Previously by George Giles: Heat and Austrian Economics
Tornadoes swept through the south this past week killing more than 340 people. This toll may continue to rise as the devastated landscape is searched by rescue squads. As of May 2 some 458 people are still unaccounted for, let us pray that they are all students that have gone home without notifying anyone. Some of the these Tornadoes (atmospheric vortices) will be rated at F4, one in particular, the one that went through Tuscaloosa and Birmingham Alabama, may ultimately be rated at the level of F5 on the Fujita scale, a real life monster.
Tornadoes are unique features of the North American continent, they rarely form elsewhere. Tornadoes form when the cold air mass out of Canada meets with the warm most air from the Gulf of Mexico. u2018Tornado Alley' as it is called runs along a diagonal line between central Texas and the Great Lakes. The tornado season happens in the spring and fall as seasons change and hot moist air from the south collides with the cold dry air sweeping down from Canada. The sun heats the water of the gulf warming it up and raising the humidity level which then flows northward into the southern states. This provides half of the necessary features that create the 'supercell' thunderstorms which are the forebears and incubators of tornado production. Cold northern air dives down from Canada across the Great Plains and rushes above the warmer air from the gulf. Hot air rises and cold air sinks as these great masses of thermal energy collide. It is the rising of the warm air into the colder air above that generates the wind vortices that make up tornadoes.
In recent years thanks to the private sector miracle of Doppler radar these weather systems can now be understood in significant detail. Giant cumulonimbus clouds form along the interface or front between these colliding air masses which are at different pressures and temperatures. These clouds can produce a wall cloud which is the tornado nursery. The collision produces massive air vortices that are horizontal to the ground and invisible to the naked eye, but not to the penetration of the Doppler radar. Inside the cloud updrafts occur which brings moist air into contact with colder dryer air and hailstones form nucleating around dust particles that are suspended in the atmosphere. These begin to fall under the influence of gravity. This creates a downdraft alongside the updraft. This mass then rotates downward towards the ground and the vortex becomes vertical and can be seen descending from the wall cloud; the tornado forms and its short malevolent life begins. The most visible tornadoes are the large ones that accumulate dust and debris from the ground. Occasionally the horizontal vortex becoming vertical can be seen during this transition. The monster that formed near Tuscaloosa Alabama was videotaped making this transition thanks to some brave, daring and close videographers.
Most tornadoes only live a few minutes because they are unstable and rapidly dissipate. However, sometimes the conditions are so ripe for formation that as the squall line, along which the super-cells are formed, move these monstrous storms can then sweep across long distances and even strengthen. These are relatively rare events, a thousand or more tornadoes form every year, yet only a few are long-lived, but this is exactly what happened on Wednesday in southern Mississippi and Alabama. Only a couple of F4's form in a year and F5 often go years without formation. The figure below shows the percentage of tornado type by the Fujita scale for the period between 1950 and 1994:
The percentage of fatalities by the Fujita class of tornado can be seen below for the period between 1950-1994:
The data shown above shows that most deaths occur in the relatively rare F4 and F5 vortices. Another benefit of the agrarian nature of the Great Plains and the Midwest is that most tornadoes do not hit large cities at all, but wreak their havoc in fields with few human occupants!
As devastating as this week's storms were the casualties could have been much worse. The National Weather Service (NWS) began deploying NEXRAD radar stations around the country in the early 1990's. These radar systems use the Doppler effect to determine relative velocity with respect to the radar antenna. This correlates very closely with rotation of the air mass. These radar systems overlap in scans thus providing complete coverage of the continental United States. Each circle continues beyond the circular boundary but sensitivity and accuracy decrease with distance which account for the small pockets of white that do not show overlap.
NEXRAD Doppler radar station locations can be seen in the image below:
Your narrator was born in Wisconsin and lived most of his life in Michigan which seldom sees violent thunderstorms and tornadoes. I moved to south to Huntsville Alabama in January 1989. The beauty of the south is that even in winter it is a rare week that does not have a few warm days. In November of 1989 a warm front pushed up out of the Gulf of Mexico and collided with cold Canadian air above Mississippi and Alabama. The storm warnings went off at work so I left about 3 PM to go pick up my children at pre-school and bring them home. We had a nice small porch facing north on our home and we sat blissfully unaware watching the rain and enjoying an after-school snack. After dinner we started getting phone calls from concerned relatives, were OK, how did we survive the storm? "What storm we asked?" "The one that killed all of those people in Huntsville", came the answer. We turned on the TV to find that a monster F4 storm had gone just south of our house by a mile or so, and had run for more than 100 miles before dissipating. Twenty people were killed when it went through one of the busiest intersections in Huntsville at rush hour.
A couple of years later a local TV weatherman named Bob Barron put together a computer graphics system using Geographical Information System (GIS) data and real-time Doppler radar imagery provided by the National Weather Service. Using this u2018storm tracker' it was possible to identify the signature of a wind vortex from the Doppler radar. One side of the vortex is moving towards the radar and the other side is moving away. This is the signature of tornadic conditions beginning and/or a tornado in progress. Over time weather forecasters realized that something called a bow or hook echo in a squall line is also characteristic of the tornadic conditions of an actual tornado. The F5 monster below is a classic hook echo, it occurred in 1999 in Oklahoma and resulted in many fatalities.
