La Nina delivers cold and rain to the islands

Brrr. It’s beginning to feel a lot like Christmas.

Or so it seems as a string of relatively frosty cold fronts and near and record low temperatures have prompted shivering Hawaii residents to reach for their blankets, jackets and sweaters in recent weeks.

Hawaii state climatologist Pao-Shin Chu said Wednesday that the La Nina global weather pattern that has developed in recent months appears to be responsible for bringing the colder temperatures and rainfall to the islands.

La Nina is the polar opposite of El Nino, the global climate phenomenon that causes winter drought in Hawaii.

There have been nearly a dozen record low temperatures recorded across the islands over the past couple of months, and Hawaii’s tallest mountains have been dusted with snow on at least a couple of occasions, including Wednesday.

Meteorologist Glenn James, the senior weather specialist for the Pacific Disaster Center on Maui, said the chilly weather is linked to a large, elongated area of high pressure, oriented north and south and parked offshore from the West Coast.

While that region of high pressure has kept the Pacific Coast unusually dry, it has opened the door to a series of cold fronts that have found their way to the tropical Central Pacific.

James, who also runs the Hawaii Weather Today website, said the cold fronts have brought lots of rain and cool air in their wakes.

“Plus, even when there are no cold fronts passing through, the winds have had a more northerly aspect than usual as they cross the state,” James said in an email. “These northerly winds bring air from more northerly latitudes down into our area. These winds often have had low relative humidity levels as well, which along with the breezy conditions make the air feel cooler.”

And there’s no sign that the cold fronts are slowing down. In addition to the one that moved across Maui and Hawaii island and caused flooding Wednesday, there’s another one expected Friday into Saturday and still another due early next week, James said.

National Weather Service forecasters posted a winter storm warning for both Mauna Kea and Mauna Loa, saying up to 2 feet of snow could pile up at the 12,000-foot level and above through early Thursday.

But is Hawaii really all that much colder than normal for this time of year?

Chu, the climatologist and a University of Hawaii meteorology professor, said Hawaii’s recent run of relatively hot and humid El Nino winters may be causing some folks to forget just how cold the average winter used to feel around here.

Chu said the islands used to regularly experience abundant rainfall and cool temperatures during La Nina years decades ago.

But global conditions changed in the 1980s, according to a study conducted by Chu with UH and National Weather Service colleagues.

The strengthening, broadening and westward shifting of the eastern North Pacific subtropical high-pressure system, coupled with an eastward lengthening and intensification of the subtropical jet stream, were found to be influential in reducing rainfall during recent La Nina seasons, the study found.

Hawaii also has experienced a series of warmer winters linked to the El Nino phenomenon, which brings summer precipitation, warmer ocean temperatures, more tropical cyclones, humidity and winter drought. Some also have suggested that climate change is playing a role.

Over the past month, however, there have been more than a few days that have been downright chilly.

“I cannot complain about the weather,” Chu said. “I can sleep a lot better when it’s cooler. It’s nice and cozy.”