Heavy migration across mid-Atlantic

Clear skies and northeasterly winds made for a big night of nocturnal migration across the region. Here’s the radar from 7:00pm last night through 5:00am this morning.

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

Base Reflectivity image from Fort Dix Base Velocity image from Fort Dix Base Reflectivity image from Dover AFB Base Velocity image from Dover AFB Composite Base Reflectivity image from the Northeastern USA

High pressure across the Northeast and mid-Atlantic set the stage for optimal migration conditions last night. All radars (except the extreme northeastern US) showed heavy migration beginning just after sunset and continuing into the early morning hours. The local radars indicate a NE->SW trajectory, suggesting that the light northeast winds are pushing birds slightly west. This bodes well for inland fall migrant traps this morning, including the southern end of the Watchung Mountains (Chimney Rock) and locations along the north shore of the Delaware Bay. Fall migrant traps throughout Pennsylvania should also be good this morning as migration was heavy over the entire state.

Good Birding

David

P.S. I’ve posted an updated migration forecast for the Mid-Atlantic on Birdcapemay.org and it looks like we’ve got some interesting migration weather on board for the Friday… so come check it out.

Please don’t forget to become a member of the Woodcreeper/Badbirdz flock today. For more information, please check out the Become a Member post.

No migration last night

Only 6 more days to take the woodcreeper/badbirdz-reloaded, online survey! To those of you who took it yesterday, thanks! It’s quick, painless, and will really help me improve the site, so please take 30 seconds to click a couple of buttons. 🙂
Thanks in advance -David

With winds out of the south and west last night, birds should have taken the night off from migration. A little peak at the radar, though, left me with a few questions to ponder. Here’s the radar from 7:00pm last night through 5:00am this morning.

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

Base Reflectivity image from Fort Dix Base Velocity image from Fort Dix Base Reflectivity image from Dover AFB Base Velocity image from Dover AFB Composite Base Reflectivity image from the Northeastern USA

Okay, so migration conditions last night were clearly poor (unless you’re a bird migrating north, when everyone else is heading south). The winds at the surface were southwesterly (~8 kts), while those aloft (3000 feet) were from the south (over DE,MD and southern NJ) and west (over PA and the rest of NJ) at about 15 – 20 kts. If we look at the base reflectivity images we do see a fair amount of “noise”, that is, low signal values (mostly gray in color), most of which is clumped near the radar (indicating that the objects (if they even are objects) are likely ground clutter. There does seem to be a pulse of activity after sunset, which could be cause by temperature inversion, which is usually identifiable using the velocity image (it will tend to show zero velocity). Instead, the velocity image shows movement across the radar consistent with the wind direction BUT apparently faster than the prevailing winds which usually suggests powered flight.

If the direction had been N->S, I could easily have said these were low-flying birds and it would have been tough to dispute it (there are some blue values mixed into the “noisy” background, which could help corroborate my story). My point is that even when the radar indicates objects moving at speeds 15-20 kts faster than the prevailing winds, it’s possible that part of the data represents something other than birds. This is especially true in the fall, when the atmosphere is a biotic stew, full of insects and pollen. So if some of this is a non-bird signal, how to explain the objects moving faster than the prevailing wind? Well, I don’t know. Right now I’m just going to wave my hands and say, it’s most likely not birds, given the direction of travel together with the very low reflectivity values and proximity to the radar. Based on intuition I’d say that what we’re seeing is a mix of ground clutter and other biotic and abiotic reflectance, mixed with some gusty winds. Of course, if anyone has any reason to believe “reverse migration” could explain part of this, I’m all ears.

Good Birding

David

P.S. Come check out my migration forecast for the Mid-Atlantic on Birdcapemay.org

Please don’t forget to become a member of the Woodcreeper/Badbirdz flock today. For more information, please check out the Become a Member post.

Light migration, crappy radar

Migration was light last night, with some birds taking flight after sunset, and heading in a northeasterly direction. Scattered thunderstorms made their way across the region overnight, but not enough to cause any major fallouts (not enough birds, either). Unfortunately both radars went down overnight (only for a couple of hours) which adds enough difficulty to the animation process to make me give up for today. If it had been a large movement, I’d go through the extra effort. Looks like things are really winding down for the season… time to begin the breeding bird surveys out here in Somerset!

Good Birding

David

More migrants over Jerze

South winds and relatively clear skies paved the way for another push of migrants into the mid-Atlantic. Here’s the radar from sunset last night through 7:30am this morning.

Frames are every 1/2 hour for reflectivity and velocity, and every hour for the regional composite. Click on the thumbnail to view the full-sized animation.

Base Reflectivity image from Fort Dix Base Velocity image from Fort Dix Base Reflectivity image from Dover AFB Base Velocity image from Dover AFB Composite Base Reflectivity image from the Northeastern USA

With June knocking at our door, this push represents one of the last major movements of Neotropical migrants into the region. Both the Fort Dix and Dover radars showed strong migration signals immediately after sunset and tapering off after midnight. The regional composite showed widespread migration across the mid-Atlantic and Southeast, with heavy migration over the Northeast. This correlates directly with the greater density of continuing migrants north of our area… a sure sign that migration is “winding down” around here.

With that I’ll declare June 1st the final day of this migration study, but will continue to post periodically if late-season events unfold. Thanks to everyone who has come by and left a comment about their birding experiences, and a special thanks to those who have supported the site financially. With your contributions I can fund the hosting for www.woodcreeper.com for another year, and have made a small donation to my computer programmer who will (hopefully) have the site more automated by Fall 2008 (if not, I’ll probably have to quit, considering I’ll be a father by late fall). In the meantime, I hope to see you all afield.

Good Birding

David

P.S. Come check out my migration forecast for the Mid-Atlantic on Birdcapemay.org

Please don’t forget to become a member of the Woodcreeper/Badbirdz flock today. For more information, please check out the Become a Member post.

Light migration last night

While winds persisted out of the northwest yesterday, some birds were able to take advantage of the clear skies and slackening winds after sunset. No radar today, but just a heads-up that some birds were on the move.

Good Birding

David