Weather Systems

Electromagnetic Spectrum.

The entire range of wavelengths of electromagnetic radiation extending from short gamma rays to the longest radio waves and including visible light. c

Wavelength – the distance between two adjacent wave crests.

Short Wavelengths = High Energy = Dangerous.

Types of electromagnetic energy include Gamma Rays Types of electromagnetic energy include Gamma Rays. X-Rays, Ultraviolet, Visible Light, Infrared (Heat), Microwaves, and Radio Waves.

The sun emits most of its radiation as visible light.

The wavelengths of visible light from longest to shortest are Red, Orange, Yellow, Green, Blue, Indigo, and Violet (Roy G Biv).

All forms of electromagnetic energy radiate at the speed of light (300,000 km/s or 180,000 miles/s).

Energy 2 types-a) Potential energy- energy related to position or phase -stored energy b) Kinetic energy- energy of motion; faster the object moves and the more mass higher the kinetic energy.

Heat energy and changes of state

Types of changes of state melting- changing of a solid to a liquid b) solidification (freezing) changing of a liquid to a solid c) evaporation/vaporization- changing of a liquid to a gas d) sublimation- changing of a gas to solid or a solid to a gas

heat energy solid > liquid > gas: Heat is absorbed b) gas > liquid > : Heat is released

Changes of state material will heat up or cool down when it is in one of the phases if the material is in the process of changing phase temp stays the same

1. Air Masses

a. An air mass is a large body of air that has similar temperature and humidity characteristics.

b. A source region is the place where a stationary mass of air gains its humidity and temperature characteristics.

c. When an air mass moves out of the source region it brings those characteristics with it, and influences weather conditions in other places.

d. Air masses are classified according to two factors.

e. The surface of the source region (water or land).

f. The latitude of the source region.

g. continental (c) means the air mass formed over land and is dry.

h. maritime (m) means it formed over water and is moist.

i. Tropical (T) air masses form at low latitudes and are warm.

j. Polar (P) air masses form at high latitudes and are cold.

k. Arctic (A) air masses form in polar regions and are very cold.

l. The five basic air mass types are as follows:

continental Polar (cP), dry and cold

continental Arctic (cA), dry and very cold

continental Tropical (cT), dry and warm

maritime Polar (mP), moist and cold

maritime Tropical (mT), moist and warm.

Fronts form where air masses meet

a. A front is the leading edge of an advancing air mass.

b. When warm air masses and cold air masses meet, the warm air is always forced upward because it is less dense than the cold air.

c. Cold Front – Occurs when a rapidly advancing cold air mass wedges underneath a warm air mass.

The warm air mass is forced upward by the more dense cold air The warm air mass is forced upward by the more dense cold air. Short, heavy precipitation occurs at the front.

d. Squall line – a line of sudden, violent thunderstorms that sometimes develops along a cold front.

e. Warm Front – Occurs when a slow moving warm air mass climbs over a colder air mass.

Precipitation occurs ahead of the front, is fairly light, and can last for one or two days.

f. Stationary front - boundary between two air masses that are not moving.

g. Occluded front – Occurs when a cold front overtakes a warm front.

When this happens the warm air mass is pinched between the two cold air masses and is lifted completely off the ground.

h. Thunderstorms are often caused by the upward movement of warm, moist unstable air associated with frontal lifting.

High and Low Pressure Centers.

a. High Pressure Center – Cool sinking air that moves away from the center at the surface (divergent), and rotates clockwise in the Northern Hemisphere.

b. Low Pressure Center – Warm rising air that moves toward the center at the surface (convergent), and rotates counter-clockwise in the Northern Hemisphere.

Isobars and Isotherms.

a. Isobar values increase toward the center of a high.

b. Isobar values decrease toward the center of a low.

c. Isotherms generally increase in value toward the lower latitudes c. Isotherms generally increase in value toward the lower latitudes. Earth is warmest near the equator.

d. Isotherms generally decrease in value toward the higher latitudes d. Isotherms generally decrease in value toward the higher latitudes. Earth is coldest near the poles.

Typical Low Pressure System.

a. Low Pressure centers in the middle latitudes generally travel from west to east and are called middle-latitude cyclones.

b. These systems generally bring stormy weather.

c. The air flow at the center is convergent and counter-clockwise.

d. Most have a cold front extending to the south and a warm front extending to the east from the enter of the low.

Hurricanes

a. Hurricanes are tropical cyclones with wind speeds in excess of 74 mph.

b. These systems can be as wide as 500 miles and they have a calm central “eye” where air is sinking.

c. They develop over tropical ocean waters and are fueled by heat and moisture.

d. Most often form in the summer when temps. are warmest.

e. Hurricanes lose their intensity when they move over cool ocean water or land.

Hurricane Tracks

a. The hurricanes that affect us form in the eastern tropical Atlantic Ocean.

b. The easterly trade winds drive them westward toward the Caribbean Islands.

c. Eventually these storms turn Northward and migrate into higher latitudes.

d. As a result, the Gulf of Mexico and the East Coast of the United States and Canada are at risk to experience one or more hurricanes each year.

Tornadoes

a. Destructive local storms of short duration.

b. Violent windstorms associated with severe thunderstorms that take the from of a rotating funnel of air that extends downward from a storm cloud.

c. Occur most often during the spring.

d. Most frequent in the Unites States between the Rockies and the Appalachians.

Cold air from Canada moves Southward and meets warm air from the Gulf Cold air from Canada moves Southward and meets warm air from the Gulf. The warm air is forced to rise rapidly, forming tornadoes.