The North Atlantic Basin includes the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. Most hurricanes that form in the Atlantic basin begin as easterly waves that begin of the coast of Africa. The winds in these waves are basically from the east, but you can see how the winds vary by looking at the blue lines.
Sea surface temperatures are very important in determining
a hurricane's strength. The position of the Bermuda High is also important.
To see how these variables may affect a hurricane's strength and movement
check out this Hurricane
Applet from the University of Wisconsin. Directions are at the bottom
of the page if you want to see what the sea surface temperatures and the
steering winds are.
If conditions are right - warm water, only weak winds
aloft, the easterly wave may develop a closed circulation where we will
see westerly winds on its south side. When this happens we have a tropical
depression. When the winds reach 34 knots (39 mph), we have a tropical
storm, and when they reach 64 knots, we have a hurricane. Hurricanes are
steered by the winds around the subtropical high. To see how this works
and also to look at the importance of water temperature, try this interactive
Hurricane
Applet from the University of Wisconsin.
You can also help determine the strength of a hurricane by seeing how cold its cloud tops are. Infrared satellite imagery lets us do this. To learn even more about how satellite images can help, see the page entitled "What does the brightness of a cloud mean on the TV weather shows?".
Hurricanes move with a forward speed, usually around 10 to 15 knots when they are traversing the tropical ocean. Forward speed can increase greatly as a hurricane moves into mod-latitudes.
A hurricane's tangential wind speed
is a measure of the actual wind speed the hurricane
possesses - these are the winds that cause the damage
and push the ocean up ahead of the hurricane causing
the storm surge.
See the University
of Wisconsin simulation on how tangential winds
are affected by the change in pressure near a hurricane
To learn a little about Atlantic hurricane climatology check out NOAA's page on Tropical Cyclone Climatology.
Historical tracks of hurricanes going back many years is can be found at NOAA's Archive of Hurricane Seasons.
Additional Hurricane Background Information:
The University of Illinois Online Meteorology Guide offers background readings along with well developed graphics and QuickTime movies to illustrate the formation and behavior of hurricanes. This is a rather extensive site and may take a up to 120 minutes to get a good grasp of the content.
Another very fine resource for hurricanes with good graphics is the USA Today's "All About Hurricanes Guide".
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