Colorado State University’s Tropical Weather and Climate Research issued its first report about the 2021 hurricane season yesterday, April 8, 2021. This is the first “Extended Range Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2021”. The team at CSU expects the coming season to have above-normal activity. “We anticipate an above-average probability for major hurricanes making landfall along the continental United States coastline and in the Caribbean,” according to authors Klotzback, Bell and Jones.
They are predicting 17 named storms compared with an average of 12 over the 30-year period 1981-2010; 80 “named storm days” compared with a 59-day average; 8 hurricanes compared with 6 on average and 4 major hurricanes (Categories 3, 4 and 5) compared with an average of 3. CSU’s site also shows a chart indicating landfall strike probabilities for all counties along the Atlantic and Gulf coastline. This data is useful for investors that may want to assign rough probabilities of storms and damage for different coastal geographies.
The National Oceanic and Atmospheric Administration (NOAA) has updated its averaging period to 1991-2020, which shows higher averages than in the 1981-2010 period. For example, compared with the figures presented above, there were an average of 14 names storms, 7 hurricanes and 3 major hurricanes (12, 6 and 3, respectively) annually between 1991-2020. NOAA expects to release its seasonal forecast in late May and CSU will be updating their forecast in the next few months to include the more recent 30-year period. Since CSU is using an older, less active time period, their forecast is for “above-normal” activity may moderate when they update the averaging period. But the upshot is that the whole scale has moved up.
The 2020 hurricane season broke records with 30 named storms and 12 that made landfall. For an interesting visualization of the active 2020 hurricane season, the Climate Adaptation Center in Sarasota presents this time-lapse of last year’s season from NASA.
Landfall probability is one important factor, however, it is important to acknowledge that storms with weaker wind force, can linger over an area, dropping torrential rain and causing storm surge. This was the case with Hurricanes Irene and Sandy, in 2011 and 2012, which devastated towns in New England, causing heavy inland flooding as well as coastal damage.
As Klotzback, et al, include in each and every one of their reports, “coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. They should prepare the same for every season, regardless of how much activity is predicted.”
