A significant outbreak of tornadoes occurred across Oklahoma and Kansas during the afternoon and evening of 03 May 1999. In excess of 70 tornadoes developed and spread extensive damage across central Oklahoma and southern Kansas that afternoon and evening, with 59 tornadoes in Oklahoma alone. This made it the largest tornado outbreak in that state's history. Hail as large as 4.5 inches in diameter was also reported in parts of Texas and Oklahoma. NWS damage surveys indicate that widespread F4 and F5 tornado damage occurred. More than one billion dollars in property damage occurred and 38 persons lost their lives.
NOAA GOES-8 visible and InfraRed (IR) imagery above show the explosive development of convection across southwestern Oklahoma after 20:45 UTC. Several overshooting tops are evident on the visible imagery, and an "Enhanced-V" signature was exhibited on the 10.7 micrometer IR imagery. A loop of 6.7 micrometer IR (water vapor) imagery shows the approach of an upper-level shortwave trough during the afternoon hours; strong upper level divergence indicated that synoptic-scale upward vertical velocities were being enhanced as a jet streak moved across Oklahoma.
The Lifted Index (LI) derived from the GOES-8 Sounder is shown below. During the morning hours preceeding convective development, a trend of rapid destabilization was evident from central Texas into Oklahoma (LI's dropped to -8 C and lower, red enhancement).
Thanks to the CIMSS GOES Gallery