ORLANDO, Fla. – The National Oceanic and Atmospheric Administration on Thursday officially declared that La Niña conditions are present. La Niña typically favors an active Atlantic basin during hurricane season, much like we’re seeing now.
It had grown increasingly likely over the past few months that La Niña conditions would be around during the peak of hurricane season. This was one of the main factors in the much above average forecasts leading up to and during the current hurricane season.
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To be declared an official La Niña or its warmer counterpart El Niño, sea surface temperature anomalies in the equatorial Pacific have to be greater than 0.5 degrees celsius in a specific region. For La Niña, that would be below average. Thursday, NOAA reported anomalies -0.9 degrees celsius.
What is La Nina?
La Niña is a seasonal ocean/atmospheric pattern that develops in the tropical Pacific. La Niña is the cool phase of El Niño Southern Oscillation or ENSO. During hurricane season, the phase ENSO is in can strongly impact tropical development far away in the Atlantic Basin.
When El Niño, the warm phase, is present, tropical development is suppressed with increased wind shear and poor atmospheric conditions in the Atlantic Basin.
When La Niña is present, waters along the equatorial Pacific, off of the coast of Peru, are cooler than normal. This happens because the trade winds strengthen in that region, pushing warm water toward Australia, allowing cooler water deeper in the ocean to come to the surface. This is known as upwelling.
When this is occurring, wind shear, which hurricanes do not like, tends to be lower in the Atlantic creating a much more favorable environment for storms to develop.
Rising air that is needed for thunderstorm development is also promoted in the Atlantic in this situation.
A dry and warm winter coming?
La Niña conditions are expected to continue through the upcoming winter.
Typically in Florida, during a La Niña winter, the season is warmer and drier than normal. This will have to be watched closely as we enter wildfire season later in the fall.
#FireYear2020: Of the 41,599 fires to date this year, 36,383 were human-caused, burning a total of 2,510,743 acres across the United States. California remained in the first spot, with 7,072 human-caused fires reported. CA is followed by TX, NC, FL, and AZ. #NationalFireNews pic.twitter.com/QWlVx82jsU— National Interagency Fire Center (@NIFC_Fire) September 10, 2020
While wildfires are the last thing on the minds of many during the peak of hurricane season, it is important to always be mindful of open flame outdoors. Florida ranks in the top five for human-caused wildfires.