Chapter 8: Air masses, fronts, and middle-latitude cyclones Air masses Air masses Fronts Fronts Middle-latitude cyclones Middle-latitude cyclones

Air masses

Source regions air mass: definition air mass: definition source regions: regions dominated by surface high pressure source regions: regions dominated by surface high pressure Because air sinks in high pressure systems, air stays in contact with the surface and acquires its temperature and moisture characteristics. Because air sinks in high pressure systems, air stays in contact with the surface and acquires its temperature and moisture characteristics.

Classification temperature and humidity temperature and humidity naming conventions naming conventions

cP (Continental Polar) and cA (Continental Arctic) air masses Continental polar Continental polar continental Arctic continental Arctic lake effect snows lake effect snows In the continental US, the coldest winter air is associated with cA air masses In the continental US, the coldest winter air is associated with cA air masses

mP (Maritime polar) air masses Pacific air Pacific air mP air often brings rain to the west coast of the US mP air often brings rain to the west coast of the US

mT (maritime tropical air masses) subtropical air subtropical air Bermuda high Bermuda high mT air brings hot, muggy air to the eastern US in summer mT air brings hot, muggy air to the eastern US in summer

Fronts

Stationary fronts front: a transition zone front: a transition zone stationary front stationary front this terminology was developed by Norwegian meteorologists shortly after World War I this terminology was developed by Norwegian meteorologists shortly after World War I

Cold fronts cold front cold front weather changes weather changes precipitation patterns precipitation patterns vertical cross section vertical cross section

Warm fronts warm front warm front overrunning overrunning weather changes weather changes precipitation patterns precipitation patterns vertical cross section vertical cross section

Occluded fronts occlusion occlusion cold occlusion cold occlusion warm occlusion warm occlusion Occluded fronts have characteristics of both warm and cold fronts Occluded fronts have characteristics of both warm and cold fronts

Middle-latitude cyclones

Polar front theory wave cyclone wave cyclone frontal wave frontal wave open wave open wave warm sector warm sector mature cyclone mature cyclone

Where do mid-latitude cyclones tend to form? cyclogenesis cyclogenesis lee-side low lee-side low Alberta Clipper Alberta Clipper Mid-latitude cyclones specific to certain areas get interesting names: Panhandle hook, nor’easter, Hatteras Low Mid-latitude cyclones specific to certain areas get interesting names: Panhandle hook, nor’easter, Hatteras Low

Developing mid-latitude cyclones and anticyclones convergence and divergence convergence and divergence convergence and divergence patterns aloft are extremely important to the development of mid-latitude cyclones convergence and divergence patterns aloft are extremely important to the development of mid-latitude cyclones

Jet streams and developing mid-latitude cyclones jet stream jet stream jet streak jet streak upper-air support upper-air support During World War II, the jet stream was used by the Japanese to carry balloon bombs across the Pacific Ocean to North America During World War II, the jet stream was used by the Japanese to carry balloon bombs across the Pacific Ocean to North America