After a record breaking season in 2020 with 30 named storms for the Atlantic basin, NOAA's Climate Prediction Center forecasts 2021 as another active season, however nowhere near the level seen one year ago.
Here's the break down:
It's predicted there will be 13-20 named storms, this is considered when winds are above 39mph. A tropical storm has winds between 39mph-73mph.
Of those storms, 6-10 will be hurricanes, wind speeds above 74mph.
Of those, 3-5 are expected to be Major Hurricanes with winds above 111mph. A Major Hurricane is considered a Category 3 or higher.
As percentages, forecasters predict there to be a 60% chance to be an above average hurricane season, a 30% chance to be average and a 10% chance to be a below average hurricane season in the Atlantic basin.
There are several factors to forecasting an above average season for 2021:
1) El Nino Southern Oscillation is neutral (ENSO-neutral) and potentially will turn to La Nina later in the season which tends to lead to a more active pattern.
2) Warmer than average Sea-Surface-Temperatures (Tropical Atlantic Ocean and Caribbean Sea)
3) Weaker Tropical Atlantic Trade Winds
4) Enhanced African Monsoon
This year, a week before the start of Hurricane season, in the Atlantic basin, Ana was already named as winds increased above 39mph near Bermuda. Hurricane season starts June 1st and runs through November 30th, however storms can form both before and after the season starts and ends.
The World Meteorological Organization created the lists and reuses each list every six years. The 2021 names will be reused in 2027, unless a devastating hurricane occurs and is retired, like Katrina, Rita and Wilma in 2005. If more than 21 named storms occur in a season, up until 2020 the Greek Alphabet was used. Because storms sounded the same and the WMO didn't want to retire the Greek Alphabet if they were devastating, they revised the rules and created a supplemental set of names to use when surpassing 21 storms. More on the background of tropical storms and the new list of supplemental names can be found here.