all right for this lecture set it's time to start talking about tornadoes and for this set we're going to talk mainly about the formation and the characteristics of tornadoes themselves so don't forget that multi-panel diagram we already talked about during thunderstorms and severe thunderstorms remember the formation of tornadoes goes along with what I've already talked about remember it was this part right in here if you're looking at the bottom panel where our tornadoes could form along our cold fronts so remember the situation that we had our low-level jet stream with our warm humid air down here but remember that air is going to be less dense than the air above it but the cold front is moving faster so that air over here overtakes the air that's below it initially okay and remember there's an upper level jet stream as well that's present so we've got the key characteristics six that are all here okay we've got a jet stream that's present to help Drive severe thunderstorms we've got a temperature inversion and we've got a cold front with lots of energy around and uplift along that boundary so remember in these bottom layers where the warm moist air is okay often times our MTG air in the United States okay remember that that air is going to get forced up eventually because as that warm than humidity builds eventually it's going to push through that layer and cause for that vertical motion to potentially result and then you can have tornadoes that have actually formed so don't forget this diagram make sure you know it pretty well for thunderstorms and especially for what we're talking about now with tornadoes okay remember too that for tornadoes to develop that wind shear is extremely important and that's also something we talked about with this diagram you can see the cold dry air and the wind direction coming in okay and you can see that Mt air with the wind direction there and so you have that rotation that can exist because you have two different directions of air okay coming into these storms so once we get that wind shear we can begin to get that rotation or a mesocyclone that forms so the first thing you have to have essentially for tornadoes to form is a mesocyclone or this broader area of circulation within that system and there's what I was trying to draw before on the previous slide okay but a little different view okay looking at that wind shear and that rotation that can drive that mesocyclone formation along that gust front and the cold front so when we get that air that's Rising upward or moving vertically then you can begin to get that spinning motion and if that spinning motion results in a wall cloud and then a funnel cloud that descends to the ground now you would have a tornado so important to remember the mesocyclone comes first and it's a area of a little bit broader circulation okay in terms of that flow than what we would have with the tornado itself so these can be a few kilometers to 10 kilometers wide in terms of their size when that rotation extends downward you then get a wall cloud that begins to form so the mesocyclone is the bigger part and then a wall cloud descends from within a mesocyclone and there's a video here you can click on in the PDF where a meteorologist talks a little bit about this process so once you have that mesocyclone for and you can see that circulation sometimes we'll see it very clearly as a hook Echo signature on radar so you can see right in here this is what meteorologists would look for in terms of a hook Echo signature and then you would issue a warning to the area over which that storm is likely to pass okay so it's gotten better over time because meteorologists can use Advanced stopler radar to actually predict these things remember decades ago we could only look and rely on train spotters that could actually see these storms and rely on areas that it already passed over to give us warning so the mesocyclone itself is what produces the hook Echo so that broader scale of circulation is what what we see on the radar remember not every mesocyclone will necessarily produce a tornado but we areir on the side of caution as forecasters making sure that once the signature shows up a tornado could possibly be present and so you would issue a warning based on that and remember too this is especially important at night and if this is going to go through densely populated areas okay so tornadoes have a distinctive hook Echo signature remember we talked about D ratios and straight line winds having a well- defined bow Echo so when we talk about the circulation associated with tornadoes it relates back to something we talked about with the jet stream angular momentum and remember we're flowing in smaller and smaller circles so if that's true remember based on the principles we talked about with the jet stream remember this point down here okay if the radius of curvature goes down velocity has to go up in order to conserve momentum so by the time you're flowing in those Tighter and Tighter circles after you go from a broader scale mesocyclone here to a smaller wall cloud and then eventually a tornado which is even smaller in diameter remember that radius of curvature is going down with each phase so in order to conserve momentum velocity has to go up since angular momentum has to be conserved so at this point we have a wall cloud that's present okay but no clear funnel cloud yet at this point okay so usually the wall cloud will precede the tornado formation by some minutes but it can be as small as a one minute interval or it could be a little bit longer than that depending on the conditions on that day right and remember a wall cloud can be larger in diameter than what we talk about with tornadoes so talking about actual tornado form okay when we get tornadoes that form remember the air is rising upward through these convective processes and as it expands it cools just like everything else we've been talking about in class with clouds and precipitation and that kind of stuff so once we get that condensation process to occur the initial stages have a tornado that's going to be whiter in nature as a result of that condensation of that moisture once that tornado is on the ground though and it begins to lift things up and interact with things on the ground the debris itself can make the tornado much darker in color over time so talking about the stages remember a mesocyclone is what is present first okay and then once we have that mesocyclone first to actually get tornadoes that form we would have a wall cloud and then we begin to get a dust whirl and then we would start to get a funnel cloud and the tornado gets more organized now if the funnel never reaches the ground well then that's good for that area okay but if the funnel reaches the ground then we have an actual tornado so once that funnel is formed and once it touches down on the ground we reach the mature stage of a tornado and now it's time to make sure you're out of that path okay and if you can't get out of the path make sure you're in an interior room or in a basement as that tornado comes through