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Tradewinds slack off

The shifting air currents not only alter humidity, but cause droughts and adversely affect the health of island watersheds

By Audrey McAvoy

Associated Press

By Audrey McAvoy / Associated Press

LAST UPDATED: 03:39 a.m. HST, Jun 04, 2013

Part of what makes living in Hawaii so pleasant is the gentle breeze. Arriving from the northeast, it's light enough that it is barely noticeable but strong enough to chase away the humidity.

It's a natural draw to the outdoors.

Nowadays, experts say, these breezes, called tradewinds, are declining, a drop that's slowly changing life across the islands.

The effects can be seen from the relatively minor, such as residents unaccustomed to the humidity complaining about the weather and having to use their fans and air conditioners more often, to the more consequential, including winds being too weak to blow away vog.

The winds also help bring rain, and their decline means less water. It's one reason officials are moving to restore the health of watersheds, the mountainous forests that hold the state's water supply, and more aggressively encouraging water conservation. Scholars are studying ways for farmers to plant crops differently.

What's behind the shift in the winds isn't clear.

"People always try to ask me, Is this caused by global warming? But I have no idea," said University of Hawaii at Manoa meteorologist Pao-shin Chu, who began to wonder a few years ago about the winds becoming less steady and more intermittent.

Chu suggested a graduate student look into it. The resulting study, published last fall in the Journal of Geophysical Research, showed a decades-long decline, including a 28 percent drop in northeast tradewind days at Hono­lulu Airport since the early 1970s.

Scientists used wind data from four airports and four ocean buoys as well as statistical data analysis for their study. Now they are working to pro­ject future tradewinds using the most recent data from the Intergovernmental Panel on Climate Change, a scientific body of the United Nations.

Luke Evslin is already noticing the dip. The 28-year-old has paddled outrigger canoes for most of his life. In Hawaii this means he rides waves generated by tradewinds. These days, though, there are fewer waves to surf because the winds are arriving less often.

"You show up and the wind is blowing in the wrong direction. So instead of a 3-hour, 45-minute race, it turns into a 51⁄2-hour race," Evslin said. "So instead of testing your surfing ability, it's testing your endurance. It's a different type of paddling."

He's thinking he'll now have to start training for races in canals and rivers to better prepare for flat water conditions.

Sometimes the winds are too weak to blow away the vog created by sulfur dioxide erupting from Kilauea volcano on Hawaii island, leaving a white or brownish haze hanging over Hono­lulu. This aggravates asthma and other respiratory problems.

For now, Chu said the most important consequence will be declining rainfall and a drop in the water supply, particularly as Hawaii's population grows and uses more water.

Tradewinds bring rain when clouds carried from the northeast hit mountainous islands built by millions of years of volcanic eruptions. This rain, together with rainfall from winter storms, is the state's primary source of water.

On Oahu the rain feeds ground aquifers that supply water to about 950,000 people in urban Hono­lulu and across the island.

Barry Usagawa, the water resources program administrator for the Board of Water Supply, said residents are reporting streams near their homes are flowing lower than before.

"What we don't know is if this is truly a downward trend or just the lower leg of a long-term cycle. Is it going to go back up?" he said. The agency has contracted Chu to develop rainfall forecasts to plan for the decades ahead.

The board is also encouraging people to fix leaks and buy appliances that use less water to reduce consumption. It's developing recycling facilities so places like golf courses will be irrigated with recycled water. Desalinizing ocean water may also be an option, Usa­gawa said.

In the meantime the agency supports efforts to improve the health of Oahu's forests so they can absorb as much rain as they get.

The Legislature this year approved a state budget with $8.5 million for watershed protection steps next fiscal year that include removing invasive weeds and keeping out pigs and other feral animals that dig up forest plants.

The drop in tradewinds, along with a separate decline in winter Kona storms, is one reason parts of Hawaii are in drought. Maui, for example, just had the driest April on record.

To cope with rainfall decline, University of Hawaii at Manoa agriculture professor Ali Fares said farmers can try to grow crops during the rainy reason and avoid months when water availability is uncertain.

Farmers could also plant more drought-tolerant crops and irrigate when crops are under the most stress. "So many people only talk about drought when there's no water, but it's too late then. We have to talk about these before they happen," Fares said.

