Lab Investigation: Air Masses and FrontsSource: Ferandez, D., JHU Weather and Climate Lab Manual, 2005.

Helpful key points:The different air mass types typically affecting the United States are:

maritime tropical (mT), maritime polar (mP), continental tropical (cT), continental polar (cP), continental arctic (cA).

The four types of weather fronts are:

cold fronts, warm fronts, occluded fronts, stationary fronts.

Strong weather fronts are typically located:

within regions of cloudiness, within regions of precipitation, along a low pressure trough (where the isobars are ‘elongated’ from a low pressure region), along tight temperature gradient regions (where isotherms are packed close together), along regions of significant wind direction change.

The ideal stages of development of a midlatitude cyclone are:

1. stationary front2. frontal wave3. open-wave cyclone4. mature cyclone5. occlusion6. dissipation

1. Air Mass Identification.

Identify the different air masses over regions A, B, & C in Figure 1.1.

Region “A” ____________________

Region “B” ____________________

Region “C” ____________________

A

B

C

Figure 1.1

2. Weather Front Identification.

a. Identify the types of weather fronts shown in Figure 1.2.

Front “D” ___________________

Front “E” ___________________

Front “F” ___________________

Front “G” ___________________

b. At what stage of development is the midlatitude cyclone system over the eastern half of the United States?

c. Based on the data from the Detroit, Michigan (“DTW”) meteogram (Figure 1.3), estimate the time of frontal passage over Detroit. Explain how

D

E

F

G

Figure 1.2

you arrived at your conclusion.

(The dates/times at the bottom of the figure are in Zulu-time; give your answer in Zulu-time).

d. What type of front passed over Detroit? Explain how you arrived at your conclusion.

Figure 1.3

3.  Weather Front Analysis.    a. In the U.S. map of surface air temperatures, Figure 1.4, draw isotherms in standard 10-degree F. increments (ex: 30, 40, 50, 60, 70 80…).

Figure 1.4

Figure 1.5

Figure 1.6

c. After analyzing your isotherm pattern (from Figure 1.4), the infrared satellite image (Figure 1.5), and the radar-precipitation map (Figure 1.6), draw a thick line on the blank U.S. map (Figure 1.7) where you believe a weather front is located on 00Z 26 March 2003.

Figure 1.7

U.S. Weather Maps and Meteogram from: AMS DataStreme Atmosphere Project, http://www.ametsoc.org/dstreme/ U.S. Radar Map from: Intellicast Weather, http://www.intellicast.com U.S. Satellite Image from: NCAR/RAP Real-Time Weather Data (Satellite), http://www.rap.ucar.edu/weather/satellite/