Eastern New Mexico, West Texas, and the Texas Panhandle have not been having the best weather the last few days as upper-level disturbances combined with a collision of cool, northern air and warm tropical air have produced persistent severe thunderstorms during the evening hours, enhanced by daytime surface heating. Below is a [textbook] radar image of a severe thunderstorm capable of producing a tornado moves from Southeastern New Mexico into West Texas, northwest of Midland and Odessa (rural Andrews & Ector Counties) this evening (September 17th).
At the time this image was produced by the radar (and warned for by the National Weather Service), it was unknown if any tornado was actively on the ground. Nonetheless, there was certainly some heavy rain, even large hail, produced by this storm, while strong indications of a tornado were present, as seen in the image on the right showing green colors adjacent to red colors (where the hook echo is noticed).
Green colors indicate airflow toward the radar, and the red show airflow away from the radar. When they are next to each other in a strong storm such as this, meteorologists read this as an indication of strong rotation.
This was a supercell thunderstorm- a large, dangerous storm. Not all create tornadoes, but nearly all can produce strong wind gusts (seen as the outflow boundaries labeled above), lots of lightning, heavy rain and flooding, and large hail.
And, they all look pretty much the same on radar. They all have some sort of hook, or rotation within them. Nearly all have a double-tail. And, in most cases in the United States, they are oriented with the hook-echo facing south, open to the southeast, and the tail facing north or northeast. This is the case because the hook serves as the inflow device for the storm...the mouth, if you will. This storm is fueled by warm, moist air....and through much of the United States, that comes from the Gulf of Mexico (to the south/southeast).
If you ever see one of these guys on the radar, go ahead and stay inside!
Dan, the Weatherman