climate, weather

More heavy rainfall for southwest Florida (H. Michael Mogil, CCM, CBM, NWA-DS*)

Rainfall for June (now almost only half over) is already at rarified levels. Many locations across southwest Florida have logged 15 to 20 inch values. And more rainfall is anticipated.

In fact, for the Naples area (my home base), the official National Weather Service (NWS) forecast is calling for 50 to 70 percent daytime rainfall probabilities each day for the next week.

And, no wonder. The atmosphere above the now, so-called “Sunshine State,” is overburdened with moisture (Fig. 1). According to NOAA’s (National Oceanic and Atmospheric Administration)’s Storm Prediction Center (SPC), precipitable water (PW) was at 1.92 inches at Miami, FL early this Thursday morning. PW is the measure of all water vapor in a column above a radiosonde (weather balloon) sounding location. For Jun. 15, the climatological average PW at Miami, FL is 1.66 inches and a 90 percentile PW is 2.00 inches. In short, if all the water vapor above a point could be condensed into liquid water and then squeezed out (like a sponge), and no water vapor moved in or out of the atmospheric column, 1.92 inches of rain would result.

Further, winds throughout the atmospheric column from the ground to some 50,000 feet above ground level are less than 15 miles per hour. That means that any storms that develop will not move very fast.

While outflow boundaries (areas marking where low-level winds blowing out of thunderstorm areas meet the environmental air mass) may interact with other outflow boundaries and sea breezes to enhance thunderstorm formation or localized movement, most storms will be slow-moving, prolific, rainfall producers. Many locations could see short-period downpours of one to two inches or more during the upcoming week or until the weather pattern changes.

© 2017 H. Michael Mogil

Originally posted 6/15/17

* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.