Ear on Chicago; What's the Outlook?: Weather Bureau; Part 1

That recorded weather forecast was heard in 1955, 23 million times. This is the first in a two -part series. We call What's the Outlook, the story of the Chicago Weather Bureau. Today we will discuss gathering of information. Our story opens at the observation station in the old terminal building at Midway Airport. That teletype sound is one of the most important parts of the United States Weather Bureau's office in Chicago. To start our story, as we said, we're coming out here to the old terminal building at 6200 South Cicero. It's called the Weather Bureau Airport Station. The job out here is observation and reporting weather conditions to not only the office of the weather bureau, but also to airplanes that come in here to Midway Airport. The old terminal building is actually what it sounds like. The first terminal building of Midway Airport, of course they've constructed since this building was

built, larger buildings farther to the north. So the weather bureau's observation headquarters is located a little bit south of the main offices of the weather of the airport. We're going to talk to the principal assistant of the Chicago Airport Station, Bill Polinsky. Now the way we want to do this story bill is to actually do the weather conditions out here at the airport. And then we'll report them to the weather bureau and also to the aircraft, to the pilots. And then we'll take our information over and see if we can't devise some sort of weather forecast from your information and from all of the other hundreds of bits of information that the weather bureau gets in order to determine the forecast. So Bill, where would you suggest that we start? I suggest that we start with the measurement of the clouds or the determination of any clouds in their height. Well there's this a mighty clear day and I don't see any clouds in the sky at all. But if there were some clouds, what do you see one? Yes there is a very thin wisp of cirrus,

rather high probably about 30 ,000 feet up to the northwest of the station. Well it's assumed that there are lots of clouds in the sky and how would you go about measuring them? Our means of measurement is by a solometer, a very powerful light projected into the sky. The reflection from the base of the clouds is picked up by photoelectric cell and run through an instrument that gives us a direct reading as to the cloud height above the ground here. Where is that powerful beacon? It is located in the field in front of the United Airlines hangar about a block in from Cicerole. Then you have an electric eye, where is that located? The electric eye with the mechanism to measure the cloud heights is located on the roof of the terminal building here directly above the weather bureau station. Now are these two instruments active at all times? Yes we have them on whenever any type of cloudiness is forecasted to occur within the next six to twelve hours. Now this small cloud that you mentioned just a moment ago, will that be measured? No it is too small an

amount and too high for our instrument which is limited probably to around twelve thousand feet. Well let's take a walk over here to the panel bill and actually look and see what the instrument is doing now. As Bill said they have that powerful beacon shooting up into the air and then the electric eye over here on top of the terminal building and that all goes to measure the cloud. Now you measure not only the cloud heights but also the amount of cloud, isn't that right Bill? The amount of cloud has to be determined by an observer actually going outside and from experience in the past determining the amount of percentage or the tenths of the sky covered by those clouds. Is that how it is measured by tenths? It is determined by tenths and it has to be done by a trained person who is familiar with the amount of cloudiness or certain types of conditions. Today Bill it wouldn't even be one tenth would it? No sir we call this a few scattered serous. Alright now let's take a look at this instrument over here. Of course there are no clouds being measured but about twenty four hours ago I think we did have some clouds. Now how

would that be measured on this instrument? Could we take a look at it? Yes the graph shows a widening of the trace as it goes from side to side of the chart by determining the widest part of that trace and comparing it against a calibrated cloud. Strip we can tell the height of the clouds above the ground. Alright Bill now we have the cloud measured actually as we said this is a very clear day and there are no clouds. Now what information would you put down on your chart here? The next in order is the visibility or how far a person can see in the city of Chicago. Well I mean Bill don't you indicate the clearness of the day on this chart here? Yes we do by appropriate symbols either clear, scattered, broken or overcast to determine the amount of coverage. Now we have the cloud height measurement, the amount of cloud and now next we're going to do visibility. Now how would how do you do visibility? Visibility is

determined largely by the observer going outside and determining certain objects or how clearly he can see certain objects at known distances from the observation point. Are there no instruments to measure visibility? Yes there are but they are rather complicated and only use a small percentage of the time. I also wanted to ask you going back to clouds once again. Are there no instruments to measure the amount of cloud? There is no instrument developed to measure the amount of cloud since it takes in a consideration of the whole dome of the sky from horizon to horizon. Alright now Bill you take a look at whatever indicator you use on a day like this and tell us what the visibility is. Well up to the northwest I can see the top of the gasometer in Maywood which we have determined to be eight miles from the airport here at Chicago. And I can see it fairly clear so that I have probably about 12 miles visibility. What about these stacks over here? A little while ago you and I

