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Overshooting into stratosphere. Entrainment of air into side of cloud. tropopause. Downburst/microburst. Downdraft cuts off the updraft and “kills” the convective cell. Lifetime about 1 h. Fig. 10-1, p.259. anvil. tropopause. Wind direction. rain. Fig. 10-2, p.260.
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Overshooting into stratosphere Entrainment of air into side of cloud tropopause Downburst/microburst Downdraft cuts off the updraft and “kills” the convective cell Lifetime about 1 h Fig. 10-1, p.259
anvil tropopause Wind direction rain Fig. 10-2, p.260
Three cells in one storm mature stage cumulus congestus stage cumulus stage rain Fig. 10-4, p.261
Tilted updraft is not cut off by downdraft Fig. 10-6, p.263
Roll cloud Base of thunderstorm Shelf cloud Fig. 10-8, p.264
30 seconds 300 mph = 8 km/min Fig. 10-10, p.265
Mainly positive charge at cloud top Large, “warm” hailstone becomes -ve Mainly negative charge, except at down draft flow of +ve charge Small, “cold” ice crystal becomes +ve Negative charge induces positive charge at/near Earth’s surface Fig. 10-19, p.272
-ve Example of a negative cloud-to-ground stroke (90% of all lighting) initiated by a flow of electrons from cloud base e - • “break down” electric field strength in air = 50,000 V/in • For comparison, household voltage = 120 V. • 10 ion pairs formed per sec per cu. cm naturally (cosmic rays, radioactivity), which eventually help to transmit current (about 100,000 amps). + +ve Fig. 10-20, p.273
Vaisala's U.S. National Lightning Detection Network founded in Tucson, AZ. http://www.vaisala.com/page.asp?Section=32531 https://thunderstorm.vaisala.com/tux/jsp/explorer/explorer.jsp Fig. 10-24, p.275
downdraft Recall tornado video Fig. 10-33, p.284
National Severe Storms Lab., Norman OK Fig. 10-26, p.279
In spring/early summer the air aloft (e.g., 500 mb) is still very cold, which combined with just a little surface solar heating, is enough to create a very unstable atmosphere (recall “instability recipe”: heat from below and/or cool from above). This is fundamentally why severe storm/tornado season is April-June in the south. DALR cold Altitude unstable warm T Table 10-1, p.281