Weather Blog

Thoughts and stats on the southern tornadoes

Thoughts and stats on the southern tornadoes
A tornado moves through Tuscaloosa, Ala. Wednesday, April 27, 2011. A wave of severe storms laced with tornadoes strafed the South on Wednesday, killing at least 16 people around the region and splintering buildings across swaths of an Alabama university town. (AP Photo/The Tuscaloosa News, Dusty Compton)

Just thought I'd take today to give some random thoughts and statistics that I ran across while keeping tabs on the tornadoes that ravaged the south Wednesday.

* The death toll is devastating and will go down as one of the worst, if not the worst, in history due to tornadoes. But I can't fathom just how much worse it would have been without current technology. As many tornadoes as there were -- and at times there were literally dozens on the ground at the same time in Alabama, there were few, if any, surprise tornadoes. The tornadoes were so intense that they were easily spotted on Doppler Radar, and that gave forecasters the ability to give several minutes of lead time to communities in danger -- some as many as 20-30 minutes or more -- even though the storms were racing at freeway speeds across the landscape.

* Let's think about that for a moment. Some of these tornadoes were moving at 50-75 mph! So next time you're on I-5 going around the speed limit, just give a quick glace to the side at how fast the world is passing you by -- and imagine a tornado going that fast across the ground. Unbelievable!

* The radar technology was not only showing 3-dimensional pictures of the storm, allowing forecasters to see how large the tornadoes were, but also was tracking debris being sucked up into the clouds. I was glued to the Weather Channel's excellent coverage Wednesday and they showed graphics depicting debris being sucked as high as 10,000 feet high.

* All that debris has to go somewhere, and it was literally raining down dozens of miles away. A Weather Channel reporter in Birmingham was showing video of plexiglass and roofing materials that were falling from the sky -- and this was as the tornado was heading into Tuscaloosa, a solid 20 miles away.

* This is said to be the worst tornado outbreak since the Super Tornado Outbreak of 1974 which left 315 dead and 5,484 injured. (Ironically, that site I hyperlinked to said "It is near speculation as to how frequently such a confluence of factors might occur. One such guess might be several hundred to five hundred years." Or, just under 40 years.). In fact, I would go ahead and say Wednesday's was worse only because the death toll is well over 250 already and that is with the aforementioned warnings. If we had the weather technology of 1974 in place Wednesday, the death toll from these storms would likely be so, so much higher.

* That said, even with the warnings, there is only so much you can do when you have a tornado of that magnitude. Many reports are speculating the Tuscaloosa/Birmingham tornado was an EF-4 or EF-5 on the Enhanced Fujita scale -- and EF-5 is the top of the chart. Unless you're in a reinforced concrete building or in an underground storm shelter, even being in a newer home and taking residence in the lower floor interior room may not be enough to survive an EF-5 tornado, which has wind speeds over 300 mph.

* The Weather Channel reported that as of 7 p.m CDT on Wednesday, there had been 279 tornado warnings -- what the National Weather Service office issues when a tornado is observed on the ground or by radar. 80 of those warning were issued by the Huntsville, Alabama Forecast office.

* At least one tornado warning was in effect from 4:15 a.m. CDT to 11 p.m. CDT in Alabama, the Weather Channel said.

* At some points during the storm, the National Weather Service offices in Huntsville and Birmingham had to be evacuated due to approaching storms. In those cases, NWS offices in adjacent cities take over issuing warnings until the threat passes. In Huntsville, meteorologists said they stepped outside to find multiple wall clouds -- which typically spawn tornadoes -- and took cover. But their building was not damaged.

* What made this such a devastating set-up? They had perfect conditions on a number of levels for severe storm development. Cold air that has been persistent over the Northwest moved into the Midwest and southeast - for example, temperatures in Oklahoma were stuck in the 50s. Meanwhile, the southeast had been hot and humid --- temperatures were in the mid 80s with dew points near 70. The cold air moving in allows the hot and humid air to rise further and create larger storms. In addition, an area of low pressure was hanging around the Midwest and a very strong jet stream was undercutting the low to the south. As the low tried to wrap around the winds to the north over the Tennessee Valley, the jet stream wanted to keep pushing them east toward Georgia and the Carolinas. That divergence creates lower pressure aloft and enhances the updrafts. So we had plenty of warm, humid air for moisture and energy, plenty of cold air aloft to allow that warm air to rise to dizzying heights (some of those storms measured over 50,000 feet/ 10 miles high!) and additional mechanisms in place to enhance the convection.

* Why is it that it always seems sunny after a tornado hits? Look at the photos of rubble of any tornado and it seems like there is blue skies the day after? Usually the pattern that creates the tornadoes causes quite pleasant weather in the storms' wakes. High pressure typically follows in behind the cold front, clearing out the skies and proving a cool, dry northwest wind that inhibits the warm humid air from the Gulf of Mexico. To wit: the weather in Tuscaloosa on Thursday was sunny with highs expected in the low 70s and very low humidity. A far cry from the 84 and 70% humidity as the storms approached.

* Looks like the South is not out of the woods yet. As the storm hitting the Northwest Thursday eventually moves into the Midwest and East, it'll trigger another round of severe weather -- looks like Sunday and Monday are the days to watch out for. Doesn't look like it'll be as severe as the last round, but still, a very rocky week ahead there.

* Finally, there is some amazing video out there of the tornadoes as they raged through the South. Some are dangerously close to the photographer. Makes me realize that we only see the videos of those who made it through. I wonder how many of the dead might have been trying to film the tornado but were too close and were killed instead of seeking shelter? We only see the survivors' film. Not that tornadoes are much of a concern around here but even if you think a tornado is at a safe distance, it can change direction in a heartbeat. And as I said, these Alabama tornadoes were racing at freeway speeds, so there was little time to react in real-time. Plus, even if the tornado isn't coming to your home, debris is getting blown around at incredible speeds, plus highs winds can shatter glass and pick up vehicles that aren't even that close to the vortex.