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Above average hurricane season is forecast

Lazaro Aleman: Greene Publishing, Inc.

With the start of the 2018 Atlantic hurricane season only a month and half away, a just-released forecast varies it only slightly from last year's historically destructive season.

The Colorado State University (CSU) Tropical Meteorology Project, which last week released its April outlook, is forecasting 14 named storms in the coming season, seven of them hurricanes and three major hurricanes. These numbers, say the experts, are slightly above the 30-year average of 12 named storms -- six of them hurricanes and two major hurricanes.

A major hurricane is defined as one that is a Category 3 or stronger on the Saffir-Simpson Hurricane Wind Scale, which means it carries winds of 111 to 129 mph and has the potential to cause significant loss of life and property damage.

According to the CSU report, the probability of major hurricanes making landfall this year are 63 percent for the entire U.S. coastline; 39 percent for the East Coast, including peninsular Florida; and 38 percent for the Gulf Coast, from the Florida panhandle westward to Brownsville, Tx.

The 2018 forecast, coming in the wake of last year's devastating hurricane season (which included monster storms Harvey, Irma, and Maria) is anything but reassuring to the island and coastal residents of the storm-ravaged Caribbean and Eastern Seaboard, respectively.

The 2017 season, according to the CSU report, was the fifth most active since such record keeping started in 1851, rating 245 percent higher than the average season. The 2018 season, meanwhile, is predicted to be 135 percent higher than the average, according to the CSU report.

Keep in mind, however, that the CSU forecast is only a projection, and an early one at that, if it is based on 30-plus years of statistical data, including sea-level pressures, sea-surface temperatures and other features of similar seasons in the Atlantic and eastern Pacific oceans.

Here, however, are some things to keep in mind relative to the CSU outlook, according to the Weather Company, whose chief journalistic mission is reporting on breaking weather news, the environment, and the sciences.

Although the Atlantic hurricane season runs officially from June 1 through Nov. 30, that doesn't mean that storms can't occur before or after this period, as has happened more than once. Nor does a strong correlation exist between the number of storms or hurricanes and landfalls on the U.S. mainland in a given season. Meaning that one, several or none of the 14 named storms forecast for 2018 may hit the U.S. Nonetheless, coastal residents are advised that they should always prepare for the eventuality of a major storm hitting.

Examples of the lack of correlation abound, per the Weather Channel. It cites 1992 and 1983 as prime examples. Despite only six named storms and one subtropical storm in 1992, one of the named storms that season was Andrew, a Category 5 hurricane that destroyed South Florida. And in 1983, only four named storms occurred. Even so, one of these, Alicia, a Category 3 hurricane, accounted for nearly as many fatalities in the Galveston area as Andrew in South Florida.

By contrast, notes the Weather Company, the 2010 season gave rise to 19 named storms and 12 hurricanes; yet, not a single hurricane and only one tropical storm hit the U.S. Mainland. In short, states the Weather Channel, "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."

Before the 2016 and 2017 seasons -- which accounted for five and seven named storms hitting the U.S. coast or territories, respectively -- the 10-year average for 2006 through 2015 was seven named storms, a record low for any 10-year period since 1850, according to meteorologist Alex Lamers of the National Weather Service. Typically, according to Lamers, the average going back to 1850 was 17 named storms per 10-year periods.

"Bottom line," underscores the Weather Company, "it's impossible to know for certain if a U.S. hurricane strike, or multiple strikes, 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."

Another factor influencing the season is what role, if any, El Niño or La Niña play in the coming months. El Niño, a natural phenomenon that accounts for the periodic warming of the central and eastern equatorial waters of the Pacific Ocean, "tends to produce areas of stronger wind shear (the change in wind speed with height) and sinking air in parts of the Atlantic Basin," according to the Weather Channel. Which developments are said to be hostile to either the formation or maintenance of tropical cyclones.

At present, there appears to be uncertainty as to the state of El Niño, according to the experts. Indications, however, are that it will be in a neutral or weakened state at the peak of the hurricane season, the say. The peak of hurricane season is August through October, with September the prime month.

Another factor with a more direct role in the development of tropical cyclones in the Atlantic, say the experts, is water temperatures, with the warmer temperature allowing hurricanes to intensify. At present, the water temperatures in the North Atlantic are cool, but what they may be during the peak of hurricane season remains a question, say the experts, noting that during the last few years, Atlantic waters have started the year colder than normal but have significantly warmed in the spring and summer. The CSU report notes that if this trend continues this year, the warm waters can help fuel another active season of hurricanes.

"Water temperatures of 80 degrees or higher are generally supportive of tropical storm and hurricane formation and development," states the Weather Channel.

Finally, say the experts, there is the factor of the Atlantic Multidecadal Oscillation (AMO), which they say is at the end of its positive phase. A climate cycle that roughly lasts 50 to 80 years, the AMO is associated with increased hurricane activity during the first half of its period and decreased activity during the second half.

"The current upward swing began in 1995, and the index that measures AMO has been in the cold or decreased phase in recent years and is near its long-term average," states the Weather Channel.

The CSU's April forecast is traditionally one of the first looks at the upcoming Atlantic storm season. Researchers will develop more detailed outlooks once the season actually begins on June 1.

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