June 1st is the official start to the Atlantic Hurricane Season and it could be another active year according to forecasters.
The season is already off to an early start with the formation of Tropical Storm Ana which developed nine days before the official start of the season northeast of Bermuda. This is the seventh consecutive year that a tropical system has formed before June 1st.
Tropical storms and hurricanes are more likely to form between the months of June through November –the typical hurricane season for the Atlantic—because oceanic and atmospheric conditions are prime for formation and evolution.
Two primary ingredients are needed for a tropical storm or hurricane to occur: warm water temperatures of at least 80°F (26.5°C), and minimal vertical wind shear allowing for thunderstorm convection to grow vertically.
While hurricane activity in the month of May is uncommon, it has been occurring more frequently, so much so that the National Hurricane Center opted to begin issuing Tropical Weather Outlooks earlier this year, beginning May 15th.
The majority of forecasters are in agreement that 2021 is shaping up to be another above-normal season, but likely not as busy as the record breaking 2020 hurricane season which saw a total of 30 named storms, 14 of which became hurricanes, and seven that became major hurricanes of Category 3 strength and high on the Saffir-Simpson Hurricane Wind Scale.
An average hurricane season generally experiences about 14 named tropical storms. About seven of those storms become hurricanes with wind speeds of at least 74 mph, and approximately three achieve major classification – wind speeds of at least 111 mph.
Forecasting agencies look at a variety of factors when predicting the number of storms each year and many are skeptical of an El Niño forming this season, a climatological phase which could significantly hinder storm development. Unlike a La Niña cycle, which contributed to the active 2020 Hurricane Season, an El Niño results cooler sea surface temperatures to the Atlantic region, which suppresses storm formation.
According to the National Oceanic and Atmospheric Administration (NOAA) La Niña conditions have ended and forecasters are estimating about a 67% chance that neutral conditions will continue through the summer season. The forecast for the fall however is less confident, with odds of a second-year La Niña currently hovering around 50–55%.
La Niña conditions may have officially concluded according to NOAA. However, that does not mean that ocean temperatures rapidly decrease. El Niño Southern Oscillations begins off the west coast of Central and South America and stretches westward towards Asia. Fluctuations in sea surface temperatures begin in this region and are therefore labeled as El Niño or La Niña. While this general area may be showing a weakening from La Niña back to a neutral phase the process is different in the Atlantic which may take longer to follow the transition.
Water temperatures continue to remain above average in some locations and were even trending warmer prior to the start of the hurricane season. Colorado State University released their first season predictions on April 8, 2021 calling for an above-average season and indicating that sea surface temperatures in the subtropical Atlantic are much warmer than average.
The subtropics are not the only concern, as of May 31, 2021 sea surface temperatures in the southern Gulf of Mexico and the Caribbean were between 80 and 85°F. These are areas where tropical cyclone formation is common for the month of June.
Regardless of the activity projected for the upcoming hurricane season residents need to be prepared and review their safety plan in preparation for the season. Now is the time to prepare and not wait until a storm is approaching.
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