The cloud top structure of the Wichita Falls tornadic storm of 10 April 1979 (and other severe storms on this day) is studied using remotely-sensed observations from radar and satellite. A comprehensive data set included 3 min interval visible (0.6 μm) and infrared (11 μm) radiances from the eastern GOES and similar 30 min interval data from the western GOES. The near synchronization of these two satellites allowed for the stereoscopic determination of cloud top heights. In addition, at 2048 GMT, TIROS-N scanned the storms within one minute of the geosynchronous stereo and provided 1 km resolution infrared blackbody temperatures.
Because internal storm dynamics are hidden from the view of the satellite, storm updraft intensity must be inferred from cloud-top minimum temperature and its rate of change. The Wichita Falls, Tex. tornadic storm could be defined in the satellite data by a point of minimum temperature which displayed temporal continuity and achieved a temperature of 208 K. A cloud-top cooling rate above the tropopause of 7 K/21 min preceded tornadogenesis. An adjacent warm area (221 K) developed downwind and was surrounded by a “V”-shaped pattern of lower temperatures. The warm area is postulated as due to subsidence in the lee of an ascending tower.
The measured stereo height of the Wichita Falls storm was 15.6 km at 2349 GMT, 1.5 km higher than severe storms 150 km downwind, although its minimum blackbody temperature was 9 K higher than that of these downwind storms. In addition, unrealistic fluctuations in the time sequence of temperature 30 min prior to the Wichita Falls tornado indicate that the IR measurements are affected by sensor response and/or field of view limitations, at least close to the anvil edge. Cross sections of stereo heights, IR temperature, and radar reflectivity at 2349 GMT demonstrate that while there is, in general, a co-location of high tops, low temperatures, and high low-level radar reflectivity, significant variations can exist in height/rainfall relationships.
A comparison of data sets at 2048 GMT between stereo height measurements and IR temperatures from GOES-East and TIROS-N revealed that anvil top features can be up to 10 K warmer in the GOES field of view (100 km2) than from TIROS-N (1 km2), and that this difference can reach 20 K for young thunderstorms, with perhaps 4 K explained by calibration differences. The lapse rate for tops penetrating the tropopause was substantially closer to the adiabatic lapse rate when TIROS-N temperature minima, rather than GOES minima, were plotted as a function of stereo determined height.
1 A preliminary version of this paper appears in the preprints of the AMS 12th Conference on Severe Local Storms, San Antonio, Tex., pp. 164–167.