Focus 580; Severe Weather

This morning in the first hour of the show we'll be talking a bit about severe weather and the kind of severe weather particularly that we have at this time of the year. We're talking about things like thunderstorms and tornadoes and lightning and hail and that sort of thing. Every once in awhile here on this program we have our own in-house meteorologist Ed Keizer on the show to talk a little bit about those sorts of things. And that's what we're going to do this time around and yet with different set of guests two guests In fact both of them from the Department of Atmospheric Sciences at the University of Illinois Donna Charlotte boy and Glenn Romano. Donna teaches courses on general meteorology and severe weather as well as the societal impacts of weather and climate She's also the co-author of a university textbook on severe weather. Glenn is a member of the convective modeling Research Group and is a storm chaser who has done that both as a hobby and occasionally as a profession. It also has participated in several field research projects investigating severe weather phenomena. I also recently contributed to a Nova program on tornadoes and were pleased they could both be here and talk will be with us here this morning and as is always the case on the program. The

idea is people who are listening can ask questions. If you have weather questions you can call us. And I know that they will do their best to give me an answer here in Champaign-Urbana 3 3 3 9 4 5 5. That's for the local folks here but we also do have a toll free line that means it would be a long distance call for you. Use that number that's 800 to 2 2 9 4 5 5. Well thanks very much for being here. Well thank you. Thank you. I know enough to understand that. If you have a a big air mass that's warm and and moist. And then if you have another air mass over here that's cold and dry and you slam those two things together you're going to have storms. I know that much but how exactly that happens that I don't know it is impossible to explain in really simple terms how it is that thunderstorms happen why they happen. Well there's there is there's actually you need. I like to think of severe weather sort of if you want to make it you need to have a recipe. Like if you're going to cook and

in order to make thunderstorms you need three things in your recipe. You need to have some moisture and of course in the summertime it's usually very moist. You need to have a way to lift the moist air which is usually a front like you talked about. And then the other thing that you need is an unstable atmosphere so that once you let the air up it kind of stays up there. And when those three things are in place it's possible to get a thunderstorm. Now that would just be your garden variety thunderstorm if you add a fourth ingredient which is what we term wind shear that will actually get the storms to potentially become severe. OK. And so that's usually when we're looking at if storms are going to develop. We look for those. Three or four thing. Well now I have to ask you to define that way. When Cher What is when Jim that's when the wind speed or wind direction changes as you go away from their service. So if you have really good hire. Yeah yeah. So if you have slow winds at the surface and then faster winds up above that would be wind shear or if they changed direction.

And anything you want to you want to add to that. No I think she pretty well covered what we can talk about this whole bit more ads and telling you that we have a caller and rather than make them wait while I ask goofy questions we will give them a chance to ask question here will go to a caller in Indiana and it's line number four. Hello. Yes two questions number one. I guess generally the statistical question because I've heard different meteorologists on TV in the radio say two different things. I live near Lafayette Indiana. And so they give the weather report for that area and oftentimes you hear of the chance for rain is 30 percent. Now I've heard that it means that in the Lafayette area 30 percent will have rain or that where I am you know living there is a 30 percent chance for rain which is two entirely different things. And the second question deals with modeling just what goes wrong with the modeling is there a particular parameter or variable

that is you use the one you usually guess wrong or wad. And I guess it's just up front the first thing you think of is. Is the second week from like today when they give the what the weather is going to be whether higher or lower precipitation things like at I I keep track of that and I sort of given up on it because it just jumps around everywhere you can go from one day and the next day to be entirely different. You know instead above temperatures you have below temperatures less rain in the day before it was above temperature and with moring. I just wondered what kind of imports. You know cause that change and which things you're guessing wrong. Thanks. OK well I'll talk about that. OK well actually I think I'll address the first question and let Glenn deal but you can take the argument right well he's a model or so. Oh OK. Yeah the 30 percent probability of precipitation is very confusing. The percentage probability what that actually means is that for the forecast area where the forecasts being issued for there is a 30 percent

chance that rain will occur somewhere in that area. So it's not for a specific point. It's not that it's going to rain 30 percent of the day. And so I think that that for meteorologists can't kind of the norm what we usually give for a forecast but the general public typically doesn't understand that even in that forecast area if it rains somewhere that's not where you're at that's still a valid forecast it was actually accurate. So if we if we said for example we're talking about if we have a 30 percent chance of rain in Champagne County today. If it rains anywhere in Champaign County. The vet will say we scored a hat that doesn't necessarily mean that at my house it's going to rain right. That's a verified forecast. OK right. And I guess it is as the caller says it is something that really confuses people is that that's just the closest you. You can't you can't really pinpoint you can't say it's going to rain it at my house or is even going to rain in the northern part of the county as opposed to the southern part of the right.

