On Monday August 5th Colorado State University (CSU) hurricane researchers issued a news release in which they continue to predict a near-average 2019 Atlantic hurricane season.
The CSU team is predicting a total of 12 additional named storms to form after August 1st . Of those, six are expected 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. These forecast numbers do not include Subtropical Storm Andrea and Hurricane Barry which formed prior to August 1.
The scientists, led by I.I.I. non-resident scholar, Dr. Phil Klotzbach, cite both near-average sea surface temperatures in the tropical Atlantic and a weakening El Niño event in the tropical Pacific as the primary reasons for the near-average prediction.
El Niño tends to increase upper-level westerly winds across the Caribbean into the tropical Atlantic, tearing apart hurricanes as they try to form. While El Niño has weakened over the past several months, they anticipate that lingering warming in the central tropical Pacific should be a slight inhibiting factor for the remainder of the hurricane season.
The tropical Atlantic currently has near average sea surface temperatures. A warmer tropical Atlantic provides more fuel for developing tropical cyclones. Increased tropical Atlantic warmth is also associated with moister air and a more unstable atmosphere, both of which foster organized thunderstorm activity necessary for hurricane development. Vertical wind shear was slightly stronger than normal across the Caribbean in July. This tends to be associated with quieter Atlantic hurricane seasons.
The team based this forecast on 40 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 2019 hurricane season is exhibiting characteristics similar to 1990, 1992, 2012 and 2014. “1992 and 2014 had below-average Atlantic hurricane activity, 1990 had near-average hurricane activity, and 2012 had above-average Atlantic hurricane activity.” said Dr. Klotzbach.
The full forecast report is available here.