Migration over most of the northeast and mid-Atlantic was stifled by the strong southwesterly flow on the east side of the latest cold front. Here’s the radar from 7:30pm last night through 5:30am this morning.
Frames are every 1/2 hour. Click on the thumbnail to view the full-sized animation.
Cold fronts are pretty much our bread-and-butter when it comes to conveying nocturnal migrants into and out of the region. In the spring, after they pass, you can usually count on northwest winds bringing birds into the mid-Atlantic. This latest front was showing some strong signs of progress up through last two nights, having triggered heavy migration along both the Central and Mississippi flyways after its passage. Last night there was some evidence of heavy migration along the western boundary of the front over the eastern Great Lakes region and even in central PA. Over the east coast, though, winds were still southwesterly into the early morning and only began to switch to the northeast near daybreak. While a few birds were likely moving with the storm, I don’t expect them to produce noticeable concentrations on the ground today. Given the northeast wind I do expect that inland migrant traps would be the best bet as they are likely to still hold birds from the last few days and may see some slight augmentation. North wind today should produce some diurnal migration and we should see our first raptors over the Cape May Hawkwatch- although the numbers will be especially dependent on when the rain begins to fall in earnest.
As I said, usually fronts pass and northwest winds build in, but in the case of this latest front the forecast has it stalling out as it interacts with Hurricane Katia. This is probably good for the east coast as the front will eventually deflect the hurricane to our northeast, but as far as birds go it means a whole lot of them being diverted inland rather than being funneled down the coast (this is one of those situations that is probably good for the birds and less-good for the birders). Tonight upper-atmospheric winds will be out of the northeast, while surface winds will blow from the east and continue through Friday, triggering some nocturnal migration each night and sending the birds inland where they will be mostly dispersed across the landscape. Depending on the magnitude of migration out of New England over the next few nights we could see birds stacking up at inland hotspots along the Delaware River such as Palmyra and National Park dredge spoils, and those along the interior ridges such as Chimney Rock. I’ll post updates as this unfolds and make sure to note any changes to the forecast. If you want to receive the most up-to-date notifications, be sure to subscribe to my twitter feed (@woodcreeper) and/or become a fan of our Facebook page here: http://www.facebook.com/pages/Woodcreepercom/154170829317 Every twitter ‘tweet’ related to the website gets automagically posted to the Facebook fan page- so you’ll always know when something’s ‘up’.
Good Birding
David
2 responses to “Full frontal boundary”
Hi David,
What effect does the continuing rain have on nocturnal migration even if a front like this passes and stalls with upper level NE winds? I’ve always assumed that regardless of how “good†the winds are, if there’s continuous rain at night, there will be little to no migration…
Thanks David for the Site!
Jason-
The effect is more often that birds will not migrate through the heavy rain. The ‘rub’ happens because the front is very infrequently a solid wall of rain from end-to-end, so depending on how high in the atmosphere the precipitation is originating from, how contiguous the rain line, how favorable the winds may be where migration is originating from (as you can see from the earliest radar last night, birds were migrating right along the west side of the front- in some cases into it, but more often right along it). If the front clears during the early morning hours, the birds right along the back edge may/will make landfall wherever that line lies at first light. If the precipitation is diffuse enough, and the winds favorable enough, there’s no reason for birds not to go- and we do see such migration events each season. Rain definitely puts birds down- so migration during a rain event can lead to some great birding conditions in the morning (especially when shorebirds are involved- as they may have continued into the daylight hours if conditions were optimal instead).
Thanks for the comment!
Good Birding
David