Chasing Storms on a Weather Map

We know meteorologists spend a lot of time chasing storms and systems across their weather maps.

Remember Katrina 2005?

What are they doing?  Their job is to analyze mid-tropospheric circulation, which usually happens between 10 and 20 thousand feet above sea level.  Maps help them do that.

Using an upper air map effectively can be incredibly enriching for students. Knowing this stuff has a lot of benefits. It's a great way to learn about meteorology. Understanding the art of predicting storms can give us a better understanding of our environment.

You can develop valuable skills by studying storm-chasing techniques and using upper air maps. Analyzing calm areas, identifying trouble spots, and understanding flow dynamics sharpen critical thinking and problem-solving skills. Besides meteorology, the skills can be applied to lots of other things.

It can also foster a sense of wonder and curiosity about nature. Understanding powerful weather phenomena opens up a world of exploration, adventure, and thrills. A solid foundation in meteorology, climatology, or related fields is provided by this course.

What do they contain?  Routine operational maps show the state of the upper atmosphere at standardized levels.  Air pressure levels of 85, 70, 50, and 25 kiloPascals.

Mid-latitude westerly winds blow here and everything moves eastward. On the map, we might see calm, clear areas chasing storms along streamlines.

Normally, changes in our weather are accompanied by bumps or waves.  Most horizontal motion in the air is caused by systems that follow features such as storms and slide across either the upper-air or surface weather map.  They call it a transformation.  And at these altitudes, systems don't change much in size over time.

This is what we call the level of non-divergence, or LND. This happens halfway up the troposphere, which is the lowest major layer in the atmosphere. 

This vertical level is set by the World Meteorological Organization at 50 kPa, or 500 millibars,  about 20,000 feet above sea level.  By using this level, air moving upwards or downwards cannot be constrained by boundaries like the tropopause or the earth's surface, which would force vertically-moving air to change directions. 

Chasing storms in any direction

How cool would it be to get your pilot's license and chase storms.  Renting one might be a better option.

You might be surprised how many different ways air can flow.  Try to understand these four quantities used to describe flow characteristics so you can read meteorological weather maps:

Storm-chasing experience

1) Translation – chasing storms horizontally across the map. Storms move from one place to another,
2) Deformation – change in shape, like squeezing a ball of dough without changing its size.  Like other fluid bodies, weather systems change shape all the time.
3) Divergence (and convergence) – spreading out and increasing (or decreasing) a parcel's flow area.   The intensity of a storm changes, and
4) Vorticity – rotation about a vertical axis, which may also be moving.  It's a good indicator of precipitation intensity to look at vorticity.  Tornadoes may also result from it.

The movie Twister with Helen Hunt and Bill Paxton is about weather people experimenting and chasing storms. Take the time to see it.

Have you seen it?  Let us know what you think (right here) of this or any similar movie.  Otherwise, read on for more about weather systems.

Weather forecasters need to know this relationship between temperature and pressure.

In some cases, all four modifications are happening at the same time and moving with weather systems to make chasing storms more exciting and challenging.

Analytical and prognostic weather maps define pressure-related systems by how high above sea level one must go until ambient pressure drops to a specified millibar level.  As you move toward the north or south pole, the height for each standard level decreases.

For example, look at a North American map with USA weather contours at 500 millibars.  Different parts of the country have heights that differ by 500 metres or more.  That makes sense thermodynamically.  The colder surface air that chases or follows storms in mid-latitudes is denser, in  grams per cubic metre, than the warmer, more humid air elsewhere.

These colder regions will have a sharper drop in pressure as altitude increases.   Comparatively, sea-level pressures don't change as rapidly.

It doesn't matter whether we're chasing storms by looking at a low spot on a height contour map like this one or a minimum pressure area on a constant altitude map, like our normal sea-level equivalent pressure maps used to show surface isobars.  Both types of maps show similar lows and highs.

Things to keep in mind.  In the northern hemisphere, the flow is counter-clockwise around lows and clockwise around highs.  Clouds are associated with lows, while clear skies are usually associated with highs.

Want to know more?  Here are some other things to consider.

Upper Air Analysis and Radiosondes

Use the first law of thermodynamics.
The radiosondes on the weather balloon in this photo gather data.  The first law of thermodynamics and other scientific principles can help you interpret this.  Keeping the balloon aloft and transporting its instruments depends on buoyancy. 

Water vapor maps and other tools.
Weather forecasters use water vapor maps, prepared with radiosonde data, to figure out moisture patterns.

Unique temperature conversions for weather forecasters
Scientists can use average temperature conversions to look at temperatures and use the information.

Wireless thermometers and weather balloons
Radiosonde instruments, like wireless thermometers and humidity gauges, have certain characteristics.

Rough weather convection currents
Instability patterns cause air mixing, weather convection currents, and sometimes severe storms.  The importance of lapse rates and inversions.

How different types of clouds form
Different types of clouds will result from different air motions.  Clouds get their shapes from air moving up and down.

Explain humidity and its consequences
Forecasters spend a lot of time explaining humidity and what can happen when it changes.  How come?  Massive heat energy easily converts into severe storms.

Find out what thunderstorm cumulonimbus clouds are.
Whenever you hear a thunderstorm, cumulonimbus clouds aren't far away.  Is it possible to forecast them?

Causes of lightning thunder and storms
Lightning, thunder, and severe storms: what causes them?  Do instability and convection just appear out of nowhere?  Possibly.

Stable air, weather inversions
When we get weather inversions, what do we see?  How do they happen? Here's what you need to know.

Reading about storm-chasing and using upper air maps gives students a compelling combination of science knowledge, skill development, and awe-inspiring weather wonders.  Last but not least, I have made it easy for you to link to this page.

Is it possible to chase storms with just a map?

Take on the exhilarating adventure of storm-chasing with an upper air map. Learn how to predict storm locations by analyzing calm areas, identifying trouble spots, and analyzing fluid dynamics closely. The thrill of storm-chasing awaits you when you unleash your meteorological prowess and harness the power of an upper air map.

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GPT-4, OpenAI's large-scale language generation model (and others provided by Google and Meta), helped generate this text.  As soon as draft language is generated, the author reviews, edits, and revises it to their own liking and is responsible for the content.