National Overview
Migration continued last night with the highest concentrations restricted to the Gulf states, from Texas to Florida, and up through the Plains region. This is due to a double whammy of frontal boundaries: one stationary front stretching E->W across the middle of the country and a second cold front running from Kansas up to Saskatchewan, Canada.
Below are the radar loops from sunset last night through 5:00am this morning
New Jersey (Mid Atlantic)
Frames are every 1/2 hour. Click on the thumbnail to view the full-sized animation.
While migration over the Mid Atlantic paled in comparison to that over the central U.S., a light movement was evident along the coastal extent of the region from the Carolinas through New Jersey. Looking at the New Jersey radars we can see a small pulse of activity early in the night which fades quickly by early morning. This is a typical pattern after several nights of poor migration weather, where migration-ready birds, ‘chomping at the bit’, decide to make a short flight. Expect a little shifting in density and diversity across the region but no major concentrations of migrants at any one location this morning.
Wisconsin (Upper Midwest)
Frames are every 1/2 hour. Click on the thumbnail to view the full-sized animation.
The Milwaukee radar is still down, which I am pretty sure now means it is in upgrade status (see yesterday’s post and below for more information). La Crosse, on the eastern periphery of this last migration event, showed a nice signal of nocturnal migration last night. Densities were moderate and the extent of migration was somewhat tight around the radar suggesting that birds were flying at a lower altitude (upper-level winds were stronger and more northerly while surface winds were light), but they were definitely moving! Direction of flight was straight S->N and new birds should be expected along the Mississippi floodplain this morning. Louisiana Waterthrush, anyone!?
Be sure to report back about what you saw!
Yesterday Max asked about how Dual Polarization would help the armchair radar ornithologist in predicting migration based on radar. That’s a great question! Without launching into a whole description of dual polarization, I will attempt to answer it (but if you’re interested in greater detail, be sure to check out the National Weather Service’s webpage on the subject here: http://www.roc.noaa.gov/WSR88D/dualpol/).
Doppler radar sends out an electromagnetic wave in a single polarity (horizontal, in the case of the WSR-88D radars I show on this website) which is then received and processed by the radar to produce a measure of density (the reflectivity images), speed and direction (the velocity images) and several other products which represent statistical calculations based on the previous two. With dual polarization the radar now will send out a second pulse in the vertical orientation which will have a different response when it encounters the same objects in the atmosphere. Used together, these two pulses can help reconstruct the dimensionality of “hydrometeors” (raindrops, hailstones, catbirds, cicadas, etc.) to better understand what’s actually in the atmosphere (hail vs. rain vs. birds vs. insects, etc.). Several new products will be added to the lineup of those already available from the radars, and one of these is called “hydrometeor classification”. This product will characterize everything in the radar view, and one of these categories is “biological”. So, for the armchair radar ornithologist there will now be a product that explicitly interprets the radar to identify biological data! Very cool, yes, but clearly not the holy grail. So to answer Max’s question, the move to dual polarization will definitely improve our understanding of what is and what isn’t biological on the radar, but to further discriminate between birds and other aerial plankton will still be up to the individuals (that’s us!). The beauty of this, though, is that the algorithms are in a constant state of development, and I see a clear move towards refining these algorithms to discriminate between different forms of “biological” scatter in the radar over the next months and years. The future is now…
Good Birding,
David