...The Ingredients for a Major Tornado Outbreak...
Meteorological conditions came together Sunday May 4th, 2003, to produce the major tornado outbreak across southeast Kansas and the Missouri Ozarks. Meteorological elements to produce a major severe weather event were in place and included a very moist and unstable airmass, strong lift and strong wind shear. The following information will provide a brief synopsis of these ingredients that produced the outbreak of destructive and deadly tornadoes.
Sunday May 4th started off relatively cool and damp as the area remained north of a warm front that stretched across northern Oklahoma and Arkansas. A very moist and unstable airmass was located south of the front. The warm front lifted northeast during the day as a strong surface low developed and tracked across Kansas. Warmer air surged north during the day with temperatures rising into the 70s across southeast Kansas and far southwest Missouri by mid afternoon. Temperatures north of the warm front remained in the low to mid 60s.
Meanwhile, a dry line surged east into eastern Kansas during the afternoon marking the boundary of very dry air to the west where dewpoints were in the 30s to the very moist air to the east where dewpoints were near 70 degrees.
Visible Satellite Radar Reflectivity
415 PM 422 PM
515 PM 457 PM
615 PM 607 PM
645 PM 657 PM
755 PM 753 PM
Thunderstorms developed rapidly around 3 PM across east central Kansas just ahead of the approaching surface low. Explosive thunderstorm development continued south along the dry line
the remainder of the afternoon as mid level temperatures cooled ahead of the advancing
upper level disturbance.
The storms quickly developed supercell characteristics across eastern Kansas. Three dominant supercells formed as the storms moved into southwest Missouri.
These supercells produced long tracked,
destructive and deadly tornadoes. Once the supercells developed, they raced eastward at 45 mph.
An intense upper level jet stream streaked across the southern Plains while a strong upper level disturbance lifted northeast from the central Rockies into central Plains. Upper level diffluence provided strong vertical lift.
This jet streak is noted by the drying (orange colors) on the water vapor imagery to the far right. Winds at 250 mb or ~35,000 ft. were ~ 125 kts, 75 kts at 500 mb or ~18000 ft.
The upper air soundings below taken at the NWS office in Springfield show the evolution of the atmosphere between 1 and 7 PM. This data provides a profile of temperature, moisture, wind direction and speed from which instability and wind shear values can be calculated.
18z (1 PM) 20z (3 PM) 00z (7 PM)
A wedge of very unstable air developed between the warm front and approaching dry line. Lifted indices approached minus 10 and CAPES were near 4000 j/kg near the Kansas border by late afternoon.
Lifted Index Cape
Wind shear is the change in wind direction and/or speed with height. Strong wind speed and directional shear was in place May 4th. Surface winds out of the southeast turned to the south then southwest through the mid and upper levels of the atmosphere. This turning with height combined with the strong instability supported the development of rotating thunderstorms called supercells.
wind profile helicity