Use of Objective Analyses in the National Weather Service's Graphical Forecast Editor to Anticipate a Localized Tornado Outbreak

On 3 April 2012, 20 tornadoes, including four significant tornadoes, (here, EF-2 or greater on the Enhanced Fujita Scale) occurred across north and northeast Texas. Fourteen of these tornadoes impacted the highly populated area of the Dallas-Fort Worth Metroplex with over 650 homes and businesses sustaining at least EF-0 damage and total estimated storm damage over $800 million. Although atmospheric conditions did not appear favorable for a tornado outbreak of this magnitude 4 to 8 hours before the event, the profiles of vertical wind shear and instability changed rapidly in the 3 hour period preceding the event. Locally generated objective analysis fields greatly enhanced situational awareness of the warning forecasters for an increasing threat of potentially strong tornadoes. The enhanced awareness of the local environment was a factor in the decision to issue “tornado emergencies” for two separate supercell thunderstorms minutes before EF-2 damage occurred in the Metroplex. This study demonstrates the advantages of using locally-created objective analyses with the Graphical Forecast Editor compared to using other popular analysis schemes.