Florida State Univ.: "Fluctuations in squall line intensity and coherence in the vicinity of the Balcones Escarpment in Central Texas"

Final Report

Project Objectives and Accomplishments

The Project was originally intended to describe and categorize the differing evolution of squall lines as they exit the Balcones Escarpment region in South Central Texas. The small number of cases collected during the primary year of the project (one of the driest on record) and, more importantly, the lack of mesoscale surface and upper air observations in the vicinity of this complex terrain presented a significant obstacle to this effort. Close examination of the detailed radar data available identified several recurring storm scale features. Recognition of the mesoscale environments in which these terrain-induced features arise and description of their temporal behavior formed the bulk of the subsequent research. Training of the staff in the recognition and behavior of these features in 1997 led to improvement in warning and verification statistics for the counties involved. Additional cases have been collected and further investigation of the temporal behavior of these features as related to recent descriptions of MCS temporal behavior is planned.

Presentations and Publications

Rydell, N., 1997: Fluctuations in squall line intensity and coherence in the vicinity of the Balcones Escarpment in central Texas. Preprints, AMS 28th Conference on Radar Meteorology, Austin, TX.

Rydell, N., 1997: Training forum Presentation, National Weather Service Austin/San Antonio.

Summary of Benefits and Problems Encountered

• Identification and behavioral description of a terrain-induced specific severe weather signature affecting three counties in the warning area.
• Heightened awareness of the severe weather threat to three specific counties from the feature mentioned above led to immediate improvement in warning lead time and verification in these counties.
• Identification of storm-scale enhancement for convection passing near openings of river valleys led to improved short-term QPF for four valleys in three counties.