GEOG 111 1st Edition Lecture 33 Outline of Last Lecture I Thunderstorms cont d a Characteristics b Development c Types d Geographic patterns Outline of Current Lecture I Thunderstorms cont d II Review for exam Current Lecture I Thunderstorm hazards a Steps in lightning formation i Because of updraft downdraft positive charges in upper part of the cloud where the Bergeron process is happening and negative charges at the bottom part of the cloud 1 Negative charges are attracting to the positive charges on the ground 2 Air between bottom of the cloud and the ground has trouble conducting electricity a Air is a very good insulator so electricity doesn t want to travel from cloud to ground so charge concentration becomes even greater b Negative ionizing path from the bottom of the cloud and positive ionizing path going up in multiple paths going from the ground upward 3 Tremendous draining of negative charges from cloud a Conductive path established b Return stroke Rapid movement of electricity from bottom part of cloud to the ground i This is the current that can kill people b Very unstable atmosphere bubbles of air convecting upward very rapidly lots of precipitation at top of the cloud in conjunction with downdraft right beside it i More lighting when atmosphere is unstable and air is going upward in a convective manner c Types of lightning i Cloud to ground lightning 1 Described above ii Cloud to cloud 1 Between two clouds or within a single cloud These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute iii Bolt from the blue 1 Starts from surface and meets cold upper parts of the cloud 2 Very unusual d Where is lightning most likely to hit i Higher places ii Metal objects are more likely e Safety i Inside a house away from windows and not in the shower 1 Water and metal pipes are conductive ii If your skin tingles or your hair stands up lightning is eminent f Thunder compression wave sound wave created by the intense heat of the lightning and rapid expansion of the air i There is a 5 second difference between light seen and thunder heard for each mile of distance this allows you to calculate distance from the storm ii What factors control the sound and loudness of thunder 1 Clouds muffle sound wave 2 Heat lightning is not due to heat necessarily you re seeing a thunderstorm from far away and the thunder dissipates iii Microburst 1 Cover a small area 2 Short duration 3 Significant threat to aviation 4 A downdraft sinking air that comes out of a storm in the very beginning that is less than 2 5 miles in scale iv Hail 1 Largest hailstones we see loop multiple times 2 Two factors that control the occurrence and size of hailstones a Strength of updraft b Freezing level i Areas of higher elevation get more hail ii We get more hail in spring because freezing level is lower II Review for exam a When looking at a surface map i What direction are winds blowing from 1 Look for nearest isobars assume 45 degree turning of winds toward lower pressure ii What location is experiencing overrunning precipitation 1 Ahead of warm front 2 4 frontal 3 3 wrap around iii Cold sector 1 In front of cold front behind warm front iv Winds don t blow in high pressure 1 Spacing between isobars is greatest so winds are weakest b When looking at 500 mb map i Wave cyclones form where there is rising air you have to remove air from bottom of column ii Air sinks immediately downstream of a ridge 1 At the surface we would expect an anticyclone or a high pressure system iii What direction are winds blowing 1 Blow parallel to lines 2 West to east 3 Geostrophic winds well above the surface c Be able to recall connections between upper level divergence rising air and surface pressure falls
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