Monday, October 3, 2011

Major hurricane Ophelia's effects recorded by NOAA buoy

On Saturday morning, October 1, as it reached category 3 strength, Hurricane Ophelia passed directly over a NOAA buoy positioned  a couple hundred miles south-southeast of Bermuda in the Atlantic Ocean.  The position of buoy 41049 is shown in the map below.

As you can see from the map, there is a network of buoys within about 50 miles of the U.S. coastline and a series of buoys much further offshore (buoys are shown as yellow and red diamonds). While it is not unusual for a landfalling tropical system to pass over a near-shore buoy, it takes pretty good aim (or a fair amount of luck) for a storm to pass directly over a buoy in the middle of the ocean!

The usefulness of these buoys is magnified when a tropical system gets close enough to one of these floating instrument platforms (see the pic of a buoy similar to 41049 below). The meteorological data that can be gathered as the storm passes aids the National Hurricane Center in forecasting the strength, movement, and other attributes (such as wind field and wave heights) of a storm through direct measurement, rather than remotely using satellite data.

In this case, the graphs below show what the wind, air pressure, and wave heights were as the storm passed overhead.  In the first graph, the air pressure (green) plummeted to about 28.10" in the eye of the storm, the wind speed (blue) reached nearly 70 knots (80 mph) and gusted to 100 knots (115 mph)!  In the second graph, the wave height reached just over 40 feet in that 100+ mph wind!  In this case, the buoy data affirmed the strength that the Hurricane Center had indicated for the storm at that time.

And finally, here is the satellite imagery for approximately the same time as Ophelia traversed buoy 41049.

Most Atlantic tropical systems are tracked on the MWN Tropical page.  Check it out whenever there are storms that pose any threat to the U.S. or other land masses.

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