Friday, June 5, 2009

El Nino this summer: wind to blow heavy, maybe

Trouble is coming.

Or, at least, in the careful terminology of government agencies, there is a slightly increased chance of unusual storm activity and low rainfall as the result a shift in the cyclical El Niño Southern Oscillation pattern.

We haven't had a strong El Niño event since 1998, when 13 named storms and nine full hurricanes launched themselves in the Eastern Pacific. Only three named storms were in the Central Pacific that year, and only one of those a hurricane. It was a low year.

But that's not the standard. The standard is more hurricanes than normal in El Niño years, when waters south of Hawai'i and east toward Central America are warmer than normal. Warm water feeds tropical cyclones. (Here's a nice primer on what's involved in an El Niño:

Since 1998, the Pacific has had a succession of La Nina (cooler than normal waters) and weak El Niño events. Storm activity for us in Hawai'i has been below normal for a decade now.

Let's do the math.

1999: Nine named storms in the Pacific, a low number. Hurricane Dora slipped by south of Hawai'i.

2000: Twenty-one named storms, but few significant ones. Tropical storm Upana went past well to the south and Hurricane Daniel cruised by, skirting the Islands to the north as it weakened.

2001: Nineteen named storms, almost all of them remaining in the eastern Pacific. Narda came in our direction but died hundreds of miles away. Tropical Depression 2C made a brief appearance far to our south.

2002: Nineteen named storms again. Tropical Storm Alika passed south but didn't pose a significant threat. Hurricane Ele formed south of us, drove west to the International Date Line, and then skittered north, well out of Hawaiian waters. Late in the season, Huko followed a vaguely similar pattern.

2003: Seventeen named storms, none threatening Hawai'i. One tropical depression formed briefly far south. A couple of storms slipped into the Central Pacific from the east but quickly dissipated.

2004: Seventeen named storms, none posed a risk to the Islands.

2005: Seventeen again, with only Kenneth threatening the islands—and only as a dissipating system.

2006: Nineteen named storms. Hawai'i was never at risk, but powerful Ioke pounded Johnston Atoll and then went on to flood and severely damage facilities on Wake Island. Daniel looked like it might cause trouble, but didn't. And Fabio brought some rain.

2007: Only 15 named storms in 2007. Cosme passed south. Flossie barely skirted South Point, but then weakened and turned southwest.

2008: Nineteen named storms. A July hurricane named Elida was briefly forecast to reach Hawai'i, but never did. A month later, Genevieve slithered in from the east, but had little more than rain showers when it finally reached the Islands.

So, a decade of largely quiet hurricane seasons for the Islands.

Why believe things might change? They might not, but after two years of La Nina conditions, we're entering another El Niño. The folks at NOAA's Climate Prediction Center on Thursday announced that there's a better than even chance that we're moving into it this summer.

Here's how they put it: “Conditions are favorable for a transition from ENSO-neutral to El Niño conditions during June − August 2009.”

These climate folks have an array of tools for prediction. They caution that some of their tools say it may simply be a neutral year—neither El Niño nor La Nina. But a pile of tools, which they call their “dynamical models” are leaning strongly toward El Niño. Read their summary at

In an average year, we get three or four named storms in the Central Pacific. (Named storms are simply the term for tropical systems strong enough to be given a name.)

In an El Niño year, there's on average about one more named storm, but shoot, that's nearly a 30 percent increase.

So, there could be trouble. Probably not. But it pays to check the front of your phone book and be sure you have your hurricane kit up to date, and you know what you're going to do if the wind blows heavy.

© Jan TenBruggencate 2009

1 comment:

Keahi Pelayo said...

It is going to be interesting to see if the prediction comes true. What is the relationship between global warming and El Nino?