Introduction to Storm Chasing

What is Storm Chasing?

Storm chasing is an attempt to intercept tornadic storms with the intent to see, photograph, or otherwise measure the conditions in and around an active tornado.

Why Chase Storms?

Most people chase storms because it is fun. It would be crazy to do something this dangerous if you did not really like it. Other reasons that contribute to chasing are being part of the public warning process (being a spotter), gathering video and images for training spotters and the public, testing forecast methods, and gathering scientific data.

What Background Should You Have?

The most important thing to have is a thorough understanding of storm structure and dynamics. There is an advanced tornado spotter course elsewhere on this site that can provide a lot of what you need for this. You can go here to find it

It is also important to be able to use camera equipment.

It is a good idea to develop the skills of a severe weather forecaster. There are several ways of developing this. Tim Vasquez has two books that will help a lot, Weather Analysis and Forecasting Handbook, and Severe Weather Forecasting. The best technical introduction to meteorology in general is Roland Stull's book, Meteorology for Scientists and Engineers. More advanced books on forecasting severe weather are Charles Doswell's two-volume series The Operational Meteorology of Convective Weather, and the classic work (available on the web) by Miller, which you can find here:

What General Preparations Should You Make?

During storm season, you should always be ready to go whenever a storm situation presents itself.

Make sure that your car is in good working order. Make sure it is gassed up and ready to go. Make sure you have safety equipment aboard. An inverter is a good idea, as you may need to charge phones and camera equipment.

Make sure you have maps of the target region.

Make sure you have a scanner and can get local weather radio reports without needing to program a specific location.

How Do You Decide When to Chase?

While it is true that tornadoes can form out of non-severe storms, those are very difficult to forecast. The tornadoes that have the most impact on us are the strong or violent long-track tornadoes. These are almost exclusively associated with what we call supercell thunderstorms.

So, all you need to do is find where supercell thunderstorms are going to be, right? Not so fast. The thing that determines whether a storm is a supercell is an intense and persistent rotating updraft. Of course, all thermal-based updrafts rotate. But there are other kinds of updrafts, too. These can occur because of topography, or the winds coming out of a storm (outflow), can intersect with other outflow boundaries and create what we call convergence. Since the winds cannot go down into the ground, converging winds are forced upward. All of these things produce the lift necessary for these storms.

These rotating updrafts are called mesocyclones. It was once believed that just identifying such updrafts would allow us to identify tornadoes long before they form. This is not the case. We now understand that tornadoes are surface-based and only 10%-15%, depending on the study, of all mesocyclones have anything to do with tornadoes.

The atmosphere is a chaotic dynamical system, so the further out you try to forecast supercells, the less accurate we are.

How Do You Decide Where to Chase?

You look for the areas, on any given day, where supercell thunderstorms are likely to form.

This is not quite enough, though. You also need a low-level phenomenon (in the lowest 1 kilometer of the atmosphere). This is called the storm relative helicity, this is a calculated value that assigns a measure of how much potential there is for low-level cyclonic rotation. You probably want to go to the place where this value is predicted to be highest.

How Do You Go About Chasing Storms?

You travel to the places where supercells are likely to form, and that have enough low-level helicity to support surface-based rotation.

Like a good chef, once you get to the target region you need to have enough patience to hang out until things get cooking.

How Do You Approach a Storm?

As the storm moves you want to position yourself on the right front quadrant of it. This is the place where you have the best inflow of warm moist air into the storm. This will give you the best view of the updraft region. This is the place where a tornado is most likely to form.

What Safety Measures Do You Take?

Always be aware that things can get confused and dangerous.

Carry phones in case you get into trouble and need to call emergency responders.

Make sure you have an escape plan. This will likely be roads carrying you away from the storm's motion.

What Do You Do When You Encounter a Tornado?

The first thing to do is make sure it is really a tornado.

If it is, make sure you are safe. What direction is it moving? How fast? Are you in its path?

Once you are safe call it in to the local National Weather Service office, if you have their number. Call 9-1-1 and let them know. If you are a trained spotter, be sure to identify yourself as such, or they will need to send a car out to verify it.

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