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The Total Energy Environment of Severe Storms

Grant L. DarkowUniversity of Missouri, Columbia

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Abstract

The distribution in time and space of the total specific energy (cpT + gZ + Lq + V2/2) of the environment of severe storms is examined. Comparison of the total energy profiles of tornado proximity soundings with the closest check soundings show pronounced differences. The tornado proximity sounding has substantially higher total energy values in the lower troposphere and lower values in the mid-troposphere than nearby stations. It is shown that the total specific energy may be approximated with negligible error by the static energy (cpT + gZ + Lw) and that this parameter is proportional to isobaric equivalent potential temperature and is similarly conservative.

A practical application of these results to severe storm forecasting is given in the form of a “Total Energy Index.” This index is readily and objectively determined from routinely transmitted upper air data. Unlike other widely used stability indices, the Energy Index indicates not only the energy release associated with the ascending, potentially warm air but also the possible contribution of the saturated descent of the evaporatively cooled, potentially cold mid-tropospheric air to the total energy release of the storm. Examples are shown of the Energy Index field on several recent tornado days.

Abstract

The distribution in time and space of the total specific energy (cpT + gZ + Lq + V2/2) of the environment of severe storms is examined. Comparison of the total energy profiles of tornado proximity soundings with the closest check soundings show pronounced differences. The tornado proximity sounding has substantially higher total energy values in the lower troposphere and lower values in the mid-troposphere than nearby stations. It is shown that the total specific energy may be approximated with negligible error by the static energy (cpT + gZ + Lw) and that this parameter is proportional to isobaric equivalent potential temperature and is similarly conservative.

A practical application of these results to severe storm forecasting is given in the form of a “Total Energy Index.” This index is readily and objectively determined from routinely transmitted upper air data. Unlike other widely used stability indices, the Energy Index indicates not only the energy release associated with the ascending, potentially warm air but also the possible contribution of the saturated descent of the evaporatively cooled, potentially cold mid-tropospheric air to the total energy release of the storm. Examples are shown of the Energy Index field on several recent tornado days.

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