Saturday, August 30, 2008

From Africa, With Love




First, a little meteorology, courtesy of http;//earthobservatory.nasa.gov:  "The most common mechanism that triggers the development of a cyclone is the African easterly wave, an area of disturbed weather than travels from east to west across the tropical Atlantic.  Essentially, an easterly wave forms because of a kink in the jet of air that flows west out of Africa. The jet is created by the strong temperature difference between the Sahara Desert and the Gulf of Guinea.  The warm air over the Sahara rises and, several kilometers above the surface, turns southward toward the cooler air over the Gulf.  The rotation of the Earth turns the air current westward to form the African Easterly Jet, which then continues out over the Atlantic Ocean.  Occasionally, a kink will develop in the jet and move from east to west, hence the name easterly wave.  Converging winds on the east side of the easterly wave trigger the development of thunderstorms, and some of these large thunderstorm systems go on to become hurricanes.  Most Atlantic hurricanes can be traced to easterly waves that form over Western Africa."

It's a rainy rainy season here in Senegal, much more so than in recent years.  Last Thursday night, by example, we had a whopping big electrical storm, as intense as any storm I recall as a kid growing up in thunderstorm-prone south Florida.  The sky was short-circuiting, lightening flashing from every which way, with loads of wind and rain, as if someone had lifted our apartment building up into the most electrically intense section of the thunderhead. 

You can hear an audio file of the storm at http://www.becauseoftime.org/Audio/Thunderstorm%208.28.mp3.

We now discover that the same system is drifting westward, over the Cape Verde Islands. The National Hurricane Center reports that "conditions appear conducive for development and a tropical depression could form in the next day or two."

From Africa, with love.