Nice View of Bird Migration Tonight

April 18, 2015

10pm Saturday…

Sometimes I have coworkers laugh at me when I mention we can see migrating birds on radar.  We can’t see specific birds (1 mallard, 2 loons, 3 Canada Geese etc…) but objects that reflect energy back to the radar.  This is what the radar loop looks like

Here is the three-hour radar loop from the Portland radar (located SW of Scappoose) ending at 10pm:

codnexlab.NEXRAD.RTX.N0Q.20150419.510.024ani

Notice under clear skies we suddenly see the radar screen fill up after sunset.  Most birds prefer to migrate in the nighttime hours when wind speed and turbulence are both (often) weaker.

This evening’s VAD wind profile from the Portland radar makes it pretty obvious what’s going on.  Keep in mind that we have north/northeast wind 10-20 mph over us this evening from just above the surface to 10,000′.  That’s from the evening sounding; the balloon that’s launched twice a day over Salem.

codnexlab.NEXRAD.RTX.NVW.20150419.503.024ani

Notice the wind is from the north before sunset, then right after the “wind” switches to the south and the radar echoes gradually rise in elevation.  That’s birds taking off and working their way up to a higher elevation.  Poor guys are battling a 10-20 mph headwind tonight!

I’ve posted about this phenomenon in the past and you can find more info in a previous post here.

Chief Meteorologist Mark Nelsen