Last updated 25 Jun 4

This is a visible satellite image of a supercell thunderstorm near Amarillo TX, taken shortly before sunset on 21 June 2004 (on the first full day of summer). It shows not only the typical anvil canopy produced by a thunderstorm, but a higher level cloud deck attached to it. This higher cloud layer is shaped like an elongated chevron or tilted letter "V". This highest cloud stream was blown downwind of a deep overshooting top at the base of the "V". The overshoot is a dome of convective clouds that is so warm and buoyant -- compared to the surrounding air -- that it punches well up above the storm's anvil before losing its buoyancy and collapsing. When overshoots are so deep, frequent and persistent that they spew off a solid, secondary, anvil deck of their own, extremely intense updrafts and severe weather almost certainly exist beneath. This storm was no exception!

The supercell rampaged across parts of the Texas Panhandle, producing several tornadoes (including this one), a pronounced wall cloud, and hail bigger than four inches in diameter. Such storms actually occur rather often across the high plains in the spring. Unfortunately, this one struck the most populous area of the plains between the longitudes of Denver and Oklahoma City. Although well warned by the Amarillo NWS office, even residents accustomed to weather extremes were stunned by the violence of this storm. One visiting, veteran storm chaser reported citizens frantically running red lights and stop signs in effort to get their vehicles under some form of hail protection. The huge hail caused great destruction over parts of western and southern Amarillo, punching holes in cars and houses, demolishing vegetation, smashing out skylights at a Wal-Mart Supercenter, and breaking many windows out of one side of a high-rise hospital building. This thunderstorm may have been the costliest in Panhandle history, with early damage estimates near $100 million.

Very unstable air, rich low level moisture, just enough vertical shear, and lift near the intersection of a cold front and outflow boundary combined to create a situation well suited for this storm. A partial surface weather map illustrates the boundaries, winds, temperature and moisture in the area. A javascript loop shows a series of visible satellite images of this storm's evolution through the end of the afternoon. A radar reflectivity image shows the storm, with its pronounced hook echo, over parts of the city. For more discussion, including a radar loop, see the website about this event by NWS Amarillo.

Thanks to the Amarillo Globe-News for kindly providing ground photography and some of the news information for this page.