As the next cold front arrives from our west, strong southerly flow has established itself along the east coast effectively shutting down migration across the region. Here’s the radar from 7:30pm last night through 5:00am this morning.

Frames are every 1/2 hour. Click on the thumbnail to view the full-sized animation.

You can see the frontal boundary in the regional composite as it marches eastward past the Great Lakes. What you can’t see in this loop is that behind the front are strong migration signals coming from the Midwest radars. In front of the front, though, is where we reside, and the radar is clearly not active with migration. Checking out the individual radars you can again see that there is very little (if any) reflectivity present, and what is present is moving on a strong S->N trajectory. Upper-air wind speeds ranged from 20-30kts out of the SSW across the mid-Atlantic and northeastern US last night, while surface winds blew between 10-15kts out of the south. Expect little change in density and diversity from yesterday with the exception being birds moving into more optimal foraging habitat.

Looking ahead, it appears that Friday and Saturday nights we might see some migration into the region as upper-level winds turn slack, but before we get slammed by Hurricane Irene. Right now it looks as if those conditions will be more favorable for inland migrant traps than coastal ones since we need northwest winds to push birds down to Cape May. This should be good news for PA and Washington DC birders, though.

The effects of a hurricane on birding conditions are highly variable and depend greatly on how close the storm tracks to the shore, whether it travels up the bay or not, etc. etc. and therefore speculating on its effects is somewhat pointless this far out (although it makes for hours of ‘fantasy birding’ in the workplace). Following the storm, though, we will see building high pressure and northwest winds bring a new wave (or waves) of birds to the mid-Atlantic. As always, I encourage you to stop back and let us know what you see. I’ll be closely monitoring Irene’s progress up the eastern seaboard and post updates as the possible effects become clearer.

Good Birding

David