Air Masses & Fronts

Cleveland is primarily affected by maritime tropical (mT) and continental polar (cP) air masses. During the summer, the maritime tropical air mass typically brings warm and humid weather, while the continental polar air mass produces cold winter temperatures. However, sometimes maritime tropical air can affect the city in the winter, bringing relatively mild days, while continental polar air can also bring unusually cool temperatures during the summer months ("Temperate Climate").

Cleveland's weather is primarily influenced by maritime tropical air masses in the summer and continental polar air masses in the winter, though sometimes this pattern can reverse itself and create unseasonably warm or cool weather.
In February of 2015 Cleveland broke its all-time record low temperature for that month since 1899 when the thermostat reached -17° F. A particularly cold air mass that had formed over Siberia--referred to as a "Siberian Express"--was responsible for bringing such cold temperatures to the region (Dolce and Wiltgen). The average low for Cleveland in Feburary is 22.5° F (Annual Climatological Summary).

The "Siberian Express" air mass formed over Siberia before moving over Cleveland, bringing record-breaking low temperatures.

Mid-latitude cyclones are common in the Great Lakes region. By the time they reach Cleveland they are typically in the cold-type occlusion stage and are responsible for abundant precipitation from October through March ("Temperate Climate"). Under the right conditions they can create severe storms.

This map illustrates a mid-latitude cyclone moving into the Great Lakes region. As the cold fronts (blue lines) catch up with the warm fronts (red lines), they become occluded fronts (purple line). In the occluded front, the cold air forces the latent heat of the warm front upwards, adding fuel to the system. In a November Gale, the warm water of the Great Lakes continues to provide the storm with warm moist air, which results in severe storms with lots of precipitation.
Source: Mace and Bentley

Mid-latitude cyclones are often produced along the lee side of the Rocky Mountains when cold dry air from the north collides with warm moist air from the Gulf of Mexico. In November, the water temperatures of the Great Lakes are still relatively high and will feed a passing storm with additional warm moist air. When the cold front passes over the lakes, the warm air rises and causes atmospheric instability. The storms that result from this phenomenon are referred to as "November Gales". 1913 witnessed the worst November Gale in history when a mid-latitude cyclone converged over the Great Lakes with a low-pressure system from the south and was further intensified by a strong jet stream aloft (Wagenmaker and Mann). Hurricane-force winds of over 74 miles per hour and massive waves led to the sinking of 12 large ships and many smaller vessels. Over 250 people perished. The storm dumped 17 inches of snow in one day on Cleveland with drifts up to 6 feet in height (Kellogg).

The position of the polar jet stream is important for determining the intensity of a mid-latitude cyclone. This diagram demonstrates how the jet stream helps to create a "November Gale" over the Great Lakes. Cool air from the north pushed the jet stream south and created a wave pattern with a western trough. The mid-latitude cyclone from the west then strengthens and amplifies the trough; it is said to be "in-phase" with the jet stream.
Source: Bentley and Horstmeyer

The "White Hurricane" of 1913 dumped a total of 22 inches of snow on Cleveland, with 17 inches falling in just 24 hours.

The blizzard of 1913 was a result of "lake effect snow", a phenomenon that Cleveland experiences every winter, though not usually that intensely. The warm moist air above the surface of Lake Erie heats and humidifies the cold continental polar air as it passes over from the north. The water vapor rises and forms clouds. When the clouds reach the 500 foot ridge on the eastern side of the city, they are forced to rise orthographically and adiabatic cooling results. Once the dew point is reached, snow falls. For this reason, the east side of Cleveland receives significantly more snow than the west ("Lake Effects").


Works Cited

Annual Climatological Summary 1989-2014: Cleveland Hopkins International Airport, OH US.
          NOAA National Climatic Data Center, n.d. Web 11 Mar 2015.

"Area Forecast Discussion." National Weather Service Cleveland, OH. 15 April 2015. Web.
           15 April 2015.

Bentley, Mace and Steve Horstmeyer. "The Witch of November." Weatherwise. University of Georgia. 08
           July 2010. Web. 15 April 2015.

Dolce, Chris and Nick Wiltgen. "Siberian Express Gripped Midwest, Northeast, South: Four
           Cities Set All-Time Record Lows." 21 Feb. 2015. Web. 14 April 2015.

Kellogg, Becky. "'White Hurricane': Remembering the Great Lakes Storm of 1913." The
            Weather Channel. 13 Nov. 2013. Web. 15 April 2015.

"Lake Effects". Green City Blue Lake. The Cleveland Museum of Natural History, n.d. Web. 08 Mar

"Temperate Climate Buffered by the Lake." Green City Blue Lake. The Cleveland Museum of Natural
          History, n.d. Web. 08 Mar. 2015.

Wagenmaker, Richard and Greg Mann. "The 'White Hurricane' Storm of November 1913: A Numerical
          Model Retrospective." National Weather Service., n.d. Web. 15 April 2015.

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