SWEAT Index

Severe Weather ThrEAT index. A stability index developed by the Air Force which incorporates instability , wind shear , and wind speeds as follows: SWEAT = (12 Td 850 ) + (20 [TT-49]) +( 2 f 850) + f 500 + (125 [s+0.2]) where Td 850 is the dew point temperature at 850 mb, TT is the total-totals index , f 850 is the 850-mb wind speed (in knots), f 500 is the 500-mb wind speed (in knots), and s is the sine of the angle between the wind directions at500 mb and 850 mb (thus representing the directional shear in this layer). SWEAT values of about 250-300 or more indicate a greater potential for severe weather, but as with all stability indices, there are no magic numbers. The SWEAT index has the advantage (and disadvantage) of using only mandatory-level data (i.e., 500 mb and 850 mb), but has fallen into relative disuse with the advent of more detailed sounding analysis programs.