Saturday, May 4, 2019

CALM BEFORE THE STORM - Storms need warm, moist air as fuel, and they typically draw that air in from the surrounding environment. 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. 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.

Storm Image Gallery Does an eerie calm precede a storm or is that just an old wives tale? See more destructive storm pictures.
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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.
Storm Image Gallery Does an eerie calm precede a storm or is that just an old wives tale? See more destructive storm pictures.
Does an eerie calm precede a storm or is that just an old wives tale? 

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