when you re looking at a storm, you think you re looking at the clouds. the deck of the clouds. look for the funnel to come down. you should be watching for that. ultimately tornadoes, they show themselves on the ground. a swirling dust swirl. some people mistake it for smoke and they don t know what they re looking for. you look for the swirl on the ground. the way the storms form, you have wind coming from multiple direction there s. the rear flank downdraft that comes wrapping back behind the storm and brings cold, dry air and that meet warm moist air. they swirl there. that s how you get the tornado to start forming and the rotation in the clouds and the atmosphere is usually horizontal. the updraft from that supercell bends that rolling down to the ground and forms the tornado. neil: scary stuff. you re not scared. thanks, aaron. good seeing you. no problem. neil: be safe. as aaron touched, we ve seen
horrible day. a tornado starts with a supercell, a rotating thunderstorm. on these tornados there is one thing that clearly stands out, especially when we look at radar. it s called a hook echo. that s an appendage on the southern flank of the storm. we know these storms aren t flat. they re vertical 40 50, 60,000 feet. let s pull this thing up and look at it. when you look at this big rotating thunderstorm and as massive as it is look at what s going on down here. look at that tornado. so just a small part but the most violent part of that supercell is right there in that tornado. so let s lift the base of this and talk about tornado genesis. a lot of the research has gone into what kicks off the tornado from the supercell? well one thing stands out, you can see this when you re in the field. it s called a rear-flank downdraft when the upper level winds get caught come through the backside. if that rear-flank downdraft isn t super cold it can actually allow a tornado to form especiall
shear. when you have an intense thunderstorm, intense updraft, that thunderstorm is able to focus the horizontal shear about a vertical axis and then like an ice skater that brings her arms in and spins faster, you have all this moisture and energy being focused around this vertical axis. in a typical thunderstorm, it usually snuffs itself out within 30 to 45 minutes. in these supercell thunderstorms, they tilt over slightly due to wind shear and that protects the warm updraft and it assistance the warm updraft so instead of dying out after 45 minutes, it goes on hour after hour and in the process you have enormous amounts of energy focusing in right around the central core and ultimately something called a rear flank downdraft, a surge of drier, cooler air pulls the circulation down to the ground and we have a tornado. out of 100 thunderstorms, maybe
is no match. there s no room left for your car or you in that car when this tornado is done with. you need to stop the car and just get out if you have to and get in the ditch. this is the time where you need to get in the ditch. you know, people always ask, should we really get in the ditch? yes. if there s nowhere else out, then yes, get out of the car because there might be this could be really chad, do you see this? i m watching it live. do you look at this. i see it, don. this is an ef-3. 130, 140 mile an hour storm. already see some gusty winds, even as far away this is the main storm that came out of norman. still very gusty winds. more than likely a rear flank downdraft. millennium 3, let s get that full screen, please. chad, you saw the size that was a downflank, a back it s so hard on television, don, to figure out what part of a storm. because i don t know which way the camera is looking. what we know is that that s not
we get that hooked up better. we re going to go to chad myers here who will tell us about where there s severe weather and the latest about the potential tornado in memphis. the warning on that has been going for about 20 minutes, the sirens going off in memphis proper. the energy and the circulation is the northern half of memphis but now rolling over the river, literally rolling over the river. i don t think i can explain it any better than i can show it to you. the storm has just been rotating all the way from arkansas. and then across the river and into memphis, tennessee. there you go, this is some of the video we ve been seeing earlier in the day. i have the video from memphis in my weather wall right behind me. it sure looks ominous now, and there we go, you see that. we believe the one on the right, this over here is the rear flank downdraft. not a tornado on the ground but under that, this would be upward wind pushing down, could get wind gusts to 80 or so miles per hour rig