Early signs point to yet another above average hurricane season. This year’s hurricane season is leaning towards above-average activity fueled by early indicators that the Atlantic multi-decadal oscillation (AMO) remains in a high positive phase, and signs that El Nino — during which trade winds are weakened and warm water is pushed back east toward the west coast of the Americas — will not happen this year.
This is according to an early forecast from the Colorado State University (CSU) Tropical Meteorology Project, which forecasts a 40 percent chance of above-average AMO occurring, while the possibility of AMO being below average and El Nino developing saw a 10 percent chance of occurrence.
According to the National Oceanic and Atmospheric Administration, AMO is an ongoing series of long-duration changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 20-40 years at a time and a difference of about 1°F between extremes. These changes are natural and have been occurring for at least the last 1,000 years.
AMO is associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricanes, NOAA said.
According to CSU researchers, when Pacific waters are warmed by El Nino, historically there are fewer hurricanes in the Atlantic. Furthermore, El Nino generates increased vertical wind shear, which can reduce hurricane activity in the Atlantic.
La Nina, meanwhile, has the opposite effect.
An above-average hurricane season typically includes 13-16 named storms, 6-8 hurricanes and 2-3 major hurricanes, according to researchers.
The 2021 Atlantic hurricane season was the third most active on record, producing 21 named storms. It was also the second season in a row after 2020, and third overall, in which the designated 21-name list of storm names was exhausted.