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4/19 IL Tornadoes
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How It Happened
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Low Level Instability
a key ingredient to tornado outbreak

The temperature and moisture profile discussed previously is evident here on the 00Z, or 7:00 PM sounding. Low level warmth and moisture is evident beneath 900 mb while a layer of sharp temperature decrease with height is found from 800 mb to 600 mb.

[Image: 0000 4/20 ILX sounding (38K)]

Once low level air is able to break through the inversion near 850 mb, such a temperature and moisture profile supports rising motion through a deep layer of the atmosphere. This is vital to the creation of deep updrafts associated with supercell thunderstorms.

warm moist air
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

wind shear