Last night afforded a great look at how weather effects nocturnal migration. In the evening a storm front was approaching the Wasatch Front over the West Desert and Great Salt Lake.
At 8:57pm the storm band stretches across the south end of the lake and out over the West Desert. There is a thin line of apparent migrants over the Wasatch already. I have always assumed these were large flocks of sparrows lifting off at dusk this time of year.
The second frame is at 9:55pm and the storm front has pressed up over the lake and to the edge of Salt Lake Valley. Migration over the mountains has picked up with some areas approaching 25-30dBz. IF you look at the south end of the storm there don't appear to be any migrants, and on the north end, migration is sparse.
At 10:58pm the storm was directly over the lake, valleys, and heading into the mountains. Migration at this point appears to have been broken up pretty good by the storm. The northeast edge shows a good migration underway, and migrants still along the front edge of the storm. The south, west, and north edges appear to be pretty dead.
At 11:56pm the storm is directly over the valleys and mountains and appears to be breaking apart. Migrations is still happening in the areas where the storm isn't hitting, but its very light. To the north and the south there is still no real movement, but to the west a large wave of migration appears to have started out over the West Desert.
One hour later at 12:59am the storm is over the mountains and moving towards Wyoming. Clear skies to the west are favorable and the migrants have taken to the sky over the Great Salt Lake Again. It's still fairly light at this point...
By 2:00am the storm is clear of the Wasatch Front, Valley,s and Lake and from here we can watch migration start to pick up over the next 4 hours before trailing off around 7:00am this morning. This is fairly typical of storms fronts this time of year with migrants taking advantage of good conditions, and tail winds ahead of and following storms. Below is a complete animation from 9:00pm last night to 7:00am this morning.
Labels: migration, night migration, radar, weather