Where and how do tropical storms form?

Step 1: Read the story map, Tropical Cyclone Wind Exposure in the United States.

Step 2: Go to the ArcGIS Online map, Tropical Storms, and explore the map.

Step 3: With the Details button underlined, click the button, Show Contents of Map (Content).

Step 4: Check the box next to the layer name, Hurricanes Wind Strength.

Step 5: Click any point on the paths of each hurricane.

• What information is stored for each point along the way?

Step 6: All hurricanes start as tropical depressions (TD). Hover on the layer name and click the button, Filter. Build the expression field – Is – value/unique. If value, enter TD. If unique, scroll down to choose a hurricane name. Click Apply Filter, and then click Zoom To.

Step 7: Where do most Atlantic storms reach TD status?

How does atmospheric pressure relate to wind speed in hurricanes?

The 2005 Atlantic storms caused $160 billion in damage and 3,913 deaths. Winds cause property damage by blowing off roofs or collapsing buildings, but they also push the surface of the water into a storm swell. Homes and small buildings do not stand a chance against storm-driven ocean swells. Winds are generated by greater differences in atmospheric pressure and the geographic size of the low pressure.

Step 8: Hover on the layer name, Hurricane Wind Strength. Click the button, Show Table.

Step 9: In the Hurricane Wind Strength table, click the WIND_KTS (wind speed in knots) column header.

Step 10: Click Sort Ascending.

• As you scroll down the table, how does the atmospheric pressure column change relative to wind speed?

What determines the path a storm takes?

• Are there areas where low pressures do not have as strong of winds?
• Why do wind speeds slow down over land?

Step 11: Close the Hurricane Wind Strength table.

Where do tropical storms get such strength?

Step 12: Click the button, Bookmark. Select Strengthening zone.

Step 13: Turn on the layer, Sea Temperature 05 (degs C).

Step 14: Click the layer name, Sea Temperature 05 (degs C). Click AvSeaTemp05 to expand the legend.

• At what temperature do tropical storms consistently pick up energy?

What other areas of the world have good conditions for tropical storms?

Step 15: Hover on the layer name. Click the button, Filter. Build the expression field – Is – value/unique. If value, enter TD. If unique, scroll down to choose a hurricane name. Click Apply Filter, and then click Zoom To.

Step 16: Click each dot. On a whiteboard, create a table of wind speeds and pressure.

Step 17: Create a graph of wind speed vs. atmospheric pressure. Wind speed should be on the x-axis, and atmospheric pressure should be on the y-axis.

• What type of relationship do these two variables have?

Step 18: Click the Home button to zoom out to the entire world.

• List two other areas in the world that would be possible targets for tropical storms?