The call for an above-average season reflects the lack of El Nino conditions for the first time in several years. A strong El Nino typically suppresses tropical development in the Atlantic by inhibiting thunderstorm development, the seeds of tropical systems.
Since 2014, much of the equatorial Pacific has been dominated by one of the strongest El Ninos ever recorded. However, since late 2016, El Nino conditions have weakened substantially.
“The outlook reflects our expectation of a weak or nonexistent El Nino, 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 NOAA’s Climate Prediction Center.
While we are currently in a neutral El Nino state, the forecast for the near future is not as clear.
“There is always substantial uncertainty in predicting El Nino or La Nina, especially at this time of year. The models are quite mixed as far as whether El Nino might develop as the season progresses,” Bell said. “And they are also mixed as to whether if in fact El Nino develops, will it become strong enough to actually impact the hurricane season.”
Any named storms that do develop this summer will be lagging. For the third consecutive year, a tropical system (dubbed Arlene on April 20) formed in the Atlantic well before the official June 1 start of hurricane season.
Today’s prediction comes on the heels of an active 2016 hurricane season, the first above-average season in the Atlantic since 2012. Last year a total of 15 named storms developed, seven of which reached hurricane status. Of those hurricanes, four were classified as major hurricanes.
The 2016 hurricane season’s most notable storm was Hurricane Matthew, the first Category 5 hurricane in the Atlantic since Hurricane Felix in 2007. Forming in late September, Matthew caused widespread devastation in parts of the Caribbean and Southeast U.S., resulting in 603 deaths, 543 in Haiti alone, and more than $15 billion in total damages.
NOAA’s annual hurricane seasonal outlook is the final major preseason forecast given by meteorology organizations and research institutions from around the world. In addition to NOAA’s outlook, the Tropical Storm Risk (TSR) Consortium in London and Colorado State University (CSU) round out the three most prominent hurricane season forecasts.
Both TSR and CSU released their outlooks in early April, and both call for a slightly below-average year in the Atlantic. Among the many factors expected to inhibit tropical activity are the return of moderate El Nino conditions and unfavorable surface winds in the tropical Caribbean region.
In addition to its outlook, NOAA also announced some major changes to the hurricane forecast products available to the public this year.
- NOAA will issue storm surge watches and warnings for coastal areas.
- NOAA will issue “potential for development” advisories for areas of tropical activity that aren’t officially a tropical storm, but may still threaten land with tropical or hurricane-like conditions within 48 hours.
- New visualization tool used to predict the exact anticipated time of arrival for tropical storm/hurricane-force winds.
- A dynamic hurricane cone of uncertainty graphic that will allow the public to click on a specific area to see how far outside the cone tropical force or hurricane force winds will extend.
NOAA will update its hurricane outlook again in early August.