were talking about them. How far away are they? Well they're used to measure visibility in a little closer. They are on about two and a half miles from our point of observation. Those smoke stacks belong to the Commonwealth Edison Company and that's the Ridgeland plant I believe isn't it? That's correct sir. That over here to the right is the Crawford plant of the Edison Company. But how far away is that? We've determined those stacks to be about two and three quarters mile from the airport here. What about extremely close distances? Well it gets down to within feet. Immediately to the north of us is a large hangar owned by United Airlines which is a block away and of course we know that that is an eighth of a mile. In further is a small ticket counter and we know that that is a half a block away or a sixteenth of a mile. And when that disappears we know our visibility is less than a sixteenth of a mile. Well now Bill it seems to me that that's a very simple operation is it not? Most people I think when they think of the weather bureau consider instruments radar

equipment panels lights everything else. But here to check visibility you merely look down the block away and see if you can see it and if you can why you have that much visibility. Yes it's true that while a great number of things can be measured rather precisely with instruments we still have to depend upon train observers for a number of the things that we measure. Well now how about night visibility you checked out with lights I suppose. Yes we have similar points where lights are known to be on at 24 hours today or on all night and by the awareness with which we can see them we determine visibility of night. Okay Bill you go ahead and put down if we have what was it what the visibility again? About 12 miles at the present time. Now following visibility Bill has already checked that off. We have the cloud height, the amount of cloud, visibility 12 miles and now I think we better talk about pressure. Pressure is measured by the mercury barometer

which is rather old instrument it consists of a glass tube sealed on one end filled with mercury. The length of the column is an expression of the pressure and by measuring the length of that column we determine the pressure here at the station. Where is that instrument? It's on the wall here just inside the door at the weather bureau. Well right over here yes let's take a look at that. Here are two long columns that looks like to me measure the air pressure. Bill has just opened up the door and is going to take a reading. Go ahead Bill. First we are interested in the temperature since the mercury in there is in a metal and it expands and contracts with changes in temperature. What was that reading? That is the temperature. The average temperature in the case with the barometer is 76 degrees at the present time. It's Fahrenheit I suppose. That is correct. All right go ahead. Then it is necessary to

adjust the pool of mercury at the bottom till it reaches the indicator point or the end to see it over the pool of mercury. Now we are ready to measure the length of that column of mercury by adjusting a Vernier slide on the tube that protects the glass with the mercury in it. We can adjust it till it is just tangent to the top of the mercury and we have a pressure uncorrected at the present time of 29. 836. That is the barometric pressure as it exists right now. 29 .836. That of course to be used has to be corrected for temperature and for instrumental air. Often some charts we have here on our observer desk. All right let's walk over there to the observer desk then and we will correct that barometric pressure. And then we will have a good part of our information concluded. Our correction is minus 132

giving us a station pressure of 29 .704 inches. 29 .704 inches. Now how important is the barometric pressure bill? It is very important since it is the pattern that this barometric pressure when plotted on a chart makes that is used in determining the extent of pressure areas and the movement of those pressure areas, determining whether they are building or dying out and the speed with which they are moving. Is that all figured in when we hear so often on the weather forecast that the high is moving over or low pressure areas? That is correct. It is by the total sum of these readings that plotted on a map that we can determine these pressure areas. Normally if we have a high pressure area do we have nice weather and a low pressure area we usually have bad weather? Well that is true most cases there are exceptions however. Okay then you put down the barometric reading on your chart bill and I would like to

ask you the next step I think I know what it is, the temperature and humidity. That is correct by the use of a cyclometer which is composed of two thermometers, a dry and wet bulb thermometer and by determining the amount of cooling on the wet bulb thermometer we can determine the due point and the humidity. Alright how do you do that? Where do you do it? We have an instrument shelter in the yard just north of the building. This is a little house right out here. That is correct. It is painted white to reflect the sunlight. Alright let's walk out there and build and take a reading on that instrument. Now as we walk out here we just stepped outside for the first time and it really is a magnificent day out today. This small white house that Bill told you about actually looks like it has shutters on four sides. It stands about three or four feet into the air and then there is a little platform on which Bill is going to step up in just a moment to read the temperature and the humidity. Now first of all Bill as we step up here you have pulled open this

doorway here and as I said the four sides of it look like a shutter. What about that? Why do you have that? That is to allow the air to pass through freely since we are interested in the temperature of the air but it still keeps the sunlight from hitting the thermometers and causing a high reading. And why do you have it out here in the open? Why don't you have it up next to the building? Well the building picks up heat from the sun shining on it and we wish to stay away from any influence of that type to try and get as accurate a temperature as possible. And I notice that you have it over the sod rather than over cement which is right next to it. That's true we find that cement reflects a considerable amount of heat from the sun and black top even more so that we keep it over a sod cover to cut down these effects as much as possible. All right now we have the panel opened and we see some instruments to the right of us are two thermometers. What do they do? Well that is our psychrometer set. One of them the dry bulb measuring the actual temperature of the air and the one on

