What drives an active hurricane season?
NEW ORLEANS (WVUE) - It has been an exhausting two years. There have been five Louisiana landfalls; Tropical Storms Claudette and Cristobal, Hurricanes Delta and Zeta, and tied for the strongest Louisiana hurricanes on record, Laura and Ida.
But it’s not just the past two years for us. Across the Atlantic Basin, we have had six above-normal hurricane seasons in a row, including the past two that finished as the most active and third-most active on record.
And we could be heading for another one.
What drives an active season? One of the big climate signals we always talk about is El Nino and La Nina. We are currently in a La Nina and most models keep us there during the heart of hurricane season.
Under normal conditions, the trade winds push warm water from South America to the west, but in La Nina conditions, those trade winds get even stronger and that causes upwelling of cooler water to the surface.
The cooler water causes air to sink, which suppresses thunderstorms in the Pacific, but the air is more prone to rise in the Caribbean, giving way to more storms and better conditions for hurricanes to thrive.
Water temperatures are another crucial component.
Across the Atlantic, the signs for a potentially active season are there. The waters in the sub-tropical Atlantic and the main development region off the coast of Africa are running warmer than normal.
The Gulf of Mexico is no different, also with above-average conditions.
When we talk about the Gulf of Mexico, we are also talking about the loop current. The loop current contains the deepest areas of warm water in the Gulf. While it’s not responsible for storms developing, the loop current can definitely add unwanted fuel to an already existing storm. It’s always there, but some years it’s strong or farther north than others.
There are many factors that determine how strong a storm gets that we might not know about until one forms, including excess Saharan dust, which keeps thunderstorms from being active, wind shear, and steering currents that might take storms out to sea.
However, overall the conditions this year still look to favor a lot of storms, but “where” is always the question.
Both the NOAA and Colorado State University call for the number of storms to likely be above average this year. NOAA’s forecast has a range, but does not drop below the average of 14 storms; seven hurricanes and three major hurricanes.
Our regular list of names begins with Alex and will end with Walter.
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