Why Keep an Eye on the Barometer?

Part A: Air Pressure and Wind Speed in Hurricane Katrina

In August of 2005, Hurricane Katrina hit the Louisiana, Mississippi, and Alabama coasts. Katrina had the third lowest air pressure reading ever made for hurricanes up to that point, and it became the deadliest and most destructive hurricane to hit the U.S. in 80 years.

You may have already examined the daily data for Katrina, or plotted or explored its storm track. Now, you'll use Katrina as a case study to examine the relationship between air pressure and wind speed.

1. Download and open the Hurricane Katrina Data (Excel 2007 (.xlsx) 12kB Aug6 18) file into Microsoft™ Excel or another spreadsheet application.

2. The data are from the HURDAT database, but they are presented in a slightly different format than you've seen before: the location, air pressure, and wind speed data are on separate lines for each of the four daily reports.

Stop and Think

1: Look over the columns of Katrina's air pressure and wind speed. Do you see a pattern between the two values? If so, describe it.

3. You won't need the location information for this activity: select the columns that show Latitude and Longitude then choose Edit » Delete.

4. Generate a double line graph. Show air pressure and wind speed in a stacked line with markers, both plotted against date/time. Label your axes and include a title and legend for the graph.

 

5. Add a secondary Y-axis label and scale for the Wind Speed data.

6. Save your file.

7. Examine the graph. Interpret the lines to figure out what they tell you about how conditions changed through the life of the storm. Use your graph plus the tabular data in your spreadsheet to answer the questions below.

Checking In

  • At what air pressure did Katrina's winds become fast enough to classify it as a hurricane? In other words, at what pressure did the wind speed reach an average of 65 knots or higher?
  • What was Katrina's minimum air pressure? What was its maximum wind speed?

 

Stop and Think

2: Look for evidence in the data that one of the variables controls the other. In other words, try to find an instance where a change happens first in one variable and its effect is seen later in the other variable. Describe what you find and how you interpret that relationship.

3: Focus in on the first several air pressure readings for the storm. What happened to the wind speed as the air pressure decreased? Give a specific example (a range of dates and times) when the air pressure decreased and tell what happened to the wind speed over that time. Describe another specific example of what happened to wind speed while pressure increased.

4: Based on your analysis, write a summary statement describing the relationship between air pressure and wind speed in Hurricane Katrina.