Last year was a record year for hurricanes in the Central Pacific with a total of 17 systems moving into or forming in the Central Pacific.
So what can we expect this year?
The Central Pacific Hurricane Center released Thursday its official outlook for the 2016 Central Pacific Hurricane Season.
Hurricane season in Hawaii runs from June through November, and this year could be very different, not only for the number of hurricanes that form, but also the amount of rain and surf we could see through the end of this year.
An average season has 4-5 tropical cyclones, which includes tropical depressions, tropical storms and hurricanes.
This outlook is based on the expectation that El Niño conditions will likely be transitioning to La Niña during the hurricane season.
Chris Brenchley, Central Pacific Hurricane Center warning coordination meteorologist, notes that this outlook is for the entire Central Pacific and “doesn’t specifically focus on how many tropical cyclones may threaten Hawaii directly.”
However, the central Pacific basin might be shifting toward a more active decadal cycle, in response to changing global sea surface temperatures patterns in both the Atlantic and Pacific Ocean. Forecasters say this combination of competing climate factors, along with model predictions for weaker vertical wind shear and warmer sea surface temperatures in the central Pacific hurricane region, suggest that the hurricane season will likely be near- or above-normal.
Hawaii’s weather is influenced by open ocean thousands of miles in each direction. The water temperature impacts the air moving above it, enhancing or suppressing the formation of tropical cyclones.
The water temperature “has decreased markedly since this winter and it’s really taken a nosedive so we could be moving into a La Nina here by the middle of summer,” said Jon Jelsema with the Central Pacific Hurricane Center.
During the months of November, December and January, the ocean water was almost three degrees Celsius hotter than normal. Since the beginning of the year, there has been a drastic reduction in water temperature to this month, and the forecast models have water temperatures well below normal for the rest of 2016.
The cooler the water temperature, the more difficult it is for hurricanes to form.
“What happens during La Nina to the East Pacific and the birthing areas of hurricanes?” KHON2 asked.
“What La Nina does is increase the upper-level winds across the Pacific Ocean and decrease the sea-surface temperatures across the Pacific Ocean,” Jelsema explained. “Those are two factors that would limit tropical cyclone activity, so all the indications are right now that with La Nina conditions, we are not going to see a season we saw with the historical tropical cyclone season of 2015.”
Brenchley says the longer “decadal” cycle of more activity adds “a little bit more uncertainty in the outlook for 2016. There’s less activity because of La Nina, but more activity because of the decadal cycle.”
Outside of decrease tropical cyclone activity, there are other impacts for the islands.
“During a La Nina season, we tend to see more more strong systems across the basin, which leads to more rainfall as opposed to El Nino, which we just came out of, which is much more drier than normal,” Jelsema said.
The wet season runs from October through April. La Nina could set up conditions for more heavy rain events such as cold fronts, upper level lows and Kona lows. La Nina could be a source of drought relief.
Another possible impact from La Nina is the surf.
“It’s not to say that we won’t see high-surf events, it’s just that the probability of seeing them is much lower,” Jelsema said. “We are not going to see the event after event after event like we saw this past year.”
Busy hurricane season or not, it only takes one to cause catastrophic damage, so residents are urged to be prepared and stay vigilant.