Temperatures and dew points across southwest Florida finally dipped below 70 degrees Fahrenheit (F), yesterday morning (Oct. 25, 2017); this is a sure sign that the area has finally entered the autumn season. The last 70-degree temperature reading at Naples Municipal Airport (call sign APF), that did not involve cooler thunderstorm outflow winds, was back on May 11 of this year. Similar comparisons can be found across southwest Florida.
The dew point drop was almost more spectacular than that of the temperature (Fig. 1). The dew point stood at 74 degrees around 9:00 p.m. last evening (Oct. 24, 2017); by 11:00 a.m. E.D.T. (Oct. 25, 2017), a scant 14-hour period, the dew point had dropped to 45 degrees (a drop of almost 30 degrees)! Dew point temperatures that low are much more typical during later in autumn and during winter.
Southwest Florida’s annual seasonal march of temperature and dew point is easily shown within this Köppen climate classification system map (Fig. 2). Southwest Florida is firmly in the Aw category, a tropical wet-dry climate region characterized by high-sun angle rains and low-sun angle dryness. The framework was devised by Wladimir Köppen, a German botanist-climatologist in the late 1800’s and was continually re-examined and revised until his death, around the start of World War II. The basis of his classification system involved climatic boundaries that matched those of various vegetation zones (biomes). This is, of course, tied directly to temperature and precipitation transitions, the two main natural drivers of plant survival.
According to Dr. Troy Kimmel, a professor at the University of Texas – Austin, an Aw climate defines a savanna, a location that “has an average monthly temperature of 64.4 degrees Fahrenheit or greater and more than two dry months (monthly precipitation below 2.40 inches).”
This doesn’t mean that warm, humid and/or rainy weather won’t return to southwest Florida during the next few months. However, it does signify that time of year when cold fronts reach and pass by southwest Florida. Both of these (warmer, more humid, rainy weather and the passage of yet another cold front) are on tap for the upcoming Saturday-Tuesday period.
In honor of this transition, I opened my house yesterday morning and gave my air-conditioner a much-needed, even if temporary, respite. My checkbook is already heaving a sign of relief.
© 2017 H. Michael Mogil
Originally posted 10/26/17
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