Right and that's actually a couple years ago I was talking to Illinois Pilots Association and they were saying you know well there's a fork and why can't you tell me where the thunderstorms are going to be so I know where Y which you know and that's really not possible not actually sort of leads into the caller's second question about the right modeling about modeling particularly as you get more as you get further and further out from today if today we can say pretty with some fair level of confidence than tomorrow. Well it's not quite as good. And then next week is not quite as good and I suppose there are people who will would claim they can tell you what's going to happen two weeks from now and they're the you know the accuracy of your forecast gets less and less. So why is it that's that's so tough and what happens that predictions end up breaking down over these long time frames. Well prediction through numerical models is is pretty challenging. It there's a lot of different scales of motion that occur within the atmosphere and some of those affect the larger scale weather patterns that maybe we can see things that are going to happen over a long term period. But most people are concerned about what the day to day weather is going to be like. And those

are kind of noise within those larger scale patterns. And then we can look at the those medium sized patterns and then they're smaller scale features within those as well. So there's lots of different scales of motions that are undergoing and we try to describe those in numerical models using sets of equations that describe those motions. But it's a difficult problem to solve because we have to simultaneously solve a number of equations at the same time and there is no perfect way to solve those. And so there's errors just in being able to solve those numerical problems as well we have to try to resolve features that are going on that are smaller than our model grids are able to resolve and so processes such as turbulence and precipitation events like individual thunderstorm cells on certain models those are not actually explicitly solved. And so we actually have to make an estimate as to what that how those will impact the larger scale atmosphere. And so as soon as errors start to arrive in that forecast then downstream of that things get progressively

worse in time. And so a small error grows into a big error in the long term and so it makes long term prediction almost impossible when you get out to the really long time periods. It's a very difficult problem but we are making steady progress and advances current seven day forecasts are about as accurate as a three day forecast used to be just about ten years ago. And so but it is a very difficult problem and it has that accuracy come because of computers and the ability to make models and put in all kinds of different variables and then have them crunch all that and come up with something earlier there and right we've advanced our models of the atmosphere considerably over time. And we've also been able to get much better computing power and that computing power allows us to get to resolve more and more of those smaller features that we earlier had to really kind of guess as to what was going on there. Well let me ask you this question and I don't know if if if there's a ready answer but say suppose that we are we're doing a forecast for central Illinois a pretty

good chunk of the state that includes the Fae ask how many different variables are there that enter into making the weather here. I mean if we just said OK we're going to we're going to make a model we're going to try to figure out what's going to happen here in the central part of the state within the next couple of days. How many different things do you have to put into that mix to get a model that's complicated enough and close to a reflection of the real world so that you could get a forecast with some fair level of confidence that it would pan out. Well I guess in terms of the actual data that you need you need to have the math that Glenn talked about. But you you can make a really complicated computer model with math and physics but if you don't tell the model what the current conditions are like it's not going to be able to forecast in the future. So just to start off with you need you know lots of standard variables like pressure and temperature moisture wind direction wind speed cloud

cover soil moisture content is important. Snow cover what kind of terrain you've got. In some cases what kind of topography and ideally you want to have all that data in a pretty what we call a kind of a tight grid. We collect the data kind of it. And if you divide everything up in grids you'd want to have it at like discrete points and obviously we don't collect weather data we collect it that way we collected wherever there are cities where we have information so you we don't have kind of a lot of initial data to begin with. But we do need all those variables that I mentioned not just at the surface but then at many points above the surface. Because really it's what's happening above the surface that drives the surface weather conditions. So we need to gather all that data and then put it into our computer model which would then have all the math and physics in it and then we would run that and the way we get the upper air data is by releasing right wing signs. The weather balloons and those are those are done by the National Weather Service.

