Colorado State University hurricane researchers are predicting a slightly above-average Atlantic hurricane season in 2018, citing the relatively low likelihood of a significant El Niño as a primary factor.
Tropical Atlantic sea surface temperatures are currently near their long-term average values. Consequently, they are considered a neutral factor for 2018 Atlantic hurricane activity at the present time.
A weak La Niña this past winter has weakened slightly over the past few weeks. While there is the potential that a weak El Niño could develop by the peak of the Atlantic hurricane season, the odds of significant El Niño development appear relatively low. 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 western tropical North Atlantic is currently slightly warmer than normal, while the eastern tropical Atlantic is slightly cooler than normal. Colder-than-normal sea surface temperatures 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.
14 named storms
The CSU Tropical Meteorology Project team is predicting 14 named storms during the Atlantic hurricane season, which runs from June 1 to Nov. 30. Of those, researchers expect seven to become hurricanes and three 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 over 60 years of historical data that include 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 2018 hurricane season is exhibiting characteristics similar to 1960, 1967, 1996, 2006 and 2011.
“The years 1960, 1967 and 2006 had near-average Atlantic hurricane activity, while 1996 and 2011 were both above-normal hurricane seasons,” said Phil Klotzbach, research scientist in the Department of Atmospheric Science and lead author of the report.
The team predicts that 2018 hurricane activity will be about 135 percent of the average season. By comparison, 2017’s hurricane activity was about 245 percent of the average season. The 2017 season was most notable for Hurricanes Harvey, Irma and Maria, which devastated the United States and portions of the Caribbean.
The CSU team will issue forecast updates on May 31, July 2 and Aug. 2.
This is the 35th year that the CSU hurricane research team has issued the Atlantic basin seasonal hurricane forecast. Recently, the Tropical Meteorology Project team has expanded to include Michael Bell, associate professor in the Department of Atmospheric Science. William Gray launched the report in 1984 and continued to be an author on them until his death in 2016.
The CSU forecast is intended to provide a best estimate of activity to be experienced during the upcoming season – not an exact measure.
Bell cautioned coastal residents to take proper precautions.
“It takes only one storm near you to make this an active season,” Bell said.
The report also includes the probability of major hurricanes making landfall:
- 63 percent for the entire U.S. coastline (average for the last century is 52 percent)
- 39 percent for the U.S. East Coast, including the Florida peninsula (average for the last century is 31 percent)
- 38 percent for the Gulf Coast from the Florida panhandle westward to Brownsville (average for the last century is 30 percent)
- 52 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.
Klotzbach and Bell update 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 2018:
Released April 5, 2018
Tropical Cyclone Parameters Extended Range
(1981-2010 Climatological Median Forecast for 2018
Named Storms (12)* 14
Named Storm Days (60.1) 70
Hurricanes (6.5) 7
Hurricane Days (21.3) 30
Major Hurricanes (2.0) 3
Major Hurricane Days (3.9) 7
Accumulated Cyclone Energy (92) 130
Net Tropical Cyclone Activity (103%) 135
* Numbers in ( ) represent medians based on 1981-2010 data.