the left there. That is correct. The one on the right has a little cotton wick over the bulb which we dip in water. It feels actually going to dip the cotton in a cup of water. The cup is, well I didn't notice the cup it's just a plain ordinary drinking cup setting inside of the housing here. Now you throw a switch on. That operates a blower that pulls the air in the shoulder over these thermometers. The one that has the dry bulb on the left of course doesn't change because it is measuring the temperature of the air directly. However the one with the wicking on it that has been dampened is being cooled by evaporation and you can see the temperature on that thermometer is falling steadily now. We will watch it until it stops falling and read it at that point. There will be a difference of probably 18 degrees today and by the use of a computer we can compute the exact humidity and the dew point temperature from this information. This happens to be a

rather cool day. What's the temperature? Our temperature right now is 60 degrees right on the nose and our wet bulb temperature is 45 degrees. I think you can probably hear the air passing over that temperature. I'm leaning inside of this little housing now and perhaps we can pick that up here. Now up here to our left bill while we're waiting are some more instruments. What happens over here there is another graph machine and here are two more thermometers it looks like. The high -growth thermograph has a chart with a clock in it and it records the temperature and humidity continuously. The other two thermometers the upper one a minimum temperature thermometer and the lower one a maximum temperature thermometer. They are at every six hours and reset to determine the highest and lowest temperatures that occurred in those six hour periods. I might explain also Bill that while we're waiting Bill is just snapped off the switch here and is about ready to read the temperature and humidity.

But you probably heard some airplanes going overhead and it's been a while since we mentioned it. We're standing out here right next to the midway airport terminal. Actually we're in the old terminal building right outside of it right now. Okay, Bill, you ready? Yes, the temperature there was 60 degrees and the wet bulb temperature of 44 .9 degrees. So what would be the humidity? We have to go inside and run this off on a calculator now to give our accurate the actual humidity. It should be down around 30%. Such a nice day. I hate to go inside. That's true. Well anyway, we've just left the little housing now and we'll walk back into the building. After we got the temperature and humidity, I'm going to ask Bill to explain dew point, which is something that I didn't know much about. We talked a little bit about a little while ago. Then we have to measure the wind and we're going to talk a little bit about rainfall, a amount of sunshine. And then we'll have pretty much all the information that we can

gather out here. Then we'll take it over to our second spot and that'll be at the University of Chicago, where we'll provide the forecasters over there with that information and with that information and much more information that they gather from around the country, they will be able to predict the weather as accurately as is humanly possible. Bill is working this instrument over here. I keep saying instruments because I don't know the names of these things. Bill, what is this? This is a psychrometric calculator. From the temperatures we obtain from the dry and wet bulb thermometers, we can compute the dew point temperature and the actual relative humidity. What did it come out to? The dew point came out to 25 degrees Fahrenheit and our humidity at the present time is 26%. What is that dew point? What is that Bill? That's the temperature that you would have to lower the air

to reach 100 % humidity. That's the temperature at which a cold drink would probably begin to form frost on the outside of a glass. And today it's 25 degrees. It's 25 degrees, yes. Our humidity is 26%. Is that right? Yes sir, this is a rather bright day. All right Bill, now the next thing we want to talk about is wind. And how do you measure that? We have on the roof of this building a post with a wind vein and an animometer mounted there. The wind blowing determines pushing the vein around determines the direction from which the wind is blowing. And the animometer with its little cups swirling with the speed of the wind through a suitable electrical means tells us how fast the wind is blowing. Are you measured over here on again another instrument? That is a remote indicating instrument and we have it on the dial here in the office. It shows our wind at the current time to be from the east, occasionally down to southeast, and the wind speed at the present time is quite

low running about two to three miles per hour. Bill, while we're here we might as well get the altimeter setting because that's right in front of us too. Yes sir, our current altimeter setting right now is 29 .35 inches. All right, now that of course is important information to the pilot. Bill will mark down that information, the speed of the wind, the direction of the wind, and the altimeter setting. Bill, while you're doing that I'd like to talk to you briefly about rain. How do you measure rainfall? We measure rain with several instruments here and try and correlate them all to get an accurate reading. Our official instrument is called a weighing rain gauge consisting of eight inch opening over a bucket which is set on a scale that measures rain in inches rather than in its weight. It is up on the roof of the building here and it is read after every heavy rainfall and regularly at six hour

intervals. What about sunshine? I understand you also measure sunshine. Yes we have a switch on the roof that is operated by the sunlight and it is recorded in the office here by a remote on a remote instrument giving us the number of minutes of sunshine that occurred during any day. Bill, while we were in here a little while ago we saw a number of children going through. What do you have school groups coming out here quite often? Yes, we have a number of school groups whenever they study the weather and the science projects in their schools, a number of the teachers arranged for visits to this station to actually see these instruments being used. Bill, most of the things or some of the things I should say that we have done have been by human observation. You go out and you take a temperature reading, you look out and see the visibility, you look up and see the amount of clouds and so on. But we are all radar

