Storms and Weather Forecasts Chapter 30

Thunderstorm Small area storms formed by a strong upward movement of warm, unstable moist air.

Air-mass thunderstorm Form within a warm, moist air mass. Often single storms. Occur mostly in spring and summer. Usually last less than an hour.

Frontal thunderstorm Usually form in warm, moist air on or ahead of a cold front. Some do occur in front of warm fronts.

Squall Lines Line of heavy precipitation and t-storms in front of a cold front.

Lightning A discharge of electricity from a thundercloud to the ground, another cloud, or cloud to ground. 28,000oC, 50,400oF

Thunder Sound created as lightning “superheats” and it expands (explodes) rapidly. Approximately 3 seconds for sound to travel 1 kilometer.

Tornado Narrow, funnel shaped column of spiraling winds that extend downward from the cloud base and touches the ground. Fujita scale F0-F5, damage related.

Tornado Peak Season From late spring to summer. Occur most frequently in late afternoon. Temperature lag is the cause. The Earth is responsible for heating the lower atmosphere.

Waterspouts A tornado that has formed over a body of water. Usually weaker than a land born tornado.

Severe Thunderstorms Has wind gust of at least 80 m.p.h., hail about 2 cm in diameter or greater, and presence of a funnel cloud or tornado.

Watch Covers an area of 100km by 200km or larger. Severe t-storms and tornadoes possible.

Warning Is issued when a severe thunderstorm or tornado has been spotted.

Hurricane Intense low-pressure tropical area with sustained winds of 120kph (74mph) or greater. Strong winds and heavy rains produce major damage. It has no fronts, powered by evaporation. Source regions include Gulf of Mexico, Caribbean Sea and east coast of Africa.

Hurricane Peak Season From late summer to early fall.

Storm Surges Formed when a hurricane “piles up” water along the shore and blows it inland. Most damaging during high tides.

Eye Central area of sinking air, usually 15-20km in diameter. No rain, calm winds, high pressure.

Eye Wall Area of intense thunderstorms surrounding the eye of the hurricane.

Tropical Cyclones/Typhoons Hurricane near equator.

Naming Hurricanes Prior to 1953: From 1953 to 1979: Identified by their date. From 1953 to 1979: Given female names, alphabetically. 1979 to the present: Given male and female names, alphabetically.

Blizzard A snowstorm with high winds and low temperatures.

Moisture Supply Differences In the United States, the midwest-Gulf of Mexico; the west coast-Pacific Ocean; the east cost-Atlantic ocean.

Computer Model A copy of the atmosphere in the computer that contains wind, temperature, pressure, humidity, clouds and precipitation.

Geostationary Means “stationary” in respects to the Earth.

GOES “Geostationary Operational Environmental Satellite” positioned to picture the 50 states.

Doppler Affect Effect caused by the movement of light, sound or wind relative to a stationary point. Winds moving toward the radar appear to have a shorter wavelength than particles moving away from the radar source.

Station Model National Weather Service based information from each recording station.