From: bath@dw3f.ess.harris.com (Kenneth Bath)
Subject: Re: weather
Date: Thu, 7 Jan 1993 23:22:27 GMT
Reply-To: bath@dw3f.ess.harris.com (Kenneth Bath)
Organization: Harris GISD

Jennifer Dickison of Bonners Ferry, ID posted a series of questions
about weather patterns.  Being a meteorologist, I thought I'd 
contribute my two-cent's worth.

Weather is kind of funny because it seems to have patterns in the
short term (5 days), in the long term (seasons), and in the very 
long term (100's of years), but we really don't notice these patterns 
over just a few years.

From personal observation, I've noticed that Mother Nature seems to get
caught in a particular pattern for a given winter.  Most of the winter
storms this year have been coming from the Aleutian Low.  This is a
permanent low pressure system found in the Pacific Ocean south of
Alaska.  Other years, winter storms seem to prefer to come from
northern Canada, down the Great Plains to the southern US.  When I
lived in Texas, we called these fronts the "Alberta Clipper".

Fronts that come from the Northwest are full of moisture that they
collected while over the Pacific Ocean.  As the front moves over
the Rocky Mountains, the air gets lifted to a higher altitude and
cannot hold as much moisture.  This means that folks who live in
the Northwest (like you) get dumped on by a ton of snow.

Fronts that come from Canada don't have this moisture and the air
behind these fronts tends to be very dry and very, very cold.  (Of
course, when you live in Florida, room temperature can seem cold.)
The air is so cold that it is too dense (heavy) to get lifted out
of the Great Plains and in to the Rocky Mountain states.  This means
that it will actually be warmer in Idaho than in Nebraska, Kansas,
or north Texas.

This year has been very mild in terms of temperature.  Freezing
temperatures have only reached the south once or twice.  On the other
hand, the whole country has been very wet and cloudy.  That's because
the fronts are coming from the Northwest.  The past few years
(especially 1989 when it went to 5 degrees in South Texas and snowed in
Florida) the storms have come from Canada the country has been cold
and clear.

Why does it do this?  I'm not real sure.  I believe that the cool
summer last year and the inactive hurricane season was caused by the
eruption of the volcano in the Philippines last year.  The ash and
other crud that it threw into the air has made for very red sunsets.  I
think that the ash had a cooling effect on the oceans, triggering the
El Nino and inhibiting hurricane formation.  (El Nino is an upwelling
of cold water off of the coast of Peru.)  Perhaps the volcano also
caused Pacific storms rather than Canadian storms this year.  The
bottom line is that we just don't know.

Finally, the change in patterns is not caused by environmental damage.
The amount of pollution put out by North American and European industry
and automobiles is small compared to what a good size volcano will do,
and Mother Nature seems to clean that up pretty well.  Remember, the
weather is driven by such things as solar heating and earth rotation.
These are very powerful forces and it takes a lot to overcome them, and
it takes a long time to determine if a change is taking place.  Also,
it's natural for some periods to be colder than others.  (Remember
Washington at Valley Forge?  That cold wasn't isolated; there was a
mini-ice age going on.)  So while is good to worry about what's being
done to the atmosphere, remember that we have a long way to go before
we wreck it completely and until then the damage is reversible.

If you have more questions about the weather or need particular weather
information, let me know and I'll see what I can find out.  I'm always
glad to help.

Sincerely,
Ken Bath
Harris Corporation
bath@dw3f.harris.com