The launch site closest to us here is in Lincoln and those are only done twice a day. Currently at 7 a.m. and 7 p.m. primarily because of cost. It's very expensive to launch them somebody has to go out and get the actual instrument package in the balloon. And you know I think there's one in Davenport. Southeastern Wisconsin so they're kind of spread apart so you're kind of you don't really have a lot of data to begin with so it's very difficult to make small regional forecasts partially because of the initial conditions. So somebody asked the question well how can you get me a more accurate weather forecast you'd say well you got to you have to give me more data the more data you give me the more of this kind information you could give me then the more accurate forecast I could make for you. Right. Yeah there's lots of different tools that are being developed nowadays to try to actually take more advantage of what limited observations that we do have in the atmosphere to start our models off in a better guess of the

initial state. And but those efforts are mostly in remote sensing methods nowadays because we simply don't have very many actual observing methods for in the middle the atmosphere. So but there are quite a few actually that exist for helping us with that problem but it's a it's a large amount of data that we have to consolidate into developing a picture of the initial state of the atmosphere. And it it's inherently going to have some air. It will never be able to have a perfect initial state for the model and so will never be able to make you know an exact forecast for a specific location out to a very very long time period so the more the farther out you want to go in time the less specific the forecasts can be. Do the models take into consideration what happened in the past. That is you know looking at that let's say last summer you know we go back a year and you look at the the various factors that influence the weather and then look at what happened does that have any kind of predictive value about what's going to happen in the future to say well OK we had

this this barometric pressure in these winds and this humidity and all these kinds of things in the past. And we saw. This these weather conditions follow. Do you take that in and put that in the mix too. For the for the actual numerical modeling there's not a lot of that that's done. But that's actually something that's actually a method of forecasting and something that is done to look at usually on longer term forecasts well in the past when we had conditions like this you know X happened afterwards. And so if we have those conditions again we could expect that we might get X again. But from an explicit standpoint usually it's on this sort of time scale. Let me introduce again our two guest for this part of focus $580 Charlie boy and Glenn are all mine they're both from the Department of atmospheric sciences here at University of Illinois. Donna teaches courses on general meteorology and severe weather. Glenn is a member of the convective modeling research group

has also done some storm chasing. And we're talking a little bit about the weather and how it works particularly the kind of weather that we have at this time of the year. Thunderstorms and tornadoes and so forth and if you have questions give us a call 3 3 3 3 3 3 9 4 5 5. Also we have a toll free line 800 to 2 2 9 4 5 5 hear someone calling from over in near Danville and Belgian 1 Number 4 0 0 0. You know this has something to do with basically the Manics I guess. OK Dawn is that a particular time. Like five fifty five this morning or something. Now is there a difference between dawn and DAYBREAK. I mean if they break the same of dawn or because about you know 10 or 15 minutes before dawn you can still see. You can see the enough to work outside.

Right yeah I'm not. And quite honestly I don't know the technical definition of those but I think what you're referring to is the period of time when there's actually light but before sunrise or after sunset and that that's referred to as Twilight. So it may also be referred to as as dawn or dusk. But yeah there's a period of a couple of minutes before the sun rises where some of the light actually kind of bends around the Earth and Earth and we can actually see there but now. But there's no there's no real difference between daybreak and dawn. I don't think so. OK OK that's just been bugging me for half a year or so. All right. Well thanks for the girl. I thank you kindly. As far as the as as when we quote those statistics I mean we figure that we give we give it here they give it on television is for sunrise sunset. And I guess I'm assuming that there is a very clear definition of what exactly that means.

Right. But that's when the actual visible portion of the sun rises which actually it's a little bit below the horizon because of the refraction of the atmosphere. We can see the sun actually before it's actually even with the horizon because it bends the light around the earth. And but technically what as soon as the sun becomes at zero degrees of the horizon it's sunrise or sunset it was so some of these other terms we might use that mean many different things to different people but as far as meteorologist people like that are concerned everybody is going to agree on what is sunrise and what is sunset. That's why it is we can say at this time to the minute it's going to be this way today and it's going to be this way tomorrow it's me this way the next day. Exactly. We have a caller in Arthur next line number one. Hello. Oh yes. Yes I have a caller. What about the different models. As far as the European model and whatever we use for North America what is it that a further