scopes and things like that that we hear about. Do you have any of those things? Yes, we have a weather search radar installed here at this station. It's been in use here in Chicago for a little over two years and it is used to determine the location of any thunderstorms generally within a 90 mile radius of Chicago. About how severe they are and whether they will hit Chicago or not. Now what about your teletype service? We keep hearing those in the background. That is a very important part of meteorology. Over these teletypes we receive hourly reports from every major city in this country and our collection starts at half past every hour. Bill, what about pilots? How do they get the information that they want on field conditions? How do they get it from you? Radio? Very seldom by radio, mostly by telephone conversations with our briefing section here at this office once in a while by actual visit themselves. Well, do you mean this is before they go out on a

trip? Yes, this is all information that they find necessary before they actually begin a trip. But what about when they are coming into the field? That information is supplied to them by radio from our control tower here at the airport. Bill, I think we have just about completed the operation here. We have measured the cloud height, the amount of cloud and as we said it is a clear day so there are no clouds in the sky whatsoever. Very small one that Bill found and I couldn't even see. We measured the visibility, the air pressure, that is the barometric pressure, temperature and humidity and wind speed and direction of wind. And that is about it, isn't it? Yes, that is a complete observation such as we take here at Chicago. Bill, one final thing I think there was a phone call a moment ago from one of the pilots, suppose we could record that conversation between you and the pilot when you give him that information. Aviation weather.

The weather here in Chicago today at the present time is clear 12 miles, the wind is east to southeast at about 2 knots and the Altimer setting is 29 .35 inches. Okay, Bill has just phoned in some information to one of the pilots that is going to fly out of Midway Airport today. I think we just about completed our recording here Bill, I want to thank you very much for telling us about your observations. It has been a pleasure having you here sir. Now we have come to the District Forecast Center that is located at the University of Chicago right on the campus. Now these teletypes in the background are carrying information for the weather bureau from all over the country. It so happens that the information that we gather just a moment ago out of the airport is now coming in here to the District Forecast Center. And you can probably hear that teletype in the background carrying it in. Now we are going to talk to

Joe Fulks who is the meteorologist in charge of the weather bureau in Chicago. Now Joe, what we are trying to do here is to establish a weather forecast for Chicago and vicinity. We have here on this teletype coming in now information which we gather out of the airport from the observer out there just a few moments ago. Such things as wind velocity, temperature, humidity, barometric pressure and so on. Now what are you going to do with this information once it completes its transmission over this teletype machine? The first thing we do is take it off the machine and plot it. You notice we have not only Chicago but many other stations and we plot all of these on a map in order to prepare a complete weather map. Now where is that plotting done Joe? Right here I'll show you. Walking out of the teletype room over here to a table where two people are working plotting figures on this huge map of what is that the United States? United States and a good part of Canada and the Pacific a little of

the Atlantic. They are plotting right now they happen to be plotting the reports over the United States. They have most of that done when they are through. There will be perhaps reports from 500 stations on this particular map. Now while they are plotting that information and it also includes as I said the information that we gathered ourselves at the airport, why don't we walk over here Joe and talk about some of the other things you have up here at the airport? At the district forecast center. Over here in front of us are a large number of facsimile maps. Now they have rack after rack of them and I guess you need this information all the time don't you Joe? That's right we plot and prepare ourselves just a few basic maps but we are actually in preparing a forecast. We use a great many different charts covering a wide area over most of the northern hemisphere and upper levels up to quite high

levels so that we need much more than we can prepare ourselves. These maps are prepared in Washington DC and transmitted over a facsimile network. They go to our stations all over the country, other stations such as this. Where is that facsimile machine? It's right here. Would you like to take a look at it? Yes, let's go back there Joe. We'll go back into the teletype room and I can see the machine now. It's way at the other end. I'm not sure that the listeners know what a facsimile machine is Joe. Why don't you explain that? A facsimile machine is simply a machine which transmits or receives pictures by where. Something somewhat similar to where a photo. Something like television except that it's a single picture. That's right and it takes about 20 minutes for one of these pictures to come through. Each one is about 12 by 18 inches in size. Something is about to come through now. I think you can probably hear that. That's right. We happen to catch it right at the moment here just between sheets. The man has just taken one

off. This particular one happens to be a prognostic chart indicating what the expected winds are at very high levels. These run about 40 to 50 ,000 feet. This was prepared primarily for aviation use. Joe, I'm afraid that's about all the time we have for this week. We have reached the point now where we're ready to prepare a weather forecast for Chicago and vicinity. And next week I'd like to discuss with you how that forecast is accomplished. Next week, part two of what's the outlook? The story of the Chicago weather bureau. This is Hugh Hill speaking.