Friday, May 7, 2010

Moderate Risk For Storms Today, Will It Compare To 1985 Tornado Outbreak?

The Storms Prediction Center is forecasting a moderate risk of severe weather across northern Ohio, northwest Pennsylvania, northeast Indiana and southwest upstate New York. I would also include portions of southern Ontario, Canada in that threat area too.

The Weather Channel's Dr. Greg Forbes has given this region a 60% chance of a tornado on his TORCON index.  SEE MORE HERE

Ironically, this same region saw a huge tornado outbreak in May of 1985 that killed a total of 88 people - 65 of which were in Pennsylvania.

The setting for the storms today is a warm front draped across the region along with an area of low pressure that will deepen and drag a cold front across the area later today. This setup is similar to the set up in 1985.

I was reading the forecast discussion for that region and forecasters were talking about a cap in the atmosphere and dry air in place. This may delay the outbreak of severe weather, but it may also result in the formation of well developed supercells, giving the storms more time to rotate.

Hopefully - if we do see a tornado event today - it won't be deadly. My hunch is that this part of the world isn't as used to tornado outbreaks as people in the south or plains states - so many were caught off guard or didn't have a tornado action plan in 1985. Not to mention it was 1985 and technology and forecasting has come a long way since then.

But if you live in this part of the world or have friends and family there - just take a little extra time today to think of what you will do in the event you find yourself facing a tornadic storm. Or call your friends and family and ask them to do the same.

REMEMBER: lowest level of the structure you are in, and hopefully in an interior room away from doors and windows. PROTECT YOUR HEAD! (either be under sturdy furniture, or use a mattress or pillow) This is key - flying debris is what often kills people during a tornado.
Forecasters look for backing winds with height during a severe weather outbreak and we definitely have that in place today across the region at risk.

The picture below is a Skew-T diagram from Detroit this morning. It is drawn as the daily weather balloon goes up and collects data. Look at the far right and you will see the wind vectors.

At the bottom right, we have southeast winds at the surface, but as you go up in height, they become south, then southwesterly. This is called backing.

Another thing forecasters look for when trying to deterine if conditions are right for a large-scale tornado outbreak is shear - that is a difference in speed as the winds back - going from slower to faster with height.

Right now it isn't a huge difference, although a little shear is present. I am sure by the afternoon balloon release this will change as the storm system evolves throughout the day.

If you are curious to learn more about the large and deadly tornado outbreak on May 31, 1985 - CLICK HERE.

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