European is can be more accurate than our own. Is that because of population density you never get more data into that system. Or just I'd like you to speak to the difference between those Hang Up and Listen thanks OK. Yeah the I'm the model that the caller's referring to is the abbreviated ECM. Yes it's kind of the governmental acronym. There's actually many different computer models that are used to simulate weather conditions and there is the European model which is it's referred to. There's an aviation model there's a model called the ADA. There's a handful of them and the European model is is actually run for the you know for North America. So we're not importing any different data into it we basically collect all the data from across the country and then we put it into each of the different models and then run the models. And so the

differences between the models have to do with the way that they're set up in the computer program the way that they solve the equations like the one alluded to before. Some of the assumptions that are made and different models will actually do a better job under different conditions and meteorologists that are at the National Weather Service that do a lot of day to day forecasting kind of know well this model's good for you know looking at winter precipitation but this model doesn't do very well with thunderstorms in the summer. And that's just based on looking at the previous track record of how how good those models did they make this prediction then you see what actually happened. Right. Right. And the caller is correct that the in general the European Center model is better at long range forecasting than our models and the exact reason for that is it's not entirely agreed upon. Not surprisingly but the European Center does use a much. Better method of starting their model

off to begin the forecast is a very high end. It's called data simulation system but that's very sophisticated and is believed to give them a better starting point. But there are completely different models and so as far as exactly how they deal with some of the physics issues that are associated with model forecasting and so the results are sometimes quite different. This again this might be might be too complicated a question to give a an easy answer to but in the in the winter time we talk about winter storms. It seems that with a winter storm you can have days of notice you can. It can be a long time before the storm arrives you can you can say with a fair level of accuracy that we're going to have a winter storm it's going to take this track and it could bring a lot of snow when it can be very cold and so forth. And it seems that in the spring and in the summer it's much more difficult to make those kinds of predictions. The storm prediction center lays out these very large areas and says within this and it can be big big pieces of entire states.

We're saying well within this area we think that there is a possibility of storms. And then as we all know it can be you know you can be going along and nothing really seems to be happening and then suddenly a storm can come up like that and it can be very surprising. What's what's really the big difference between what's happening in the wintertime and the summer that we can have this long time long lead time with a winter storm. But with a say a severe thunderstorm could could pop up very quickly without much warning. Yeah that has to do primarily with the size of the storms. If you think about like if you look at the weather map a weather map in the wintertime these storms are our big areas of low pressure with very very large cloud areas cloud shields that extend hundreds you know a thousand sometimes fifteen hundred miles if you cover like half the United States whereas the storms that we typically think about in the summer the thunderstorms. Our much smaller scale. So there much

cover a much smaller area. And that's actually directly related to kind of how well we can forecast them and how far in advance and it goes back to that issue of modeling and putting all that data on grid points you can imagine if you put a grid over Illinois. And where are the points where they all intersected. That's where the model is going to calculate conditions in the atmosphere. So you can imagine you know a typical grid maybe there's a point in Champaign one up near Pontiac You know so maybe 50 miles or something square. Well you could have a thunderstorm inside that square and the computer models only going to be really kind of calculating what's happening at those grid points whereas if you think about a winter storm that covers thousands of miles now you've included lots and lots of those grid points you've got lots of data so it's actually able to get a much better picture of what's going on. The other factor is that those storms tend to last much longer period of time several days. You get a winter storm that you know creates snow in Colorado and then tracks all the way across us over a period of

five days whereas thunderstorms last about five hours. And so the time scale becomes a factor as well. OK very good we're already at our midpoint here. Questions are welcome 3 3 3 9 4 5 5 toll free 800 to 2 2 9 4 5 5 our guest Donna Shaw the boy and Glenn are all mine from the Department of atmospheric sciences here at University of Illinois by the way we had someone call in and said for people who are just curious that the U.S. Naval Observatory website has all of the information you could ever want about sunrise and sunset. So if you're interested and you have internet access you can go there and I'm sure that it would be easy to find the next caller we have here to talk with someone Rantoul line number two. Hello good morning. Yes I was just kind of curious. They were talking about the upper atmosphere for observation. Why are is that maybe not possible to use aircraft. You know we have so many commercial aircraft flying different altitude.

Can they read the data from a commercial aircraft you know put sensor back on or something like that. Yeah actually they do. There is part of the system I mentioned just the weather balloons because that's our primary method and that most people are familiar with but there's actually another system an acronym is a car's aeronautical. It's something something. But the system probably right. But basically they have instrumentation on commercial aircraft and of course the aircraft have regular flight patterns and you can actually go online and if you do a search for a car's ACARS you can probably find a recent map that shows all the flight paths and so they tend to get a lot of information for takeoff and landing and then also cruising altitude and that information is made available to some forecasters primarily I believe with the National Weather Service. So they do utilize that that system actually has other information and it's a

