The low and high pressure systems of mid-latitude surface weather maps are migratory. Often these systems appear to take preferred, seasonal tracks across the country. As an exercise, we can track these systems over several days or a week.

Movement of these systems can be monitored on a tracking chart. Positions of systems from surface weather maps are plotted on the tracking chart at regular intervals to give a picture of their progression.

WHAT IS NEEDED

Using a blank US base map such as that found on the DataStreme Homepage, you can:

• Locate the centers of the lows (cyclones) and highs (anticyclones) on the 0Z and 12Z surface maps from the DataStreme homepage. You should select only those well-defined cyclones or anticyclones that have at least one closed isobar and that can be found twelve hours later. Plot the location of the centers of cyclones and anticyclones at 12 hour intervals (00 and 12 Z) from the surface analyses onto your base map. For clarity, you may want to use separate base maps for cyclones and anticyclones.
• Mark the position of the pressure center (H or L) on the tracking chart with a circle and neatly plot the time above that location.
• Connect the location circles for the same cyclone/anticyclone with a black line.

As an additional feature, you could also inspect the upper air charts for the same time interval. Often times, the surface weather systems are steered by the mid tropospheric winds. Therefore, inspect the 500 mb analysis charts for 0Z and 12Z from the DataStreme homepage. Look at the direction of the 500 mb flow above the particular surface weather feature.

WHAT INFORMATION CAN BE DETERMINED

While you are monitoring the movement of weather systems, you may want to consider and identify:

• In what direction(s) did the cyclones move? Did you detect any preferential tracks? If so, where were these tracks located?
• In what direction(s) did the anticyclones move? Did you detect any preferential tracks? If so, where were the tracks?
• How do these surface pressure features move with respect to the upper level flow patterns?
• Did you find that any systems formed in the region during the interval? If so, where did these systems appear?
• Did any systems decay? If so, where did they finally disappear?
• What happened when a system moving east from the Pacific approaches the Western states? Could you track these systems across the mountains and into the Plains states?

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URL: datastreme/learn/w_sup.html
Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.