ATMS 120: SU 2017 Snodgrass Name and NetID:_________________________________________ Weekly Challenge Problem #5: Severe Storms Part #1 - Wind Shear Supercell thunderstorms in the US form most often in the central states (i.e., Oklahoma). The ideal wind shear profile consists of southeast winds at the surface that strengthen and become more westerly with altitude. Shown below are 4 vertical wind profiles taken from 4 different soundings. Which is the ideal vertical wind profile for a supercell? Wind shear is calculated by finding the difference between the wind speed values at two different heights. Using the profile you identified above, next you will calculate the 0-1 km and 0-5 km wind shear values. This means we will find the difference between the surface wind (lowest wind barb on the sounding) and the speed of the wind at 1km and 5 km. The atmospheric pressure at 1km above sea level is typically very close to 850 mb. The pressure at 5 km above sea level is very close to 500 mb. Please calculate the 0-1 km and 0-5 km wind shear values in knots (kts). 0-1km shear value _________________ 0-5km shear value _________________ Part #2 Hail Damage A powerful thunderstorm produced large hail that damaged hundreds of cars at a dealership in town. When the insurance adjuster arrived to assess the situation, she discovered that most of the hundreds of dents these hailstones left on the tops of the cars had two sizes - one set of dents were 4 inches in diameter and the other set was 6 inches in diameter. See if you can use the information below to find the mass, diameter, circumference, fall speed, and total kinetic energy for these two different sized hailstones. Be very careful with the units!! (Show all of your work!) What you need to know... Kinetic Energy = 0.5 * Mass * Velocity2 (Units: Mass kg, Velocity m/s) Density of the ice in the hail stones = 57 lbs/ft3 The volume of a sphere is (4/3) r3 The fall velocity of a hailstone in still air can be approximated using this equation V = k d where k = 20 if d (the diameter of the stone) is given in centimeters. V will have units of meters per second (m/s) as long as d is in cm. Diameter of the dent = 1.5 * diameter of the hailstone Density = Mass/Volume Smaller Hailstone Larger Hailstone Mass in lbs and kg Fall Velocity in m/s and mph Diameter in inches Circumference in inches Total Kinetic Energy (kg m2/s2) 2017 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign 1 ATMS 120: SU 2017 Snodgrass Part #3: Oklahoma Tornadoes Please download the spreadsheet linked below which contains data from the Storm Prediction Center on Oklahoma tornadoes since 1950. Answer each of the questions below. Please calculate your answers in Excel (or other spreadsheet software) and submit a screen capture with all of your answers, similar to the example below. http://www.atmos.illinois.edu/~snodgrss/Oklahoma_Tornadoes.xlsx (There is an underscore in the filename Oklahoma_Tornadoes.xlsx) Questions: 1. Which decade had the most tornadoes? 2. Which year had the most tornadoes? 3. Which decade had the most fatalities? 4. What is the average tornado track length (in miles)? 5. What is the average tornado track width (in yards)? 6. What is the average F-Scale (EF-Scale) rating? 7. What is the total number of tornadoes that have hit the Oklahoma since 1950? 8. What was the longest tornado in this database? What year did it occur? 9. What was the widest tornado in this database? What year did it occur? 10. What is the probability of a tornado hitting any square mile in the state of Oklahoma each year? Follow the formula below to calculate this value. Area of Oklahoma = 69,960 miles2 You will need to calculate; Average number of tornadoes each year in Oklahoma Average length of tornadoes in Oklahoma (over all years) (in miles) Average width of Oklahoma tornadoes (over all years) (in yards) First calculate the average area affected by tornadoes each year by multiplying the average number of tornadoes each year in Oklahoma by the average width and length of Oklahoma tornadoes. Be sure to convert average width of Oklahoma tornadoes to miles before you calculate the area! Formula (average area in Oklahoma affected by tornadoes each year) / (total area of the state of Oklahoma) 2017 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign 2