Study Guide Weather (SOL 4.6) Grade 4 Created by Jennie M. Carr – Rockingham County Public Schools – 2010 Revised by J. Segerson and J. Copeland – Loudoun County Public Schools - 2010 WEATHER TERMS Weather Tools Temperature - The measure of the amount of heat energy in the atmosphere. Thermometer measures Temperature Barometer measures Air Pressure Air Pressure - The weight of the air, which is determined by several factors including the temperature. Anemometer measures Wind Speed Rain Gauge measures Precipitation Wind Speed – How fast the wind is blowing. Precipitation - The amount of water, which falls from the sky. Wind Vane measures Wind Direction Hygrometer measures Humidity Wind Direction - The direction in which the wind blows. F R O N T Humidity – The amount of moisture in the air. Air Mass A meteorologist uses weather instruments and data to predict weather patterns. A front is a boundary between air masses of different temperature and humidity. A cold front is formed when a cold air mass pushes into a warm air mass; may produce thunderstorms. A warm front is formed when a warm air mass pushes into a cold air mass; may produce light rain. Different atmospheric conditions produce the four types of precipitation: rain, snow, sleet, and hail. CIRRUS A feathery cloud, usually associated with fair weather, but often indicates rain or snowfall in several hours. Air Mass Low Pressure: usually brings clouds, rain, and wind; formed when air is warmed. High Pressure: usually brings dry, clear conditions; formed when air is cooled. CUMULONIMBUS Four Cloud Types A dark, tall, billowing cloud that produces rain and thunderstorms. STRATUS CUMULUS A gray, smooth cloud that covers the whole sky and blocks all sunlight. Light rain and drizzle usually occur. A white, fluffy cloud with a flat bottom usually indicating fair weather. EXTREME atmospheric conditions create a variety of storms: Thunderstorm: Hurricane: Tornado: A common storm with winds, rain, thunder, and lightning. A storm which forms over water with heavy winds. A violent storm with a rotating column of air.