Weather Fronts

What is a front? Fronts are areas of rapid changes in weather conditions and often sites of unsettled and rainy weather

What is a Front? When different air mass meet, very little mixing of the air occurs. Moves from West to East A sharp transition zone forms between the air masses

Cold Front Forms along the leading edge of a cold air mass that is advancing against a warmer air mass The cold air mass is denser than the warmer air ahead of it, so it pushes against and under it like a bulldozer.

Cold Front This rapidly forces the warmer air upward ahead of the front and results in heavy precipitation and thunderstorms. After the passage of the front, the temperature drops sharply and the pressure rises rapidly

Warm Front Forms when a warm air mass overtakes a cold air mass ahead of it. Warm air is less dense so it rises up and over the colder, denser air

Warm Front As it moves over the cold air, the warm air expands and cools which causes condensation to occur over the wide, gently sloping boundary Results in thickening, lowering clouds and widespread precipitation

Occluded Front Cold air masses move faster than warm air masses and fronts because cold air is denser and exerts more pressure. If a slow-moving warm front is followed by a fast-moving cold front, the cold front will sometimes overtake the warm front

Stationary Front Forms along the boundary between a warm and cold air mass when neither moves significantly in any direction Rain and clouds persist for a long period of time until another air mass comes along with enough force to get it moving

Air Masses Large regions of air with fairly uniform characteristics Identified by its average air pressure, temperature, moisture content and winds Characteristics are determined by the geographical region over which it formed. This is called its source region

Air Masses The longer the air remains stationary over a region, the larger it becomes and the closer it matches the characteristics of the region

Air Masses For example, a cold air mass moving south out of Canada will gradually become warmer as it moves farther and farther south

Arctic APolar PTropical T formed over extremely cold, ice-covered regions formed over regions at high latitudes where temperatures are relatively low Maritime m formed over water, moist mP-cold, moist Formed over North Atlantic, North Pacific mT-warm, moist and formed over Gulf of Mexico, mid-Atlantic, Caribbean, Pacific, S. of Calif. Continental c formed over land, dry cA-dry, frigid and formed north of Canada cP-cold, dry and formed over northern and central Canada cT-warm, dry and formed over SW United States in summer

Wind Wind is the natural movement of the air along, or parallel to, Earth’s surface Result of uneven heating of the Earth’s surface Flows from high to low pressure

Jet Stream Very fast wind currents in the upper atmosphere Does not follow surface winds Flows from West to East Influences development and movement of weather systems

The Westerlies west-to-east motion of the atmosphere, centered over the middle latitudes of both hemispheres. When there a storm in California, it will most likely be in our area in 3-4 days