During the last decade of the millennium Huntsville Alabama was the largest city in the country with the dubious distinction of having the most tornadoes within 25 miles. One of Huntsville's TV stations went so far as to purchase their own weather Doppler radar so that they would not be dependent upon external data feeds in times of dire need. A classic market solution if ever there was one!
Virtually every television station in the south now has a storm tracking system of some kind available to their weather man and thus their viewing audience. Many stations provide continuous coverage of the weather using storm tracking when the National Weather Service has issued a tornado warning. A tornado watch is when conditions are favorable to the formation of super-cell thunderstorms. A tornado warning is issued when Doppler radar shows that wind vortices and or hook echoes are forming. A tornado does not have to be seen in order for warnings to be posted. The NWS only need observe the proper conditions.
This past week's death toll from the super-cells tornadoes is testimony as to how serious this issue is in some parts of the country. When conditions are right diligent attention needs to be paid to the weather as many lives, including one's own depend upon it. The Weather Channel provides spectacular coverage of these and other crucial weather events with experts continuously monitoring the conditions in order to provide this essential information to their viewers. The Weather Channel goes so far as to send meteorologists into harm's way when forecasts predict that these tornadic atmospheric conditions are expected. Southerner's, like myself, knew that Wednesday was going to be a really bad weather day; the warm moist air had been rushing northward from the gulf for several days before the well-defined cold front began approaching from the plains.
The Weather Channel's Jeff Morrow was live on the scene in Birmingham to cover Wednesday's events. Forecasters knew Birmingham was going to be in the middle of these super-cell storm conditions far enough in advance to send him and his television crew there from Atlanta. Large tornadoes often throw debris in advance of the onrushing funnel cloud. In this case the debris was being thrown 10 miles or more, a grim indication of a massive tornado event. Morrow set up on a tall ridge south of Birmingham looking north when the F4 monster appeared on the left side of the screen. You can watch this incredible video on YouTube.
After the Weather Channel was displaying the information live the government issued a "Tornado Emergency" meaning a trained a spotter had seen the funnel cloud and that people must take cover immediately.
These wondrous technologies saved thousands of lives on Wednesday. While it was a terrible tragedy that so many lost their lives, the death toll could have been very much higher. The combination of Geographical Information Systems and NEXRAD weather data provided the viewing audience with warnings sufficient to take cover.
Bob Barron's storm tracker uses wind velocity and trained meteorologists to produce warning down to the street level on a minute by minute basis. While science cannot predict exactly when and where tornadoes will form these empirical systems in the hands of trained operators can always give a few minutes warning before one arrives. So here in the 21st century it is possible to never be surprised by the appearance of a killer tornado. These systems are so accurate that a tornado will only sneak up on the unwary. TV stations all over the south were telling viewers that Wednesday would be bad.
I have lived in Nashville since 1999 and our local weather forecasters were saying on Monday that bad storm conditions were setting in for Tuesday and Wednesday evenings. Weather radios that sound a shrill alarm that can be configured county by county and state by state which will awaken the sleeping who can then tune in the cable TV and find out what should be done.
In a scene of no small irony the Emergency Broadcast System took over the Weather Channel cable TV feed for a few minutes on Wednesday around 5 PM. It is a plain grey background with white letters saying a Tornado warning exists, and then it lists the counties covered. Keep in mind this provides small to zero localized information. Some counties in this country are 300 miles long so knowing which county the storm is in or approaching from is not nearly accurate enough in comparison. The cable TV channels are required by law to let this occur! The irony is that the storm tracking systems which are giving minute by minute predictions on a town by town, street by street basis have to surrender to a system that is 1950's era relic of black and white television that provides little to no useful information. Just what one comes to expect from our sclerotic, bureaucratic, and centralized Federal leviathan having no accountability. This idiocy preempts and interrupts the system that is actively and actually saving lives. Classic governmental legerdemain if ever there was one! All of these technologies GIS, NEXRAD, Doppler, cable TV, and weather radios are the product of the free market economy, and as seen in Huntsville local television stations will purchase these expensive radar systems and operate them uninterrupted by commercials during storm conditions. They do this so they do not have to rely on the government and be at the mercy of unaccountable bureaucrats.
In closing let us all say a prayer for the departed, the victims of Wednesday's tragedy that lost everything to a malevolent wind. Let us loudly praise the men and women working in the free market developed the technology that saved thousands of lives on Wednesday, and will continue to save lives into the future by using all the tools conjured up by the minds of free men now available to predict and monitor these horrific events. In my 21 years in the south I have had 4 different tornadoes within a mile of my home, so needless to say I stay tuned in!
P.S. Rep. Ron Paul and Sen. Rand Paul please introduce a bill into Congress so we can get laws changed so that the useless Emergency Warning System can stop interfering with a warning system that has been proven to work time and time again over the last two decades, and never so vividly and wonderful as it did this past Wednesday.
George Giles is an independent writer in Nashville TN. He studied atmospheric physics under the Alabama State Climatologist.