Weather and Migration #F44's Weather Ways Analysis by Glen Schuster glen@us-satellite.com There is a wonderful weather story about the 1000 mile flight of our veteran friend, Bald Eagle F#44, and her Journey North this season. It starts on April 6th, and lasts nearly three weeks. Just like in 1998, we find she stops along the way, near the Moore Reservoir in Northern New England, before resuming her northern flight. How long will she stop this year? Let's recapture her flying conditions and her story throughout her Journey. The cool spring days throughout March fly by and the first week of April begins. When things feel just right the Eagles' thoughtful decision to go North will likely be made. In 1998, the date #44 began a surge North was April 4th. This year, take note on April 6th. April 5, 1999 On April 5th, a day or so before heading North, at her wintering ground in New York State, early morning skies were crystal clear and temperatures were in the 30's. A brisk northwesterly wind was blowing at 15 knots. The bald bird asks, "Might I be under the influence of a HIGH pressure area? Will the weather be good to go? Since weather features like Highs and Lows normally move from West to East along with the Jet Stream, is it possible that the HIGH could shift to the East, and the wind not be a factor for me tomorrow? I will wait and see." April 6, 1999 She waits. By 6:00am the next morning, April 6, the winds have died down. Skies are basically clear, and she is unaffected by any weather system. A few hours later, as the HIGH continues drifting eastward, a light southerly wind kicks up. The ground is heating under sunny skies. Thermals, or warm pockets of air near the surface float upward. All aboard! Ride the warm air currents and make the first move! How far will F#44 go? She probably doesn't realize clouds are racing Eastward from the Midwest in conjunction with a cold front! Let's look at conditions for the next few days! Note the satellite data shows significant movement north of #F44 between April 6th and April 8th. April 7, 1999 By April 7th, the conditions change. Winds in the upper atmosphere--along with the Jet Stream with the passing of the cold front--are now strong from the West. Even at the surface, winds are blowing brisk from the Northwest at 15 knots! Our eagle is determined to make it to her customary stopping ground in Northeastern Vermont. She battles chilly 20 knot (22 miles per hour) northwest winds at the surface. Or does she? Hmm... might she have flown the entire trip from just northwest of New York City to Northeast Vermont late in the day on April 6th? April 8th How far is that? She arrives at her Vermont visit successfully by April 8th. It is a lucky thing! You can see the clear land areas to the South in this authentic satellite image. Notice Cape Cod, and coastal Massachusetts. Look at the thick clouds to her North! With wind and rain just to the North, it's time to camp out for a bit. When will she surge North again? Will she stay in Vermont all summer? Consider the weather day by day from April 8th. From April 9th through the 14th, the temperatures for the eagle struggled to hit 40 degrees. It was cloudy most days. Although the temperature hit 50 degrees on April 15th, it was not until April 16th that she observed wind from the South, finally! By late on April 16th, the temperatures were in the 50's with a few sunny breaks. This was the last April 17, 1999 April 18, 1999 reported day of the Vermont visit. Between April 16 & April 19th, she soared northward. Some travel had to occur at least on April 17th or April 18th. Look at the maps and station models, for Northeast Vermont. Which day(s) do you feel she flew? She awoke in the early AM on the 17th there was light rain, but on the 18th, winds were calm with temperature 37. This looks pretty promising, but later, temperatures were only in the 50's with winds out of the Northwest. It wasn't even sunny! #44 must have been on a tight schedule. Except for warmer temperatures than the previous week, conditions were not ideal for flying! Onward she surged, apparently traveling 1 degree of latitude each day from April 19 to the 25th. The conditions were not always ideal for flying, although there were no major storms. infrared April 26, 1999 Notice in the data, a 2 degrees of latitude average northerly movement each day, from the 25th to 27th! Look at the interesting satellite imagery for midday on the 26th. The infrared image shows no cloudiness (unless the clouds are warm-- because the whiter the feature in the image, the colder it is) for the bird. The eagle is basking and taking advantage of a band of sunshine racing to her destiny. However, the visible image shows a good deal of white in the area. Is #F44 flying through fog? No. It is snow! F#44 doesn't even wait for the snow to melt to take it all the way home. Might we expect thermals to occur with snow cover? Thermals are the warm currents of air that eagles can glide on when solar radiation (heat) is reflected by the earth. Since snow reflects visible radiation (light), a classic thermal would be unable to fully develop. On the other hand the snow cover isn't too thick. Maybe some warmth did indeed radiate from earth to aid her. F#44 took to the north with a vengeance. She didn't require warm air temperatures all the time, nor did she wait each day for a southerly wind. However, when push came to shove, she barrelled north where she belongs. April temperatures in East Central Canada are never warm. Whatever the reasons for her timely movement, we showed that a little bit of sunshine goes a long way! Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form