Weather Patterns Tuesday, December 7, 2010

Opening: Use the words below to fill in the blanks and tell about clouds forming and precipitation: SNOW, HAIL, WARM MOIST AIR, STRATUS, CUMULUS, RAIN, CIRRUS, SLEET, WATER VAPOR, CLOUDS ___ rises, expands, and cools. ___ condenses into tiny droplets. Droplets suspend in the air, forming ___ . Three types of clouds are ___, ___, and ___. Four kinds of precipitation come from clouds: ___, ___, ___, and ___.

Yesterday’s classwork: Workbook pgs. 180 – 182 Look at: New Vocabulary Factors that determine weather Forming clouds Classifying clouds

Weather Patterns Air mass – is a large body of air that has properties similar to the part of Earth’s surface over which it develops. Air mass over land is drier than an air mass over water. Weather changes day to day depending on the air mass movement. *See figure 9 on pg. 462

Air pressure Air pressure is measured using a barometer. Wind blows from a center of high pressure to areas of low pressure. High pressure is associated with fair weather. Low pressure is associated with stormy weather.

Fronts A front is a boundary between two air masses of different density, moisture, or temperature. There are four types of fronts: cold, warm, occluded, and stationary. Each front has its own symbol:

Cold Front Cold front occurs when colder air moves toward warm air from below. As the warm air is lifted up, it cools and water vapor condenses forming clouds (Remember the water cycle) If the temperature difference between the cold and warm air is large enough we get thunderstorms or tornadoes.

Warm Front Warm front form when lighter, warmer air moves over (on top) on the heavier cold air. A warm front can lead wet weather or rain.

Occluded Front An occluded front occurs when a cold air mass moves toward cool air with warm air between the two. The colder air pushes warm air upward and closes the warm air off from the surface.

Stationary Front A stationary front occurs when a boundary between air masses stops advancing or moving. These fronts can cause light wind and precipitation

Tomorrow: We will look at severe weather Thunderstorms Tornadoes Hurricanes