It happens once a year; the huge nocturnal (night) migration of ducks, geese, swallows and all those other birds from warmer regions on our planet to northern/cooler areas. Think about this; there are probably birds flying right over your home tonight that will end up spending the warm season in the Yukon or even near the Arctic Ocean! Oh, and they may have spent the winter in Mexico or Costa Rica too. That part doesn’t sound too bad does it?
Because birds are large compared to precipitation (rain/hail/snow) they show up quite well on radar and it doesn’t take that many to trigger an “echo” on the radar screen. Of course you might be wondering like me why we don’t see birds on the radar screen all through the warm season? We usually don’t because those birds don’t have any reason to move high up into radar range (more than a thousand feet or so). But when migrating they go high to avoid low level wind fields, instability, and denser surface air.
Tonight they are quite visible on the “VAD” wind display. Check out the current wind field over us, from the Troutdale Wind Profiler:
The area in yellow is the latest info (9pm) showing light west wind (less than 10mph) from the surface up to around 3,000′. Then a light north or northwest wind from there up to 8,000′.
Now take a look at the wind profile from the Portland radar. The radar is located up around the 2,000′ elevation just west of Scappoose.
Time goes from left to right. The first column labelled “0228” means 2:28z or 7:28pm. The last column is then 9:05pm. Until about 30 minutes after sunset you see that light west wind the Troutdale profiler shows. Then look at the 8-9pm hour…the echoes turn to straight southerly “wind” at 15-25 kts. That’s all bird action. It’s also fascinating that the highest echoes (birds) gradually increase in altitude…those guys are working hard to get up to their “crusing altitude”. Ducks have been known to fly up around 30-50 mph!
This is what it looks like on the “regular” radar screen as the birds take off, from an earlier blog post:
By the way, there is a movie called WINGED MIGRATION (a documentary) produced about 10 years ago using hand-raised birds. They follow the birds (usually geese) while flying and migrating using some sort of very light aircraft. Or, actually I suppose the birds follow the aircraft since they imprinted on humans at hatching. That means they think humans are part of their family. Now, believe me, this is no “party movie”, actually it’s REALLY slow, but great visuals for little kids to watch. Filming was done all over the planet. Here’s a clip for a little mid-day relaxation:
Chief Meteorologist Mark Nelsen