast says its effects might linger at least into the early part of the season.
La Niña also might sometimes help suppress hurricane activity in the eastern Pacific, and those effects could linger into the summer, Bell said.
And while the chances of an eastern Pacific hurricane moving far enough north to affect Southern California are low, La Niña is known to affect rainfall in the region.
This winter was supposed to be a dry one, for instance, in keeping with most past La Niña episodes.
It might have turned out that way if not for a dramatic “negative Arctic oscillation,” which allowed cold, moist air to break out of the Arctic and wreak havoc in the lower 48.
That brought snowfall over much of the nation and helped pump rainfall in Orange County and the rest of Southern California to above-normal levels.
John Wayne Airport has seen 18 inches of rain since the start of rainy season July 1, more than five inches above normal.
