Midlatitude
Cyclones
(Storms)
• Extratropical cyclone or
wave cyclone or
frontogenesis or storm
• Low pressure area with
counter-clockwise
circulation.
• Atmosphere collects
water as water vapor in
evaporation from oceans,
lakes.
• It is returned via
precipitation, often
caused by storms.
Storms
Center of intense low pressure with
cyclonic circulation and resultant
precipitation.
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Midlatitude Cyclone
Hurricane
Tornadoes
Not thunderstorms, no cyclonic motion.
Cyclogenesis in Action:
Mid-latitude (extratropical) cyclones
Air Masses
Definition: volume of air with same temperature and
humidity characteristics
Source Regions: where air masses come from.
Classification: warm or cold, moist or dry
Air Masses Affecting North America
Frontogenesis
Occluded Front: The Death of a
Storm
Occluded
Front
Weather Maps
Today’s Weather Map
Weather Maps
Storm Tracks: North America
Storms (Storm Tracks) generally travel from
West to East in North America all year
They shift North
in summer &
South in Winter
AverageActual
Storm
Storm Tracks
Tracks
Moving(1991)
West
To East
Midlatitude Cyclone
Characteristics
Motion: these storms move across the
midlatitudes at about 30 m.p.h. from west to
east as they rotate once around a low
pressure center.
Size: roughly 1,000 miles in diameter, the
largest of storms
Lifespan: 3-6 days to develop, 3-6 to dissipate
Pressure: center roughly 990-1000 mb (1-2 %
drop)