This is a fun blog to write. Most people underestimate their knowledge of weather. Most weather education for the public comes from the media. Due to the varying degree of folks in the media that are truly knowledgable about weather, there are many opportunities for miscommunication or inaccurate information being presented.
This happens both from a local and national perspective. The larger the event, the more people that cover it. The more people covering an event, the more chance they have less knowledge than those that cover it every day or have a background in it.
All that said, the basics of meteorology are known by most folks – believe it or not. The atmosphere is a ever changing stream or areas of air that interact causing weather. Most people get this. In addition, most people are aware of high and low pressure. These are areas of the atmosphere that are sinking or rising in relation to the air around it.
So far, most people get this as well. What becomes magical is when a meteorologist will use a station tool to show something that seems horribly complicated. In reality, most of these things are not complicated at all! Actually, some media meteorologists don’t even fully understand what they are showing to you!
I am going to pick three things we see a lot in severe weather coverage. Each of these are fun little things to show, but are not as complicated as it seems.
The first, and perhaps my favorite aspect is what is called the “Bound Weak Echo Region” or BWER for short. This is what meteorologists are looking for when they go into a cross section scan of the cell in question. The cut the storm in pieces via their tools to look for two things. First they are looking for cell cloud heights and the second is BWER. All BWER is – is the area in a strong/severe storm that shows a weak area of reflectivity between areas of stronger reflectivity. In other words, this is the “vault” or updraft of a strong thunderstorm. Without being bound, or having reflectivity on both sides, then it would just be a weak echo region. So are you ready for what all this mumbo jumbo means?
A BWER is another way for measuring/confirming a strong updraft in a storm that is looks on radar like a “hook echo.” It’s just a hook echo signature that is the classic sign of a tornado.
Here is a bit more on the progression and associated views of the radar image and the evolution of a thunderstorm.
http://weather.cod.edu/sirvatka/lt.html
BWER is the horizontal view of a hook echo. Magical, huh..lol
The second, and misunderstood, aspect is what is called VIL. Vertical Integrated Liquid. Way to complicated sounding! This just means the amount of reflectivity in a column of air. As radar picks up on raindrops to reflect back to show the storm structure, VIL is just the amount of reflectivity in a specific area of the storm.
The BIG misconception is that VIL alone is an indicator of hail, how big, and defines a hail core.
THIS IS WRONG. If I hear Tornado Horner say VIL again in describing hail will be one time too soon. It is ONE indicator. It is not the SOLE indicator of hail. In fact, VIL readings can be very misleading. Here is some information regarding VIL:
“VIL was a "fad" and was most popular when the WSR-88D radar was first installed.”
..” The VIL values correlation to hail size depends on season, synoptic environment, elevation, storm speed, storm structure, hail reflectivity characteristics etc.”
http://www.theweatherprediction.com/habyhints/242/
VIL is easy. Just means there is a lot of rain or possible hail in a given column of air. Beyond that, it really doesn’t mean much more.
Sounded much more important before, didn’t it?
The last item to discuss is TVS. Tornado Vortex Signature. You will see these on many media radar systems. This is reflected by a purple triangle, swirling icon, or many other icons. It is to represent circulation in the storm.
This isn’t too complicated either, but there are some things to be aware of. This is an algorithm that looks for adjacent gate to gate sheer recordings. All this means is where wind is moving away from the radar and moving to the radar next to each other.
Here is the kicker…depending on the location of the storm to the radar station and the height of the beam, you could be looking at many different parts of the storm without knowing it. The further away the storm is, the higher in the storm you will be looking.
So, it is possible to see a TVS type signature from a far away storm and really be looking at a storm with some mid level rotation with nothing at the ground.
Here is a bit more info….
http://www.theweatherprediction.com/habyhints/242/
For those that are a bit more adventurous, I would recommend tracking a mesocyclone in SRV mode to watch for the inbound/outbound winds and look for gate to gate. It was the most amazing thing I have ever done when tracking the Greensburg tornado seeing the HUGE amounts of gate to gate sheer and the enormous size of the vortex!
If I can find it, I will insert in the SRV image I captured about five minutes after the devastation of Greensburg. Incredible!
So…with all this, we have gone over some seemingly difficult things to see how simple they are and gone over the basics which people probably already knew but didn’t know they knew it. LOL
Next time you see the horizontal scan, just yell at the TV..”Look for the hook echo” or see VIL..well you can generally dismiss it while putting on your bicycle helmet, or see a TVS…wonder if the rotation is at the surface…
Here is a question. Do you want the media to treat you in the same ignorant manner as they do, or would you prefer they explain some of these things when they show you storm structure so that you can become more educated?
Just curious…
