Long Term Prognosis - Hans T.

Looking out to late Saturday morning, the current GFS run shows precipitation is in store for an area northwest of Lake Huron that extends from Ontario to Quebec with a maximum 3 HR precip of 0.42 inches at 15UTC Saturday. (See first image)

A diagnosis of the cause for this precipitation and rising motion can be explained at least in part by the Quasi-Geostrophic forcing terms, geostrophic absolute vorticity advection and the laplacian of temperature advection.

A VORT MAX is indicated by a lovely black and gold heart (See second image) just near the border of Ontario and Quebec. To the east, there is an area of positive vorticity advection (PVA) and to the west there is negative vorticity advection (NVA).

As for the temperature advection (See third image), the majority of positive areas is a bit further to the east of the point of interest. However, there is no overlapping area of negative values.

Together, these forcing terms result in a positive forcing, producing lift and resulting in precip. Since the temperature advection term is weak, the overriding term is the positive vorticity advection.

Image 1 - 3 HR Precipitation 10/25/2014 15UTC

3 HR Precipitation - 10/25/2014 15UTC

Image 2 - Geostrophic Abs Vorticity Advection by the Geostrophic Wind 10/25/2014 15UTC

Image 3 - Geostrophic (Laplacian) Temperature Advection (Horizontal) 10/25/2014 15UTC