Fri 14 Oct 2011

First image is of the winds aloft at 850 mb (approx 5000 ft). Light and variable.  Decent conditions for migration ready birds in the area.

Second image is of the surface winds and pressure.   Over Oregon the surface winds are light.  Shouldn’t pose any barrier to southbound birds.

Third image is a snapshot of the base velocity showing the north to south directionality at a peak of 15 to 20 knots.

Fourth image is the animated gif with snapshots every half hour of the base reflectivity above radar station RTX.  There was movement over Portland last night but not anywhere near as heavy as yesterday.  Looks like the habitats along the Columbia are going to be the best bets for birding today.

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.)

Taking a look at the regional mosaic we can see that to the north of us is where the action was last night.  Just the reverse of yesterday.  Speculatively; yesterday there was light movement to the north of us which may be why today there is relatively few birds on the move in Oregon. Perhaps the pipeline is filling up for the weekend?

One thing that a static image can’t show is the development of a widespread storm system in the Seattle-Tacoma area last night around 2 AM PDST.  So i put an image up from 3:27 AM PDST (1027 UTC) to show how a large precipitation event cuts off migration.  Southbound birds running into that will put down.  In Texas or along the eastern seaboard this would be called “fallout” conditions.  In the Pacific Northwest it amounts to very little.  But if i lived up there i’d probably head out to Nisqually today.

Sunset last night was at 6:29 pm pdst.

Good birding!

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