Enjoy today’s unseasonable warmth. The downhill slide begins tomorrow (Tues., Jan. 14, 2014) and continues through the upcoming weekend. A series of three cold fronts (with a mixture of Pacific and polar air) will send southwest Florida temperatures and dew points tumbling. On Thursday, temperatures may not even make it to 60 degrees. By Friday morning, readings should be in the low 40’s in downtown Naples and Fort Myers and even into the upper 30’s in inland locations. For the rest of the week (through Sunday), daytime highs across southwest Florida will be stuck in the 60’s and overnight lows in the 40’s.
These readings will put temperatures some 10 to 15 degrees below seasonal average and be the coldest of the current winter season. Still, it does not appear as though frosty weather will be on the radar screen. However, this series of cold fronts will create the longest and most pronounced cold spell for southwest Florida since March 2013.
The key to this unfolding weather pattern is the upper level wind pattern. A persistent west coast ridge and corresponding east coast trough (Fig. 1) will continue to ensure that cool to cold air funnels into the eastern half of the U.S. Florida will receive some of this chillier than average air.
Upper level ridges (in the Northern Hemisphere) are in the shape of an upside down, “U.” Winds on the west side of a ridge tend to blow from a southerly direction; winds on the east side from a northerly direction. In troughs, shaped like the letter, “U,” winds flow from north to south on the west side and south to north on the east side.
The first cold front should pass through southwest Florida Tuesday afternoon. This front will have cloudiness and showers. By late Wednesday, a second cold front will sweep the cloudiness to the east, allowing clearing skies. The third cold front, with dry air firmly in place, will pass by without much fanfare on Saturday morning.
With a predominately northerly wind flow aloft to our west, low-level cold air can easily infiltrate the southeast U.S. This air is also dry. At night, the lack of atmospheric moisture (water vapor is the main atmospheric Greenhouse Gas) allows Earth’s energy to easily escape to space via radiative processes. This allows temperatures to drop dramatically. Starting off with low temperature readings makes it that much tougher to warm up during the day. Due to periodic breezy periods while the cold air is in the area, it will feel even chillier than the thermometer indicates.
© 2014 H. Michael Mogil