Lab 8 Tornadoes

Geology 116, Spring 2023 Name __________________ Lab 8 Tornadoes You can find a lot of information about tornadoes on the Online Tornado FAQ Page . We’ll be using a number of links from the page, but feel free to explore more! Section 1: Tornado Scale The intensity of tornadoes is generally measured in the U.S. using the Enhanced Fujita damage scale ( http://www.spc.noaa.gov/efscale/ ). This is modified from a less quantitatively based scale devised in 1971 by Dr. T. Theodore Fujita; the enhanced scale provides more accurate values of the wind speeds associated with different levels of damage. Tornadoes often occur in outbreaks, with multiple tornadoes being produced along one frontal boundary, sometimes close in both space and time. One of the highest number of tornadoes in an outbreak occurred when 412 tornadoes touched down between May 1 and 10, 2003. One of the hardest hit areas was near Pierce City, Missouri. 1) Use the links below and the storm path map and photos of damage to try estimating damage yourself based on the Enhanced Fujita damage scale. 2) Watch the video that shows examples of damage at various EF levels: . 3) Review the EF-scale, including the general criteria and damage results, as well as the illustrations below.

Damage at different EF levels, Greenburg KS tornado 4) Based on the descriptions and photos for these different levels of tornadoes, estimate the EF-scale number and description of damage for the photos from the May 4 2003 tornado outbreak in Missouri that are shown on the next page. City EF Estimate Wind Speed Est. Description of Damage Pierce City, MO 3 136-165 mph Whole building has damage. Cars damaged. Clever, MO 1 65- 80 mph Pretty much no damage except for some broken trees. Battlefield, MO 2 11-135 mph Roof not there but building is standing. Cars damaged and on top of each other. 5) Find information from internet sources about the effects of the tornado at the three locations listed on the next page. What was the full extent of damage? There were multiple tornadoes during the outbreak in the region. How did this tornado compare with others in the outbreak? Along this path there were hundreds of large trees uprooted and snapped off, many power poles were snapped at their base that caused numerous power outages, especially in Monett. Also, numerous brick and wood

test the hypothesis that the location of most common tornadoes shifts from south to north and back south during the year, in response to shifts in the jet stream (farther south in the winter, farther north in summer). The National Weather Service has compiled maps of monthly tornado frequency for the period 1989-2013 here . Use these maps to answer the following questions. 1. What states have the most frequent tornadoes in (a) winter (Dec-Feb) Texas and Mississippi , (b) spring (Mar-May) Texas, Oklahoma, and Kansas (Midwest) , (c) summer (Jun-Aug) Middle States and Florida , and (d) fall (Sep-Nov) Texas, Florida, Oklahoma, Mississippi ? 2. Which season(s) has/have the most frequent tornadoes? Spring 3. How does the location of the most frequent tornadoes shift during the year? Do the data support the hypothesis described above? Goes north-Midwest late spring – early summer, shifts south late summer early fall. Does support the hypothesis above, spring has the most tornadoes. 4. Florida is also a tornado “hot spot”. When are tornadoes most frequent there? Most frequent late summer-fall Why? They occur from an aftermath of hurricanes. The frequency of tornadoes also varies year to year, as shown in the maps here . Is there any correlation between the frequency of tornadoes and the impacts of El Niño and La Niña events in the Pacific? Construct a table or spreadsheet with: (a) whether tornado occurrence in the year was relatively low, medium, or high; (b) the geographic distribution of tornado frequency for each year -- greater concentration of tornadoes in the north, central, or southern third of the country; (c) column showing if the year had an El Niño or La Niña event. 1. What criteria did you use to characterize the relative frequency of tornadoes? a. When the numbers were…: 1-20=high, 21-40=med, 41-60=low 2. What states/areas do you describe as north, central, or south? b. North: Washington, North Dakota, South Dakota, Minnesota, Wisconsin, Michigan, lowa, Wyoming, Idaho, Oregon, New York, Ohio, Indiana, Pennsylvania, New England. c. Central: California, Nevada, Utah, Arizona, New Mexico, Colorado, Kansas, Missouri, Kentucky, West Virginia, North Carolina, South Carolina d. South: Texas, Louisiana, Mississippi, Alabama, Georgia, Florida 3. Do years of high tornado frequency correlate with either El Niño or La Niña events (see table on next page)? With strong or weak events? What about years of low tornado frequency?

a. 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Tornado vs La/El Niñ(a/o) Frequency Tornado Occurrence Intensity (out of 3) Tornado Location El Niño / La Niña intensity Intensity of EL/LA Quantified Yeah, there’s a correlation between those kinds of events and tornados. 4. Does the distribution of tornadoes correlate with either strong El Niño or La Niña events? In other words, do years of greater concentration of tornadoes in the south correlate with strong or weak El Niño or La Niña years? What about years when tornadoes are more concentrated in the north or center? a. According to the data, it seems as though the Southern region had a stronger correlation between high frequency and strong events. 5. What conclusion, if any, can you draw about the relationship between El Niño and La Niña and the frequency and distribution of tornadoes? a. When there’s a La Niña or a El Niño event there is a high likelihood of there being a tornado as well. El Niño La Niña Weak - 12 Moderate - 7 Strong - 5 Very Strong - 3 Weak - 10 Moderate - 5 Strong - 7 1952-53 1951-52 1957-58 1982-83 1954-55 1955-56 1973-74 1953-54 1963-64 1965-66 1997-98 1964-65 1970-71 1975-76 1958-59 1968-69 1972-73 2015-16 1971-72 1995-96 1988-89 1969-70 1986-87 1987-88 1974-75 2011-12 1998-99 1976-77 1994-95 1991-92* 1983-84 2017-18 1999-00 1977-78 2002-03 1984-85 2007-08 1979-80 2009-10 2000-01 2010-11 2004-05 2005-06 2006-07 2008-09 2014-15 2016-17 2018-19 2019-20