GEOL 118 Lecture Notes - Lecture 26: Lightning, Cold Front, Fujita Scale
6 Apr 2016
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Geol 118 - lecture 26 - severe weather iii. In mid-latitudes, thunderstorms are associated with cold fronts. Usually late afternoon or early evening when air and ground temperatures are highest. Need very warm moist air that gets heated, causing air to rise and rain. Hot, dry air aloft prevents full-scale rising action. Cold front hits, removes hot, dry lid and allows full-scale rising action. Condensation releases more heat, causing air to rise farther and faster (strong updrafts and downdrafts of heavy rain) Very high, anvil-shaped (cumulonimbus) clouds can develop. Cloud top smeared out by jet stream. Hail develops when upper level air is very cold, causing rain to freeze. Strong updrafts keep hail aloft, adding ice layers. Hail size can range from pea to grapefruit. Eventually downdrafts of cold, dryer air dominate. Storm loses intensity with only light rain. Develops during mature stage of thunderstorm due to air convection (water drops, ice and dust particles, gases rub against each other)
