Update to Severe Potential Wednesday Morning

Luckily it will be coming through in the early morning hours... it it were afternoon with some daytime heating, this might be a bad day for a lot of people.

The GFS/NAM are still showing a high shear/low CAPE event. I want to update you with some severe parameter maps for 7 AM Tuesday morning, and what those mean in terms of severe weather. More on this later.

Storm Motion Speed - This maps shows the speed in knots and the direction of the storm motion.

0-6 km Bulk Shear - The Boundary Layer through 6-km above ground level shear vector denotes the change in wind throughout this height. Thunderstorms tend to become more organized and persistent as vertical shear increases. Supercells are commonly associated with vertical shear values of 35-40 knots and greater through this depth.

0-1km Bulk Shear - Surface-1-km Vertical Shear is the difference between the surface wind and the wind at 1-km above ground level. These data are plotted as vectors with shear magnitudes contoured. 0-1-km shear magnitudes greater than 15-20 knots tend to favor supercell tornadoes.

Significant Tornado Parameter - Right now 1 or less. A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), and surface parcel LCL height (sbLCL). This version of STP mimics the original formulation presented by Thompson et al. (2003) by using fixed-layer calculations of vertical shear, and substitutes the surface lifted parcels as an alternative to the ML parcels in the "effective layer" version of STP.

0-1 km Storm Relative Helicity - SRH (Storm Relative Helicity) is a measure of the potential for cyclonic updraft rotation in right-moving supercells, and is calculated for the lowest 1-km and 3-km layers above ground level. There is no clear threshold value for SRH when forecasting supercells, since the formation of supercells appears to be related more strongly to the deeper layer vertical shear. Larger values of 0-3-km SRH (greater than 250 m**2/s**2) and 0-1-km SRH (greater than 100 m**2/s**2), however, do suggest an increased threat of tornadoes with supercells. For SRH, larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells.

Surface Based CAPE - A multiple ingredient, composite index that includes 0-6 km bulk wind difference (6BWD), 0-1 km storm-relative helicity (SRH1), surface parcel CAPE (sbCAPE), and surface parcel LCL height (sbLCL). This version of STP mimics the original formulation presented by Thompson et al. (2003) by using fixed-layer calculations of vertical shear, and substitutes the surface lifted parcels as an alternative to the ML parcels in the "effective layer" version of STP.