Information from the June 19, 2007 Wind event

The best way to describe the severe weather events of June 19th would be the realization of potential. Essentially, the air mass in place over the Texas and Oklahoma Panhandles was highly unstable. However, there was also a sizable cap in place which initially appeared to be strong enough to prevent any storm development. The “cap” or “lid” is also known as a temperature inversion which occurs when an area of warm air exists above the surface of the earth. If you think about a hot air balloon; the balloon rises because the air inside the balloon is warmer than the air outside of the balloon. However, if the air outside the balloon is warmer than the air inside the balloon, then the balloon will not rise. This is the same idea that occurs during a “capped” environment. The air near the surface of the earth heats up with the afternoon sun and begins to rise. But if that parcel of air runs into warmer air above the surface, then that parcel of air will not be able to rise any further. This will prevent any storms from forming as rising air is an essential ingredient to get storms going.

You can tell when the atmosphere is capped because afternoon cumulus clouds will form, but then the clouds will dissipate in the early evening and no storms will develop. On some occasions, the atmosphere has the ability to break this cap though and in fact a slightly capped environment can benefit storms. When a cap is in place, the storms will hold off until the perfect moment when they can break the cap. In order to break the cap, the air near the ground needs to heat up enough that it can overcome the warmer air above the surface. In other words, the balloon operator needs turn on the flames. In fact, there is a specific temperature each day that determines the heat required to break the cap. This temperature is known as the “convective temperature”. Based on the afternoon upper air balloon data from June 19th, the convective temperature required to break the cap was about 96°F here in Amarillo. But wait, our high temperature on the 19th was only 93°F, so why did we get thunderstorms?

If you were watching the storms on the 19th, then you would remember that storms originally develop west of the Amarillo in Oldham and Deaf Smith counties around 5:00 pm. There were two significant differences that allowed the storms to form in the western Texas Panhandle. First, the elevation in Oldham and Deaf Smith counties is a few hundred few higher than in Amarillo. This slight change in elevation can lower the temperature needed to break the cap. And second, the high temperatures in Oldham and Deaf Smith counties were two to three degrees warmer than Amarillo. So these areas were in a much better position to break the cap. In addition, a surface low pressure center was sitting over this same area and helped provide a focus for storm development.

Once the first storms popped up in Oldham County, the near storm environment begins to modify. The initial storms help change the atmosphere to become more supportive for additional storms. Essentially, the existence of a cap became less important and less restrictive for thunderstorm formation. These storms moved east across the Panhandles producing mostly 1 inch size hail (about the size of a Quarter) with the largest hail size maxing out at 2 inches. Additional storms then moved south into the Oklahoma Panhandle from Kansas. These storms formed a line and produced strong winds and more large hail up to the size of Golf Balls. Wind speeds from the storms maxed out at 86 mph in Texas County Oklahoma, with multiple reports of wind speeds between 65 mph and 75 mph!

Wind damage was widespread across the central to western panhandles, but the most intense damage occurred in Miami Texas where part of a lumber yard building was destroyed. The roof from this building then blew into the street and knocked down power lines causing power outages. There was also building damage in Wellington Texas where half of a large aluminum sided building was destroyed and a few houses also experienced minor damage. The pictures from Miami and Wellington are shown below. Notice the many power lines that were snapped or knocked over. As a result, there were many power outages reported across the panhandles during this wind event. The storms then moved south of the Texas Panhandles after 1 am…but the winds did not let up. Strong winds were reported as the line of storms moved into Southwest Oklahoma and North Texas. The highest wind gust from this line of storms was reported in Wichita Falls, Texas where an observation station recorded a 94 mph gust!

The picture on the left shows the remnants of a lumber yard building in Miami Texas.