WX MODEL 24: Vorticity Generation


Vorticity is generated through a combination of Earth, shear and curvature vorticity. The greatest positive combination of these will be found around the base of a trough. One reason is due to the stronger wind speeds. In particular, the wind speed changes significantly over distance. Near the center of the low, the winds are light while the winds are much stronger moving away from the trough base. Another reason is due to strong curvature, or turning of the wind. The wind significantly changes directions when going through a trough. For example, a northwest wind can turn to westerly and then southwest over a short distance.

The image below shows a region of high vorticity in red. The red region has the greatest combination of both shear and curvature vorticity combining to turn the air. This has important forecast implications since the downwind side of a wind flow through the region of high vorticity results in upper level divergence and thus rising air. This will increase cloud cover and precipitation chances.