 Low-shear simulations |
 Moderate-shear results |
 Observed cases of interest |
We know that thunderstorms often occur along well-defined mesoscale boundaries such as fronts and drylines. Truly isolated convection is rare in the sense that mid-tropospheric forcing or low-level boundaries are absent. Are these mesoscale processes of any importance other than assisting parcels to condensation and subsequent convective initiation?
This study is designed to investigate the longer-term role of the forcing and the more realistic environments which accompany it. We have found this role may be significant - storms simulated with and without the mesoscale environments differ, even though their local buoyancy and shear profiles are the same.
The forcing here is a cold front, modeled in two dimensions with the same cloud model. Some of the earlier idealized 2D simulations are discussed here. The evolution of the vertical velocity field (domain: 4000 km wide by 18 km high) is depicted here (mpeg, 225k) | (MooV, 1.9 MB). The broad region of rising motion ahead of the surface front collapses to a narrow updraft at the leading edge, eventually taking on a "split updraft" shape (see the page mentioned earlier for more details).
The initiation procedure results in frontal forcing (based on a collapsed Eady wave, but with a tropopause and variable stratification and shear) as well as desired along-front profiles of buoyancy and shear. The result is a somewhat complete initial state with which to study squall lines.
Click on an image below to see further details.
Low-shear simulations |
Moderate-shear results |
Observed cases of interest |