Colorado State University hurricane researchers continue to predict a below-average Atlantic hurricane season. They cite both a cooler than normal tropical Atlantic and the potential development of a weak El Niño event as the primary reasons for the below-average prediction.
The tropical Atlantic remains much colder than normal. A colder tropical Atlantic provides less fuel for developing tropical cyclones. Vertical wind shear was much stronger than normal across the Caribbean in July. This also tends to be associated with quieter Atlantic hurricane seasons. The tropical eastern and central Pacific is currently slightly warmer than normal. There is the potential that El Niño conditions could develop over the next few months. If this occurs, it would tend to increase vertical wind shear in the tropical Atlantic, tearing apart hurricanes as they try to develop.
Nine additional named storms
The CSU Tropical Meteorology Project team is predicting a total of nine additional named storms to form after Aug. 1. Of those, researchers expect three to become hurricanes and one to reach major hurricane strength (Saffir/Simpson category 3-4-5) with sustained winds of 111 miles per hour or greater. These forecast numbers do not include Tropical Cyclones Alberto, Beryl and Chris which formed prior to Aug. 1.
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 1968, 1986, 1993, 1994 and 2002.
“All of these analog seasons experienced below average Atlantic hurricane activity,” 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 70 percent of the average season. By comparison, 2017’s hurricane activity was about 245 percent of the average season.
This is the 35th year that the CSU hurricane research team has issued the Atlantic basin seasonal hurricane forecast. The late William Gray, professor in the Department of Atmospheric Science for over 40 years, launched the report in 1984.
The CSU forecast is intended to provide a best estimate of activity to be experienced during the upcoming season – not an exact measure.
Michael Bell, associate professor in the Department of Atmospheric Science at CSU and co-author of the report, cautioned coastal residents to take proper precautions.
“It takes only one landfall event near you to make this an active season,” Bell said.
The report also includes the post-July 31 probability of major hurricanes making landfall on U.S. soil:
- 35 percent for the entire U.S. coastline (full-season average for the last century is 52 percent)
- 20 percent for the U.S. East Coast including the Florida peninsula (full-season average for the last century is 31 percent)
- 19 percent for the Gulf Coast from the Florida panhandle westward to Brownsville (full-season average for the last century is 30 percent)
- 28 percent for the Caribbean (full-season 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.
Atlantic Basin hurricane forecast for 2018
Released Aug. 2, 2018
Tropical Cyclone Parameters Extended Range
(1981-2010 Climatological Median Forecast for 2018 in parentheses)
Named Storms (12)* 12**
Named Storm Days (60.1) 53
Hurricanes (6.5) 5
Hurricane Days (21.3) 15
Major Hurricanes (2.0) 1
Major Hurricane Days (3.9) 2
Accumulated Cyclone Energy (92) 64
Net Tropical Cyclone Activity (103%) 78
* Numbers in ( ) represent full-season medians based on 1981-2010 data.
** Forecast numbers include tropical cyclones that formed prior to Aug. 1.
Read more stories about research at Colorado State University.