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From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.
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And I'm Robert Siegel. Optimism and hurricanes are not words we usually utter together, but the Atlantic hurricane season begins June 1st, and today government forecasters offered some cautious optimism. They are expecting a relatively quiet year. Here's NPR's Jon Hamilton.
JON HAMILTON, BYLINE: Officials from the National Oceanic and Atmospheric Administration issued this year's hurricane outlook from New York City's Office of Emergency Management. It's just a mile or so from areas of lower Manhattan that were under water after Hurricane Sandy in 2012. NOAA's administrator, Kathryn Sullivan, offered a preview of 2014.
KATHRYN SULLIVAN: NOAA predicts the Atlantic hurricane season in 2014 will have a range of eight to 13 tropical storms, three to six of which will become hurricanes.
HAMILTON: That's fewer tropical storms and hurricanes than in an average year. But Sullivan also cautioned that predictions are about probability not certainty.
SULLIVAN: Any section of our coastline can be hit by a severe tropical storm. And one storm, whatever the probabilities are, one storm can wreak tremendous havoc.
HAMILTON: Sullivan has reason to be cautious about seasonal forecasts. A year ago, NOAA predicted a busy season with at least seven hurricanes. They got just two and they were small ones. Still, NOAA's May forecasts are right about two-thirds of the time. And forecasters say this year there is strong evidence that conditions in the Atlantic won't be conducive to hurricane formation. One reason is water temperature. Gerry Bell, who is in charge of NOAA's seasonal forecast, says that since 1995, hurricanes have been fueled in part by unusually warm waters in the Atlantic.
GERRY BELL: This year, the Atlantic Ocean temperatures have cooled off and the computer models are indicating that we'll have a continuation of these near normal Atlantic temperatures through the season.
HAMILTON: Another factor likely to discourage hurricanes is what appears to be an emerging El Nino. El Nino starts in the Pacific but ultimately, it changes the wind patterns halfway around the world, in the Atlantic. Ben Kirtman, from the University of Miami's Rosenstiel School, says El Nino produces winds with more vertical shear, meaning the strength or direction is different at higher altitudes than it is closer to the ground.
BEN KIRTMAN: Hurricanes like to form where there's very little change with height in the strength of the winds. And so if there's a big change in strength with height, you just have this shearing effect that tends to reduce the number of hurricanes.
HAMILTON: And if the shear is strong enough, it can actually rip them apart. Kirtman says El Nino hasn't arrived yet. But he's pretty sure it will, based on his monitoring of about 100 different forecasts from across North America.
KIRTMAN: And I would say 65 or 70 percent of those 100 forecasts are calling for El Nino conditions to develop in the next two or three months. So, that's certainly good reason to have fairly high confidence that we are going to get an El Nino.
HAMILTON: Kirtman says El Nino conditions do more than discourage hurricanes. They also tend to increase rainfall in the southern part of the U.S.
KIRTMAN: And in fact, if this El Nino persists through the winter season like we think it's going to, there might be a little bit of a break in terms of the California drought, which has been very, very severe.
HAMILTON: However, the arrival of El Nino doesn't guarantee either rainfall or protection from potentially devastating hurricanes. During an El Nino in 1992, Hurricane Andrew became a Category 5 storm that destroyed Homestead, Florida. Andrew eventually killed 65 people and caused $26 billion in damage. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.