in conjunction with the FAA and Noah they work together so they collect other information besides weather weather data. All right. Hey I appreciate that. Thank you. I think you for the go let's go on here and I think the next person in line is in Bloomington Indiana. One number three. Hello. Could I ask about the severe weather warnings which interrupt television broadcast that you are. Do you know anything about the policies of those warnings. I mean they interrupt. Did they interrupt the broadcast with a signal which is quite unpleasant. And they sound the signal three times. Why not make a very pleasant sound and only sound it wants. I'm sure a lot of people agree with you. Yeah I think that the reason that they use the unpleasant sound is of course it gets your attention and they want people to pay attention you know. I'm not sure

what the standard is behind doing it three times. And then they sounded three times again when they're going off the air. I mean after they've already given us the warning why do they have to have to sound that very unpleasant sound three times more. Good good. Could that policy be changed. Why not. Why not give us a present signal and only found it once. Well I thought I kind of think what Donna says is right I think someone has decided that it has to be really irritating to get your attention and they do want to get your attention particular I mean if we were talking about something like a tornado warning. If it's one of those things where we're trying to say to people there was a tornado and it's coming down your street. So take cover right now I think the idea is that you want to get people's attention. But whether there is I honestly don't know if that if so if the FCC has set some policy or that there is some sort of policy that all stations do follow in how it is they do that. I honestly it I mean we have a weather policy here. For example

AWOL that our own meteorologist has developed but whether there's some kind of overall policy you know I actually I don't know it. Do you know from having living lived in different parts of the country. It's it seems to be more choice of local stations and how they choose to broadcast the information. I would envision a situation where they might not have their on air meteorologist available to disseminate the information particularly during. Hours that are like late at night where they simply may not have someone there and so they may have an automated system to make sure that the information still gets out to the public when they don't have someone who can present the information to you. As far as why they give the alert tones at both the beginning and the end of the message I can't honestly say where that decision came from but I'm sure it's associated with just trying to make sure that you have they have your attention during that time period and you know there's an important message between those tone alerts.

May I ask in general guidelines how severe does a thunderstorm have to be before you were interrupt a broadcast. Well there's actually specific criteria that make thunderstorms severe when they actually interrupt the broadcast to let you know that there is severe weather or when there's the potential for severe weather because sometimes they're able to let you know. You know we think that these thunderstorms are going to become severe. And again I'm I'm not sure who sets the policy for individual stations to do that. But once a thunderstorm has either. Hey all that's larger than three quarters of an inch in diameter. It has a tornado or it has caused wind damage or has wind gusts over 58 miles an hour those three criteria that has any one of those three is considered severe. And it would be the people in the part of the thunderstorm who would need to want I mean if you're in the thunderstorm you know it right. You have to be warned. But it's the people who are downwind who who are in the path of a thunderstorm or need to be warned isn't it.

Correct. That is correct and actually with the technology that we have now that is used by the National Weather Service they actually have automated systems that can look at how strong the storm is what direction it's going and how fast it's moving and it will project out the storm is expected to be near champagne at this time. St. Joseph at this time Danville at this time and that's all done automated by the computer so that they do let the people that are in the path of the storm know what. Thank you very much. Thank you. And then for us for example for a broadcast station they're not the they're not making this decision about the weather. If a warning is issued the Weather Service issues the warning. So if they say if they issue a warning for a severe thunderstorm or for a tornado. We get it on our news wires. And then we're going to go on the air with it. If there is a warning and it's for the air like you know like you're a deadly Well we said within this geographic area if there are warnings we're going to give them and we're we are going to get them as soon as we possibly

can. And they do the weather service also. And I think this is only for tornado warnings. And my apologies as our member for severe thunderstorms but they also at when they put the warning out they request you to give that you know whatever it is you use that's the thing that gets people's attention. They actually request you to do that to use your emergency notification thing so that as as we were talking earlier that I think that that is the basic idea. They want to make sure that they get your attention and you hear that and that if indeed you're in the path of the storm you know you go to the basement or wherever it is that you that's the safe place for you to go. Right and you know is the center on this topic I just want to kind of. Let people know that one of the best things that they can do is purchase a NOAA weather radio because if you don't happen to have the radio on or have the television on and you won't hear those broadcasts. If you have a NOAA weather radio which you can get Radio Shack in many different places it will automatically sound an alert when there is severe weather in your area and they're advanced

