WoodsLab3_Tornadoes_ONLINE

Earth Science Lab Name: Natasha Woods Hazardous Weather: Tornadoes Objectives · Understand how the physical geography of the earth affects hazardous weather globally · Understand and interpret data in satellite imagery · Formulate questions and testable hypotheses based upon qualitative analysis of satellite imagery and visualizations Laboratory Materials · Computer with internet access · Images in Appendix A from the lab manual (see Blackboard) Pre-lab Assignment Prior to lab, complete the Tornadoes tutorial in Blackboard. This tutorial will review weather hazards and ensure you are prepared to complete this lab. Exercise: Tornadoes Tornadoes are an exciting aspect of weather that causes fear in some and excitement in others. In this lab, we will investigate the factors that control where tornadoes occur globally. Part 1: Air masses To begin to understand where tornadoes form, we must understand why they form. As you learned in the pre-lab tutorial, tornadoes are associated with cold fronts which form when a cold air mass displaces a warm air mass. Air masses get their properties from where they form and are described by their general temperature (cold (P) or warm (T)) and their relative humidity (moist (m) and dry (c)). In the principal world air masses map shown below, continental Arctic (cA), continental polar (cP) air masses are cold and dry . Continental tropical (cT) air masses are hot and dry. Maritime polar (mP) air masses are cool and moist . Maritime tropical (mT) and maritime equatorial (mE) air masses are warm and moist .

Map of principal world air masses. http://kids.britannica.com/comptons/art-166713/In-the-principal-world-air-masses-continental-Arctic- continental-polar 1. What would you label an air mass forming over Wisconsin? Explain your reason. Over Wisconsin an airmass that forms would probably be a cP air mass. Given the context of the photo above, a cP air mass seems to be closest to Wisconsin. Also, it would be continental since it formed over land and most likely cold due to our location. 2. What would you label an air mass forming over Florida? Explain your reason. Florida is surrounded by water, as the picture would suggest most likely the air mass in the area formed over the gulf and is considered an mT. This is because it is formed over the gulf where the air is warm and moist. Part 2: Tornado Formation Let’s use what we now know about the location of air masses to think about how tornadoes form. A tornado begins in a severe thunderstorm called a supercell. A supercell can last longer than a regular thunderstorm. The same property that keeps the storm going also produces most tornadoes. The wind coming into the storm starts to swirl and forms a funnel. The air in the funnel spins faster and faster and creates a very low pressure area which sucks more air (and possibly objects) into it.

Oklahoma, Texas, Nebraska Part 3: U.S. Tornado Occurrence You’ve probably heard the phrase “tornado alley” as the location where tornadoes occur with the highest frequence in the U.S. Now, we’ll take a look at where tornadoes occur in the U.S. To begin, go to: : https://en.wikipedia.org/wiki/Tornadoes_in_the_United_States#/media/File:Improved_Av erage_Annual_Tornado_Reports.svg 6. Which two geographical areas in the continental U.S. have had the fewest tornadoes? The West and Northeast United States 7. Which geographical area in the continental U.S. has had the highest number of tornadoes? Midwest and the South 8. Propose an explanation for why tornadoes happen more frequently in this area than in others. Your explanation should be based on your understanding of fronts from Part 2. Tornadoes happen more frequently in the Midwest and the South because this area is what connects the cold front from the north with the warmer front from the south. (cP to mT) Part 4: Global Tornado Occurrence Now, we will investigate how tornado frequency varies globally to get a sense of where and why they occur. To begin, read Kathryn Prociv’s 2013 web article “From Domestic to International: Tornadoes Around the World and then answer the questions below: http://www.ustornadoes.com/2013/07/25/from-domestic-to-international-tornadoes- around-the-world/ . 9. Outside of the United States, which country experiences the highest frequency of tornadoes? Canada

10. List three other countries which experience tornadoes. Russia, Germany, Bangladesh 11. During which months do tornadoes seem to occur in the northern hemisphere? Explain why there is a ‘seasonality’ to the occurrence of tornadoes. NOTE: Remember what is needed to form a tornado. Tornadoes seem to occur mostly in April, May, June, July in the North. This is because tornadoes mostly form in the spring/summer. This is because the warmer weather is met by a cold front. In the winter you don’t have that warm air needed to create that circular draft of air necessary for a tornado to form. 12. Between which latitudes are tornadoes found in the southern hemisphere? Explain why tornadoes occur in these locations. NOTE: Remember what is needed to form a tornado. In the middle latitudes is where tornadoes are most often found in the Southern hemisphere. This is between about 20-50 degrees south latitude. In these middle latitudes there is not a clashing of a warm and cold front. This is the condition needed to produce a tornado. It was noted in our lecture that an unstable condition is needed for a tornado to form and this occurs in these areas. 13. Consider the requirements for tornado formation. In which physical areas on Earth would you expect to see no tornadoes at all? Explain your reasoning . The poles would be one area I would expect to never see tornadoes. In the poles you have majorly cold air which does not provide optimal conditions for tornado formation. I don’t believe you would see tornadoes around the equator either because you would need that cool front in order to make optimal conditions.

