Observations of Right-Moving Supercell Motion Forecast Errors

Observations of Right-Moving Supercell Motion Forecast Errors AbstractTwo shear-based supercell motion forecast methods are assessed to understand how each method performs under differing environmental conditions for observed right-moving supercells. Accordingly, a 573-case observational dataset is partitioned into small versus large values of environmental and storm-related variables such as bulk wind shear, convective available potential energy, mean wind, storm motion, and storm-relative helicity (SRH). In addition, hodographs are partitioned based on tornado damage scale, as well as where the storm motion falls among the four quadrants.With respect to the 573-case dataset, the largest supercell motion forecast errors generally occur when the (i) observed midlevel (4–5 km AGL) storm-relative winds are either anomalously weak or strong, (ii) observed 0–3-km AGL SRH is large, (iii) supercell motion is fast, (iv) convective inhibition is strong, or (v) the surface–500-mb RH is low. Moreover, significantly tornadic supercells are biased 1.2 m s−1 slower and farther right of the hodograph than predicted by the Bunkers forecast method, but show very small bias for the modified Rasmussen-Blanchard method (though errors are a little larger for this method). Conversely, the smallest errors occur when, relative to the overall sample, the (i) observed upper-level (9–10 km AGL) storm-relative winds are strong, (ii) supercell motion is slow or the mean wind is weak, (iii) surface–500-mb RH is high, or (iv) convective inhibition is weak. Errors also are relatively small when storm motion lies in the lower-left hodograph quadrant. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Weather and Forecasting American Meteorological Society

Observations of Right-Moving Supercell Motion Forecast Errors

Weather and Forecasting , Volume preprint (2017): 1 – Nov 22, 2017

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0434
D.O.I.
10.1175/WAF-D-17-0133.1
Publisher site
See Article on Publisher Site

Abstract

AbstractTwo shear-based supercell motion forecast methods are assessed to understand how each method performs under differing environmental conditions for observed right-moving supercells. Accordingly, a 573-case observational dataset is partitioned into small versus large values of environmental and storm-related variables such as bulk wind shear, convective available potential energy, mean wind, storm motion, and storm-relative helicity (SRH). In addition, hodographs are partitioned based on tornado damage scale, as well as where the storm motion falls among the four quadrants.With respect to the 573-case dataset, the largest supercell motion forecast errors generally occur when the (i) observed midlevel (4–5 km AGL) storm-relative winds are either anomalously weak or strong, (ii) observed 0–3-km AGL SRH is large, (iii) supercell motion is fast, (iv) convective inhibition is strong, or (v) the surface–500-mb RH is low. Moreover, significantly tornadic supercells are biased 1.2 m s−1 slower and farther right of the hodograph than predicted by the Bunkers forecast method, but show very small bias for the modified Rasmussen-Blanchard method (though errors are a little larger for this method). Conversely, the smallest errors occur when, relative to the overall sample, the (i) observed upper-level (9–10 km AGL) storm-relative winds are strong, (ii) supercell motion is slow or the mean wind is weak, (iii) surface–500-mb RH is high, or (iv) convective inhibition is weak. Errors also are relatively small when storm motion lies in the lower-left hodograph quadrant.

Journal

Weather and ForecastingAmerican Meteorological Society

Published: Nov 22, 2017

References

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