enough now that you can actually program for specifically your county. So if you're in Champaign County it will only sound an alert when there's a severe thunderstorm warning or tornado warning for shipping. And I know that some I assume that sometimes people are irritated by these warnings if it doesn't affect them. Right. If they're not particularly affected and I guess all of we would say is that well keep in mind that somebody is affected. And when we give warnings like that or other stations give them what we're trying to do is to is to help people out with a potentially very important information so you know if you can kind of deal with it and if it's not for you you know be patient and know that we're trying to help somebody else someplace else. Let's go let's talk with some of the folks Bloomington Illinois is next in line for. Yeah. I had a question of the weather forecasting and politics. I wondered if listening to the experts Signet this and the Bush administration dig up you know to say there is no global warming. If that's sort of the equivalent of

listening to a supposed scientist. To say smoking it is not. Enjoy yourself. You know I think it's pretty. Except it isn't among weather people that there is global warming. That was my question. Thank you. OK. I would agree that most scientists are in agreement that global warming is occurring that that's pretty well agreed upon. It's what's causing that global warming that seems to be where most of the debate surrounds. There's clear evidence that carbon dioxide levels have increased in the atmosphere. That's pretty hard to refute. But what impact that is having on the actual global temperatures is where people are arguing there's a great deal of politics involved in these type of issues. And it turns out that there are scientists on both sides of the fence. And so if you want to find someone who

will agree with you that global warming is not important there are people who will do that and not necessarily that doing it in a in an in a. Dishonest way but through their own research they've convinced themselves that that is the issue. There are others who are on the other side of the fence and believe that while it is clear evidence that our contribution to the atmosphere has caused considerable global warming. And then there's the issue of well we try to predict what maybe impacts these are going to have in the future and we're concerned about increases and severe weather events and we're concerned about changes in precipitation and temperature patterns. And we have made attempts to try to forecast what those might look like. But there's a lot of differences in what those people have decided the future might look like. And so it leaves a lot of open doors for policymakers in trying to make decisions because they're getting a lot of conflicting information.

And it's unfortunate that we can't present them with a more clear picture of what we think is going to happen. So you don't see it as the equivalent of the tobacco supposed scientists who went around saying tobacco with OK. You don't see it is that clear cut. I do not believe that there are any scientists who are really trying to work for the power industry or you know people who are producers of large amounts of global warming gases. I doubt that they are hiring people who are providing them with favorable outlooks because I don't know that those people would have a great deal of credibility come from industry it will be very difficult for people to assume that you have an unbiased opinion. But there are plenty of people just within the academic world who are still on both sides of the fences and they don't necessarily have a reason to be biased towards one side or the other.

Right thank you Don. Well you know one of the criticisms that's often made of media and how we cover in issues like this is that we're taught to find balancing opinions. So if we go on and we interview somebody who says global warming is real and it's because of human activity and I think it's going to get worse than what you suppose do is go out and find another guy who says well I don't really think that that's true and you know they're long time cycles in the climate and we really don't know that it's going to get worse and turn around the criticism that it's made is that then that in the mind of the listener that leaves the idea that 50 percent of the scientists think one thing and 50 percent think the other thing which says well the scientific community is it's a toss up and they really don't know. If you ask the question OK suppose we get a representative sample of 100 scientists are 50 of them going to say one thing and 50 the other. Or is is there a prevailing. You know view on the question

that that well more or more is going to be on one side or more going to be on their side. I'm not a client climate scientist so I can't speak for them but my experience with those that I do know is that it would not be a 50/50 split. The vast majority are of the opinion that we are causing global warming. The extent of that global warming impact is not agreed upon among them. So the IPCC is probably the authoritative national agreement for global warming. And their opinions about what the global warming impact is going to be changes with every time they come out with a new report. But in general it's always predictive of warming conditions. The amount of warming over a time period is not entirely agreed upon. But and what impacts that will actually have on local communities such as Illinois if you're concerned about what it'll have perhaps on the farming agricultural industry within

Illinois 100 years from now. That's a very difficult problem to try to guess without with the tools that we have available to us today. Yeah I suppose if you're having a hard time saying what the weather's going to be like two weeks from now it's going to be like a hundred years from now is even that much more difficult. All right. Our guest here this morning are both from the Department of Atmospheric Sciences at University of Illinois Donna Charleville and Glenn are online teaches courses on general meteorology and also severe weather as well as societal impacts of weather and climate She's the co-author of a university textbook on severe weather glens member of the convective modeling research group has done storm chasing and involved in different kinds of research projects investigating severe weather. And as I mentioned beginning the program he recently contributed to a Nova program dealing with tornadoes that was called the hunt for the super twister. If you have questions about weather and how it works that's what we started out talking about here this morning. 3 3 3 9 4 5 5 toll free 800 to 2 2 9 4 5

