Why NOAA forecasters even more confident of below-average storm count in 2015 hurricane season _lowres


Forecasters with the National Oceanic and Atmospheric Administration are now more confident that this Atlantic hurricane season will be below average, lowering their prediction for how many storms are expected to form.

Gerry Bell, NOAA’s lead seasonal hurricane forecaster, said that prognosis is based on lower-than-normal Atlantic Ocean temperatures, strong wind shears that can stop a storm from forming or getting stronger and a stronger El Niño than forecasters saw in the spring.

The forecast released Thursday, which comes at the height of hurricane season, calls for six to 10 named storms, with one to four of those becoming hurricanes.

Of those, either zero or one is expected to grow into a major hurricane.

In late May, NOAA’s forecast predicted a slightly below average season of between six and 11 named tropical storms, with three to six becoming hurricanes and two or fewer of those storms to strengthen into a major Category 3 or higher hurricane with winds of at least 111 mph.

The 30-year average is 12 named storms, with six becoming hurricanes and three of those growing into major hurricanes.

So far this year, there have been only three named storms, with Tropical Storm Ana hitting North Carolina, Tropical Storm Bill making landfall in Texas and Tropical Storm Claudette forming off the East Coast and staying out at sea.

Since 1995, the Atlantic Ocean has been in a higher activity phase that can last for decades, and the past few quiet years still don’t indicate that overall active period is coming to an end, Bell said.

Although tropical Atlantic Ocean temperatures are cooler than normal right now, this is the first year that’s been seen. Normally when the switch to a less-active, multidecade period begins, the ocean temperatures will be below average for a number of years, he said.

The lower-than-average season forecast this year is typical for a strong El Niño year, he said.

El Niño conditions occur when sea surface temperatures in the Pacific Ocean are warmer than normal, which means stronger wind shear can develop over the Atlantic Ocean and the Caribbean, helping limit the formation of storms.

Even with the lower forecast, Bell warned that there will still be more storms that form this year and that all coastal residents need to be prepared.

The last storm to hit Louisiana was Category 1 Hurricane Isaac in 2012.

Although the storm had relatively low wind speeds, the storm surge brought widespread flooding to parts of south Louisiana. The slow-moving, large storm even caused the Mississippi River in Baton Rouge to rise 8 feet.

Follow Amy Wold on Twitter, @awold10.