Sunday, August 21, 2016

Flight? Flight.

[Graphical weather forecast from Sunday, August 21 2016 at about 9:15 a.m., courtesy of NOAA. Click to enlarge.]

An additional very useful tool in the hocus pocus of predicting bird migration is the National Weather Service's graphical forecast, like the one above. I mainly look at the second row, which shows forecast wind direction and velocity. In fall, what I want to know three things:

1. When is the wind going to come around to northwest (as it invariably does at least for a little while when a cold front crosses the cape)? Above we can see that sometime in the middle of the night Sunday that will happen. This is good, but it would be better earlier. However, we also need to consider conditions well to the north, up to several hundred miles, because that is our "sending zone:" the place our Monday birds will be coming from. It looks like the front will only clear the western part of New York and New England in time for birds from those areas to migrate Sunday night, which is a bit of a bummer.

2. When the wind does shift, what will it's speed be? I like to see speeds in the teens - strong enough to drift birds to the coast (and therefore also cause them to engage in re-directed morning flight). Wind in the 20's or higher can be too strong for some migrant landbirds.

3. How much of a west component will the wind have and how long will it last? It looks like beginning around midnight Sunday night, there will be plenty of west component until the middle of Monday night, when the little flags on the graph start leaning to the right - i.e. east. This is also a bummer, because it means Tuesday will be less good than it would have been if the winds had stayed west.

The forecast above is actually about perfect for a hawk flight, except for one thing: the date. There will be hawks in Cape May on Monday - Ospreys, harriers, an eagle or three - but not the piles of hawks there would be if this was a forecast for mid-September or later.

The upshot for Monday: definitely a flight of landbirds, but perhaps not as many as if the front were to fully clear the northeast early in the night. Then hawks. A good day.

No comments:

Post a Comment