By CSU Tropical Meteorology Project
Colorado State University hurricane researchers are predicting a slightly below-average Atlantic hurricane season in 2019, citing the relatively high likelihood of a weak El Niño as a primary factor.
Tropical Atlantic sea surface temperatures are currently slightly below their long-term average values and are consequently considered an inhibiting factor for 2019 Atlantic hurricane activity as well.
A weak El Niño has recently developed in the tropical Pacific. CSU anticipates that these weak El Niño conditions are likely to persist through the peak of the Atlantic 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. 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 (Saffir/Simpson category 3-4-5) 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 dynamical model. Both of these models are built on about 40 years of historical data and evaluating conditions including: 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. “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, 2018’s hurricane activity 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 their 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. Bill Gray, who originated the seasonal forecasts, launched the report in 1984 and continued to author them until his death in 2016.
The CSU forecast is intended to provide a best estimate of activity in the Atlantic during the upcoming season – not an exact measure.
As always, the researchers caution coastal residents to take proper precautions.
“It takes only one storm near you to make this an active season,” Bell said.
Landfalling probability included in report
The report also includes the probability of major hurricanes making landfall:
- 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)
- 39 percent for the Caribbean (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.
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.
The CSU team updates the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State University in Massachusetts.
Funding for this year’s report has been provided by Interstate Restoration, Ironshore Insurance, the Insurance Information Institute, Weatherboy and a grant from the G. Unger Vetlesen Foundation.
Extended range Atlantic Basin hurricane forecast for 2019
Released April 4, 2019
Tropical Cyclone Parameters Extended Range
(1981-2010 Climatological Average Forecast for 2019
Named Storms (12.1)* 13
Named Storm Days (59.4) 50
Hurricanes (6.4) 5
Hurricane Days (24.2) 16
Major Hurricanes (2.7) 2
Major Hurricane Days (6.2) 4
Accumulated Cyclone Energy (106) 80
Net Tropical Cyclone Activity (116%) 90
* Numbers in ( ) represent averages based on 1981-2010 data.
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