Large Hail Parameter

A multiple ingredient, composite index that includes three thermodynamic components [MUCAPE, 700-500 mb lapse rates, the depth of the hail growth zone (-10 to -30 C)], as well as three vertical shear components [surface to EL bulk shear, the direction difference between the ground-relative winds at the EL and in the 3-6 km layer, and the direction difference between the storm-relative winds in the 3-6 km and 0-1 km layers].

The index is formulated as follows:

If if 0-6 km BWD < 14 m s -1 or MUCAPE < 400 J kg-1, LHP = 0. If both the shear and MUCAPE are >= to the above conditions (a loose supercell check):

LHP = (TERM A * TERM B) + 5

TERM A = (((MUCAPE-2000)/1000) + ((3200-THKHGZ)/500) + ((LR75-6.5)/2)) where THKHGZ is the depth of the hail growth zone (the -10 to -30 C layer), and LR75 is the 700-500 mb temperature lapse rate.

TERM B = (((ShearEL-25)/5) + ((GRWdirEL+5)/20) + ((SRWdirMID-80)/10)) where ShearEL is the magnitude of the vector wind difference between the surface wind and the mean wind in the 1.5 km layer immediately below the EL height for the MU parcel, GRWdirEL is the directional difference between the ground-relative mean wind in the 1.5 km layer below the EL and the mean wind in the 3-6 km layer AGL, and SRWdirMID is the directional difference betweem the mean storm-relative winds in the 3-6 km and 0-1 km layers.

The LHP is meant to discriminate between significant hail (>= 2 inch diameter and smaller hail).

Additional information can be found here. (Please open this link in another browser window.)