Middle Latitude Cyclones

1. Middle Latitude Cyclones By Jenny Barnes

2. An Introduction: • Mid-Latitude cyclones are also known as extra-tropical or frontal cyclones • These weather systems are named for occurring in the middle latitudes of earth. • They are classified as large, traveling, cyclonic storms up to 2000 kilometers in diameter with centers of low atmospheric pressure. • Cause the extreme weather conditions in the middle latitudes, including ours.

3. The Development of a Mid-Latitude Cyclone: • Mid-Latitude cyclones are the result of interacting of the warm tropic and cold polar air at the polar front. • In their mature stage, mid-latitude cyclones have a warm front on the east side of the storm's center and a cold front to the west. The cold front travels faster than the warm front. Near the end of the storm's life the cold front catches up to the warm front causing a condition known as occlusion. • The polar front theory of a developing wave cyclone (previous known as the Norwegian cyclone model) shows this progression from birth to decay:

4. A: show the development of the wave.B: the cyclonic circulation and the establishment of a low pressure area C: the cold front overtakes the warm front and an occlusion-front is formed D: the development of the occlusion continues and the cyclone has reached its mature stage.

5. Direction of Mid-Latitude Cyclone • The wind travels from High to Low pressure. Mid-Latitude has a very low pressure, therefore what direction would the wind be traveling in a mid-latitude cyclone found over the US ??

6. Like always, wind will travel around a low pressure area (in the Northern Hemisphere) counterclockwise and inward!!!!!! (This is important, remember it)

7. Effects of Mid-Latitude Cyclones • Normally, exist for about 3 to 10 days moving in a generally west to east direction. They are rarely motionless and travel around 1200 kilometers a day directed by the polar jet stream. (1) • Various types of precipitation can occur including rain, freezing rain, hail and snow. • latitude cyclones cause far less damage than tropical cyclones or hurricanes. Although rare, mid-latitude cyclones can have winds as strong as what is associated with a weak hurricane.

8. Examples of past Mid-Lat cyclones: • March 1993: East coast had reported winds of up to 90 knots had over 50 billion tons of snow. • Ice Storm in Oregon, 1998 and 2004

9. The affect of Climate Change/ Global Warming • As sea/land temperatures are increasing, the difference between the tropic warm air meeting the cold polar air would decrease therefore possibly weakening mid-latitude cyclones or causing them to occur less. • However, with sea surface temperatures increasing, this would cause hurricanes, tropical cyclones, or tropical storms to happen more frequently or more intensely due to their energy arriving from the warm waters.

10. Sources Used: • PhysicalGeography.net, Fundamentals of Physical Geography < http://www.physicalgeography.net/fundamentals/7s.html>. • Wikipedia: < http://en.wikipedia.org/wiki/Extratropical_cyclone>. • Realclimate: <http://www.realclimate.org/index.php?p=181>.