ATMS120_Lab4_SU23
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ATMS 120: Summer 2023
Name and NetID:_________________________________________
Lab #4: Tropical Cyclones
75 points. Remember to turn in a picture of your iCard along with your submission.
Part #1 Hurricane Basics
8 points (2 points each)
Imagine it is October 5
th
, 2026, and the 4
th
named tropical cyclone just formed in the Caribbean and is forecast to
move toward the Florida Panhandle. Answer the following questions.
1.
Would you consider the 2026 hurricane season to be
above average, average,
or
below average
in terms
of hurricane activity?
2.
If this tropical cyclone were to achieve a maximum sustained wind speed of 102 mph, where would it rank
on the Saffir-Simpson Scale?
3.
What would its name be?
4.
Examine the map below, which has two arrows that show two possible tracks for the eye of this hurricane.
Which hurricane track (#1 or #2) would produce the worst possible situation for Tampa, FL, in terms of
storm surge and wind damage? Please explain why in one or two sentences. (Tampa’s distance from both
tracks is exactly the same.)
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
1
ATMS 120: Summer 2023
Part #2 Pressure vs. Wind
6 points (2 points each)
The figure below represents the observed relationship between the air pressure measured at the center of circulation
and the maximum sustained winds for all tropical cyclones in the Atlantic Ocean from 1979-2015. Answer the
following questions. (
NOTE: the winds speeds are given in knots, not mph and 1 hPa = 1 mb.
)
1.
Tropical Storm Bret (2023) occurred June 19-24 and never obtained hurricane status on the Saffir-Simpson
scale and passed just north of Barbados and directly over St. Vincent with maximum sustained winds of 70
mph
. Use the graph below to estimate Bret’s minimum pressure at that peak intensity.
2.
Hurricane Fiona’s (2022) pressure bottomed out around 930 mb. According to the chart, what was Fiona’s
wind speed (in knots) when its pressure fell to 930 mb? What rank on the Saffir-Simpson scale did Fiona
achieve when its pressure was at 930 mb?
3.
The color shading on this graph represents the number of tropical cyclones at each wind and pressure
interval that were used to create this plot. Based on the shading on this graph, are strong hurricanes or weak
hurricanes more common?
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
2
ATMS 120: Summer 2023
Part #3 Evacuating Fort Myers
15 points
Evacuation for Hurricane Ian could be considered quite messy. Fort Myers, Florida ordered a mandatory evacuation
less than 24 hours ahead of Hurricane Ian’s landfall. There are a lot of logistics to consider when deciding
evacuation orders. Let’s look at the situation mathematically and see how long it would take to evacuate the Fort
Myers area
if
everything ran smoothly (i.e., people were prepared and there were no accidents blocking roads, etc.).
Using the information below, calculate how long
(in hours)
it would take to evacuate all 105,000 people from the
Fort Myers area. (Show all your work!
)
Assumptions:
Assume all the people evacuate by car and that each car carries an average of 2.5 people
Assume that all cars evacuate using major roadways (Interstates, expressways, highways) and that there are a total of
22 outbound lanes leaving the Fort Myers area
The rate of cars exiting the metro area is 1 car per 3.5 seconds per lane.
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
3
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ATMS 120: Summer 2023
Part #4 Hurricane Maria’s eyewall speed
15 points
After Hurricane Maria hit Dominica, it moved into the Caribbean and began tracking toward Puerto Rico. At the
time this satellite image was created, a weather station on St. Kitts and Nevis measured a wind speed of 25 mph.
This weather station was 70 miles from the center of Maria’s eye. The diameter of Maria’s eye was measured at 23
miles. Use this information to solve for the wind speed at this time in Maria’s eye wall. Use this wind speed to find
the Hurricane Maria’s rank on the Saffir-Simpson scale when this image was taken. (Show all your work!
).
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
4
ATMS 120: Summer 2023
Part #5 Coriolis Effect
15 points (10 for calculations 5 for the question)
We learned that the reason hurricanes rotate is due to a balance of two forces – the Coriolis force and the pressure
gradient force. Rather than performing calculating the Coriolis force on a hurricane, let’s see how much the rotation
of the earth impacts the flight path of a game-winning Hail Mary touchdown pass for the Illini at Memorial Stadium.
The equation below represents the east-west deflection due to the Coriolis force for objects that are moving south to
north. Assume that the football was thrown a distance of 53 m in the air.
Show all of your work!
∆ x
=
Ωv
0
t
2
sin
θ
Ω
= angular velocity of the Earth =
2
π
86164
s
= 7.292*10
-5
1/sec
v
0
= south-to-north velocity of the football = 22 m/s
t
= total time of travel for the ball = 2.5 seconds
φ
= latitude (keep in degrees) = 40°N
Δx
= east-west deflection (meters)
If a football pass is thrown off target such that it is intercepted by the opposing team, is the Coriolis force to blame
for this? Briefly discuss
(5 points)
.
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
5
ATMS 120: Summer 2023
Part #6: Graphing Hurricane Irma’s Winds and Pressure
16 points, 10 for the graph and 2 per question
Hurricane Irma was a powerful Category 5 hurricane as it hit the island of Barbuda. Hurricane strength is
categorized using the Saffir-Simpson Scale, which ranks hurricanes based upon sustained wind speed. We have
learned that wind is a result of a change in air pressure (i.e., the pressure gradient). Let’s use this idea to analyze data
taken from Hurricane Irma. Download the spreadsheet of Irma data from Moodle.
Column A: Date and Time of the observation
Column B: Wind Direction
Column C: Sustained Wind Speed (m/s)
Column D: Wind Gust Speed (m/s)
Column E: Wind Gust Speed (mph)
Column F: Pressure (mb)
There are no data in columns B, C, and D after 5AM on Sept 6, 2017, because the anemometer was destroyed by the
hurricane’s winds. However, the barometer, which was measuring the atmospheric pressure, continued to work.
Please complete the following tasks:
1.
Calculate the wind gust speed in mph (miles per hour) in column E using the data in Column D. 1 mph =
0.447 m/s
2.
Create a graph of the wind gust speed and pressure as a function of the date and time. Please graph the
entire data set even though there are no wind speed data after 5AM on Sept 6. Set the primary y-axis values
to wind gust speed and the secondary y-axis to pressure (your own graph should look just like the Figure
below). Please turn in a screenshot of your graph including the answer to the questions below.
Questions:
1.
What relationship do you see between the pressure line and the wind speed line on your graph? (Hint:
Remember that pressure gradients, not low pressure itself creates strong winds.)
2.
The anemometer broke in the eyewall of the hurricane when the wind speeds reached 155 mph. After the
eyewall passed over the weather station, the pressure dropped to its lowest value of 919.6 mb. At that point,
there was no pressure gradient. What do you think happened to the wind speed at this point? Briefly explain
why. (Hint: Remember that pressure gradients, not low pressure itself creates strong winds.)
3.
Please draw on your graph (or else sketch below) what you think the rest of the wind speed line would have
looked like if the anemometer would not have failed and continued to operate until 23:54 Sept 6, 2017.
© 2023 Dept. of Atmospheric Sciences, University of Illinois-Urbana Champaign
6
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