Tuesday, December 27, 2011

Tornadoes Possible This Afternoon as Severe Risk Increases

There is a tornado risk today for the eastern regions of North Carolina and South Carolina. It is interesting, as the 5% region of the tornado risk is unusually large. This is indicative of an increased tornado risk, but not enough to rise to 10%. Let's take a look at some maps indicative of the severe weather risk.
Mesoscale Convective System Maintenance
A mesoscale convective system (MCS) is basically a cluster of thunderstorms. Maintenance means the ability to upkeep. Putting it together means that this graphic indicates the potential for a cluster of thunderstorms to upkeep itself. Right now, we are seeing over a 90 in the Carolinas into the Virginias. This means that conditions are favorable for a cluster of thunderstorms. Clusters of thunderstorms typically are not as conductive for tornadoes as single cells are. If you're thinking that this is just one parameter of many, you are wrong. This MCS Maintenance parameter contains over 340 other parameters.
300mb wind speeds (jet stream)
We are seeing a split flow in the jet stream with these storms. If you follow the jet stream along the Gulf Coast, we come to a separation of the main path the jet stream takes as well as a smaller, almost nonexistent mini jet stream. This is what's called a split flow. Split flow patterns happen when the force of rising air is able to divert the jet stream off its original path. The split flow pattern is a good indicator that some severe weather is possible.

Here's a little indicator we've put together of severe weather using many severe weather indices.
Region: North Carolina, South Carolina

Chance for...
Severe Thunderstorms: 80%
Hail: Up to 45%
Damaging Wind: 60%
Tornadoes: 30%

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