Use of a Mesoscale Model to Forecast Severe Weather Associated with a Cold Front Aloft

Stanley F. Rose Department of Atmospheric Sciences, University of Washington, Seattle, Washington

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Peter V. Hobbs Department of Atmospheric Sciences, University of Washington, Seattle, Washington

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John D. Locatelli Department of Atmospheric Sciences, University of Washington, Seattle, Washington

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Mark T. Stoelinga Department of Atmospheric Sciences, University of Washington, Seattle, Washington

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Abstract

A forecast of severe weather and the potential for tornadoes associated with a cyclone that developed in the lee of the Rocky Mountains on 19–21 June 2000 is evaluated. The forecasting methods used by the National Weather Service for this case, which focused on the position of a surface trough and the location of favorable quasigeostrophic jet dynamics, poorly predicted the extent and location of the severe weather. Application of a conceptual model for cyclones east of the Rockies, which highlights the importance of cold fronts aloft (CFA), shows that a CFA was an important trigger to convection in the 19–21 June 2000 cyclone. A simple forecasting method is demonstrated that emphasizes the importance of lifting for cases that involve CFA. This method is applied to the 19–21 June 2000 cyclone and is found to improve greatly the determination of where severe weather occurred.

Corresponding author address: Peter V. Hobbs, Dept. of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195-1640. Email: phobbs@atmos.washington.edu

Abstract

A forecast of severe weather and the potential for tornadoes associated with a cyclone that developed in the lee of the Rocky Mountains on 19–21 June 2000 is evaluated. The forecasting methods used by the National Weather Service for this case, which focused on the position of a surface trough and the location of favorable quasigeostrophic jet dynamics, poorly predicted the extent and location of the severe weather. Application of a conceptual model for cyclones east of the Rockies, which highlights the importance of cold fronts aloft (CFA), shows that a CFA was an important trigger to convection in the 19–21 June 2000 cyclone. A simple forecasting method is demonstrated that emphasizes the importance of lifting for cases that involve CFA. This method is applied to the 19–21 June 2000 cyclone and is found to improve greatly the determination of where severe weather occurred.

Corresponding author address: Peter V. Hobbs, Dept. of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195-1640. Email: phobbs@atmos.washington.edu

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