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Information About the April 29-May 1, 2012
Severe Weather and Heavy Rainfall Event


Approximate Damage Paths for the April 30, 2012 Tornadoes

Storm Total Precipitation Estimates for April 28-May 1, 2012

Weather Synopsis for the April 30, 2012 Tornado Event in North Central Oklahoma

On the morning of April 30th, a shortwave trough was positioned over Eastern Oklahoma and was propagating to the east away from the Norman weather forecast office's (WFO) county warning area (CWA). However, another shortwave trough was taking shape over the Four Corners region. This second shortwave trough provided large scale ascent (rising motion) over the Texas, Oklahoma, and Kansas region by mid-afternoon. At the surface, a north-to-south-orientated dryline was situated from near Dodge City, KS southward through near Lubbock, TX and provided the necessary lift for thunderstorm initiation. In addition to the dryline, an old outflow boundary from the morning thunderstorms associated with the first shortwave trough was draped from near Dodge City east-southeastward across Southern Kansas and Northern Oklahoma. This outflow boundary not only provided lift for thunderstorm development just like the dryline, but it also enhanced the low-level wind shear across Northern Oklahoma by directing the surface wind direction to be more easterly than southerly.

Instability certainly was not lacking on this day with convective available potential energy (CAPE) indices exceeding 3000 J/kg everywhere east of the dryline and south of the outflow boundary. Convective inhibition (opposite of CAPE) was near zero in that same area by mid-afternoon, so no obvious factor was limiting the development and sustenance of thunderstorms. Additionally, vertical wind shear (change of wind direction and speed with height) was favorable for organized convection (for example, supercells and bow echoes) as indicated by deep layer wind shear values around 45 to 50 knots and low-level wind shear values around 30 knots.

Given the above ingredients, three separate clusters of severe thunderstorms developed near Lubbock, TX, Amarillo, TX, and Dodge City, KS. The cluster of storms near Lubbock had no impact on the Norman WFO's CWA. The Amarillo cluster of severe thunderstorms eventually moved into Western Oklahoma during the early evening hours. This cluster of storms continued eastward and produced wind damage in some spots in Central Oklahoma around the Oklahoma City metro. The third cluster of severe thunderstorms near Dodge City propagated east-southeastward along the outflow boundary into Northern Oklahoma. These storms took advantage of the enhanced low-level shear near the boundary and produced several brief tornadoes, along with large hail and strong winds, between Dodge City, KS and Ponca City, OK. Additionally, a supercell developed east-southeast of the propagating cluster of severe storms along the outflow boundary and produced a couple of longer track tornadoes, as documented under the other associated tabs at the top of this webpage.

More weather information (storm reports, weather maps, soundings, etc.) about this day can be found at this link: http://www.spc.noaa.gov/exper/archive/event.php?date=20120430


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