5 next is color in Champaign Illinois in one. Oh yeah good morning. Wanted to get back to the warning issue and the tone that they transmit. I believe that those times they transferred at the beginning and end of the warnings are not only alert tones but they also contain a sub audible tone that actually turns on your weather radio. If it's in the standby mode and probably also does the same over the cable systems and if you happen to have a same uncoated radio which is the one that you can program down to the county you hear that you don't hear the tones when it comes on you hear the alert but when the when the broadcast is finished you hear the first tone and that actually turns off your radio and then when they finish up but I believe they transmit those tones at the beginning and end to 2 to enable the alert and then to turn it off after it's over with. So in addition to getting your attention. OK very good. I just want to throw that in there our thanks again from Asian. We break it down let's go on to somebody else. This caller is in Atlanta

Illinois. One number two. Hello good morning. Very interesting. Particularly on the European versus American models I was interested in otherwise my colleagues would say exactly what the person before me said that it was probably to turn the normal radio weather radios on and start of I don't know that's what I know but oh OK well let's go to another call and this will be Urbana. I believe line number three. Hello. Yes good morning. I would like to thank W I L L for their update continually and especially at night and you know I don't want to know necessarily what's going on in Champaign-Urbana. You know I might want to know about Ford in Europe because that me. B the weather that's coming toward us. So I just want to put in a plug. Thank you w i l l for continually breaking in and telling us the weather.

Oh OK I'm glad that somebody finds it useful because sorry to hear that some people find it irritating. You know I guess we're trying to try to strike a balance between interrupting the programming and also then providing information that we write I think it's important information. All right well very good of you. Thank you. Let's see where we go next. Danville. On one. Hello. Yeah good morning. One word a quick question for you no hang up and listen to the answer but I was wondering I mean it just seems like in the last few years that the weather forecasting has become a little more inaccurate and I just wondered if that did have anything to do with global warming and the models changing you know in their calculations. Thank you Ari. Thank you. Well that sort of presupposes that weather forecasting has become less accurate in the last few years. I would expect you'd want to you want to say otherwise. Well remember the forecasting we've talked about models and forecasting and their ability to forecast situations but of course a person makes a forecast and they use that model information as part of their forecast. A good forecaster also uses current

observational trends their knowledge of how models behave in certain situations. And so that that the full forecast problem involves more than just whether the model is good or bad. So first specific location if the you feel the forecasts have been better or worse that it may have a number of possible reasons for that. But unfortunately I couldn't quote on the statistics for your particular location as to whether they've been better or worse and I don't know what your source of weather information is if it's from the National Weather Service or if it's from a local media. Most meteorologists make their own forecasts or at least try to make their own forecasts. And that. That will necessarily work. Almost always require that they be different. And so you may see a lot of disagreement between different forecasts. But a lot of them are using the same information and they may not necessarily read it in the same way. But individual skill in forecasting it it takes a lot of

practice and a lot of time put into it to become a good forecaster. And so I guess my answer is that I don't know why. Yeah well I just go back to something that you said early on and it did I hear this right that one of the things we can say is that now the 7 day forecast is now as accurate as where is good at 7 days as we used to be at 3 days. So when you go seven days out we're pretty good. There was a time when we could really only go about 3 days out with that kind of conference and now we can go a whole week out with that kind of confidence. Right. The models are getting progressively better with time. When you go out into that kind of timeframe it's very difficult to look at observational trends and try and make an estimate of what the weather is going to be like in the long term c become increasingly dependent on model forecasts as you go farther out. Of course those model forecasts are progressively worse as time goes out as well. He also mentioned I think he was concerned about maybe whether global warming would have an impact on the.

