Analyzing Severe Weather Data

Transcription

1 Chapter Weather Patterns and Severe Storms Investigation A Analyzing Severe Weather Data Introduction Tornadoes are violent windstorms associated with severe thunderstorms. Meteorologists carefully monitor atmospheric data to predict where thunderstorms might develop. They also attempt to predict whether these storms might spawn powerful tornadoes. To aid them in this task, meteorologists use thermodynamic indices. Thermodynamic indices are sets of numbers that indicate the state of the atmosphere at a given time and place. Three important thermodynamic indices are the dew-point index, the lifted index, and the storm relative helicity index. The dew-point index indicates the amount of moisture in the atmosphere. The dew-point temperature of an area usually needs to be at least 0 F for a tornado to develop. The lifted index indicates how fast or slow air is rising or sinking. Air must be rising for a thunderstorm and therefore, a tornado to develop. The storm relative helicity index indicates whether or not the air is rotating. For a tornado to develop, air must be turned or spun as it rises. In this investigation, you will use thermodynamic indices and weather maps to predict where a tornado might strike. Problem Where are tornadoes most likely to occur? Pre-Lab Discussion Read the entire investigation. Then work with a partner to answer the following questions. 1. Posing Questions Write a question that summarizes the purpose of this lab.. Forming Definitions What is the dew-point index? For the purposes of this investigation, how does it relate to tornadoes? Earth Science Lab Manual 13

2 3. Formulating Hypotheses What conditions are most favorable for the development of a tornado? Materials (per pair of students) 3 colored pencils Procedure Part A: Analyzing Dew-Point Index 1. Study the weather map in Figure 1. The map shows dew-point temperatures in the United States on April 6, 03.. Choose a colored pencil and shade in the states that have dewpoint temperatures that are conducive to the formation of tornadoes. 3. Make a list of the shaded states. If you need help with the names of the states, use Figure, the labeled map of the United States. Part B: Analyzing Lifted Index. Study the weather map in Figure. The map shows the lifted index for the United States on April 6, 03. Data Table 1 includes a scale for the lifted index.. Choose a different colored pencil and shade in the states whose lifted indices are conducive to the formation of tornadoes. 6. Make a list of the shaded states. If you need help with the names of the states, use Figure, the labeled map of the United States. Part C: Analyzing Storm Relative Helicity Index 7. Study the weather map in Figure 3. The map shows the storm relative helicity index for the United States on April 6, 03. Data Table includes a scale for this index.. Choose a different colored pencil and shade in the states whose storm relative helicity values are conducive to the formation of tornadoes. 9. Make a list of the shaded states. If you need help with the names of the states, use Figure, the labeled map of the United States. Earth Science Lab Manual 1

3 Figure April 6, 03 7:00 AM CDT Figure DATA TABLE 1 Lifted Index > 0 Air is sinking; very stable atmosphere 0 Stable atmosphere 1 to 3 to Stability Slightly unstable (severe thunderstorms most likely) Unstable (severe storms, hail, maybe smaller tornadoes) Very unstable (severe storms, larger hail, possibly larger tornadoes) 1 April 6, 03 7:00 AM CDT Earth Science Lab Manual 1

4 Figure April 6, DATA TABLE Helicity Amount of Rotation > 0 Some storm rotation > 0 Enough rotation to support supercell thunderstorms and some tornadoes > 0 Enough rotation to support dangerous tornadic thunderstorms WA OR NV CA Figure ID AZ UT MT WY CO NM ND SD NE KS OK TX MN IA WI IL MO AR MS LA IN MI TN AL KY OH GA WV PA NC SC VA FL NY VT ME NH MA RI CT NJ DE MD Earth Science Lab Manual 16

5 Analysis and Conclusions 1. Interpreting Diagrams Considering only the dew-point data, in which states could a tornado have possibly formed on April 3, 03?. Analyzing Data Considering only the lifted index data, in which states could a tornado have possibly formed on April 3, 03? 3. Interpreting Diagrams Based only on the storm relative helicity data, in which states could a tornado have possibly formed on April 3, 03?. Predicting Study your combined data, then predict which states are most likely to have experienced a tornado.. Evaluating and Revising What criteria did you use to make your decision? 6. Applying Concepts Imagine that a cold front moved across the southeastern United States on April 6, 03. Would this front have increased or decreased the chances of tornado formation? Explain your answer. Earth Science Lab Manual 17

6 Go Further Thermodynamic indices are available on the Internet. Search the Internet for Web sites that post data about these indices. Select a state, then gather data about its dew point, lifted index, and storm relative helicity on one particular date. Predict whether the state is likely to experience a tornado. Earth Science Lab Manual 1