Atmosphere And Weather

Anatomy of a Storm Surge



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A storm surge also known as a storm tide, and tidal surge. Is a rise in the level of water that is pushed to shore in the form of waves before the storm makes landfall. Depending on the speed of the wind it can be a very violent rush of water.

It is the result of a storm brewing in the ocean whether it is a tropical depression, tropical storm or a hurricane. All of these storms produce storm surges.

TROPICAL DEPRESSION SURGE

A tropical depression is an unorganized low pressure system. Which produces storm surges equivalent to high tide which occurs twice a day once at sunset and once at moonset.

TROPICAL STORM SURGE

Is slightly more organized than a tropical depression and is on its way to becoming a fully formed storm system, a hurricane. It the storm makes land fall before it reaches hurricane status the storm surge will most likely only reach two to three at the most.

HURRICANE SURGE

The hurricane surge is what really defines a storm surge and is based on a few factors one being the central pressure of the hurricane which is the Atmospheric pressure at the time the hurricane makes landfall, the category of the hurricane which determines the wind speeds and the estimates storm surge based on the central pressure reading and how high the winds are.

The Saffir-Simpson Hurricane Scale is used to categorize hurricanes with this information the category number of the hurricane will provide a fairly accurate storm surge. Scale found at www.nhc.noaa.gov

SAFFIR-SIMPSON HURRICANE SCALE

~ Category One: Winds of 74-95 mph - Storm surge four to five feet
~ Category Two: Winds 96-110 mph - Storm surge six to eight feet
~ Category Three: Winds 111-130 mph -Storm surge nine to twelve feet
~ Category Four : Winds 131-155 mph - Storm surge thirteen to eighteen
~ Category Five: Winds greater than 155 mph - Storm surge above eighteen
The storm surges are in addition to the normal tide. If the hurricane reaches landfall at high tide the surges will be higher than the estimated amount for each category.

It's also important to know that the moon cycles effect the tide as well for example if a category three hurricane where to hit landfall at high tide during a full moon the storm surge could reach sixteen to eighteen feet which is a surge of a category 5 hurricane.

HISTORICAL SURGES

The Long Island Express hurricane in 1938 that came ashore as a category 3 hurricane and swept though New England at 70 miles an hour had a storm surge of 30 feet!

Hurricane Katrina in 2005 the worst hurricane to hit the United States in over 80 years. Sadly as you all know way too many lives were lost or destroyed. Three years later the survivors are still struggling to rebuild their lives. The highest storm surges were along the Mississippi-Alabama border, measuring 20 feet.

Cyclone Mahina, March 4, 1899 hit Bathurst Bay, Australia, as a category 5 storm. After 109 years this storm still holds the record for the largest storm surge in history at 48 feet!

The storm surges can be as devastating as the actual hurricane and in many cases cause more damage and loss of life. All by the simple process of water being pushed inland.

Sources
http://www.noaa.gov/
http://www.nypress.com/print.cfm?content_id=13427
http://www.nhc.noaa.gov/HAW2/english/storm_surge.shtml
http://en.wikipedia.org/wiki/Cyclone_Mahina
http://www.nasa.gov/mission_pages/hurricanes/archives/2006/sealevel_nyc.html

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