front_lab

Front Lab

Purpose and Set Up

      The goal of this lab exercise is to give you experience in a number of aspects of analyzing sea-level pressure maps. Specifically, you will be drawing contours of sea-level pressure, locating the center of a cyclone, and locating a cold front while identifying the relationship between isobars, winds, fronts, and lines of constant dew point temperature.

      You have been given two surface weather maps valid at 12Z friday October 13, 1995. One surface map has isodrosotherms (contours of constant dew point temperature) already drawn on it in intervals of 4 degrees F. The other surface map has a warm front and several isobars drawn on it. This is the map you will be analyzing, the isodrosotherm map is to be used as a reference.

     NOTE: the two analyses you will be doing cannot really be separated from each other. You may approach them in the following order, but do not finalize the isobars until you have located the cold front.

1. Isobar Analysis

      Analyze isobars at intervals of 4 mb. Sketch them in lightly at first using a pencil. Use 1000, 1004, 1008, 112, 1016 and 1020 mb for this map. Not that the contours for 1004 and 1020 mb are already drawn. Pay attention to the winds, and try to make the isobars consistent with the wind directions and speeds.

      Be sure to place a "L" where you think the lowest sea-level pressure is on this map. Remember that it may not happen to coincide with a reporting station location.

      After you have an idea where the low center, warm and cold fronts, and isobars are located, go back and finalize the isobars. To finalize the isobars:

  • label them with the last two digits of the pressure,
  • make them relatively smooth,
  • ensure that they curve appropriately at fronts

    2. Frontal Analysis

          Make sure you have an idea of the isobars before starting this part. You will find the isodrosotherms helpful in locating the cold front on this map. Rememeber the various characterisitcs of cold fronts, such as:

  • a shift in wind direction across the front
  • a sharp drop in temperature across the cold front
  • a sharp drop in dew point temperature across the cold front

          After you have finalized the isobars, finalize the cold front by placing the appropriate symbols on it.