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Weather and Migration
Eagle #F43's Journey North

Spring ,1999

Glen Schuster, of the U.S. Satellite Laboratory, stepped in with this blow-by-blow weather report for Eagle #F43's trip north. Let's see what his expert eyes see:

Dear Students,

Eastern Bald Eagle Migration
As of 4/4/99

After months of wintering in New York, our veteran Eagle #F43 has soared to the North and East for the 1999 nesting season. From Peter Nye's satellite data for F43, Wednesday, March 17, is the last day of her New York State residence for Winter. Was she thinking during the 16th and 17th it may be time to Journey North?

Let's find out how weather might have influenced her travel plans.

March 16
By the late afternoon on the 16th, the weather in Eastern New York State was very pleasant. Winds across the region were generally blowing lightly from the southwest to the northwest about 10 knots. The skies were mostly sunny. But the temperatures were chilly, around 40. Time for our gal (#43) to head North?

Here are two good reasons she might decide to travel.

Courtesy of Ohio-State Atmospheric Sciences

1. Sunny Skies. When the sun bakes the surface of the earth, there is a nice layer of warm air just above the ground. We call these 'thermals'. Eagles like to soar along the thermals for a "free ride". Thermals that setup nicely in the spring, because of the increasingly long daylight hours.
2. Southwest Winds. In the Northern Hemisphere when winds blow from the South, warmer air is generally flowing into a region. This is because the sun shines it's energy for longer periods of time each day over areas south of the U.S.. If the winds were from the Southeast, the cold March Atlantic waters would help to put a chill in the air in the New York region. With the winds of the land,the Southwest is the warmest weather direction for the Northeast U.S.

March 17

Courtesy of Ohio-State Atmospheric Sciences

On March 17th, weather must have looked perfect to our feathered friend. Here's why it would be a good day to depart and get a jump start!
  • The sun was shining in full force; there was barely a cloud.
  • The Southwest winds across the region were established.
  • Two more reasons to take off:
    1. The temperatures were pushing the low 60's during the afternoon.
    2. A warm front was about to push into the region, so there was some added lifting to the air, making today's ticket North one to ride on.

March 18


S. F. State University Weather Dept.

By March 18, at about 5000 feet in the atmosphere (the earth's troposphere), winds were established from the Southwest. (Image on left.)

And, in the morning of March 18, observe the alley of clear skies in GOES-8's visible satellite image from space. Sunshine! This is the best time for our feathered friend to glide away! (Image on right. )

March 19

Courtesy of UNISYS.

By the 19th the weather took a turn for the worse. Colder air was spilling in from Canada. For a while, however, with the dense air lifting the relatively warmer air, the sailing could be smooth. That is until the cloud cover became overwhelming and the cold air replaced the warm air.

Was Eagle #F43 determined to push on in weather conditions that seemed more like fall than spring? Would less desirable conditions be enough for her to want to retreat south, or would the taste of spring she enjoyed, and the longer daylight hours, be enough to know that any cooling and cloudy conditions were just temporary? Let's see!

March 19-23
Onward she soars! Between March 19 to the 21, she had made her way to at least her 1998 summer nesting area under less than desirable conditions. Let's review the weather, blow by blow:

S. F. State University Weather Dept.

Ohio-State Atmospheric Sciences

NASA-U Hawaii

On March 19, now hovering in and over New Hampshire:
  • A cold front sliced through the region. Some light rain was to the West of her and afternoon temperatures were in the 30's. The cold front marched across the area rather quickly and clouded things up too fast for her to stay ahead of it entirely.
  • Sky conditions had a mix of sun and clouds. The station models show various conditions. Depending on where whe was at a cetain time, she could have had a lot or very little sun
  • She may have seen some snowflakes near Bangor, Maine!

NASA-U Hawaii

But she persevered! There was no major rain of snow, or storm circulation to stop her. But it may have been a struggle to get East of Maine on thermals on March 20--she may have resorted to "flapping flight". Look at the dense cloudiness about 2:00 EST, over Maine!

A safe 1999 Journey North appears complete,--IF she stops where she did last season!

Glen Schuster, Meteorologist
U.S. Satellite Laboratory
Tarrytown, NY
Technology for Remote Sensing in Schools

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