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Calm Before The Storm
Is there really a 'calm
before the storm'?
JESSIKA
TOOTHMAN
Have
you ever spent an afternoon in the backyard, maybe grilling or enjoying a game
of croquet, when suddenly you notice that everything goes quiet?
The
air seems still and calm -- even the birds stop singing and quickly return to
their nests.
After
a few minutes, you feel a change in the air, and suddenly a line of clouds ominously
appears on the horizon -- clouds with a look that tells you they aren't fooling
around.
You quickly dash in the house and narrowly miss the
first fat raindrops that fall right before the downpour. At this moment, you
might stop and ask yourself, "Why
was it so calm and peaceful right before the storm hit?"
It's
an intriguing phenomenon that people have recognized for centuries, but what
on Earth causes
this calm?
And
why do whip-like winds, dropping temperatures and rumbling thunder sometimes
precede storms instead of a peculiar and eerie calm?
Do
you want a hint at what might be at the root of this old sailors' adage?
Think
of all the different types of storms you've seen -- one variety of storm can
have a different effect on the atmosphere than another.
There
are brief thunderstorms that rattle through like a couple of rowdy frames at
the bowling alley, and there are long, tumultuous downpours that drown the
streets.
And
then there are the strongest of all, like massive, violent hurricanes or
spinning, furious tornadoes.
All
these different manifestations of intense weather happen because the
interactions in the atmosphere can unfold in a variety of different ways, to
vastly different effects.
So,
if the weather is calm and fair for your backyard barbeque, does that mean you
should make backup plans indoors?
The Calm Before the Storm
So
is there a calm before the storm? You may have already guessed the answer.
Sometimes
there is; sometimes there isn't.
Under
the right conditions, an eerie or peaceful calm will befall your picnic before
a storm moves in.
Other
storms skip the calm and proudly announce their presence by instantly
unleashing bad weather.
Let's
take a look at what goes on inside a storm to understand more about how this
works.
Storms
need warm, moist air as fuel, and they typically draw that air
in from the surrounding environment.
Storms
can draw in that air from all directions -- even from the direction in which
the storm is traveling.
As
the warm, moist air is pulled into a storm system, it leaves a low-pressure vacuum
in its wake. The air travels up through the storm cloud and helps to fuel it.
The
updrafts in the storm, however, quickly carry the air upward, and when it
reaches the top of the cloud mass, this warm moist air gets spit out at the
top.
This
air is sent rolling out over the big, anvil-shaped head of the thunderclouds or
the roiling arms of hurricanes.
From
there, the air descends -- drawn back toward lower altitudes by the very vacuum
its departure created in the first place.
What's
important for our purposes is that descending air becomes warmer and drier (a
good thing after its trip through the cloud, which involved cooling and condensation).
Warm,
dry air is relatively stable, and
once it blankets a region, it stabilizes that air in turn. This causes the calm
before a storm.
On
the other hand, different situations can produce weather that's quite a bit
uglier and not at all calm before a storm hits.
For
example, think of large storm systems. They're more complex than a single,
unified storm, and their interactions usually don't produce any type of
calmness.
Though
we understand weather better than in years past, predicting it with perfect
accuracy (calm or not) still remains somewhat of a mystery.
THE NAME GAME
The
names of weather systems can get somewhat confusing because of their tendency
to overlap. All circling weather patterns with low-pressure centers are
technically referred to as cyclones.
This
means that hurricanes and tornadoes fall under the cyclone designation.
Cyclone
can refer to anything in the category that fits that description, no matter its
power or size.
Also,
within this category are middle-latitude (or midlatitude) cyclones -- huge
weather systems that can cover a continent.
Remember
that storms referred to as hurricanes in certain parts of the world are
commonly called cyclones in other regions and typhoons in the remaining areas.
A
hurricane begins east of the international date line, and typhoons spawn to the
west of it. If you're in the Indian Ocean, you have yourself a cyclone.
About Jessika Toothman
Jessika has traveled to 47 of the 48 continental
United States -- New Mexico, you're the last one left, but she hopes to visit
you soon. Of course, it's helped that she's lived all across the U.S. -- in
Washington, New York, Wisconsin, Colorado and her current digs, Atlanta. There,
she earned two undergraduate degrees from Georgia State University, one of
which is in print journalism, but after spending some time in the newspaper
biz, she decided the Web was where it's at.
Besides being a staff writer and blogger for
HowStuffWorks.com, Jessika enjoys painting, expanding her vegetarian recipe
repertoire, walking her cat and spending afternoons by the pool. She's also a
junkie for modern American literature, although she pours over nonfiction books
from time to time, too. As co-captain of the How-to Stuff blog,
Jessika is always willing to explore fresh topics and try new tasks, getting
down in the trenches so others can reap the benefits of what she's discovered.
Her plants know this all too well, for example, as Jessika's cheerful
hit-or-miss gardening experiments usually end with green thumb goodness, but
sometimes turn into learning episodes loaded with botanical bereavement.
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Does an eerie calm precede a storm or is that just
an old wives tale?
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