Let's see if I can remember from my storm chasing days in El Paso County...
NSSL = National Severe Storms Laboratory
CAPE = Convective Available Potential Energy
This. CAPE values, in simple terms, measure the uplift potential. Anything above 1500 can result in enough uplift to generate thunderstorms. Above 2500 and you get into storms with severe potential. 3500 and up attracts storm chasers like rotten meat brings buzzards.
We're at a truly unique geographic point when it comes to storm potential. The warm, dry desert air to our west meets cool, moist gulf air to our east. When those air masses collide it can form a tight boundary we refer to as the dry line. Dew points can swing from low 20s to mid 60s in a span of a few dozen miles. It's normal to see the division be 20-30 miles and I've personally witnessed a 30 deg swing in less than five miles. The line will set up just west of the Texas/New Mexico state line in early afternoon then progress east as increased surface temps in the New Mexico desert start expanding the dry air mass. It will retreat west overnight as surface temps subside. We're one of only a handful of places in the world where it's a normal atmospheric event. Ours is known worldwide in meteorological circles for its combination of intensity and consistent occurrence.
The dry line alone isn't something of concern until you toss in CAPE values above 1500. At that point the boundary turbulence becomes an initiation point for thunderstorms. Every spring we will have a couple weeks to upwards of a month of regular afternoon thunderstorms. (We have a similar, slightly lesser season in late September as we transition to winter weather patterns.) These will be generic events that might have enough energy to produce hail and wind, but normally that's it. Up the CAPE values to 2500+ and things become more interesting. Now there's enough updraft potential to push cloud tops beyond 40k feet and updraft velocities that will support 1.5-2.0" hail. Throw in a shift in mid-level winds that make for a 90-180 deg shear in excess of 15-20 knots net and the twisty thingies start spinning up.
Sometimes we will get these lovely things called triple points. A tightly defined dry line, a frontal boundary, and an upper air disturbance getting all comfy and cozy right overtop us. Given sufficient moisture that's a guaranteed thunderstorm event unless we get extremely lucky and there's a hard mid-level atmospheric cap in place. Storms will initiate on the plains and the system rides the frontal boundary up through Oklahoma and Kansas. If we get a triple-point event that just so happens to also include an extremely well defined dry line, dew point swings in excess of 30 deg F, maximum dew points in the mid to upper 60s, and CAPE values exceeding 4000, it's gonna be an interesting day. If CAPE hits 5000 and there's a solid 50-70 knot shear, well,... BO,GYK,AKYAG. That's when Youtube starts filling up with videos of entire neighborhoods wiped clean to the foundation.
Now ask me about the Caprock and orographic lift. I dare ya...
Brad
