Fog!                                               11/25

     1.  What causes a hurricane to build initially over the ocean?
             Tropical cyclones can form wherever there are atmospheric conditions that cause a buildup of a number of
                thunderstorms in a relatively small area, coupled with favorable conditions which enable those thunderstorms to
                become organized in a systemic circulation pattern.  The most likely initial situations involve (1) an easterly wave,
                (2) a kink in the ITCZ and (3) a cold front moving in from middle latitudes.

    2.  Why do all [most North Atlantic] hurricanes eventually turn to a northeast trajectory?
             The general North Atlantic air circulation is dominated by the clockwise circulation about the Bermuda high. 
                Eventually this global-scale pattern steers hurricanes into a northeast trajectory which carries them over colder
                waters where they dissipate.

    3.  Is the water in the southern hemisphere colder?
             Along the west coast of the American continents the cold water in the southern hemisphere gets all the way to the
                equator while it doesn't in the northern hemisphere.  This is also true along the Euro-African west coast.  The
                primary reason for this north-south difference lies in the shapes of the continents.  This difference, of course,
                favors formation of tropical cyclones in the northern hemisphere.

    4.  Why are there more very intense tropical cyclones per unit area in the western Pacific than in the Atlantic,
         if the Pacific Ocean is warmer than the Atlantic.
             The Pacific Ocean is not warmer than the Atlantic.  Because of the clockwise northern hemisphere gyres and the
                counterclockwise southern gyres, all driven by the circulation patterns around subtropical highs (which are a
                consequence of the Coriolis force), at a given latitude the eastern side of an ocean basin has colder waters than
                the western side.  That is true of both the Atlantic and the Pacific basins.  Therefore at a given latitude the waters
                adjacent to the west coast of the United States (cold east-side Pacific waters) are colder than the waters adjacent to
                the east coast (warm west-side Atlantic waters).  However, it you consider the Eurasian land mass, the waters
                adjacent to the west coast of Eurasia (cold east-side Atlantic waters) are colder than the waters adjacent to the east
                coast (warm west-side Pacific).  The greater number of intense storms in the western Pacific than in the Atlantic is a
                consequence of the much greater size of the entire Pacific basin including the size of the area in which tropical
                storms can form.  To see this clearly, visit the current sea surface temperature link. 

     5.  Why does warm water aid the development of hurricanes?
             The principle energy source of all tropical cyclones is the latent heat of condensation released as warm, saturated
                air rises and its water vapor condenses.  Even though the surface air above both warm and cold oceans tends to be
                nearly saturated, because of the rapid increase in saturation vapor pressure with temperature, there is far more
                water vapor in the air and therefore far more available energy as latent heat of condensation above warm oceans
                than above cold oceans.