Sun 02 Oct 2011

First image is of the winds aloft at 850 mb (approx 5000 ft). Winds are light and out of the SW ahead of the advancing cold front developing offshore.   Migration ready birds have nothing really holding them back except the occasional shower which they can avoid if necessary.  It doesn’t look like any of the showers were particularly heavy except one system around Salem and south around 1 or 2 AM this morning.  It moved NNE So some birds may have put down in the advancing edge of that one.  But you can see it did not slow any body down over the Portland area.

Second image is of the surface winds and pressure.  Light and variable.

Third image is a snapshot of the base velocity showing north to north to south directionality at a peak of 20 to 25 knots.  This is an interesting image as it shows both birds and the showers.  The showers are moving WNW and you can see a band of them just west of Clatskanie.  This shows up as a yellow band as it moves away from the radar.  Note the blue bands on either side moving at 10 to 15 knots into the wind — definitely south bound birds.

Fourth image is the animated gif with snapshots every half hour of the base reflectivity above radar station RTX.  The radar was in precipitation mode last night so density readings are shifted a bit, but it does not appear to be very heavy. Animation runs from around 8:00 pm pdst yesterday evening through 5:00 am pdst this morning. (Click on the thumbnails to view the full-sized images and animation.)

Sunset last night was at 6:51 pm pdst.

Good birding!