2. How do meteorologists study and predict weather? How does the movement of air masses affect weather? How do clouds and rain form?

3. Weather = The state of the atmosphere at a specific time and place What is meteorology? ▫The study of patterns of weather What does a meteorologist do? ▫A specialist who studies processes in the earth's atmosphere that cause weather conditions. What tools and technology are used in weather forecasting?

4. Thermometers measure air temperatures. Temperature is a measure of how much heat energy the air molecules possess Thermometers work because matter expands when heated. Most thermometers are closed glass tubes containing liquids such as alcohol.

5. A barometer measures air pressure. There are two types of Barometers: Mercury and Aneroid. Average reading: 29.92 inches ▫Increasing = sunny ▫Decreasing = possible storm

6. A Mercury Barometer consists of a glass tube inserted into a dish of mercury or colored denatured alcohol. The surrounding air presses down on the mercury in the dish and forces some of the mercury up into the tube. The height to which the mercury rises gives a reading of atmospheric pressure.

7. Used to gather and measure the amount of liquid precipitation over a set period of time Most rain gauges generally measure the precipitation in millimeters

8. A psychrometer measures the humidity of the air. One of the two thermometers has a wick (cloth cover) which is dipped in water. Evaporation of water from the wick leads to cooling. The temperature difference between the two thermometers gives the relative humidity of the air

9. This is an example of the type of table you would use. Difference Air Temp Humidity (%)

10. When air moves— “wind”—we feel both its direction and speed (force.) Direction is measured with a “vane”—an arrow or other shape that points into the wind. Speed is measured with an “anemometer.” The faster the cups spin, the faster the wind. Vane Anemometer

11. The Forecast Radar image shows where area of precipitation are expected to be. Colors show the strength and physical phase of water

12. To measure weather above the surface, the National Weather Service (NWS) releases weather balloons with an attached instrument package called a “radiosonde.” Radiosondes contain: ▫Temperature sensor ▫Relative humidity sensor ▫Barometer ▫Radio transmitter ▫Battery ▫Parachute ▫String to attach to balloon

13. Weather balloons are launched twice a day At 6 a.m. and 6 p.m. Ground antennas receive the radioed signals as the balloon rises Computers interpret the signals and send them to the NWS network

15. Tend to bring cloudy, wet weather Tend to bring fair, dry weather. Air rises near ow Pressure Areas Warm, rising air cools; water vapor in the air condenses to form clouds/precipitation Air sinks near igh Pressure Areas Cool, sinking air warms and dries out.

16. Actual winds around highs and lows

17. Air masses have different temperatures and humidity Form over water: ▫Maritime Polar – cool temperature; moist air ▫Maritime Tropical – warm temperature; moist air Form over land: ▫Continental Polar – Cool temperature; dry air ▫Continental Tropical – Warm temperature; dry air

19. Colliding fronts cause cloud development and weather changes

20. Cold Front Cold air advances Warmer Colder Warm Front Warm air advances Colder Warmer Stationary Front Warmer Colder

21. Occluded Front = ▫When a fast moving cold front catches and overtakes a slower moving warm front Stationary Front = ▫When cold and warm fronts meet and neither is strong enough to push the other; front stops moving

22. Jet Streams Jet Stream ▫Narrow bands of wind in the upper atmosphere ▫The Jet stream always blows from west to east across the U.S.