NOAA Atlantic Hurricane Season Forecast Issued; Near-Average Season Likely

The 30-year historical average for the Atlantic basin is 12 named storms, six hurricanes and three major hurricanes. NOAA's forecast calls for a 70 percent likelihood of:

- Ten to 16 named storms (including January's Hurricane Alex).- Four to eight of which would become hurricanes.- One to four of which would become major hurricanes – those of at least Category 3 strength on the Saffir-Simpson Hurricane Wind Scale.

According to NOAA, "this is a more challenging hurricane season outlook than most because it is difficult to determine whether there will be reinforcing or competing climate influences on tropical storm development."

The main challenge in this year's forecast is the uncertainty as to whether climate factors will be reinforcing or competing. More specifically, it is unknown if the "warm Atlantic Multi-decadal Oscillation (AMO) and high-activity era for Atlantic hurricanes which began in 1995 has ended, and whether a cool AMO and low-activity era, similar to that observed during 1971-1994, has begun."

NOAA points out that the AMO "sets the backdrop upon which other climate phenomena such as El Niño and La Niña overlay." In addition, the rate that El Niño dissipates and the rate at which La Niña develops and intensifies will also play a role in the Atlantic hurricane season.

The Weather Company, an IBM Business, issued its seasonal forecast earlier in May calling for the 2016 Atlantic hurricane season to be the most active since 2012. A total of 14 named storms, eight hurricanes and three major hurricanes are forecast during the coming season, the outlook said.

Colorado State University's forecast, which is headed by Dr. Phil Klotzbach, said the Atlantic will see 13 named storms, six hurricanes and two major hurricanes.

An important note about all three outlooks is that the seasonal forecast numbers include Hurricane Alex, a rare January hurricane that struck the Azores. Though the official hurricane season spans the months from June through November, we occasionally see storms form outside those months.

(MORE: Hurricane Alex Recap)

Here are three questions about this outlook and what it means for you.

What Does This Forecast Mean For the U.S.? 

There is no strong correlation between the number of storms or hurricanes and U.S. landfalls in any given season. One or more of the named storms forecast to develop this season could hit the U.S., or none at all. Therefore, residents of the coastal United States should prepare each year no matter the forecast.

A couple of classic examples of why you need to be prepared each year occurred in 1992 and 1983.

The 1992 season produced only six named storms and one subtropical storm. However, one of those named storms was Hurricane Andrew, which devastated South Florida as a Category 5 hurricane.

In 1983, there were only four named storms, but one of them was Alicia. The Category 3 hurricane hit the Houston-Galveston area and caused 21 direct fatalities there, almost as many as Andrew did in South Florida, which was 23 deaths.

(MORE: Hurricane Central)

In contrast, the 2010 season was active. There were 19 named storms and 12 hurricanes that formed in the Atlantic Basin, but despite the high number of storms that year, no hurricanes and only one tropical storm made landfall in the U.S.

The U.S. averages between 1 and 2 hurricane landfalls each season, according to NOAA's Hurricane Research Division. However, the number of U.S. landfalls has been much below average in the last decade.

The current 10-year running total (2006-2015) of U.S. hurricane landfalls is seven, according to Alex Lamers, a meteorologist with the National Weather Service. This is a record low for any 10-year period dating to 1850, and is considerably lower than the average of 17 per 10-year period dating back to 1850, Lamers added.

(MORE: Florida Hurricane Drought Continues)

Bottom line: the U.S. is due for another hurricane strike sooner rather than later, but it's impossible to know if that will occur this season. Keep in mind, however, that even a weak tropical storm hitting the U.S. can cause major impacts, particularly if it moves slowly, resulting in flooding rainfall.

Will El Niño or La Niña play a role?

The strong El Niño we saw this winter has faded away and may transition to its counterpart, La Niña, by this fall. If this transition to La Niña conditions occurs, it could happen during the middle of the 2016 hurricane season.

Klotzbach said that the transition from El Niño to neutral or La Niña conditions during the 2016 hurricane season makes this particular April hurricane outlook very uncertain.

The transition could cause the early part of the hurricane season to be less active while the second half of the season may more active, according to The Weather Company's outlook.

Using the El Niño intensity classification scheme from consultant meteorologist Jan Null, we examined five previous hurricane seasons following strong El Niños. The statistics from each of those seasons are below.

As you can see, there's quite a spread, ranging from a record low four named storms in 1983 to 14 in 1998. The 1998 season featured seven U.S. landfalling tropical cyclones, three of which – Bonnie, Earl, and Georges – were hurricanes at landfall. 

Despite only four named storms in 1983, two of those made U.S. landfall, including Category 3 Hurricane Alicia in southeast Texas. This again illustrates the poor correlation between the number of named storms or hurricanes and landfalls. 

In all, there have been a total of six U.S. hurricane landfalls in the five post-strong El Niño seasons dating to 1958, for an average of roughly one a season. Two of those five seasons were without a U.S. hurricane landfall, however.

Klotzbach found that the chance of a U.S. hurricane impact rises dramatically in a La Niña or neutral (neither El Niño or La Niña) season compared to an El Niño season.

Without El Niño contributing to stronger wind shear and dry air in the Caribbean Sea like we saw in 2015, it loads the dice toward an increased chance of tropical cyclones surviving into the Caribbean Sea, or forming there in 2016, particularly later in the season as El Niño disappears farther in the rear-view mirror.

What Other Factors Are in Play?

The three previous Atlantic hurricane seasons featured either few named storms (2014; 8) or a greater number of storms, but few survived long or became hurricanes (2013 and 2015).

The 2013 and 2014 seasons featured prohibitive dry air and/or wind shear during a significant part of the season, but El Niño was nowhere to be found.

In 2015, El Niño likely played a significant suppressing role in the 2015 Atlantic hurricane season. Klotzbach found that from June through October 2015, Caribbean wind shear was the highest on record dating to 1979. Klotzbach said the magnitude of dry air over the Caribbean Sea in the peak season months of August and September also set a record.

As you can see, dry air and wind shear can be detrimental to tropical storm or hurricane development whether El Niño is present or not. This is one factor to watch in the 2016 season.

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