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Re: Raptors and Gliders

From:

Patricia Valdata

Reply-To:

Maryland Birds & Birding

Date:

Mon, 16 Aug 2004 11:00:19 -0400

Bill, it makes perfect sense to me. Except I don't know
any glider pilots who say "thermal updraft velocity." We
just ask "how's the lift?" If the answer is "booming," it will be
a good day for glider pilots and hawks. I personally define
"booming" as lift above 400 feet per minute (fpm) in
numerous closely-spaced thermals. Out west they probably
think a 400 fpm thermal is ho-hum and not worth circling in.

When we get soaring weather, we are given figures for the thermal index (TI),
which is a measure of thermal strength, the expected maximum height of the
lift
(thermal top), and the trigger temperature (when usable thermals will start).
Knowing that last number can be very useful, assuming you have a
thermometer around.

Unfortunately, there aren't that many weather stations that report soaring
weather. I think we can get a forecast from the Frederick area, and
another from Atlantic City or thereabouts, but Maryland has so many
"microclimates" that those predictions aren't always valid, and
because they are predictions, not measures of actual conditions,
a day can turn out to be different from the forecast.

Still, it might be worth getting a soaring forecast on hawk watch days
and then seeing how well it correlates with our observations.
Thanks for the links.

Yesterday at the airport we had a nice flyby of an immature bald eagle
and a sharp-shinned hawk.

At 08:05 AM 8/16/2004, you wrote:
>Pat:
>
>Since you hawk watch and glide, have you heard of the recent
>suggestion that the "thermal updraft velocity" that is so
>important to glider pilots is also excellent for predicting the
>quality of raptor migration days?  Paul Summerskill (of Canada)
>studied it intensively, and reported his results -
>www.ideasbypaul.ca
>
>He recommends recording this datum, along with the weather data
>usually reported, with each hawk watching report.  His results
>are pretty convincing.  Our Sue Ricciardi (Fort Smallwood Park
>hawk watch) helped with the study.
>
>Previous days' thermal updraft velocity data are available at -
>http://www.drjack.info/BLIP/RUC/
>
>Successful hawk watching does not require early rising, except
>for the thermals!
>
>Bill Ellis
>Eldersburg
>Carroll County, MD

--Pat

Pat Valdata | 
"The natural function of the wing is to soar upwards
and carry that which is heavy up to the place where dwells the race of gods.
More than any other thing that pertains to the body
it partakes of the nature of the divine." --Plato