Spring Time Brings Spring Weather

Normally, I would inform you on specific weather phenomena's that are experienced on a day to day basis, but this one calls for more than one phenomena and more of a serious situation than the others.  Now I am sure you are thinking that the NWS is crying wolf on this because the last two storm systems have been considered as tornado outbreak risks, but the most that came out of it were wind reports.  This storm, however, actually and literally has the potential and ingredients to create a tornado outbreak for the Southeast.  What makes things so different this time?  Good question.  Here is the current surface chart that shows you how things are setup right now. 

There is a surface low that is centered over the Oklahoma and Kansas borders.  Now this is an interpretation from HPC, but they typically are not too far off of what is actually going on.  The unique thing about this low is that there are about 5 fronts attached to it.  The important ones are the cold front in western Texas, the dryline in central Texas, and the warm front in eastern Texas.  Right now it may not seem like much, but the dryline is expected to move as far east as MS.  Not impressive enough?  How about if I tell you that typically drylines will make it close to eastern Texas before they go away?  Impressed now?  Good.  Now why would it be different than usual this time?  Drylines are typically common this time of year for western Texas, but western Texas has been under a drought period and have had a lot of fires burning several hundreds of acres of land.  With a westerly wind, this pushes all of the dry air from the fires eastward creating drier air to push further east than usual.  Along with that, the Gulf of Mexico is gradually getting warmer and, with the surface low being somewhat close to the Gulf, will bring in a lot of warm and moist air from the Gulf inland by the rotation of the low.

If this isn't enough information to show the signifcance of this event allow me to go into more details.  We covered temperatures and moisture near the surface, but what about everything else in the atmosphere?  First I will show you where SPC is showing to be at the highest risk of severe weather and significant severe weather. 


The first one shows the area with the highest risk of severe weather.  The second image shows the probability of severe weather and where the moderate risk is is where the highest chance of severe weather is and on top of that it is hatched which means a probability of 10% or higher of significant severe weather.  Keep in mind that the time issued for this is between Friday morning at 7 AM CST to Saturday morning at 7 AM CST.  I will show you the best time that the NAM model is showing what that area us under such a high risk.  The NAM was chosen because it compared better to the current data than the other models did.  Here are the wind speeds at 850mb to show where the low level jet (LLJ) will be.  

This may look like a bunch of colors, lines, and wind barbs, but what this is showing is that the area under the moderate risk has winds ranging from 45 knots to 60 knots.  This is important because the direction of the winds are from the south/southeast which enhances warm air advection and moisture into the moderate risk area.  This can help generate rotation for the possibility of tornadoes.  Now let's look a little higher in the atmosphere at 500mb.  

This is showing relative vorticity and what it's good for is showing areas of lifting and sinking.  The red outline indicates that the area inside of it is an area of lifting which will increase the chance of severe storms to develop.  If you remember where the moderate risk area it is you will see that the center of the red outline is in the same location.  So now you have seen that there will be more moisture, warm temperatures, southerly winds, warm air advection, and lifting in the mid-levels of the atmosphere.  Seems like a great setup so far, what else needs to be in place?  Excellent question.  We will go higher in the atmosphere where we look at the jet stream. 

The jet stream is pushing pretty all the way to the Gulf Coast which is pretty far for this time of the year, but this is a good setup for severe weather.  Reason for that is because there is a jet streak, an area of strong winds, to the west of Mississippi.  The area that is enclosed in the orange outline is an area of divergence and diffluence in the upper levels of the atmosphere.  What this means is that there is lifting in the upper levels of the atmosphere.

So now let's recap, there is, and will be, a lot of moisture at the surface with warm temperatures which is important because storms feed off of moisture that they can bring in, there is southerly winds and warm air advection with the low level jet at 850mb which help promote rising or lifting of air, there is positive vorticity advection at 500mb which further promotes rising of the air, and there is divergence and diffluence at 250mb which further enhances the rising of air.  All of these are right over the moderate risk area.  Now all that we can do is keep monitoring the models, the current weather, and continue to watch this event unfold.

Stay safe and keep your eyes and ears to the tv, radio, and NOAA weather radio if you have them.