A large body of air in the lower troposphere that has similar characteristics throughout
are any large body of land or water where air derives its characteristics.
sun angle (closer to equator the warm you get)
A = Arctic or Antarctic
P = Tropical (20 - 35 N/S)
T = Polar (50- 60 N/S)
E = Equatorial
North American Source Regions
Principal air masses in North America. Five major types of air masses periodically flow into the continent.
-continental Polar (cP)
-maritime Polar pacific/atlantic (mP)
-continental Tropical (cT)
-maritime Tropical pacific/gulf/atlantic (mT)
the boundary line where air masses meet.
This type of uplift occurs when air is forced to rise along the boundary between two air masses of different temperatures (and, therefore, different densities).
moving weather front along which a warm air mass slides over a cold air mass, producing stratiform clouds and precipitation
forms when cold air moves under warm air which is less dense and pushes air up (produces thunderstorms heavy rain or snow
Midlatitude Cyclones : Interactions at Polar Fronts
an area of low pressure that is characterized by rotating wind thats moves toward the rising air of the central low-pressure region; the motion is counterclockwise in the Northern Hemisphere
Review of Chapter 6
-Wintertime brings strong temperature contrasts
-Buildup of cold air forces polar front south
-Forms the undulating jet stream and Rossby waves
-Creates areas of frontal lifting and low-pressure
Midlatitude Cyclones : Upper Air Flow
what controls a low pressures systms path and intensity.
an elongated area of elevated air pressure in the upper atmosphere that is typically associated with sunny skies and calm winds
created between two high pressure cells (cool, dry vs warm, moist); is where the wave cyclone begins to form
Interaction of Upper and Surface Air Flow
Linkage of upper air flow and surface air flow in a midlatitude cyclone. These systems form through a complex interaction of upper air and surface air flow. Under the high-pressure system, the weather is stable with clear sky. Where the cyclone forms, however, the atmosphere is unstable.
Evolution of a Midlatitude Cyclone
1.Stationary Front Stage
4.Closing of Open Wave
Evolution of Thunderstorms
1. Cumulus Stage
2. Developing Stage
3. Mature Stage
4. Dissipation Stage
Evolution of a Lightning Strike
(a) Lightning begins when a separation develops in the electric charge between the bottom and top of a cloud.
(b) Negatively charged electrons begin to move down toward the ground from the base of the cloud. At the same time, positively charged electrons begin to move upward through conducting material on the ground.
(c) The circuit completes when the upward- and downward-moving electrons meet in the air. The process begins the visible lightning strike.
(d) The lightning strike drains the cloud of excess negative electrons.
(e) A massive lightning storm.
large, rotating single-cell thunderstorm, can cause tornadoes, large hail, frequent lightning, heavy rain, strong winds
A low-level, wedge-shaped cloud attached to the thunderstorm. It forms above the gust front as warm air ahead of the storm rides over the cool outflow from the thunderstorm.
These clouds appear to be hanging, rounded protuberances or pouches on the underside of the cloud. With thunderstorms, it is usually seen under the anvil and often accompany severe thunderstorms.
an area on the flank of a supercell storm characterized by rotating clouds, precede tornado formation
violent, spiraling winds that move in a narrow path over land.
Enhanced Fujita Scale for Tornado Classification
0 (65-85 mph) Least Dangerous
1 (86- 110 mph)
2 (111 - 135 mph)
3 (136 - 165 mph)
4 (166 - 200 mph)
5 (over 200 mph) Most Dangerous
Peak Tornado Season
Between April and July
A region of especially frequent tornado occurrence, often defined to be in the Great Plains from Texas to Kansas
Tornado Monitoring (2 types)
Tornado Watch - This is an alert issued when weather conditions are right for a tornado.
Tornado Warning - A warning issued when a tornado has actually been sighted in an area or is indicated by radar
Large, rotating, low-pressure tropical storms
A low pressure center in the tropics with winds less that 63 km/h, wich is the threshold for a tropical storm.
when the winds of a tropical depression begin to blow even faster and thunderstorms move in spiral bands toward the area of lowest air pressure
a severe tropical cyclone usually with heavy rains and winds moving a 73-136 knots (12 on the Beaufort scale)