National Weather Service United States Department of Commerce

Severe Thunderstorm and Flash Flood Threats Early This Week

The threat for severe thunderstorms and flash flooding are likely from the central and southern Plains into the Ohio/Tennessee Valleys and Mid-Atlantic early this week. A couple of slow moving systems will track west to east, while a plume of moisture focuses near a stalled front. Some of the thunderstorms could contain damaging winds and large hail, while flood watches extend from MO/IL to DE/NJ. Read More >

Showalter Index

by Tim Brice and Todd Hall
 
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Enter the 500 millibar parcel temperature: °C Answers:
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What does my answer mean?

Showalter Index greater than 0: Stable, but weak convection possible for SI = 1-2 if strong lifting is present.
Showalter Index between 0 and -3: Moderately unstable.
Showalter Index between -4 and -6: Very Unstable.
Showalter Index between less than -6: Extremely Unstable.

 

What is the formula for the Showatler Index?