PEMBROKE PARK, Fla. – Has this winter felt unusually cool to you? If so, there is a good reason for it; so far, it has been our coolest winter since 2010-2011.
Even during winter, our temperatures here in South Florida tend to remain on the mild side. The average low during the coldest part of the year (early January) is only around 60 degrees, while the average high is in the warm mid-70s. Hardly much to cause a shiver.
But on occasion, even we get (often brief) tastes of a winter chill as cold fronts from the north usher in frigid nights (by our standards anyway). Miami International Airport has recorded four nights with lows in the 40s since December.
Meteorological winter is defined as December through February. It differs from astronomical winter in the fact that it follows the seasonal temperature cycles instead of the position of the earth in relation to the sun. Your calendar will show a season beginning based off of a solstice or equinox.
So far this meteorological winter (since December 1), Miami has recorded an average temperature of 68.8 degrees. This ranks it in the middle of the pack in the record books, at 40th coolest of 84 seasons on record. The last time we were cooler was ten years ago. The entire winter of 2010-11 (again, December through February), had an average temperature of 66.8 degrees, ranking it 20 of 84. By comparison, last winter was in the top three warmest, ranking 82 of 84.
Data shows our winters have been warming, especially since the 1990s.
But it is important to remember that we still have the rest of January and February to go, so a warm remainder of the season could change our ranking.
Why is this happening? It is unusual and somewhat unexpected, as we are under a La Nina pattern. This is an atmospheric setup where unusually cool waters in the Pacific affect the flow of the jet stream, keeping arctic air held far north. South Florida typically experiences warmer-than-average winters during La Nina years, and this pattern is forecast to continue through the rest of winter.
But La Nina isn’t the only show in town. This year, we have had a wild card. A shorter-lived opposing weather pattern called the North Atlantic Oscillation has overpowered the La Nina setup. When this setup is in a “negative” phase, it allows the jet stream to push unusually far south. This unleashes cold outbreaks upon the eastern U.S., and indications are this will remain in this “negative” phase through January.
While we will still see plenty of warm South Florida days between the cold fronts, the ingredients are there for continued occasional chilly stretches.