Here, the mid-latitude prevailing westerly winds come into view as everything moves eastward normally. Then we may see calm, clear areas chasing storms along
streamlines
on the map
Changes we hear about in our weather forecasts show up as bumps or waves on these continuous curves.
Meteorologists deal with a range of altitudes where nearly all horizontal motion in the
air
consists of systems following storms and sliding across the either the upper or surface weather map. They call this transformation. And systems at these altitudes have a minimum change in size over time and distance.
Technically we call this the level of non-divergence, the LND. And it happens about halfway up the troposphere, the bottom layer of the atmosphere earth has.
Formally, the World Meteorological Organization has set this vertical level at
500 mb,
which is about 20,000 feet above sea level. This convenient level is used because air moving up or down can continue moving up or down easily without needing to change directions. For example a sudden change in direction would occur after hitting a solid boundary such as the earth's surface or an impassable layer like the stratosphere.
Wouldn't it be cool to get your
pilot's license
and chase storms in a plane. Better use a rented one.
How many different ways can air flow?
To help you figure out how to read meteorology weather maps with their curves and funny symbols, you might want to understand these four flow variables:
1)
Translation
chasing storms horizontally across the map. Storms move from one location to another, 2)
Deformation
change in shape, like squeezing a ball of dough without altering its size. Weather systems change shape all the time, 3) Divergence (and convergence) spreading out and increasing (or decreasing) a parcel's flow area, or apparent size. This one relates to changes in a storm's intensity, and 4)
Vorticity
rotation about a vertical axis, which may also be moving. A good indicator of precipitation intensity. It may also lead to tornadoes.
A good fictional film about weather people
experimenting
and chasing storms is
Twister
with Helen Hunt and Bill Paxton. See it sometime.
See contributions from other visitors to this page...
Twister = good, Bill Paxton = bad
I'm from Kansas, so my favorite weather related movie will always be The Wizard of Oz. I can't help it. This is programmed into us at birth.
However,...
never got a chance to watch it.
I have heard of the movie Twister but I never got a chance to watch it. It seems very interesting. I'm probably going to watch it.
I think this is ...
The Perfect Storm
Also a great movie that i like is The Perfect Storm... they show you a real-life situation, and what must be done in a time like that.
Barry's Response ...
I thought it was good.
I watched the movie Twister a few times and I thought it was pretty decent. I remember another movie about tornadoes, I think it was called "Night of the ...
I loved the movie Twister.
I thought Twister was a great movie. It was also a good way to learn something you might otherwise not be interested in finding out about.
The article ...
Interesting Weather Facts
Twister is a great movie that is both fun and informational. I think that people of all ages can enjoy the action in the movie, but also get a taste of ...
I loved it.
Not rated yet
Twister was a very intense movie. Iv'e watched it many many times. I would recommend it to people who havnt seen it. Great movie!
Barry's Response ...
weather movie
Not rated yet
Absolutely LOVE any weather movie. As weather changes every single day we tend to take it for-granted.
Barry's Response - Weather and natural disaster ...
It was alright
Not rated yet
My first impression was that the movie was very good. It was interesting, but the science was bad. The science, which was somewhat explained here, was ...
Okay
Not rated yet
Some of the science materials was completely made up, and fake but the acting wasn't bad.
Barry's Response - It was about special effects as much ...
Sometimes all four of the modifications mentioned above are happening to the same air parcel at the same time,
moving with weather systems to make chasing storms more challenging.
Pressure
related systems are defined at higher levels by the altitudes above sea level one must go until the ambient pressure decreases to a specified millibar level. Generally the height for each standard level decreases as you move toward the north or south
pole.
For example, look at a North American map with USA weather contours at 500 millibars. Here you will see heights differing by 500 metres or more in different parts of the country. From a thermodynamic point of view, that makes sense. The colder surface based air following or chasing storms in mid latitudes is more dense, in
grams per cubic metre
than the warmer, more
humid
air found elsewhere.
Therefore, one should expect a sharper decrease in pressure with increasing altitude in the cold regions. Considering that the corresponding sea-level pressures do not differ too greatly.
It makes little difference whether were chasing storms by attending to a low spot on a height contour map like this one, or a minimum pressure area on a constant altitude map, such as our normal sea-level pressure maps. The lows and highs shown behave in similar fashions.
Things to keep in mind. The flow goes counter-clockwise around a low and clockwise around a high in the northern hemisphere. Lows are associated with increased cloud, while highs are often located near clearer skies.
Apply the first law thermodynamics.
Weather balloons carry radiosondes that gather data. You can use the first law of thermodynamics and other scientific principles to interpret this information. Of course the balloon relies on
buoyancy
to transport its instruments.
Water vapor maps and other tools.
Meteorologists use water vapor maps from radiosonde data to incorporate vital moisture information into their forecasts.
Unique temperature conversions
for weather forecasters
A new way to look at temperatures - average temperature conversions for scientists.
Rough weather convection currents Patterns of instability cause air mixing, weather convection currents and maybe severe storms to chase. Lapse rates and inversions and the role they play.
How different types of clouds form
Different air motions result in different types of clouds. Air moving up and down give the clouds their shapes.
Explain humidity
and its consequences
Forecasters spend great effort to explain humidity and its implications. Why? It easily converts into heat energy which drives severe storms.
Causes of lightning thunder and storms
What are the causes of lightning thunder and severe storms? Do instability and convection appear out of nowhere? Possibly.
Stable air, weather inversions What conditions do we get with weather inversions? What causes them? Get the brief rundown.