Atmos 5110/6110 Lab VII: Conceptual Models of Cyclone Evolution

Answer the following questions concerning the evolution of extratropical cyclones. Be thorough in your explaination. To research your answers, refer to Bjerknes (1919), Bjerknes and Solberg (1922), Godske et al. (1957), Reed (1990), and Shapiro and Keyser (1990).

Part 1

Describe the four phases of cyclone evolution as proposed by Bjerknes and Solberg (1922). How was this conceptual model influenced by the regional and local characteristics of northern Europe and Norway?

Part 2

Identify and describe four modifications and extensions that should be made to the Norwegian Cyclone model based on scientific advances over the past 75 years. Explain why these modifications are necessary.

Part 3

On 20 January 1993 a major extratropical cyclone developed over the eastern Pacific and made landfall on the northern Washington/southern British Columbia coast producing wind gusts of up to 88 miles per hour in the Seattle Metropolitan area. Using output from a high resolution mesoscale model, analyze the forecast frontal structure of the storm at forecast hours 6, 9, and 12 following the conceptual model of Godske et al. (1957) or Shapiro and Keyser (1990). Choose the conceptual model to use based on which one you believe best fits the simulated evolution. Note that these are color plots of sea level pressure (every 2 mb) and 900 mb temperature (every 2C; not plotted where the 900 mb surface is under ground) that should be spooled to the color printer.

Part 4

Explain your choice of conceptual model. Some questions you might want to address include: Does frontal fracture occur? Does the cyclone exhibit a "T-bone-like" frontal structure with the cold front moving perpendicular to the warm front or does the classic process of occlusion appear to occur? Be sure to turn in your 3-hourly frontal analyses with your write up.