Monthly Archives: July 2013
Wisconsin experienced a small heat wave July 16-19, when heat indices around the state reached above 100 F.
The heat index, or apparent temperature index, indicates how hot it feels. When our bodies get hot, we cool down by sweating. It is not the sweating that cools our bodies; it is the evaporation of the sweat. If the air has a high humidity, then the rate of evaporation is reduced. This hampers the body’s ability to maintain a nearly constant internal body temperature. When the temperature is high and the relative humidity is high, the heat index is high and it seems hotter than it really is. In these cases, the heat index is greater than the actual temperature. Continue reading
A monsoon is a seasonal reversal in wind patterns over a region. The word “monsoon” comes from the Arabic word mausim, meaning “season.” The seasonal wind shift is usually accompanied by a dramatic change in precipitation.
The best known example of a monsoon occurs over the Indian subcontinent. In summer, the sun warms the land and the air above it. With cooler air lying over the oceans that surround the subcontinent, a horizontal pressure gradient is established that generates winds directed from the ocean to land. Continue reading
In heat lightning you see the flash of light from the lightning, but you don’t hear the thunder the lightning produces. All lightning produces thunder when the bolt heats the air around it. This rapid heating causes the air to … Continue reading
Recent episodes of severe weather both here in southern Wisconsin and around the country have included reference to “derechos.” Forecasters worried a storm that passed through Wisconsin on June 11-12 could become a derecho, although it never became that severe. Continue reading