Heavy migration last night over the entire Northeast and most of the Mid-Atlantic as winds were blowing from the N/NW toward the frontal boundary that had passed over our area during the day yesterday. Here’s the radar from sunset last night through sunrise 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.
The signal is quintessential “bird migration”. Base reflectivity appears as growing concentric circles as birds take to the sky after sunset; the circles appearing to “grow” as more birds reach higher altitudes which the radar picks up at increasing distances from the radar station, and “shrink” as birds descend and land before sunrise. If you check my post from last night, you’ll see that the winds were light (5-10kts), yet the base velocity shows objects moving across the radar at 20-30kts in a general N–>S direction. This is exactly what we would expect, since when winds are favorable birds migrate at 15-20kts faster than the prevailing wind speed.
The front, a true boundary, separated these northerly winds from the southerly winds, and hence demarcates the limits of the major migration event. Since the front had cleared New Jersey before this morning, birds moved relatively freely over the state and birding conditions are probably best at coastal fall migrant traps such as Sandy Hook (north) Island Beach State Park (central) and especially Cape May (south). All local patches should be checked, however, since the influx of birds from the north was quite large. Please stop by and post your observations!
P.S. Come see what’s happening down south on woodcreeper’s sister site: Badbirdz - Reloaded
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Posted by: David La Puma
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