14. Think of the damaged caused by a tornado that you have seen, live or on TV. Describe what did the tornado did, including how much damage it caused. Be as specific as possible, including information about the types of structures that were affected and what happened to those structures. I saw a video recently of the damage a tornado did in Oklahoma. It was categorized as an F3. It flipped a small airplane, ripped apart roofs and walls of homes, and took down powerlines. It destroyed the roof of a Lowes garden center and even overturned a semi. All the structures affected seemed to have been dealt a great deal of damage. 15. Now, go to http://www.spc.noaa.gov/efscale/ef-scale.html and scroll down to the second section titled “Enhanced F Scale Indicators.” Read through the damage indicators listed and select the one that best matches your description above (ie a McDonald’s fast food building would be Number 8). Click on the number to the left of the indicator you’ve selected. This will open a new tab in your browser. Read through the table that opens and record the Degree of Damage (DOD), the expected estimate of wind speed (EXP), the lower bound of wind speed (LB) and the upper bound of wind speed (UB) in the table below. An example has been included in the first row. Describe the structure Damage Indicator Number Describe the damage that occurred Degree of Damage (DOD) Expected Estimate of Wind Speed (EXP) Lower Bound of Wind Speed (LB) Upper Bound of Wind Speed (UB) McDonald’s fast food restaurant 8 Windows broken, a few roof tiles missing 3 86 72 103 Lowes Garden Center 12 Small part of the roof torn open, wood beams sticking out 3 103 87 123 17. The Enhanced Fujita Scale designation is determined using the Expected Estimate of Wind Speed (EXP) based on the degree of damage (DOD) that occurred at the structure observed (Damage Indicator). In the example above, the EXP is 86 miles per hour. To determine the Operational EF Scale of this tornado, we go back to http://www.spc.noaa.gov/efscale/ef-scale.html . The 86 mph burst corresponds to

the EF Number 1, which has a 3 Second Gust of 86-110 mph, in the “Operational EF Scale” column of the table. Based on the data you recorded for your observed tornado, what is its Enhanced Fujita (EF) Number? It is a F1 tornado as well considering its estimate wind gust value of 103. 16. Now, you will reclassify several tornadoes using the Enhanced Fujita Scale. To begin, look through the Tornado Damage Images at the end of this lab. Make your observations from the images and record them in the table below. Once you have recorded your observations, go to http://www.spc.noaa.gov/efscale/ef-scale.html and record the Damage Indicator Number, DOD, EXP, LB and UB for each image. Finally, determine the Enhanced Fujita (EF) Number for each tornado. It will likely be different from the original Fujita Number assigned. Figure Observations (type of structure, damage, etc) Damage Indicator Number Degree of Damage (DOD) Expected Estimate of Wind Speed (EXP) Lower Bound of Wind Speed (LB) Upper Bound of Wind Speed (UB) Fujita Scale Enhanced Fujita Scale (EF) 1 Broken medium sized trees, toppled over small trees 27 -Hardwoo d Trees 4 110 93 134 0 1 2 Roof torn off a home, some siding ripped off, walls still standing 2- Single/Mul ti family home 4 97 81 116 1 1 3 Roof is absent, walls are still there but falling over or moderately torn up 2- Single/Mul ti family home 7 132 113 153 2 2 4 Frame of house is no longer visible, walls are gone except for one, the roof is nonexistent, trees appear to 2- Single/Mul ti family home 8 152 127 178 3 3

The enhanced Fujita scale considers the damage being produced by tornadoes instead of just the wind speed in order to classify them. Using just wind speed to determine the category of a tornado was leaving room for error when it came to F3 and above. I do believe the enhanced scale is more accurate in terms of measuring a tornado. Each photograph apart from one, matched its listed category accurately. The strength of the damage directly correlates to the wind speeds which then can accurately predict the category a tornado should go in. 2. Houses with basements are common in the Midwest but are not common in the west. Propose two reasons for this and explain your reasoning. Basements are virtually unaffected by tornadoes. Anything above ground level has the potential to be blown over or away by a tornado. Since the west does not see tornadoes, they have virtually no need for a basement. In the Midwest where tornadoes are frequent it is necessary for shelter. 3. Next week we’ll be talking about hurricanes. How do you think they will be similar to tornadoes? How do you think they will be different from tornadoes? I know very little about hurricanes, but I think hurricanes are also directly created from wind patterns due to their rotation. They also move towards land, which might be a direct result of the regional wind pattern on earth. The two types of weather are similar in that they produce high wind speeds that damage areas and can be classified on a scale based on those numbers. I think they will be different from tornadoes because hurricanes require water to form and they will not develop directly over land.