Hurricane Earl

Hows the Water - August 30, 2010

(reprinted with permission from the Oyster Bay Enterprise Pilot)

As I am writing this column, hurricane Earl is heading up the eastern seaboard, and no one is yet sure what path the storm will take, or what the impact may be.  Boaters are securing their vessels, making sure the anchorages are secure, removing sails, and in some cases pulling them out of the water.  Birders are wondering what the impact will be on the early migrants, and what rarities might be blown off course and to our shorelines. 

So where do these hurricanes come from anyway?  Hurricanes are intense tropical storms which form in the North Atlantic.  To be classified as a hurricane, wind speeds have to reach at least 74 mph.  There are certain conditions which are necessary for a hurricane to form:  80 degree or warmer water temperatures, which is at least 150 feet deep; a low pressure area with wind disturbance; a lack of stability in the air, which allows clouds to develop; a centrifugal force, known as a Coriolis Force, which stems from the earth’s rotation; moist air in the lower portion of the atmosphere, and low level winds with directional changes (wind shear).

Tropical storms form when a system of thunderstorms converge and begins to rotate in the atmosphere.  This vortex is a tropical depression.  Heat is drawn up from the ocean surface through the vortex.  Water vapor condenses to form rain around the perimeter of the vortex.  High winds are generated by energy from the heat of the ocean.  When winds reach 35 mph the system is considered a tropical storm, and is assigned a name by the National Hurricane Center.  Hurricanes are assigned categories based upon their wind speeds.  A category 3 or higher storm (wind speeds of greater than 111 mph) is a major hurricane. 

According to the Union of Concerned Scientists, global warming may be making the impact of hurricanes worse.  “Sea level is rising and will continue to rise as oceans warm and glaciers melt. Rising sea level means higher storm surges, even from relatively minor storms, which increases coastal flooding and subsequent storm damage along coasts. In addition, the associated heavy rains can extend hundreds of miles inland, further increasing the risk of flooding.  Recent scientific evidence suggests a link between the destructive power (or intensity) of hurricanes and higher ocean temperatures, driven in large part by global warming.”  We can only wait to see what hurricane Earl will bring, and what other storms may form this year. 

The water in the Oyster Bay/Cold Spring Harbor Estuary is very warm, with temperatures as high as I have seen them while performing water quality monitoring for Friends of the Bay.  Friends of the Bay volunteers recorded temperatures in the 75 to 77 degree Fahrenheit range this week.  The dissolved oxygen levels appear to have reached their lowest levels for the season, and are beginning to rise again.   The DO levels were mostly at 4.0 mg/L of dissolved oxygen, which considering the extremely hot summer we have had, is quite good.