Class Activity_Ch 19_Storms

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Florida Gulf Coast University *

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1000C

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Geology

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Apr 3, 2024

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Florida Gulf Coast University Introduction to Earth Science ESC1000C, Fall Semester, 2023 Chapter 19 – Storms Group Members: Dylan Singleton and Shannelle Puetz We’ll look at hurricanes and storm surges today. First, we’ll use NOAA’s Historical Hurricane Track Database to look for storms. https://coast.noaa.gov/hurricanes/#map=4/32/-80 1. Copy-paste the following coordinates in the search box: 26.5°N, 81.8°W That should take us right over our neck of the woods in SW Florida. You’ll see all the storms that have passed within 60 nautical miles of the area since records began. That should be around 87 since 1859. On the left side of the webpage, the storms are sorted chronologically by default. The most recent is Hurricane Ian. Click on Hurricane Ian to see it’s path from the time it was born in the southern Caribbean to the time it dissipated over North Carolina. Fill in the table below with data from the points along Ian’s track: Location Central Pressure (mb) Wind Speed (miles/hr) Saffir-Simpson Category Western Cuba 947mb 126mph H3 60 NMi offshore FL 937mb 161mph H5 Cayo Costa, FL 941mb 149mph H4 Georgetown, SC 978mb 80mph H1 2. When you select a storm, you’ll notice in the lower left corner of the screen that a plot of the storms wind and pressure is shown. For Ian, it’s shown in the figure below.
How would you describe the relationship between the central pressure in a hurricane and the maximum wind speed? The relationship between the central pressure in a hurricane and the maximum wind speed is inversely proportional. As the central pressure decreases the maximum wind speed tends to increase and vice versa. 3. Next, we’ll look at hurricanes that have impacted all of Florida since records began. Let’s pull out some numbers from the datasets. Search for coordinates: 28°N, 84°W and then change the search radius from 60 to 250 nautical miles. That should draw a circle around the entire state of Florida. You can select different types of storms in the Category drop-down menu. For this exercise, we’re only interested in hurricanes (Category 1-5) and major hurricanes (Category 4-5). You can search for single or multiple years by selecting the Year drop-down menu. We’re interested in the years shown in the table below. Enter the corresponding dates and adjust the selection for storms to fill in the table below. Note that the number of matching storms is shown in the top left of the left panel. # Storms during Period 1871 – 1900 1901 – 1930 1931 – 1960 1961 – 1990 1991 – 2020 Hurricanes 39 24 26 20 30 Major Hurricanes 1 7 9 2 10 % Major Hurricanes 2.5 29.2 34.6 10 33.3 What can you say about the trend in the number of hurricanes and major hurricanes over time? Has it been increasing, decreasing or fluctuating? Are major hurricanes becoming more frequent within the total number of hurricanes? It has been fluctuating over the years however this last time period major hurricanes are more common. 4. Next let’s look at Hurricane Katrina and it’s storm surge that flooded New Orleans in 2005. Most of you were probably quite young then, but the surge was even more devastating that Hurricane Ian! The following website shows a simulation of this surge: https://www.nhc.noaa.gov/surge/HistoricalRuns/?large&parm=2005_katrina#contents
You can click on “Loop Forward” to play the simulation, and adjust the speed with the “Slower” and “Faster” buttons. You can also click through one frame at a time using the “>” and “<” buttons. The track of the eye of Hurricane Katrina is shown by circle and black line moving northward as it makes landfall. What was the maximum surge height on the coast as Katrina made landfall? 24-28 ft Was the surge highest on the western or eastern side of the storm? 12-16ft on the westside 4-8ft on the east Why is there a difference in surge between the east and west side? (Hint: Note which direction the storm spinning, and which side of the storm winds are blowing onshore versus offshore). The direction of the storm was moving north west so the west side of the storm had a higher surge than the east side. 5. Finally, reflecting a bit on your response to Question 3, we’ll look at a recently published article titled “Can we detect a change in Atlantic hurricanes today due to human-caused climate change?” https://www.climate.gov/news-features/blogs/beyond-data/can-we-detect-change-atlantic-hurricanes- today-due-human-caused It’s difficult to know exactly how many storms happened in the past since data isn’t very precise. But there does seem to be cyclical trends in storm occurrence in the Atlantic basin. When do we tend to have more active hurricane seasons? Between mid-August and late October What causes the multi-decadal swings in hurricane activity? Temporal changes in anthropogenic aerosols and internal climate variability associated with Atlantic Ocean circulation changes. Is it easy to relate this to human-induced climate change? Yes, because humans are constantly letting aerosols and harmful things into the air which heat up the atmosphere and cause an increase in the intensity of a storm.
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