Ever think that weather forecasters just make up their predictions? While they don’t always get it right, weather forecasters have a great deal of information at their disposal, as this lesson demonstrates.
Tools for Weather Forecasting
Well, it seems that your constant angry letters to the local TV station may have finally gone too far. According to your notes to the producer, the weatherman never gets it right. He gets up there, he tells a few corny jokes about how weathermen never can get it right all the time, and then gives that same cheesy smile back to the sports reporter. In your last three letters, you’ve said that if the station can’t find a better weatherman, then you’d do the job just to prove how easy it was.That was last week. Now, you’ve been given the chance to come down and do your own weather clip.
Tomorrow morning, you’ll be introduced as the station’s new trainee. Oops. Needless to say, tonight will be spent trying to learn as much about weather forecasting as possible. For you, that means a bunch of maps and images.
Surface and Upper-Level Maps
Two of the most important maps that you’ll have to use in order to prove how much better of a weatherman you are than the current one are surface maps and upper-level maps. As you’d imagine, surface maps portray some aspect that is happening on the ground, such as ground temperature, pressure, dew points, and even measured precipitation. Needless to say, this is all very important in being able to describe to your viewers what is going on.
However, you remember from physical science class that a great deal of what goes on with reference to the weather actually happens thousands of feet up in the air. For that, you need to have access to upper-level maps. Upper-level maps show weather trends as they are happening higher up in the atmosphere. These maps have different uses from surface maps. A surface map could tell you the temperature on the ground, while an upper-level map could show where the air mass that is causing the high temperatures is going.
Still, the best upper-level maps only cover a few thousand feet up into the air.
Wouldn’t it be useful to have a tool that could measure how big systems are moving over large areas? After all, hurricanes are easy enough to spot if you have an eye in the sky.That’s what satellite images offer. These are maps produced miles above the Earth’s surface.
Satellite images are most useful for tracking large storm systems, especially hurricanes. This is because they can do it from safety and also because such storms have easily recognizable patterns. Namely, hurricanes move in a circular pattern around the center.
Satellites are useful for finding big storms like hurricanes, but have much less use in finding afternoon thunderstorms. This is because a cloud largely shows up like a cloud to a satellite. It is the pattern of movement that helps scientists ascertain if a storm is a hurricane or just a cloudy day at the beach.Luckily, we can use radar to find out more about storms like this. Radar uses the idea that sound moves at a constant speed through clear air, but is slowed by storms that are holding a great deal of rain.
This causes the radar signals to indicate that the clouds that showed up on satellite images are either a bad day at the beach or a thunderstorm. Radar also shows movement of storms relative to the point of radar. As such, the range of radar is relatively limited, only a few dozen miles.
This is why many metro areas have many radar sites, with weathermen showing a composite image of their signals along with any others that they have access to.
With few exceptions, the other images that you’ve had to use so far are pretty self-explanatory. Maybe you will be able to show up that weatherman and his cheesy smile, after all. Well, that is until you hit the thermodynamic images.
These are definitely not maps but instead, graphs with a great deal of information on them.However, many of the symbols that you are used to are here. You see on the right that there are wind speed indicators, just like you may have seen on some upper-level maps. Also, along the bottom, the temperature is given in degrees Celsius.
Finally, across the left, you see that there are atmospheric pressures as well as the altitudes at which each pressure is reached. As different atmospheric pressures permit different weather systems, this is valuable information to be able to have.But still, what are all those crazy lines? Let’s start with the yellow lines.
Those are called dry adiabats. They show the changes in both pressure and temperature of a defined imaginary block of air as it moves in the atmosphere. Meanwhile, the blue dotted lines are moist adiabats, which show how that same packet of water would perform if it had water vapor.
The solid red line is a result of a weather balloon finding at what point pressure and temperature meet for a given area.
Meanwhile, the red line to the left indicates the dew point.
After reviewing this lesson, you should be able to identify and describe the different tools used by weather forecasters to predict the weather.