Weather Fronts

It is another one of those hot sweltering days. As the temperature soars towards 100 degrees, you and your big brother decide it's time to head to the community swimming pool. Before you go to the pool, you quickly gobble down a grilled cheese sandwich and some chicken noodle soup for lunch. You finish lunch with a popsicle then quickly run to your room to grab your towel. As you head out the door, you suddenly realize that the weather has changed dramatically. The blistering heat has been replaced by a a cool breeze from the north. Your plans have suddenly changed. You no longer need the pool to cool you off, it seems that Mother Nature has already taking care of that.

What happened in the above story to cause such a sudden change in the weather? Why was it blistering hot before lunch, and a bit nippy after your grilled cheese sandwich?

There are giant masses of air that move in the atmosphere over the Earth. These air masses form over different parts of the Earth and can be either warm or cold, dry or moist. When two different types of air masses meet, a front forms. When a front moves over an area, the weather changes.

Meteorologists use special symbols on maps to show where weather fronts are located. A line with half circle shows where warm fronts are located. A line with arrow points or triangles on it represents a cold front. A stationary front is represented by both symbols.

Click on the weather forecaster to the left to see a Web page of a weather map of the United States and then do the following. 

1. Print the map if possible.
2. Locate a warm front on the map. Circle it in red.
3. Locate a cold front on the map. Circle it in blue.
4. Locate a stationary front on the map. Circle it in another color.
5. Use the map to find out if there are any changes coming to the area where you live.

Cold and warm air behave differently. It is difficult to see how they behave because air is invisible to us. You will use water to demonstrate what happens when cold and warm air meet. Cold and warm water behavior a lot like cold and warm air.

• Clear bowl, large fish bowl (minus the fish), clear plastic tub, or small aquarium
• Room temperature water
• Very cold ice water
• Very hot tap water
• Blue food coloring
• Red food coloring

1. Fill the clear container with room temperature water.
2. Add a few drops of blue food coloring to the very cold ice water.
3. Slowly pour the cold blue water into the tub of clear water. Pour the water very slowly so that it doesn't stir.
4. Explain what happened. Draw a picture of what you observed.
5. Add a few drops of food coloring to the very hot tap water.
6. Very slowly pour the hot water into the tub of water.
7. Observe what happens and draw a picture to represent your results.

In the above activity you probably noticed that the cold water mostly sank to the bottom. Cold water is heavier, or more dense, than room temperature water. The hot water probably stayed at the top. Hot water is lighter, or less dense, than room temperature water. This is also true of air. Warm air rises. That is why hot air balloons rise into the air when the air is heated. Cold air sinks. When masses of cold and warm their meet, it causes changes in the weather. Cold fronts produce violent weather such as blizzards and thunderstorms. The weather caused when a cold front moves over an area usually does not last too long. Warm fronts also produce stormy weather. The weather associated with warm fronts however, is not as severe as cold front weather. Storms associated with warm fronts may last for several days.

Study the weather maps in your local newspaper. Identify the fronts that are approaching Utah. As different fronts move through the state, predict what you think may happen. Be sure to take your wind vane and anemometer outside with you. If you do not know what those are or how to make them, go to the lesson on wind. Have a fun!