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Colorado State report predicts near-average hurricane season

Researchers at Colorado State University have upgraded their April forecast for this year’s Atlantic hurricane season, now saying that indicators are pointing to near-average activity.

That would be 14 named tropical storms, six of them hurricanes and, of them, two major, which means Category 3 or higher. The average is 12 named storms, 6.5 hurricanes, with two of them major, according to Colorado State’s report, issued June 1, which marks the official start of Atlantic hurricane season.

Since their call in April for a below-normal season, “the odds of a significant El Niño in 2017 have diminished somewhat,” and areas of the tropical Atlantic have warmed, said Philip J. Klotzbach, research scientist, and Michael M. Bell, associate professor, in their updated report.

This comes on the heels of a prediction for a likely above-normal season, issued May 25 by the National Oceanic and Atmospheric Administration’s Climate Prediction Center.

Forecasters there predict a 70 percent likelihood of 11 to 17 named storms, of which five to nine could become hurricanes. NOAA said two to four of those storms could be major hurricanes, meaning Category 3 or higher.

A dozen named storms — with six becoming hurricanes and three of those considered major — is considered an average season, according to NOAA’s forecasters.

Though Atlantic hurricane season runs from June 1 to Nov. 30, there can be outlier storms, such as this year’s Tropical Storm Arlene, which formed in April over the eastern Atlantic and is figured into both NOAA’s and Colorado State’s numbers.

Colorado State’s update was issued on the same day that the Associated Press reported on how weather forecasts have been becoming more accurate as they’re giving longer lead times, with the improvements “most noticeable during Atlantic hurricane season.”

“Hurricane forecasts were twice as good last year than they were in 2005, when the National Hurricane Center predicted the paths of 28 storms, including Hurricane Katrina,” AP said. “Then, predictions where a storm would be 36 hours out were accurate within 97 miles. Last year, they were about that accurate 72 hours before a storm hit.”

Most of the credit goes to “bigger and faster computers” that crunch weather data in “complex computer models that simulate the weather that may be coming tomorrow, next week and even later in the month.”

This year’s outlook from NOAA “reflects our expectation of a weak or nonexistent El Niño, near- or above-average sea-surface temperatures across the tropical Atlantic Ocean and Caribbean Sea, and average or weaker-than-average vertical wind shear in that same region,” said Gerry Bell, lead seasonal hurricane forecaster with the Climate Prediction Center, in a statement.

NOAA said that strong El Niños and wind shear “typically suppress development of Atlantic hurricanes, so the prediction for weak conditions points to more hurricane activity this year.”

Impacting weather conditions worldwide, El Niño is a climate pattern that starts with especially warm sea surface temperatures in the equatorial Pacific and tends to increase upper-level westerly winds in the Atlantic, “tearing apart hurricanes as they try to form,” according to a posting on Colorado State’s website.

Still, uncertainty does remain, with models “quite mixed” as to factors of El Niño’s development, NOAA’s Bell said on a media call. That is one factor reflected in “comparable probabilities for an above-normal and near-normal season,” NOAA said.

The Colorado State researchers also said that their next updates, planned for July 3 and Aug. 4, would reflect any shifts in conditions over the coming months.

And, as they do with each report, they reminded coastal residents “that it only takes one hurricane making landfall to make it an active season for them” and “they should prepare the same for every season, regardless of how much activity is predicted.”

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