Hurricanes will be the final topic that we cover this semester.

On average, hurricanes kill 20 people per year in the United States and cause about $5 billion of damage. 

Year
 Deaths
 Total Damage
(billion $ ))
2000
 0
 < 1
2001
 24
 6.5 B
2002
 51
 1.7 B
2003
 14
 2.3 B
2004
 34
 22.9 B
2005
 1016
 107.5 B
2006
 0
 < 1
2007
 1
 < 1
2008
 11
 7.9 B
2009
 2
 < 1
2010
 0
 < 1

2005 was, of course, the year hurricane Katrina hit New Orleans.  Three of the ten strongest hurricanes ever observed in the N. Atlantic occurred in 2005 (Wilma was the strongest and the new record holder, Rita was 4th and Katrina 6th strongest).  The deadliest hurricane in US history is the 1900 Galveston hurricane which caused 6000 - 12,000 deaths.  The Great Hurricane of 1780 killed over 20,000 people in the Lesser Antilles.  Historic rainfall amounts (75 inches perhaps in some locations) and flooding associated with Hurricane Mitch killed over 19,000 people in Honduras, Guatemala, and Nicaragua in 1998.



Satellite photographs and sketches of the two largest types of storm systems found on the earth are shown below.








2 similarities, 8 differences (size, where they form, latitude, movement, season, air masses, precipitation types, names)







An easterly wave is one of the ways of initiating or triggering hurricane development.
Normal hurricane activity in the Pacific Normal hurricane activity in the Atlantic
16 tropical storms per year
8 reach hurricane strength
0 hit the US coastline		 10 tropical storms per year
6 reach hurricane strength
2 hit the US coastline

In an average year, in the N. Atlantic, there will be 10 named storms (tropical storms or hurricanes) that develop during hurricane season.  2005 was, if you remember,  a very unusual year.  There were 28 named storms in the N. Atlantic in 2005.  That beat the previous record of 21 names storms that had been set in 1933.  Of the 28 named storms, 15 developed into hurricanes.
















Hurricane Katrina making landfall on Aug. 29, 2005. (source)


The Saffir Simpson Scale is used to rate hurricane intensity (just as the Fujita Scale is used for tornadoes).  The scale runs from 1 to 5.  Remember that a hurricane must have winds of 74 MPH or above to be considered a hurricane.  Category 3,4, and 5 hurricanes are considered "major hurricanes" (in other parts of the world the term super typhoon is used for category 4 or 5 typhoons).















The converging surface winds associated with a hurricane sweep surface water in toward the center of a hurricane and cause it to pile up.  The water sinks and, in deeper water, returns to where it came from.  This gets harder and harder to do as the hurricane approaches shore and the ocean gets shallower.    So the piled up water gets deeper and the return flow current gets stronger.

The National Weather Service has developed the SLOSH computer model that tries to predict the height and extant of a hurricane storm surge (SLOSH stands for Sea, Lake, and Overland Surges from Hurricanes).  You can see some animations of SLOSH predictions run for hurricanes of historical interest (including the Galveston 1900) hurricane at a National Hurricane Center website (http://www.nhc.noaa.gov/surge)