The tradewind decline may be too subtle to affect the state's biggest industry, tourism, and keep away any of the 8 million travelers who visit the islands each year. After all, even without tradewinds, humidity is mild compared with Hong Kong or Tokyo. And the heat here is nothing compared with summer in Texas or Arizona.

"We do have the best weather in the planet. We really do," said Jerome Agrusa, a travel industry management professor at Hawaii Pacific University. "Once you leave to go visit somewhere else, you realize, I go away and I think, ‘What did I go for?'"

The frequency of northeast tradewinds decreased based on wind data collected and analyzed from four airports and four ocean buoys from 1973 to 2009. The findings were published in the Journal of Geophysical Research:

210 Number of days there were northeast tradewinds in 2009 at Honolulu Airport
291 Number of days northeast tradewinds occurred in 1973 at Honolulu Airport

-28% Percentage change

Shifting tradewinds mean:

>> Vog from Kilauea volcano lingers over the islands.
>> Less rain, resulting in drought in some parts of the state.
>> A decline in replenishment of water supplies for the state’s growing population.

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Wazdat wrote:
Without the trade winds Hawaii is not as inviting. I pray this does not keep getting worse. As for the water supply, WHY are we building dozens of new towers for the rich mainlanders and foreigners ??
on June 4,2013 | 03:01AM
Leinanij wrote:
Because there is money to be made. Locked up inside their tall towers they won't need tradewinds. It's the rest of us that will suffer.
on June 4,2013 | 07:51AM
allie wrote:
agree...things are gloomy for hawaii i fear
on June 4,2013 | 12:04PM
GeoDiva wrote:
Without the trades, we'll end up being Guam!
on June 4,2013 | 04:47AM
Maneki_Neko wrote:
This is the front page headline? Come on.
on June 4,2013 | 08:16AM
Morimoto wrote:
Best weather on the planet? I think not. Unless you like going to the beach everyday or are homeless.
on June 4,2013 | 12:34PM
Hapa_Haole_Boy wrote:
There's two concerns: what we can do to help reverse this (if anything), and what we can do to help ensure we have enough water regardless of the outcome of the first concern. Re the first point, it's too bad we don't have a larger data set than just to 1970. Like mentioned in the article, it could be a natural cycle which, aside from weather control devices (admittedly speculative at best), we may not be able to alter. But without a large enough data sat, it's hard to say. Of course global warming people will make a clamour, for which we need actual evidence that it is in fact a factor. Re the second point, we need to explore additional sources of fresh water. Desalinization is an obvious alternative, albeit not viable on a widescale basis at this point. Larger, more efficient, water capture solutions would also help-- there is so much rain water that goes right into the ocean during and just after storms, so much more water could be captured for us to utilize.
on June 4,2013 | 01:03PM
localguy wrote:
Agree more rain water should be captured, the question is where. Unlike the mainland, the Nei lacks the land for natural lakes and there is no area to make a dam to hold water. Other than digging the few natural lakes we have deeper, there is little we can do in this area. One area we could work is to follow the mainland's lead in water conservation. Sad to say our BWS has no idea what this is. We could make water submetering the standard for every condo, townhouse and apartment built, and retrofit those that can. Amazing how much water you save when you pay for it. Also, make low flush toilets and water saving appliances the standard in the Nei. Water wasting toilets and appliances barred from sale here. Also require EPA water sense faucets and shower heads in all new home construction. Again, Nei standard. Each time a home/condo/townhouse is sold, all water related items must meet standards or be replaced. We can fix this problem, too bad our dysfunctional bureaucrats have no idea what to do. Work is not something in their vocabulary.
on June 4,2013 | 09:36PM
berrygood wrote:
The amount of home and skyscraper building on Oahu does indicate a water shortage does it?..Or do they just ignore that little tid bit..You know that people might need water to live..Lol..Well..Anyway, doesn't the extended La Nina affect have something to do with the wind directions?..Less trades..More Vog..But much less hurricane activity and extreme weather..Not sure which is better..The amount of rainfall Oahu needs to support this ever growing population is going to be huge...Small Island..Lots of people...Stay thirsty my friends...
on June 4,2013 | 10:39PM