Updated

Updated · The Weather Channel · Aug 19

Southern Heat Wave Breaks Records With 100-Degree Highs as 110 Heat Indices Persist

Updated

Updated · The Weather Channel · Aug 19

Southern Heat Wave Breaks Records With 100-Degree Highs as 110 Heat Indices Persist

Q: How exactly does a massive cloud of Saharan dust manage to choke off South Florida's much-needed cooling thunderstorms?

A Saharan dust plume suppresses South Florida thunderstorms mainly because it arrives as the Saharan Air Layer, a deep mass of very warm, very dry, dusty air that makes the atmosphere more stable. South Florida’s usual summer cooling storms depend on hot, humid surface air rising quickly, often helped by the sea breeze. When Saharan air moves in, it does two things that work against that process. The dry air mixes into growing clouds and causes droplets to evaporate. That evaporation cools and weakens the updrafts before they can build into tall thunderstorm towers. At the same time, the Saharan layer is warm aloft, which acts like a “cap” or lid on the atmosphere, making it harder for surface air to keep rising. The dust itself also helps filter sunlight and creates hazy skies, but the bigger storm-killing factor is the air mass that comes with it: dryness, warmth aloft and often stronger winds. Forecasters also noted high pressure and a weaker or less effective sea-breeze setup, which further reduced the triggers that normally spark afternoon storms across South Florida. The result is fewer showers and thunderstorms, less cloud cover and less rain-cooled air. With the normal afternoon storm relief choked off, more sunshine reaches the ground, heat builds longer into the day, and temperatures and heat indices climb faster. That is why Saharan dust outbreaks are often linked not just to hazy sunsets, but to hotter, drier and more oppressive conditions in Florida.

3 articles · Updated · The Weather Channel · Aug 19

Miami hit 100F Tuesday for only the second time since 1895, while Fort Smith reached 109F Wednesday as daily records fell across Arkansas, Texas, Florida, Georgia and Alabama.
A double-barrelled heat dome is locking triple-digit highs and heat indices above 105 to 110 across much of the South, from Texas to Florida and the Carolinas.
Nighttime relief is limited, with many lows staying in the 70s, raising heat-stress risks for people without air conditioning, especially in dense urban areas.
Cooler air may edge into parts of the region late this week, but much of the South is expected to stay unusually hot through next week or longer.