Unless the local weather and the yet to think of global warming as being a much much larger scale slow change in patterns and in subtle to look at day to day weather and and compare it to global warming are really very different phenomena. Global warming might have changed the mean temperature. Point 1 degrees and so the impact of that maybe has on local weather is going to be quite small. But in the long term there could be changes in the overall weather patterns. But those won't be as noticeable on a day to day basis. Yeah I think you know the last two months really in central Illinois we've been below normal for temperatures you know and there's always run into somebody says well there's no global warming because it's been very cool this summer and you can't extrapolate to such small time scales because global warming that they're talking about is you know

over the period of hundreds of years. So looking at a couple of a couple of months or even over a period of five years the global warming signal if you will isn't going to show up. OK well we've got one more call or at least your line number two this is someone in Urbana below. Hi I have a more basic question. I would like to know how the wind blows. Basically what causes the spread. Perfect. Fabulous question. That's actually is it. Well you know actually when I when I teach the basic weather classes at the University that's one. This is the one thing that I always tell students that they have to know when they leave because it's something that's kind of fundamental that the pressure changes is what causes the wind to blow. You basically if you think of a weather map you've got high pressure and low pressure and the air always blows from high towards lower pressure and you can think of this sort of a no. Analogously if.

If you had a kind of a column of air there's lots of air molecules in it the air molecules have mass and weight and so they exert a force on the surface and the atmosphere is always trying to get into equilibrium Mother Nature likes to be in equilibrium and so it tries to get rid of those pressure differences and it pushes air towards a lower pressure. The reason for those pressure differences actually has to do with differences in temperature. And when we have differences in temperature that actually causes differences in pressure. Think of the ideal gas law backed science. And those temperature differences are actually caused by the even heating of the earth's surface by the sun because we live on a sphere. So there's more heating near the equator and less heating near the poles so you get these temperature differences with the sun can generate pressure differences which then generate wind. That's kind of the big the big picture of it. OK does that does that answer the question for you. Yes thanks. Okay great.

Very good. Was there anything else that you wanted to add on to that. No. Okay very good. I'll go onto line number one in another panel. Caller Hello. Yeah thanks for having the program and thanks for the preview to the previous caller for actually asking the question because you reminded me of something I've been wondering about. As the sun goes as the sun goes over the over the earth effectively it's always heating the ground directly below it so whatever part of the earth that it's you know noon that part of the Earth is getting warmed and then the air above the ground gets warmed up. And my understanding is that that's what creates a lot of the the westerly breezes is basically if if it's afternoon a little a few hundred miles east of here then the air is being warmed up. And and it's rising and so it's in the air rises.

I used to hear that creates a vacuum that sucks all the air from from where we are. Sucks it in the in the West from Union and toward the east and that's it. So I'm wondering if that is not how it works because I know the lady it went to from the West and and so I just want to have this that is of what use it makes the westerly breeze. OK actually both of the things that you're saying are correct but I'm not sure to what extent they're related You're absolutely correct in that the sun doesn't actually heat up the air directly it heats up the ground and then the ground transfers heat to the air and that creates vertical motions that's why we see a lot of clouds in the middle of the afternoon because you get a lot of rising air. The issue of the westerlies why the winds tend to blow from the west in middle latitudes that has to do with the general circulation patterns. And in middle latitudes where we live we typically have a west east wind flow pattern primarily due

to the general pressure pattern that you find a cry. The Globe and you tend to have a lot more higher pressure regions kind of around what they call something permanent high pressure near roughly 30 degrees latitude and you get some a permanent low pressure systems that tend to form around 60 degrees latitude and so then you get you get a force that goes from essentially south to the north so you would think well the wind will blow towards the north. But because we're on this rotating Earth there's something called the Coriolis effect which turns winds to the right in the northern hemisphere so instead of going from south to north actually turns to the east so it gives us kind of our westerly wind flow pattern. I don't know if you want to add anything to that gun. I would just add that oftentimes we we almost always see this sort of westerly wind pattern in the atmosphere as an average but as the afternoon goes on and we start heating at the surface. These It forms little thermal bubbles near the ground in those small bubbles rise up in the

atmosphere and we can sometimes see those as as cumulus clouds when they rise high enough that they form clouds. But as we heat the surface more and more during the course of the day those thermal bubbles tend to rise higher and higher up in the atmosphere and the wind speeds tend to be higher as you go up higher in the atmosphere. And these well we see these thermals going up. There's also air that has to sink back down to the surface and those sinking air masses coming back to the surface tend to bring gusts of wind with them. So you often notice Ana that the gusty as time of day is often during the late afternoon and that's when these thermals are rising very high of or higher up into the atmosphere and then sinking back down bringing some of that higher wind speed momentum from aloft back into the ground. Well I hope that answers the question because we're going to have to stop. We've used the time for this time around and we want to say thanks very much to Donna Charlevoix and Glenn are all mine from the Department of atmospheric sciences here you know River City Illinois for being here and talking with us. THANK YOU THANK YOU THANK

YOU. We appreciate it.