Freight and logistics companies should prepare for a potentially busy Atlantic hurricane season. Meteorologists with the Colorado State University’s (CSU) Tropical Meteorology Project have released their outlook for 2020, and they expect more storms than normal.
The group is forecasting 16 named storms, with eight of them becoming hurricanes (sustained winds of at least 74 mph) and four becoming major hurricanes. A major hurricane is one that ranks as a Category 3 or higher on the Saffir-Simpson scale, with winds of 111 mph or greater. This forecast is above the 30-year average (1981 through 2010) of 12 named storms, six hurricanes and three major hurricanes.
Though the official Atlantic hurricane season runs from June through November, storms can occasionally develop outside those months. Recent examples are Subtropical Storm Andrea in May 2019, Tropical Storm Alberto in May 2018 and Tropical Storm Arlene in April 2017.
The CSU outlook is based on more than 30 years of statistical factors combined with data from seasons exhibiting similar features of sea-level pressure and sea-surface temperatures in the Atlantic and eastern Pacific oceans.
Landfalling tropical storms and hurricanes can cause havoc in freight markets, resulting in dramatic rises in volumes as well as tightening capacity. Getting ahead of the storms is the best way for everyone in the logistics industry to better respond to recovery and rebuilding. FreightWaves SONAR subscribers can easily track tropical system data and forecasts in the Critical Events platform.
Landfalls
There is no strong correlation between the number of named storms or hurricanes that develop and how many make landfall in the United States. One or more of the 16 named storms that CSU has predicted to develop this season could hit the U.S., or none of them could. But Dr. Philip Klotzbach, a research scientist on the CSU team, noted that a number of storms could make landfall this year.
“We anticipate an above-average probability for major hurricanes making landfall along the continental United States coastline and in the Caribbean,” Klotzbach said. “As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. They should prepare the same for every season, regardless of how much activity is predicted.”
The 1992 season produced only six named storms and one subtropical storm. However, one of those named storms was Hurricane Andrew, a Category 5 hurricane that devastated South Florida. In 1983, only four named storms developed, 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 Atlantic season produced 19 named storms and 12 hurricanes. Despite the high number of storms that year, not a single hurricane made landfall in the U.S. and only one tropical storm made landfall.
In other words, a season can have many storms with little to no impact, or few storms with major impacts. The U.S. averages one to two hurricane landfalls each season, according to NOAA’s Hurricane Research Division statistics.
In 2019, two hurricanes made U.S. landfalls – Barry in Louisiana and Dorian in North Carolina. In 2018, four named storms impacted the U.S. coast, most notably hurricanes Florence and Michael within a month of each other. In 2017, seven named storms impacted the U.S. coast, including Puerto Rico. These included Harvey, Irma and Maria, which battered Texas, Florida and Puerto Rico, respectively.
Before that, the U.S. had been on a bit of a lucky streak. The 10-year running total of U.S. hurricane landfalls from 2006 through 2015 was seven, according to Alex Lamers, a meteorologist at the National Weather Service. This was a record low for any 10-year period dating to 1850, and considerably lower than the average of 17 per 10-year period dating to 1850.
None of the U.S. landfalls from 2006 through 2015 were major hurricanes. The bottom line is it’s impossible to know for certain if a hurricane will make landfall this season. Keep in mind that even a weak tropical storm hitting the U.S. can cause major impacts, particularly if it moves slowly and triggers flooding.
Effect of La Niña and El Niño
El Niño/La Niña, the periodic warming/cooling of the equatorial eastern and central Pacific Ocean, can shift weather patterns over a period of months. Its status is always one factor that is considered in hurricane season forecasting. But please understand that the status of the El Niño-Southern Oscillation (ENSO) is notoriously difficult to predict. This is especially true from February to May, when the “spring predictability barrier” is in play, a period when forecast skill is lower than the rest of the year.
As of early spring, a weak El Niño was in place, but waters in March slowly cooled. Klotzbach noted that a transition to neutral (neither El Niño nor La Niña) or potentially a weak La Niña is likely by this summer or fall. The CSU team anticipates neutral conditions through the first half of the hurricane season consisting of June, July and August, with either neutral or La Niña conditions in the second half of the season, September, October and November.
El Niño – cooling waters in the estern Pacific – usually increases vertical wind shear in the Atlantic basin, which includes the Gulf of Mexico and the Caribbean Sea. Shear occurs when winds increase dramatically in speed, or change direction, with altitude. Wind shear tears apart hurricanes. A lack of El Niño this hurricane season means less wind shear is likely over the Atlantic, possibly resulting in a high number of named storms/hurricanes.
The La Niña years of 2010 and 2011 are among several tied for the third-most-active Atlantic seasons on record (both years had 19 named storms). The next La Niña year, 2016, was also quite active, with 15 named storms that included Category 5 Matthew and three other major hurricanes. La Niña conditions recurred midway through the hyperactive and catastrophic 2017 season that produced Harvey, Irma and Maria.
Other factors
Klotzbach and the CSU team are also looking at sea surface temperatures (SSTs) in the Atlantic Ocean, Caribbean and Gulf of Mexico. SSTs in parts of the Atlantic basin are already above average, and climate models suggest that most of, if not the entire, basin will be warmer than average in the peak of the hurricane season.
An above-average number of tropical storms and hurricanes is more likely if temperatures in the main development region between Africa and the Caribbean Sea are warmer than average. Conversely, below-average ocean temperatures can lead to fewer tropical systems than if waters were warmer.
Meteorologists will also have to watch the amount of dry air that rolls off the coast of Africa. Even if water temperatures are boiling and there is little wind shear, dry air can still disrupt developing tropical cyclones or prevent their development.
Hurricanes need a rather precise set of factors to come together in order for them to develop and strengthen. Meteorologists will have to keep track of all these factors.
