By Chris Dolce and Jon Erdman and Linda Lam From The Weather Channel

Hurricane Season Forecast Increased

Meteorologist Danielle Banks explains why the total named storms, hurricanes and category 3 or higher hurricanes have increased by 1.

Story Highlights

The number of expected named storms for the 2016 Atlantic hurricane season has increased.

The most active hurricane season since 2012 is anticipated.

The number of forecast tropical storms and hurricanes for the 2016 Atlantic hurricane season has increased slightly in the latest forecast released Friday from Colorado State University. This ongoing Atlantic hurricane season is expected to be near historical averages.

A total of 15 named storms, 6 hurricanes and 2 major hurricane are expected this season, according to the forecast prepared by CSU, which is headed by Dr. Phil Klotzbach.

This is close to the 30-year average of 12 named storms, six hurricanes and three major hurricanes. A major hurricane is one that is Category 3 or stronger on the Saffir-Simpson Hurricane Wind Scale.

Numbers of Atlantic Basin named storms, those that attain at least tropical storm strength, hurricanes, and hurricanes of Category 3 intensity forecast by The Weather Company (right column), NOAA (second from right column) and Colorado State University (second from left column) compared to the 30-year average (left column).

The CSU outlook is based on a combination of 29 years of statistical predictors, combined with analog seasons exhibiting similar features of sea-level pressure and sea-surface temperatures in the Atlantic and eastern Pacific Oceans.

The two main factors that CSU expects will lead to the near average season are the “potential development of a weak La Nina and cooler-than-normal far North Atlantic sea surface temperatures.”

The Weather Company, an IBM Business, updated its seasonal forecast in mid-June, increasing each category by one storm, calling for the 2016 Atlantic hurricane season to be the most active since 2012. A total of 15 named storms, 9 hurricanes and 4 major hurricanes are forecast, the outlook said.

The National Oceanic Atmospheric Administration (NOAA) issued their forecast at the end of May, calling for 10-16 named storms, 4-8 hurricanes and 1-4 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.

The forecasts also includes the three tropical storms that have already formed: Bonnie, Colin and Danielle.

Here are three questions about this outlook and what it means for you.
Q: 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 12 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 almost as many direct fatalities there as Andrew did in South Florida.

In contrast, the 2010 season was active. There were 19 named storms and 12 hurricanes that formed in the Atlantic Basin.

Despite the large number of storms that year, not a single hurricane and only one tropical storm made landfall in the United States.

In other words, a season can deliver many storms, but have little impact, or deliver few storms and have one or more hitting the U.S. coast with major impact.

The U.S. averages between 1 to 2 hurricane landfalls each season, according to NOAA’s Hurricane Research Division statistics. 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 to 1850, Lamers added.

U.S. hurricane landfalls the last 10 years. Note: Sandy in 2012 is not shown since it officially made landfall as a non-tropical cyclone.

Of course, the record-breaking 2005 hurricane season is now outside that current 10-year running total. 2005 was also the last season we saw a Category 3 or stronger hurricane (Wilma) hit the U.S., the longest such streak dating to the mid-19th century.

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.
Q: Will El Nino or La Nina play a role?

The strong El Nino we saw this past winter is now gone, and its counterpart La Nina, is possible by this fall. Of course, if this handoff from El Nino to La Nina conditions occurs, it could happen during the middle of the 2016 hurricane season.

Using the El Nino intensity classification scheme from consultant meteorologist Jan Null, we examined five previous hurricane seasons following strong El Ninos. The statistics from each of those seasons is below.
Named Storms Hurricanes Cat. 3+ Hurricanes U.S. Hurricane Landfalls

As you can see, there’s quite a spread, ranging from a record low four named storms in 1983 to 14 such storms 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 Nino 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 Nina or neutral (neither El Nino or La Nina) season compared to an El Nino season.

Without El Nino contributing to stronger wind shear and dry air in the Caribbean Sea like we saw in 2015, it at least 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 Nino disappears farther in the rear-view mirror.
Q: 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 of which survived long or became hurricanes (2013 and 2015).

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

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

2015 Atlantic Tropical Cyclone Tracks

As you can see, dry air and wind shear can detrimental to tropical storm or hurricane development no matter whether El Nino is present or not. This is one factor to watch for in the 2016 season.

Klotzbach said that wind shear enhanced by El Nino is likely to dissipate the next several months. However, he added that the northern Atlantic Ocean has water temperatures that are colder than average which can cause atmospheric conditions to be unfavorable for the development and strengthening of Atlantic hurricanes.

For more on this story go to: https://weather.com/storms/hurricane/news/2016-hurricane-season-forecast-atlantic-colorado-state-csu-twc-noaa