Weds 27 Jul 2011 — National Composite

First image is the winds aloft at 850 mb (approx 5000 ft). Second image is a snapshot of the base reflectivity from all the radar stations across the USA, providing a composite image at 10:00 pm pdst.

Note the effects of the strong winds from eastern Texas to Nebraska and across southern Florida.  Migration is practically absent in these areas and the birds are moving to areas where they don’t have to fight 40 knot winds.