Make us your home page

Today’s top headlines delivered to you daily.

(View our Privacy Policy)

Science behind NOAA outlook for 2013 hurricane season

A NOAA satellite image on Sept. 26, 2004, shows Hurricane Jeanne slicing across Central Florida with a girth of 400 miles.

Associated Press

A NOAA satellite image on Sept. 26, 2004, shows Hurricane Jeanne slicing across Central Florida with a girth of 400 miles.

Scientists with the National Oceanic and Atmospheric Administration say the Atlantic region could see an "active or extremely active" hurricane season in 2013.

But they say that every year, right?

NOAA forecasters annually estimate how many storms might emerge during hurricane season and how strong they could be. This year, NOAA believes there is a 70 percent chance that between 13 and 20 named systems (storms with wind speeds above 39 mph) will develop from June 1 to Nov. 30.

If that seems like an old prediction, it's probably because forecasters have been calling for active seasons a lot lately, said Gerry Bell, lead seasonal hurricane forecaster at NOAA's Climate Prediction Center.

"That's because there are more hurricanes threatening," Bell said.

Since 1995, the Atlantic region has been in the warm phase of a cycle that historically has created decades of increased tropical storm activity at a time, he said. Scientists call it the AMO, short for Atlantic Multidecadal Oscillation.

Meteorologists look to established indicators like ocean temperatures and wind strength to read the AMO and forecast the hurricane season. Warm phases generate more cyclones and can last 25 to 40 years, followed by equally long cooler periods of decreased activity.

Bell said in the 18 years since the latest warm phase began, the Atlantic region has experienced 12 hurricane seasons with above-average activity.

In some ways, generating the annual outlook is just guesswork. But the NOAA specialists behind it are not in the business of wild speculation.

"There's really a strong scientific basis for making the seasonal outlook," Bell said.

Signs of an active season this year include warm water in the Atlantic Ocean, a strong West African monsoon, and less than normal rainfall in the Amazon Basin, according to Bell.

Conversely, during the last down period for storms from 1971 to 1994, rainfall was heavier in the Amazon Basin. During those decades, Bell said, the Atlantic experienced only two above-average hurricane seasons.

Bell said the lack of an El Niño in the west, which would hamper the formation of Atlantic hurricanes, could also support high storm activity in 2013.

Yet, despite all the data, the outlook is inexact and has obvious limits.

Forecasters cannot predict how many hurricanes will reach land or where they will hit. Bell said landfall is only predictable up to about a week in advance because it depends on local weather patterns when a storm approaches.

Even if the Atlantic plays host to 20 named storms in the coming months, it's possible that none would hit Tampa Bay and the season would seem inactive for local residents. When the last hurricane to strike the area hit in 1921, the Atlantic was actually in a period of low activity.

"The utility of the seasonal forecast even for the insurance companies or FEMA is still pretty limited I think because you can't definitely say with the seasonal outlook what that means for landfall," said Chris Landsea, science and operations officer at the National Hurricane Center in Miami.

The long-term outlook is more a measure for science than public safety, said Pinellas County emergency management spokesman Tom Iovino.

"It really doesn't weigh on our decisions in terms of preparedness," he said.

The forecast does, however, generate hype each year that forecasters and emergency planners say can help grab residents' attention.

"The seasonal forecast gets us talking about hurricanes and reminds us that the season is upon us," said Rick Knabb, director of the National Hurricane Center.

Around Tampa Bay, that is especially important. Decades have passed since the last direct hit, and it's easy to become complacent about preparedness.

But Knabb said a storm will come. He created a list of American cities that were overdue for a hurricane in 2011. Tampa was number five on that list.

"It really is just a matter of when, not if, a major hurricane will impact the Tampa Bay area," Knabb said.

Zachary T. Sampson can be reached at or (727) 893-8804. Twitter: @zacksampson.

Science behind NOAA outlook for 2013 hurricane season 05/31/13 [Last modified: Friday, May 31, 2013 9:21pm]
Photo reprints | Article reprints

© 2017 Tampa Bay Times


Join the discussion: Click to view comments, add yours

  1. Pasco deputies investigate vandalism at Crystal Springs Cemetery (w/video)


    Times Staff Writer

    CRYSTAL SPRINGS — Pasco County deputies are looking for one or more suspects linked to vandalism of two grave sites in this community's small cemetery.

  2. Republicans struggle to marshal votes for health care bill


    WASHINGTON — Republican leaders scrambled for support Tuesday before a vote to take up legislation repealing the health care law, negotiating, pressuring and cajoling Republican senators but preparing for another embarrassing setback for President Donald Trump.

    Senate Majority Leader Mitch McConnell of Ky., center, talks with his chief of staff Sharon Soderstrom, right, and communications staff director Antonia Ferrier, left, as they walk to his office on Capitol Hill in Washington, Monday, June 26, 2017. Senate Republicans unveil a revised health care bill in hopes of securing support from wavering GOP lawmakers, including one who calls the drive to whip his party's bill through the Senate this week "a little offensive." [Associated Press]
  3. Provocateur targets CNN with hidden camera video while Trump takes another swipe


    NEW YORK —A conservative provocateur posted a video Tuesday of a man identified as a CNN producer commenting on his network's coverage of President Donald Trump and connections to Russia.

    Anthony Scaramucci, a senior adviser to President-elect Donald Trump, talks to reporters in the lobby of Trump Tower in New York. [Associated Press]
  4. Shakira coming to the Amway Center in Orlando


    Don't lie, Shakira. Not your hips, not your lips, not anything. Tell us: Why won't you come back to Tampa?

  5. Jameis Winston held his pro day at Florida State's indoor practice facility. His pro team will be getting one soon.