Experts involved with Colorado State University’s (CSU) Tropical Weather Project have released an update to their 2021 seasonal outlook for the Atlantic, and it doesn’t look good: even more storms in what was expected to be another above-normal hurricane season are forecast. Weatherboy.com is a sponsor of this annual research.
The initial seasonal outlook was unveiled in April at the National Tropical Weather Conference. The event, usually a large conference attended by a variety of meteorologists and related professionals in South Padre Island, Texas, shifted online for the second year in a row due to the ongoing global pandemic. The initial outlook called for a total of 17 named storms of which 8 are expected to be hurricanes and 4 are expected to be major hurricanes. In addition to a greater than average number of storms, odds also favor that a major hurricane will make landfall along the U.S. East or Gulf Coast: odds are 130% of the long-period average. Today’s updated outlook will be updated once again on August 5.
Based on a review of the forecast data and analysis of current conditions, the CSU team increased their forecast which now calls for a total of 20 named storms, 9 hurricanes, and 4 major hurricanes. These numbers include the 5 named storms and 1 hurricane that have already formed, including Elsa which first made landfall on Florida days ago and brought heavy rain, gusty winds, and tornadoes to the Mid Atlantic and New England yesterday.
In a typical Atlantic hurricane season, which runs from the beginning of June to the end of November, there are 12.1 named storms, from which 6.4 become hurricanes. In a typical year over the last 100 years, there’s a 52% chance that a major hurricane will strike somewhere along the U.S. East or Gulf coasts; the average is 32% for the U.S. East Coast including the Florida peninsula, 30% for the Gulf Coast from the Florida panhandle west to Brownsville, Texas. There’s also on average a 42% chance that a major hurricane will make landfall somewhere in the Caribbean.
The study only examines and forecasts activity in the Atlantic basin; however, data from around the globe is used to assemble the outlook.
An active 2021 forecast comes on the heels of an over-active 2020 which saw a record-breaking number of storms. A record 30 named storms, 13 hurricanes, and 6 major hurricanes formed, with a record 12 named storms making landfall in the United States. Due to the excessive number of named storms, the National Hurricane Center had to rely on letters of the Greek alphabet to name storms. In 2021, the National Hurricane Center will now use names from a back-up list rather than using Greek letters.
The first named storm of the 2021 Atlantic Hurricane Season will be Ana, followed by Bill, Claudette, and Danny. If the CSU outlook is accurate, names all the way through Victor could be used.
The scientists involved with this study are citing the likely absence of El Nino as a primary factor to the expected above-normal forecast. The report adds, “Tropical Atlantic sea surface temperatures are near their long-term averages, while subtropical Atlantic sea surface temperatures are much warmer than their long-term average values. The warmer subtropical Atlantic also favors an active 2021 Atlantic hurricane season.” The team bases its forecasts on a statistical model, as well as a model that uses a combination of statistical information and model output from the European Centre for Medium-Range Weather Forecasts.
According to report authors, 2021 appears to be similar to the 1996, 2001, 2008, 2011, and 2017 hurricane seasons. “All of our analog seasons had above-average Atlantic hurricane activity, with 1996 and 2017 being extremely active seasons,” said Phil Klotzbach, research scientist in the Department of Atmospheric Science and lead author of the report.
Overall, the team predicts that 2021 hurricane activity will be about 140% of the average season. By comparison, 2020’s hurricane activity was about 170% of the average season.
The Tropical Meteorology Project team also includes 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.
Bell warns that all coastal residents should keep an eye on the tropics regardless of past seasons or current conditions in the ocean. “It takes only one storm near you to make this an active season,” Bell said.
In addition to Weatherboy, funding for this year’s report has been provided by Interstate Restoration, Ironshore Insurance, the Insurance Information Institute, and a grant from the G. Unger Vetlesen Foundation.
The full report and verifications of past outlooks can be seen here: