IT'S A GEOGRAPHY QUESTION

I used to get this question a lot.  What is Tornado Alley?  I hate to upset all the meteorologists out there but it's really a geography question, right.  I would go as far as to say that reduced to a simple form most average weather ( climate ) where you live is directly related to your relationship to mountains and large bodies of water.  By plotting all reported tornadoes on a map you can get a good idea of what we call Tornado Alley.  This particular map above is a summary of all tornadoes reported up to 1995.  So you can easily see where, more or less, Tornado Alley is located. But why is it where it is?  Ahh...it's all related to mountains and water and the wind.

Here's a topographical map of North America.  Lets take a closer look at the major players here.

Rocky Mountains to the west.  BTW no idea who took this pic but it's spectacular!

Gulf of Mexico to the southeast.  I captured this sunrise at Surfside Beach, TX.

The figure above begins to show how the relationship between mountain chains, big bodies of water and air flow come together to shape weather patterns. Since these geographical features are basically timeless the weather patterns created repeat themselves over and over again everything else being equal.

Do you ever wonder why LA doesn't have arctic blasts?  Well, think about it.  In our Winter, cold air builds up north in the Arctic and heads south into the lower 48 states.  Cold air is dense, heavy and sinks close to the ground like molasses.  As the cold heavy air surges south it spreads out into the plains in all directions but the cold air can't rise above the Rocky Mountains.  The mountains act as a natural barrier damming up the cold air on the east side of the rockies and protecting the west coast from frigid winters.  The cold air has no choice and is directed straight south into the plains and into Oklahoma.  Thus, the Blue Norther!

Have you ever driven to Galveston, TX?  From my driveway in NW OKC to the driveway of the beach house near Galveston, TX is a 10 hour drive.  I've got three children so that's with several stops along the way.  The point I'm trying to make is that warm, muggy air on the Gulf Coast is a day away and it doesn't take long with a good south wind to yank that stuff up here.

Here's how this plays out in a general sense.  The jet stream, which is the strong winds in the mid and upper levels of the atmosphere, blow on average west to east across the United States.  As these strong winds flow across the tall rockies you get lift on the east side of the mountains and this causes the pressure to drop.  So a low pressure system forms on the leeward side of the mountains usually near eastern Colorado and winds around a low pressure system blow counter clockwise in the northern hemisphere.  Therefore, looking at the map above if the low forms in Colorado it's a south wind from the Gulf into Oklahoma bringing warm moist air northward and a north wind on the back side of the low ushering in the cold air and a southwest wind coming in from New Mexico bringing hot, dry air.  All these boundaries with different air types come together in the plains and Tornado Alley is born.  So you see it's all about the mountains, the water and the wind. If we didn't have this unique geographical set up then no Tornado Alley.  Next time some out of towner asks you about Oklahoma weather you tell them it's geography.

Here's the upper level wind and weather pattern forecast for later this week and this next weekend. Now I want you to compare this forecast map with the map describing how Tornado Alley forms. Do you see a similarity here?  It's called pattern recognition.  Starting Tuesday / Wednesday this next week all the conditions are coming together for possible severe weather just like on the Tornado Alley map.

Here's how the surface plot looks.  You can see the low pressure to the north with south winds coming up from the Gulf Coast and north winds across Colorado and hotter dry air with southwest winds coming out of New Mexico.  The warm moisture, the cold air, the dry line!  

The dew point map shows the moisture flowing northward!  It's all here, it's all coming together!  It happens here in Tornado Alley.  Don't over think it.  There will be severe weather next week.  

Over the coming days as new data comes in we'll try and define on a more local scale exactly how things might play out.  Right now it's way too early for details but just know there will be some rough weather next week at times.   

FYI this probably isn't the kind of weather pattern that produces huge monster tornadoes.  This is just regular severe weather.  Strong to severe thunderstorms with large hail, damaging winds and regular tornadoes.  Good news, more significant rainfall for many of us!!

I need a license plate that says....Weather Happens.

Later Slater