Science Says: Hawaii hurricanes rare, but getting less so
Hurricanes rarely get close to Hawaii. It's even rarer for one of the islands to take a direct hit.
Hurricane Lane already drenched the island chain. Even more rain could be on the way.
The last time a major hurricane hit Hawaii was in 1992. That was Hurricane Iniki. It was a Category 4. It caused billions in damage. The central Pacific hurricane region includes Hawaii. It sees about four or five storms moving through. But that may be changing. This is due to global warming.
A look at the hurricane season in Hawaii:
WIND IS KEY
Usually wind is what keeps storms from hitting Hawaii. Most eastern Pacific hurricanes form in the warm waters off Mexico. Then they often head west. Wind currents usually stop them before they get too far. The winds cause them to circle back toward the coast. The storms that stay a bit further south are the rare ones. These make it to the central Pacific. That's according to Gabe Vecchi. He is a Princeton University climate scientist.
This year, those winds aren't quite steering storms back east. Adding to that are weaker than normal winds aloft. These winds usually shred storms. Winds at that level would normally be 23 mph to 29 mph. Now, they are less than half as strong. This allows storms to stay alive. That's according to Phil Klotzbach. He is a Colorado State University hurricane scientist.
That also happened in 2014 and 2015. Those years were busier than normal years for storms getting close to Hawaii. There were four in 2015. There were three in 2014. This included Iselle. It hit the Big Island. But it was a weakened tropical storm.
But the central Pacific is a big area. And the islands occupy a small area. So most storms aren't likely to come too close.
Hurricanes are fueled by warm water. The water temperature in the region is about 2 to 3.5 degrees warmer than normal. That's according to Vecchi. That was also the case in 2014-2015. "We've come to learn that an unusually warm ocean in the subtropical Pacific will tend to increase the number of hurricanes around Hawaii," Vecchi said.
The Pacific has more storms during a strong El Nino. It is a weather event. It warms the water. Meteorologists expect an El Nino to form in the next couple months. But right now El Nino conditions are still more neutral than hot. Vecchi and others attribute the warming to a natural cousin of El Nino. It is helped from climate change. Warming from that north-south weather pattern is much more connected to causing more storms than east-west El Nino. That's according to Vecchi.
So far this year, the area is much more active with more storms. It has stronger ones. They are longer lasting ones than normal. That's according to Klotzbach. On average, the region gets 15 named storms for the total season. Lane formed Aug. 15. It was far off Mexico. It is already the 12th named storm. It is the second to get close to Hawaii.
In contrast, the Atlantic region is running around its average for this point in the season. In the Atlantic, stormy conditions have slowed down recently. Storms get named when winds reach 39 mph.
August is the biggest month for central Pacific hurricanes. September is the biggest month for the Atlantic. The central Pacific hurricane season runs from June through November. This is the same as the Atlantic. The eastern Pacific runs from May through October.
Climate scientists are reluctant to link individual weather events or even seasons to global warming. But they can make the connections with detailed studies. Hiro Murakami is a National Oceanic Atmospheric Administration climate scientist. He studied the 2014 hurricane season around Hawaii. He studied them with Vecchi and others. They found it was "made substantially more likely" by climate change. This was caused by emissions. These came from burning coal. They came from oil. And they came from gas. It also got a natural boost from El Nino.
They did a study last year. It connected global warming to 2015's record number of major storms in the region. This included three Category 4 hurricanes. These were in the central and eastern Pacific at the same time. These studies are limited. This is because of weak records of storms in the area before 1970, Vecchi said.
Many climate studies recently predict that as the world warms, the globe overall and the Atlantic region will have fewer named storms. But the storms will be more intense. However, the central Pacific bucks that prediction.
Several studies forecast that the central Pacific will become busier. It will have more storms These will be stronger storms. And they will be faster developing ones. That's according to Vecchi. A Murakami study used computer simulations to predict a noticeable increase in storms around the Hawaiian Islands.
It's once again because of winds and water. The water in the region is predicted to warm faster than elsewhere around the globe. This is because of a weakening of trade winds, Vecchi said.