1. Weather Instruments

2. Measure wind direction with a wind vanewind vane A wind vane is a tool for measuring wind direction. Knowing the direction of the wind helps meteorologists determine in which direction a storm or weather system will travel.

3. Determine air pressure with a barometer.barometer To measure air pressure, weather forecasters use a barometer. When the air pressure is rising, good weather is on the way. When air pressure is falling, the weather will get stormier.

4. Calculate wind speed with an anemometer.anemometer Meteorologists use anemometers to measure wind speed in one area. With this data, they can determine how quickly a storm, or weather system, will travel to other areas. Use a rain gauge to measure how much rain falls in a given period of time.rain gauge Measure temperature with a thermometer.thermometer

5. Wind- A windsock is a tube designed to indicate wind direction and relative wind speed. ***Remember wind direction is the opposite of the direction in which the windsock is pointing

6. A contrail, also known as a condensation trail, is a cirrus-like trail of condensed vapor (often resembling the tail of a kite) that is produced by jet aircraft flying at high altitudes.

7. Contrails are produced at altitudes high enough for water droplets to freeze in a matter of seconds before they evaporate. Temperatures at such altitudes are typically below -38 degrees Celsius.

8. Contrails are clouds formed when water vapor condenses and freezes around small particles that exist in aircraft exhaust

9. A contrail forms because one of the components of jet engine exhaust is water. Jet fuel is made of carbon and hydrogen When jet fuel burns with oxygen, most of the exhaust consists of CO 2 (carbon dioxide) and H 2 O (water). The water is generally an invisible vapor.

10. When you exhale, your breath contains a great deal of invisible water vapor as well. You may have noticed that on certain days in the winter, your breath will form a cloud of condensation when you exhale.

11. In the summer, however, you don't see your breath. Cold air can hold a lot less moisture than warm air, so in the winter, when the moisture in your breath hits the cold air, the moisture condenses into a visible cloud.

12. The same thing happens when a jet engine "exhales." If the temperature, winds and humidity in the upper atmosphere are right, long, white contrails form when the moisture in the exhaust condenses.

15. What are clouds?

17. Cirrus Cirrus clouds are thin, wispy clouds blown by high winds into long streamers. They are considered "high clouds" forming above 6000 m (20,000 ft). Cirrus clouds usually move across the sky from west to east. They generally mean fair to pleasant weather.

18. Cirrus Clouds

19. Stratus Clouds Stratus clouds are uniform grayish clouds that often cover the entire sky. They resemble fog that does not reach the ground. Usually no precipitation falls from stratus clouds, but sometimes they may drizzle. When a thick fog "lifts," the resulting clouds are low stratus. These clouds form below 6,000 feet from the ground

21. Cumulus Cumulus clouds are puffy clouds that sometimes look like pieces of floating cotton. The base of each cloud is often flat and may be only 1000 m (330 ft) above the ground. The top of the cloud has rounded towers. When the top of the cumulus resembles the head of a cauliflower, it is called a towering cumulus. These clouds grow upward, and they can develop into a giant cumulonimbus, which is a thunderstorm cloud.