[CT Birds] Radar Active

Roy Harvey rmharvey at snet.net
Sun May 8 17:58:04 EDT 2016

I received a request to explain how to use the radar page I mentioned last night.

The page is here http://weather.rap.ucar.edu/radar/.

In the choices at the top, in the left-hand column, I select "Regional reflectivity".

On the right side I set the End date, End time, and Duration.  This can be tricky because it is based on UTC, which is effectively what we used to call GMT.  That means, depending on the time of day, it is four or five hours different than our time.  A moment ago I used "Most recent" and the result was marked 21:11:18 UTC, rather than 17:11 EDT (Eastern Daylight Time).

Once those choices are made I click on the map.  First, click on the words "Contiguous U.S." to see all 48 states together.  That combines All the different radar stations into a single view.  The map we are aiming for is much like that but for a smaller area, showing more detail.

On the map there are also many three-letter codes representing individual weather radar stations.  I generally click on the on one on Long Island, but sometimes to see farther south on the one in NJ.  If I forgot to set "Regional reflectivity" that shows the a single radar station's results in a circle.  With
"Regional reflectivity" selected it shows a larger area.  There is a faint plus sign at the center representing the radar station I clicked on, and other plus signs for the other radar stations within the view.  If I clicked on the Long Island radar point the map goes down past the end of Delaware to the south.

I played with the selections to show last night's radar activity.  THE SITE ONLY KEEPS A FEW DAYS OF HISTORY, SO THIS CAN ONLY SHOW LAST NIGHT FOR A FEW DAYS.  My choices were Today (May 8), 1000 UTC, and 10 hours.  The resulting radar map:


Note the line of weather running North/South over PA and western NY.  Once the page has time to load all the images, click on Play at the center top.  The weather moves east, and then something appears over DE (Delaware) and NJ.  THOSE ARE BIRDS!  Pretty soon you forget the weather because there are so many areas of birds.  Toward the end of the animation you can see the birds fading away as morning arrives and they land.

Weather radar wasn't designed to track birds, so these results are incomplete.  Radar sensitivity to birds varies by distance.  They can't see birds too close or too far from the radar station so they can end up looking like donuts.  They don't reach to the next station, so it looks like there are gaps without birds.  They are not gaps in birds, but rather gaps in coverage.

It is interesting to compare the above with the night before, when hardly anything moved into CT.

Or look at last night for the entire country.  You can see the effect of sunset as it moves west.

Play with it to get used to how it works and what the birds look like.  Again, all these examples are transitory, you can only see them for the next couple of days but the general ideas apply any time.

One last point... when the evening shows birds appearing over CT, those birds are leaving.  Too often I have seen great activity here but had few birds because what I saw was the birds departing.  The ones to get excited about are the ones that start farther south and end the night here.

I am hoping tonight will be just as interesting as last night, or more so!

Good birding!

Roy Harvey
Beacon Falls, CT

----- Original Message -----
From: Roy Harvey via CTBirds <ctbirds at lists.ctbirding.org>
To: CT Birds <ctbirds at lists.ctbirding.org>
Sent: Saturday, May 7, 2016 10:53 PM
Subject: [CT Birds] Radar Active

This evening the radar shows substantial bird migration activity to our south.  The radar in NJ is very busy right now, and the one on Long Island shows activity over western LI, Westchester County and Fairfield County.  Hopefully that will increase overnight, including stretching farther into Connecticut.  I think there have to have been a lot of birds waiting for such a night.  Tomorrow night looks promising too.

The radar web site I use is http://weather.rap.ucar.edu/radar/, with the Regional Reflectivity option checked.  Note that times on that site are all UTC (what we used to call GMT, or Greenwich time).

Roy Harvey
Beacon Falls, CT

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