ATMS120_Lab_6_SU23
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ATMS 120 Summer 2023
Name and NetID:_________________________________________
Lab #6: Mesoscale Convective Systems, Supercells, Hail and Tornadoes
75 points. Remember to turn in a picture of your iCard along with your submission.
Part #1 – Wind Shear
10 points total
Strong wind shear is a crucial ingredient for severe thunderstorm development. Wind shear is defined as the change
in wind speed and direction with height. Supercell thunderstorms form most frequently on the Great Plains of the
central US. The most common supercell wind profile exhibits southeasterly winds at the surface that strengthen and
become westerly with altitude. The most common wind profile for a squall line (a.k.a. mesoscale convective system)
is unidirectional, meaning that the wind speeds increase with height but the direction of the wind does not change
with height.
Five different wind profiles are below. Place a triangle around the letter beneath the most common supercell wind
profile and place a circle around the letter beneath the most common MCS wind profile
(2 point each)
.
Bulk wind shear is calculated by finding the vector difference between the winds at two different heights. Using the
supercell wind profile you identified, calculate the 0-1 km and 0-6 km bulk 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 1 km
and 6 km. The atmospheric pressure at 1 km above sea level is typically very close to 850 mb. The pressure at 6 km
above sea level is very close to 500 mb. Please calculate the 0-1 km and 0-6 km wind shear values in knots (kts). For
simplicity, assume that the surface winds are due southeasterly, the 850 mb winds are due southerly, and the 500 mb
winds are due westerly. Show your work- its not just subtraction!.
(3 points each)
0-1 km shear value _________________
0-6 km shear value _________________
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
1
ATMS 120 Summer 2023
Part #2 Questions about Severe Storms
18 points total
1.
Which type of thunderstorm is the largest in terms of size and area covered? Ordinary Thunderstorm,
Mesoscale Convective System (MCS, squall line), or Supercell Thunderstorm
2.
If a shelf cloud from an MCS were to pass over you, how does the temperature and wind speed change?
3.
What is the most frequent type of damaging severe weather from thunderstorms? Straight Line Winds, Hail,
or Tornadoes
4.
Label the clouds types pictured below (indicated with arrows).
a.
____________________
b.
____________________
c.
____________________
d.
____________________
e.
____________________
5.
Where is the safest place to be during a tornado warning?
6.
Which is more threatening to life and property for the region in which it is issued – a severe thunderstorm
watch or severe thunderstorm warning?
7.
What is tornado alley?
8.
List 4 problems with using the Fujita/Enhanced Fujita Scale to rank tornado strength.
9.
“Weak” tornadoes account for ______% of all tornado reports and ______% of all tornado fatalities.
“Violent” tornadoes account for ______% of all tornado reports and _____% of all tornado fatalities.
10.
If a large, violent tornado is approaching your location and you are on an open roadway (with no strong or
sturdy buildings nearby), what is the safest course of action?
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
2
ATMS 120 Summer 2023
Part #3 Hail Damage
15 points
Texas’s largest hailstone in 2023 was just shy of breaking record set in 2021. This new stone fell on June 15
th
, 2023.
The circumference of that hailstone was 18.5 inches. Using the circumference and the information below, answer the
following questions. Show your work.
What you need to know…
Kinetic Energy = 0.5 * Mass * Velocity
2
(Units: Mass
kg, Velocity
m/s, yielding Joules J)
Density of the ice in the hail stones = 31 lbs/ft
3
The volume of a sphere is (
4
/
3
)
× π × r
3
The fall velocity of a hailstone in still air can be approximated using the 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.
Density = Mass/Volume
Assume the hailstone was spherical
What was the diameter of the hailstone in inches? _____
What was the volume of the hailstone in cubic inches? _____
What was the fall velocity of this hailstone in m/s? ______
What was the total mass of the hailstone in kg? _____
What was the total kinetic energy of this hailstone in Joules? _______
Part #4: 2017 Hail Data
10 points total
Download the US hail reports for 2019 from January through June from Moodle. Using these data complete the
following tasks. Use the help video on Moodle for guidance.
1.
How many people were injured in this period of 2019 by hail
(1 pt)
?
2.
How many people were killed by hail in this period of 2019
(1 pt)
?
3.
What was the total economic loss of all hail events combined in this period of 2019
(1 pt)
?
4.
What is the total number of hail reports in this period of 2019
(1 pt)
?
5.
Create a bar graph that shows the hail reports for each day of the year through June
(2 pts)
.
6.
Create a line graph that shows the cumulative hail reports throughout this period of 2019
(2 pts)
.
7.
Which day had the most hail reports in this period of 2019
(1 pt)
?
8.
What was the largest hailstone diameter in this period of 2019 and in which state(s) did it fall
(1 pt)
?
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
3
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ATMS 120 Summer 2023
Part #5: Wind Force on a Tree
8 points
In one of your instructor’s neighbor’s backyards is a huge pin oak tree. How fast would the wind need to be in a
thunderstorm to uproot this tree and knock it over? The force required to uproot this tree is approximately 640,000 N
(640,000 kg m/s
2
). How fast would the wind have to be (in mph) to generate this force against this tree? Use this
information below to solve this problem. Show all of your work and be careful with units!
F
=
(
ρC
D
A
2
)
v
2
F = Force applied by the wind = 640000 kg m/s
2
ρ = Air Density = 1.22 kg/m
3
C
D
= Drag Coefficient = 0.78 (this is a ratio and therefore has no units)
A = Area of the leaves on the tree. Each leaf is 10 in
2
and there are 63,500 leaves on this tree. Consider the area of
the branches and trunk to be negligible.
v = wind speed in m/s
Part #6 Illinois Tornadoes
14 points- 1 points for 1-9, 5 points for 10
Please download the Illinois tornado database file on Canvas. This spreadsheet contains data from the Storm
Prediction Center on all Illinois tornadoes from 1950 – 2019. Each row of the spreadsheet represents data from a
separate tornado. Answer each of the questions below. Please calculate your answers in Excel (or other spreadsheet
software or write a program to calculate your answers) and submit screenshots of your Excel spreadsheet with all
your answers
. Make sure your answers are easy to find! Following a similar format to the example at the bottom of
this page (you do not need to screenshot the entire dataset). Giving a correct answer but not having your equations or
work shown in excel will result in a loss of ~2/3 points.
Questions:
1.
Which decade had the most tornadoes in Illinois?
2.
Which year had the most tornadoes in Illinois?
3.
Which decade had the most fatalities in Illinois?
4.
What is the average Illinois tornado track length (in miles)?
5.
What is the average Illinois tornado track width (in yards)?
6.
What is the average F-Scale (EF-Scale) rating for tornadoes in Illinois?
7.
What is the total number of tornadoes that have hit Illinois since Jan 1, 1950?
8.
What is the longest tornado track in this Illinois tornado database? What day did it occur?
9.
What is the widest tornado width in this Illinois tornado database? What day did it occur?
10.
What is the probability of a tornado hitting any square mile in the state of Illinois each year? Follow the
formula below to calculate this value. Show your work!
Area of Illinois = 57,915 square miles
You will need to calculate:
Average number of tornadoes per year in Illinois
Average length of tornadoes in Illinois (over all years,
in miles
)
Average width of Illinois tornadoes (over all years,
in miles
)
First calculate the average area affected by tornadoes
each year by multiplying the average number of
tornadoes each year in Illinois by the average width
and length of Illinois’ tornadoes.
Formula
(average area in Illinois affected by tornadoes each year)
/(total area of the state of Illinois)
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
4