Jet stream A fast moving, narrow current of wind in the upper troposphere that has a powerful influence on weather patterns in North America. It carries weather systems across our continent from west to east.

El Nino/La Nina Oscillation of water temperatures in the Pacific Ocean on the west coast of South America. El Nino refers to the warmer waters in the Pacific near the equator. La Nina refers to colder waters in the same area. El Nino occurs toward the end of the year (Christmas time) and La Nina occurs after an El Nino. Remember in South America the seasons are opposite ours. It is summer in our winter and winter in our summer. But around the equator there is no summer or winter because the temperatures are consistently the same.

Trade winds A belt of winds around earth moving from high pressure zones towards the low pressure at the equator (0 to 30 N and 30 S)

Major movements of water in the oceans Water current Major movements of water in the oceans

Gulf stream current Warm water surface current in the Atlantic Ocean that moves from the south of Florida up the eastern seaboard and then across the Atlantic towards Africa.

Prevailing Westerlies Winds that blow from the west to the east that are constantly changing and bring stormy weather; these are this winds that bring weather systems across the United States (30 N to 60 N and 30 S to 60 S)

Polar Easterlies These are the winds that blow from east to west around the north and south poles (60 N and 60 s to the poles)

Cold Front A front where cold air moves in under a warm air mass; they pass through quickly and bring thunderstorms, wind and hard rain; the weather turns clear & cooler after it passes

Warm front A front where warm air moves in over a cold air mass; usually associated with stratus clouds that linger and can bring light rain/snow; weather is warm and clear after is passes

Stationary front A front that happens when a warm air mass and a cold air mass meet, and doesn’t move

Occluded front A front that happens when a warm air mass is caught between two cold air masses and is pushed upwards

Rain shadow effect A dry area on a mountain-side facing away from the direction of the wind. The mountains block the passage of rain, casting a “shadow” of dryness behind them

Isobar A line on a weather map connecting places with equal air pressure.