San Francisco State University Name___________________________________
Department of Earth & Climate Sciences

ERTH 260:Laboratory 9
Joplin Tornado Day, May 22, 2011
Weather Pattern and Thunderstorm Potential Diagnosis
(150 points)

Lab Due (with Presentations) on Wednesday 18 April 2018. Organizational Work among the groups done on Friday 13 April. Background for Questions 3 and 4 will be done on 11 and 13 April.

This exercise has you analyzing and examining weather charts to infer the conditions that occurred prior or during the time of the Joplin MO tornadic thunderstorm. Please put verbal answers on separate sheet of paper. Everyone is responsible for completing all exercises on their own, although you may work together.

You already have the 500 mb and 700 mb charts from Lab Exercise 6.

Presentations: Organizer for a particular chart or group of charts in bold face. For Questions 1 and 2, and 4, organizer will put together people in group so that each person has something to say in the presentation.

  1. 16 UTC Surface Chart (18 points) (Gave you 16 UTC by mistake, should have been 12 UTC)
    1. Place values on the isobars (this is a so-called subsynoptic plot; isobars are conventionally drawn at 2 mb intervals on such a chart) (2 points)
    2. Label Lows (there are no Highs)(use proper colors). (2 points)
    3. Draw Streamlines (color coded; blue=cold; red=warm moist; brown=warm dry) (2 pts each for 6 points total)
    4. Analyze the boundaries labeled A, B, C and D (use proper symbols and colors). (2 points each, for 8 points total)
  2. 500 mb and 700 mb Charts (12 points)
    1. Analyze troughs and ridges, highs and lows. (5 points each chart)
    2. Briefly comment on the wind directions and speeds over the Joplin area.(2 pts)
      The winds at 500 mb (~18000 ft) and 700 mb (~10000 ft) are southwesterly. They are varying between 30 and 40 knots through that layer.
  3. Soundings for Sites north and south of Springfield Missouri: Convective potential in the morning. (60 pts total)
    1. Little Rock AR 12 UTC 22 May 2011
      1. Specify how this sounding resembles the prototype "Loaded Gun Sounding"; (complete sentences, please) (5 pts)

        The Little Rock sounding has a Deep Moist Layer surmounted by a dry layer, the Elevated Mixed Layer, surmounted by the Pacific Air. Between the Deep Moist Layer and the Elevated Mixed Layer is a capping inversion. Despite these things being present, the Little Rock sounding is not the best example of the Loaded Gun Sounding, because the surface winds are not southeasterly.

      2. Analyze for morning convective potential...determine LCL, LFC, EL, show CAPE and CIN areas. (15 points); (Indicate these things right on the sounding, and make sure you show the parcel ascent curve)

        The LCL is near the ground and the LFC is near the 700 mb level. Although there is great potential implicit in the CAPE area (the red area) for buoyant updrafts to develop, a surface parcel would have to be lofted through a layer of negative buoyancy, the CIN, more than 50-75 mb, the nominal amount of lofting that nature can conceivably produce. No convection should be expected in the morning.

      3. Characterize the stability characteristics of this morning sounding. (Complete paragraph please) (10 pts)

        The sounding is conditionally unstable. There is great potential in the sounding, but it is predicated on a surface parcel being lifted nearly 10000 feet or roughly 300 mb, to the 700 mb level.


    2. Topeka KS, 12 UTC 22 May 2011
      1. Specify how this sounding resembles the prototype "Loaded Gun Sounding";(complete sentences, please) (5 pts)

        The Topeka KS is a much better example of the Loaded Gun Sounding. The sounding has a Deep Moist Layer surmounted by a dry layer, the Elevated Mixed Layer, surmounted by the Pacific Air. Between the Deep Moist Layer and the Elevated Mixed Layer is a capping inversion.

      2. Analyze for morning convective potential...determine LCL, LFC, EL, show CAPE and CIN areas. (15 points)(Indicate these things right on the sounding, and make sure you show the parcel ascent curve)

        The LCL is near 900 mb and the LFC is near the 700 mb level. Although there is great potential implicit in the CAPE area (the red area) for buoyant updrafts to develop, a surface parcel would have to be lofted through a layer of negative buoyancy, the CIN, more than 50-75 mb, the nominal amount of lofting that nature can conceivably produce. No convection should be expected in the morning.

      3. Characterize the stability characteristics of this morning sounding.(Complete paragraph please)(10 pts)

        The sounding is conditionally unstable. There is great potential in the sounding, but it is predicated on a surface parcel being lifted nearly 10000 feet or roughly 300 mb, to the 700 mb level.

  4. Surface-based CAPE and CIN Analysis. Notice the locations A, B and C. (10 points)
    1. If thunderstorms develop, at which of the three locations would thunderstorm updrafts at the Equilibrium Level be the strongest and why? (3 pts)


      At Location A the CAPE values are over 6000 J/kg...the highest values in the continental United States. Since the vertical velocities at the EL are directly proportional to CAPE, any thunderstorms that develop at Location A would have the strongest updrafts.

    2. At which of the three locations is there the least chance of thunderstorms and why? (3 pts)

      At Location C although there is CAPE, the CIN values are -100 J/kg or less. Thus, there is an unsurmountable area of the sounding in which the air parcel would be too cool relative to its environment. Surmountable values of CIN are -50 J/kg or less negative.

    3. At which of the three locations is thunderstorm development most likely at the time of the chart and why? (4 pts)

      At Location A there is CAPE and no CIN. Thus, thunderstorms are free to develop in that area.
  5. Presentations: Question 1 (Rami and Allen) ; 2(Cynthia);Question 3a (Kellen Tanay, and Emma) Question 3b (Linda, Nicholas, Yan Tung); Question 4 (Wyndham and Nicolas). (50 pts)