Blog #2: Ann Arbor

The air mass that mainly affects Ann Arbor, Michigan is the continental polar air mass during the winter, which stretches from northwestern Canada through Michigan. This air mass is cold and dry due to its origins over inland Cananda and southern movement towards the continental United States.

Ann Arbor is also affected by the maritime tropical air mass during the summer, bringing warm, humid air to the area.

Relative humidity in the area is above average, ranging from around 40%, which is considered comfortable, to near 100%

Relative humidity highs and lows throughout the year in Ann Arbor, Michigan:

Ann Arbor, Michigan does experience some mid-latitude cyclone activity. Mid-latitude cyclones are the result of baroclinic conditions. Because there is an energy and temperature imbalance between earth's poles and equator, pressure surfaces cross one another in the atmosphere and isobars and isotherms cross paths as opposed to barotropic conditions, where the isobars and isotherms are parallel. Winds caused by the westerlies create divergence and convergence, resulting in areas of both high and low pressure at Earth's surface.

A few years ago, Ann Arbor was affected by a mid-latitude cyclone for the duration of several days:
https://www.youtube.com/watch?v=n4rJX4IIRaU


These mid-latitude cyclones are the result of a cold front from the north (continental polar) and a warm front from the south (maritime tropical). Maps for the upcoming days show a warm and cold front moving over Michigan, but no cyclonic activity is likely to occur. Map for April 15, 2014:

 Map for April 17, 2014:

Light showers are expected for Friday the 18th, but the weekend is likely to be in the 50s and no cyclonic activity is predicted.

There is one local phenomena that influences the weather in Ann Arbor and throughout the eastern portion of the state. Because Michigan is surrounded on three sides by the Great Lakes, proximity to water has some consequences for the area. For example, cool air from Canada moving across the Great Lakes will cause water to evaporate if the Great Lakes are warm enough. Depending on wind speed and direction, the moist air may reach higher elevations over land. Once over cool land, moist, unstable air is forced to ascend, either causing or enhancing precipitation. This is referred to as the "Lake Effect."


 Lake Effect snow storm video and animations:

http://www.bing.com/videos/watch/video/lake-effect-snow-guns/8lmyn5a1


Resources:

http://www.srh.noaa.gov/jetstream/synoptic/airmass.htm

http://www.cmmap.org/scienceEd/summercourse/summerCourse11/docs/KateThursdayPM.pdf

https://www.youtube.com/watch?v=n4rJX4IIRaU

http://www.accuweather.com/en/us/national/weather-surface-maps

http://www.mlive.com/news/index.ssf/2011/09/cyclone_sticks_on_michigan_see.html

http://weatherspark.com/averages/29652/Ann-Arbor-Michigan-United-States