Friday, July 22, 2011

July 22 Chicago Storms Q & A

Q: Why were these storms so full of rain?
A: PWAT (Precipitable Water) in the air was very high. For example: when you hear a weatherperson on TV say 'There's 1 inch of water in the air', that means that if all the air were compressed in a column space, there would be one inch of water in that column. Today's storms had upwards of 1.5 inches, producing very heavy rain.

Q: Was this a derecho, like earlier this month?
A: No. Derechos are high-wind events that stick around for at least a few minutes and produce damage. Today, there were only a few reports of 50-60 mph wind reports at max.

Q: I saw a cloud that looked like a bowl upside down. What was that?
If you saw a cloud that looks like this, you were seeing a 'Shelf Cloud'. These clouds look like the title indicates- like a shelf. Shelf clouds can be associated with tornadoes. Shelf clouds are formed when a thunderstorm's outflow, or cooled air, spreads down and out. Warm air condenses this cool air into clouds, and this the shelf-like formation is created. Shelf clouds were sighted in this line of Chicago storms.

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