A Dash of Atmosphere: Western US Storms, Inverted V variety

A few weeks back, Arizona was taken over by quite a few "Haboobs". You can go back in my older posts to see some images of this. A Haboob is a major dust/sand storm and in the US deserts areas are most commonly associated with the outflow of thunderstorms.

Older blog posts: http://chicagoirishmatt.blogspot.com/2011/07/photos-haboob-moves-across-south-valley.html or http://chicagoirishmatt.blogspot.com/2011/07/haboob-part-ii.html

Today, a few inverted-V profiles (named so because of the temperature/moisture profiles that are plotted from the weather balloon data ... images to follow in this blog post.) were around in Arizona and thunderstorms did result. Click on the next image to see the radar animation.


Click to see this animated gif!

About pic: The lines of blue moving around are called radar fine lines. In this case, they show the leading edge of thunderstorm outflow moving around. More about this in this next paragraph...

Basically, the situation exists where at the surface and the low levels of the atmosphere, it is very warm or hot and quite dry, thus a very low relative humidity. However, moisture in the mid levels of the atmosphere over the area allow for storms to form. What happens? You get storms to form and produce rain. The rain sinks into air that becomes drier and drier (increasingly lower relative humidity as rain gets closer to the ground.) Most of the rain evaporates in the very dry air. When water evaporates, the air cools. (See subjects like Latent Heat, Specific Heat, etc, for an understanding of this process.). The colder the air, the more dense it is. Dense air sinks as it is surrounded by less dense air. This cool, dense, air sinks to the ground and spreads out. This process is simply named "thunderstorm outflow". In the case of the Inverted-V, you get very strong evaporation and thus can get very strong outflows. And because it is so dry and so little rain hits the ground, this can be a huge fire hazard! Why? Imagine lightning strikes with little rain and lots of wind? Bad bad news!

About the Haboob situation. When you have these strong storms, and "dry" storms at that, over an arid/desert type ground, guess what happens? Lots of wind over a surface with lots of dust and sand means walls of sand/dust moving along. A Haboob is born! :) (Again, see more in my blog or just check out Google for images/info on Haboob storms.)

So, lets see a few soundings (weather balloon data.) First, what is called a STUVE. It is more easily understood by the non meteorological minded viewer. And I put a few labels on there to show you what is going on. The next 2 will be the more common Skew-T profiles for both the mets that might care about this blog as well as show you why it is called an inverted-V. Notice the upside-down V profile at the lower part of the sounding. The Tuscon Skew-T really shows the Inverted-V profile well.

Couple of notes for non-mets. When red and green lines are close, that means the RH is high. When they are far apart, it is dry -- the RH is quite low. The lines might be confusing but just know this is a plot of temperature w/ height and moisture w/ height.