CSU Team Predicts Slightly Below Average Hurricane Season

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A boat is driven ashore by the winds of Hurricane Earl in 2010. (File photo)
A boat is driven ashore by the winds of Hurricane Earl in 2010. (File photo)

Hurricane researchers at Colorado State University predicted a slightly-below average Atlantic hurricane season for 2019, pointing to the effects of a weak El Nino system, which will keep wind shear slightly above average, and slightly below-average surface temperatures in the Atlantic.

The CSU Tropical Meteorology Project predicts 13 named storms, with a 39 percent chance of a landfall in the Caribbean. The entire, 35-page report can be downloaded here.

The researchers included their annual caveat, “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 CSU team also noted its forecast is intended to provide a best estimate of activity in the Atlantic during the upcoming season – not an exact measure.

A weak El Niño developed in the tropical Pacific last month. CSU anticipates that these conditions are likely to persist through the peak of the hurricane season. El Niño tends to increase upper-level westerly winds across the Caribbean into the tropical Atlantic, tearing apart hurricanes as they try to form.

The tropical Atlantic is slightly cooler than normal right now, according to the report. Colder-than-normal sea surface temperatures in the tropical Atlantic provide less fuel for tropical cyclone formation and intensification. They are also associated with a more stable atmosphere as well as drier air, both of which suppress organized thunderstorm activity necessary for hurricane development.

13 named storms
The CSU Tropical Meteorology Project team is predicting 13 named storms during the Atlantic hurricane season, which runs from June 1 to Nov. 30. Of those, researchers expect five to become hurricanes and two to reach major hurricane strength (3, 4 or 5 on the Saffir/Simpson scale) with sustained winds of 111 miles per hour or greater.

The team bases its forecasts on a statistical model, as well as a new model that uses a combination of statistical information and forecasts from a dynamic model. Both of these models are built on about 40 years of historical data and evaluating such conditions as Atlantic sea surface temperatures, sea level pressures, vertical wind shear levels (the change in wind direction and speed with height in the atmosphere), El Niño (warming of waters in the central and eastern tropical Pacific), and other factors.

So far, the 2019 hurricane season is exhibiting characteristics similar to 1969, 1987, 1991, 2002, and 2009, the report’s authors write.

“1987, 1991, 2002 and 2009 had below-average Atlantic hurricane activity, while 1969 was a very active hurricane season,” said Phil Klotzbach, research scientist in the Department of Atmospheric Science and lead author of the report.

The team predicts that 2019 hurricane activity will be about 75 percent of the average season. By comparison, the team had predicted a below average season for 2018 and the hurricane activity that year was about 120 percent of the average season.

The 2018 season was most notable for Hurricanes Florence and Michael, which devastated the Carolinas and portions of the Florida Panhandle, respectively.

The CSU team will issue forecast updates on June 4, July 2 and Aug. 6.

This is the 36th year that the CSU hurricane research team has issued its Atlantic basin seasonal hurricane forecast. Recently, the Tropical Meteorology Project team has expanded to include Michael Bell, associate professor in the CSU Department of Atmospheric Science, and Jhordanne Jones, graduate research assistant in the same department.

Landfall probability
The report also includes the probability of major hurricanes making landfall, predicting a 39 percent chance of a major hurricane making landfall somewhere in the Caribbean. The average for the last century is 42 percent.

The forecast team also tracks the likelihood of tropical storm-force, hurricane-force and major hurricane-force winds occurring at specific locations along the coastal United States, the Caribbean and Central America through its Landfall Probability website.

That website gave:
– A 31 percent chance of one or more named storms tracking within 50 miles of the U.S. Virgin Islands,
– A 14 percent chance of one or more hurricanes tracking within 50 miles, and
– A four percent chance of one or more major hurricanes tracking 50 miles of the territory.

The site provides information for all coastal states as well as 11 regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine. Landfall probabilities for regions and counties are adjusted based on the current climate and its projected effects on the upcoming hurricane season.

Other landfall predictions for the season were:
– 48 percent for the entire U.S. coastline (average for the last century is 52 percent)
– 28 percent for the U.S. East Coast including the Florida peninsula (average for the last century is 31 percent)
– 28 percent for the Gulf Coast from the Florida panhandle westward to Brownsville (average for the last century is 30 percent)

Original Source: https://stjohnsource.com/2019/04/04/csu-team-predicts-slightly-below-average-hurricane-season/