A meso-high pressure area is usually present behind the accelerating thunderstorms. A meso-low pressure area is usually present at the crest of the wave. A 3-dimensional region in a storm that rotates cyclonically and is closely correlated with severe weather. An accelerated surge of drier air on the backside of a bow echo, usually associated with damaging straight line winds. The rate of change of the vector wind in a specified direction normal to the wind direction.
Vertical shear is the variation of horizontal wind in the vertical direction.
The SI is dependent upon 850 mb data and is most reliable when the moist layer extends above the 850 mb level. The SI is determined by following the moist-adiabat from the 850 mb based LCL to 500 mb, and then subtracting the found temperature from the 500 mb sounding temperature. The depth of the circulation must be at least 1.5 km. A vector measure of local rotation in a fluid flow. The wall cloud is usually located in the southwestern part of a severe thunderstorm in the main updraft to the southwest of the main precipitation region.