Mesocyclone Strength Index
The mesocyclone strength index (MSI) is a vortex rotation strength index used in tornado prediction and mesoscale meteorology. Produced by the National Severe Storms Laboratory as one of the five parameters for the mesocyclone detection algorithm (MDA), it is usually found on doppler weather radar velocity.[1]
Detection
[edit]MSI values
[edit]
Mesocyclones after detected by the MDA get a computer-calculated MSI value alongside the Tornado Vortex Signature (TVS). Values greater than 3,600 MSI are considered tight, with tornadic formation usually likely in the mesocyclonical region.[2]
In various radar programs, MSI is usually shown by hovering or tapping on TVS.[3][4]
Calculation
[edit]MSI is automatically calculated via vertically integrating maximum values of windshear's vorticity and multiplying it by 1000, accounting for air density spanning across the radar site's beamwidth at the top of the windshear's origin, then vertically integrating the whole of the vortex, with the result divided by depth of beamwidth, to normalize the depth of various mesocyclones.[5][2]
MSI of Notable tornadoes
[edit]- [to be determined]
- 1999 Dover–Hennessey tornado - MSI value of 7,477[6]
- 1999 Mulhall tornado - MSI value of 4,233[6]
References
[edit]- ↑ BROWN, RODGER A. (17 August 1999). "Impact of WSR-88D Scanning Strategies on Severe Storm Algorithms" (PDF). Weather and Forecasting. 15: 7.
- 1 2 Jones, Thomas A.; McGrath, Kevin M.; Snow, John T. (October 2004). "Association between NSSL Mesocyclone Detection Algorithm-Detected Vortices and Tornadoes". Weather and Forecasting. 19 (5): 872–890. Bibcode:2004WtFor..19..872J. doi:10.1175/1520-0434(2004)019<0872:ABNMDA>2.0.CO;2. ISSN 0882-8156. Archived from the original on 2026-02-08.
- ↑ Skow, Kevin (May 2020). "Gibson Ridge 2 Analyst Program for Dummies!!!" (PDF).
- ↑ "RadarOmega User Guide" (PDF). 2024.
- ↑ Stumpf, Gregory J.; Witt, Arthur; Mitchell, E. DeWayne; Spencer, Phillip L.; Johnson, J. T.; Eilts, Michael D.; Thomas, Kevin W.; Burgess, Donald W. (June 1998). "The National Severe Storms Laboratory Mesocyclone Detection Algorithm for the WSR-88D*". Weather and Forecasting. 13 (2): 304–326. doi:10.1175/1520-0434(1998)013<0304:TNSSLM>2.0.CO;2. ISSN 0882-8156. Archived from the original on 2026-02-17.
- 1 2 "NSSL SWAT Case Study - 03 May 1999 Oklahoma City Tornado Outbreak". www.nssl.noaa.gov. Retrieved 2026-08-02.
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