when that funnel is near vertical it's at its most intense point because now we're concentrating that rotation around that tight radius of curvature which results in the velocity of the Winds increasing so remember mature stage vertical funnel conservational momentum equals maximum wind velocity as that tornado begins to weaken the funnel begins to tilt and now it's not as concentrated okay the winds begin to decrease but you're not totally out of the woods yet that funnel is still on the ground so it's still a tornado and so you can still get damage it's just not likely to be as intense as a huge tornado that's tilted vertically that's not breaking down at all and then we finally get to the Decay stage and you get this more rope like texture or appearance and remember the the winds can still cause some damage but now the tornado is beginning to break down and dissipate with tornado sometimes you can have multiple vortices that exist depending on what the setup is for that storm that day and if you get this you'll have a pretty random pattern of damage because there's multiple V vortices that are going through an area and if they're a little bit separated right you could have a house right in the middle between these that is unaffected while there's complete Devastation around it we can also have cluster outbreaks and so this is relatively common in the southern Great Plains and in the southeastern United States so we've seen tornadoes with as many as five appearing at a given time as a result of the really intense weather conditions on a given day remember I want you to know a little bit about the damage patterns that we get with our severe weather because that helps weather forecasters and analysts go out and see what the actual event was if the wind speeds were similar now remember our biggest tornadoes are going to have more intense winds than any of the other storms that we talk about however our smaller tornadoes can have similar damage in terms of the impacts to houses and roofs as are der ratios and other things and micr burst so remember sometimes with our smaller tornadoes we got to go out and look to see if it was a spiral pattern or the pattern of a tornado or it's a Micro Burst out from the center or if it was straight line winds like a deratio and we get tornadoes all across different parts of the country so sometimes we think of the Southern Great Plains and the southeastern United States as the main parts of Tornado Alley but when that empty air can push further into the continent you can get tornadoes other places so these are actually some photos that were taken on Lake Michigan in my hometown in southeastern Wisconsin so let's talk a little bit about the characteristics of a tornado beyond the formation and things that we've already gone through so first I want you to know that their extent is not that wide in terms of the extent compared to some other storms we're going to talk about hurricanes which can impact a much greater diameter area D ratios can impact a much greater diameter area tornadoes the largest tornado was about 2 miles across so that's a relative ly narrow path of damage compared to a lot of the other storms that we talk about remember that's the largest our average size is actually you know less than a half mile typically these tornadoes are going to advance on the ground at a speed of about 35 miles per hour and their winds can range anywhere from 50 mil an hour all the way up to 300 so remember the 300 mph storms at that point you know a tornado occurred without having to figure out the wind direction because no other storm we're going to talk about is going to reach a 300 mph speed however when you get down to those 50 to 100 mph winds you can see those as a result of micro birst and dur ratios in terms of duration to I also want you to be able to compare tornadoes to the other storms typically a tornado is not going to last more than a couple hours okay and most tornadoes are only going to last a few minutes remember dur ratios can actually last for half a day or a day depending on how long it takes them to work across the country a Micro Burst very quick okay so when we compare these different things make sure we know that tornadoes are not as long as hurricanes they're not as long as the ratios but they can last a bit longer than our microburst on average so the longest tornado that was actually recorded was the tristate tornado in March of 19 25 they call it the Tri-State Tornado because it went through Southeastern Missouri right on through Illinois and then it continued into in Indiana before it actually decayed and so you can see some of the towns that it went through here in the mid to late after noon okay and some of these towns were totally destroyed because it was a very intense tornado so remember that tornadoes usually aren't on the ground for very long the average is about 4 Miles because most of our tornadoes aren't that intense the ones that tend to make the news are ones that are much more intense and much larger the trate tornado was on the ground for 219 miles and remember in 1925 they didn't have the same type of Warning Systems that we have today so even though the sou Southeastern part of Missouri Southern Illinois and Southwestern Indiana don't have really huge cities this storm this tornado actually killed almost 700 people and you can see the types of buildings that were destroyed this is a brick School building and it was greatly impacted by this tornado which tells us as we'll find out in a future in the future lecture set on tornadoes this tells us that this storm was very intense and that we probably had an ef4 or EF5 type storm that went through this area we also had one in relatively recent recent times that went through Mayfield Kentucky and so it had a path that kind of paralleled where we were at in the Tri-State Tornado remember the trate tornado went somewhere through like right here and so the Mayfield tornado the actual path looks longer when you look at the radar but when they actually figured out how long it was on the ground it was on the ground for a little bit less than the other Tri-State Tornado so this actually went through Northeastern Arkansas parts of North Western Tennessee on into Kentucky and so this was one of the longest live tornadoes in more recent times and it had devastating impacts and deaths related to a Candle factory getting decimated and homes in some of these smaller towns along the path remember that there's warning signs for tornadoes and they're often preceded by hail they're often preceded by really severe weather clouds sometimes mamist clouds and so to get a tornado remember you have to have severe thunderstorms or supercell thunderstorms that are already in place tornadoes don't just arise out of the Clear Blue Sky they're phenomenon that are associated with a lot of the same things we already talked about with thunderstorms okay so those are some of the main characteristics and the basics of tornado formation we'll talk about tornado impacts and intensity and those things in a subsequent lecture