March 12, 2006

Tornado Outbreak

Kansas/Missouri/Illinois/Oklahoma

Editor:  Putnam E. Reiter

Forecast/Setup -

Risk Area:  High Risk - Missouri/Illinois/Kansas Moderate Risk - Oklahoma/Arkansas

During the week a longwave trof had been setup over the western U.S.  On Wednesday the 8th the initial longwave trof lifted out of the mean western U.S. position towards the central U.S.  A moderate risk was issued due to favorable atmospheric conditions across the region.  Due to a variety a factors the event was mitigated and only limited severe activity occurred.  One cause was the phasing of the subtropical jet with the longwave trof as it moved into the region.  Thick subtropical moisture spread north-northeast across the threat region to Chicago resulting in limited solar heating.  This upper system departed on Thursday with a cold front moving into Texas.  By Friday the next longwave trof moved into California resulting in southerly flow across the region.  Severe thunderstorms developed in Oklahoma Friday and Saturday evenings.  Large hail was the only threat.  Late Saturday night additional activity occurred in Kansas and Missouri.

On Sunday the second upper system was progged to move into the central U.S. with the dynamics primarily affecting Kansas.  With rich Gulf moisture still in-place across the region, instability would not be a problem.  Additionally, skies were progged to be clear with cirrus causing minimal heating problems.  While not completely unusual the warm front was in northern Kansas/Missouri.  Dewpoints in the upper 60s were located across Texas with mid 60s in Oklahoma/Arkansas and lower 60s near the warm front.

The warm front initiated first with storms developing by early afternoon.  The dryline took several more hours to light up and in Oklahoma didn't fire until 17:30 CST.  On all accounts, once storms did develop, supercells were favored.  Several storms developed in Oklahoma with one supercell being the dominate storm.  This storm developed south of Shawnee and moved northeast at about 40mph.  It produced a tornado in Cherokee County into Delaware County.  The most significant activity of the day occurred in Missouri eastward into Illinois.

Below are model data and SPC products.

SPC Products:  SWO Day 1 Graphics:  Risk Area - Tornado Prob - Damaging Wind Prob - Hail Prob - Storm Plot - LSRs
Surface Maps:  Temperature - Dewpoint - Wind Speed - CAPE - LI - Moisture Convergence
Sounding:  Springfield, MO - 00z 03/13
Text Products:  Mesoscale Discussions
Mesoeta 00z Initialization:  Surface Pressure - CIN - 0-1km Helicity - 850mb Temperatures - 850mb Dewpoints - 850mb Windspeed - 850mb Vertical Velocity - 850mb Relative Humidity - 700mb Wind - 700mb Temperatures - 700mb Relative Humidity - 700mb Vertical Velocity - 500mb Vertical Velocity - 500mb Temperature - 500mb Vorticity - 500mb Wind - 500mb Relative Humidity - 250mb Wind - 250mb Relative Humidity