Tuesday, May 31, 2011

Types of thunderstorms Part 2

          I will continue where I left off the other day. Supercells thunderstorms are truly an awe inspiring sight to see up close and personal; the first time I saw one it took my breath away.  Supercells are the most likely type of thunderstorm to produce long lived violent tornadoes.  As I said, it's the  rotating updraft in a supercell that makes it so very different from all the other types of thunderstorms. Various sections of a supercell consist of different types of precipitation. Medium sized hail exist near the gust front with large to giant sized hail in the central section of the storm. This area of the storm is often called the hail shaft. The region where the flanking line meets the storm is where wall clouds and tornadoes normally develop. A flaking line is a line of cumulus clouds that lead up to the main updraft tower. This will often look like steps leading up into the storm. I will go into this in a lot more detail in the next installment.  Severe weather is almost always associated with supercell thunderstorms. However, not all supercells produce wall clouds or tornadoes; these can  only form when the conditions are perfect.

Types of supercell thunderstorms:

            There are three types of supercell thunderstorms: Classic supercells, HP (high precipitation) supercells, and LP (low precipitation supercells).  The amount of  low  level moisture and the value of precipitable water (Precipitable water is the total amount of atmospheric water vapor in a  column of air) is the main factor that determines which type of supercell will form.


            Most supercell thunderstorms  are this type .  The base of the updraft is very large and normally has a wall cloud. The classic supercell is notable for the dark area of precipitation that it produces, The mesocyclone pulls this behind the wall cloud.  Because of this, storm chasers will often try to attack a classic supercell from the southeast to eastern side of the storm; from this vantage point you can get a clear view of the storm. whereas, the west side of the storm will be hidden behind a curtain of heavy precipitation.  Classic supercells have varying degrees of straight line winds strength,  hail size, and the strength of any tornadoes that are produced.  The next blog post will deal with thunderstorm structure, however a classic supercell has the inflow band in the front,  the rear-flank downdraft at the rear, and the rain-free updraft base in the center.

                                                     A classic supercell

Low-Precipitation Supercell:
            LP supercells are sometimes called  rear flank supercells. This is  because the updraft is located in the rear flank of the cell. Therefore, any precipitation that occurs is away from the updraft. As you can see an LP supercells inflow a lot different than a classic supercell. These cells typically produce very little rain. One thing that makes them particularly dangerous,  they can be hard to identify as supercell storms on radar because of their low amount of precipitation. This type of supercell tends to produce very powerful straight line winds and very large hail. However, tornadoes are generally weaker as compared to other supercell types. This is because the forward flank downdraft and rear flank downdrafts are not as well defined. Storm chasers like the LP supercell, because any tornadoes that do develop are very visible due to the light amount of precipitation.
                                                      Image of an LP supercell
High-Precipitation Supercell:
            This type of supercell is also called a front flank supercell because of the location of the updraft. High precipitation supercells can have so much precipitation that it can surround the updraft as well any accompanying wall cloud. HP supercell are very dangerous to chase, tornadoes are difficult to spot until they are right on top of you. In this type of supercell, hail is normally smaller in association with the other supercell types. However, flash flooding is always a concern due to the tremendous rainfall associated with an HP supercell. The makeup of this type of supercell is very  similar to the classic supercell.

                                                     Image of an HP supercell

          I hope you have learned something from this blog post on supercells.  Supercells are my favorite type  of severe storm; no two ever look the same. Like I said above, the next installment will be on thunderstorm structure. Observing storm structure can be enjoyable. For me, knowing how to read structure is very important, It allows me to know what a storm is doing,  so I don't waste my time chasing the wrong storm. I feel everyone should know how to read structure;  it will help you know what's coming your way, so you can protect yourself.

Rebecca Ladd.


  1. Totally Awesome! you make complicated things sound interesting.

  2. Andy & Rebecca, I like this new blog format. I've learnt quite a bit over the last 4 post.

  3. In the blog you wrote it's best to be on the east side of a classic supercell. Is this true all the time?

  4. Thank you for the kind comments

    That is a good question; the answer is it depends on which way the supercell is moving. What I put in the blog post was true for a classic supercell that was moving from the SW to the NE, a vast majorty of supercells move in this direction. Let’s say your intercepting a NE moving supercell from the north. In this situation I like to move way east of the storm and drop south. If everything works out you will find yourself in a southeasterly position, this approach also allows you to miss the hail falling out of the storm. When you’re on the SE side of a storm you have to pay attention to is storm structure and environment. Over half of the supercells will veer to the right and put you in danger. The toughest intercept is a situation when you're northwest of a mature supercell. Because as you negotiate and fight the roads twists, turns, and towns, all while the storm continues moving away. When you're dealing with HP storms, it's especially important to stay ahead of them, If the cell was heading ENE as it turns right, you can find yourself in the core of the storm because it is now moving to the SE. LP supercell are not a problem, because there is normally not a bad seat in the house. As a chaser you should become VERY familiarized with all types of supercellular radar structure. If you keep dry ... you usually can maintain better points of view to the storm than if you are in precip. That's a very broad and grossly oversimplified rule of thumb, however. Every storm is individual and will require a different attitude and approach. The important thing is that YOU know what to look for and what to expect when you approach a supercell. I want to emphasize that storm chasing is not without risk, you should learn about storm structure and learn from someone who is experienced before you try it by yourself.

  5. Thank you for the answer.


Thank you for taking the time to comment, I will answer as soon as I can.