September 3, 2011 by staff
Hurricane Katia, From 2004 to 2008, with a brief respite in 2006, the United States was beaten by a hurricane after another, hurricanes Ivan, Katrina, Rita, Wilma and Ike, the name of the most infamous. Then there were three years of silence, in which no hurricanes made landfall here.
But this year’s hurricane season in the Atlantic has been at the top, with 12 named storms in three months and 13 on the road if the tropical depression 13, is currently moving through the Gulf of Mexico toward New Orleans, becomes a tropical storm. For perspective, which is the total number of named storms in a normal view of six months of the season. Only two, Irene and Katia have been hurricanes – the rest remained tropical storms or tropical depressions – but with the season only half over, the more is without doubt.
Why is the 2011 season proving to be more active than 2009 or 2010 seasons? Why were less active season than those from 2004 to 2008? And what explains the anomaly of 2006, after breaking the record, the 2005 season?
Typical explanations of variance from season to season in hurricane frequency and severity are Ni? O or Ni? One, which are periodic phenomena characterized by unusually hot or cold temperatures in the equatorial Pacific Ocean, respectively. Affecting weather patterns worldwide, including the formation of hurricanes in the Atlantic. Climatologists believe El Ni? O increases the frequency of hurricanes in the Pacific Ocean and decreases the frequency in the Atlantic Ocean, and vice versa for the Ni? A.
But this year, is not only a very weak La Ni? One, so how do you explain the unusually active season?
“So far this season, the wind structure in the upper levels of the troposphere has allowed more storms to form,” said Corene Matyas, a hurricane expert at the University of Florida, IBTimes. “The tropical Atlantic has experienced wind shear is less than normal. High wind shear prevents the formation of tropical systems or weakened if they are formed. He has been wetter than normal the middle and upper troposphere over many parts of the Atlantic basin. ”
Merriam-Webster defines the wind shear as “a radical change in the speed and wind direction that occurs at a very short distance,” either from east to west or north-south. Tropical storms and hurricanes gain strength the heat released by condensation of water vapor in the liquid, according to Weather Underground, and wind shear inhibits this process by removing heat and humidity and the vortex distorting or inclination of a storm. “A vortex inclined usually a less efficient heat engine – the delicate balance of the tributaries of low level winds and upper-level winds emanating to vent the storm broke,” the Weather Underground’s Web site says.
The terminology is a bit dense, but the point is simple: wind shear weakens the forces that tropical storms and hurricanes of energy, and wind shear is low this year, so more storms have been able to uninhibited form.
A much longer-term factor is the Multidecadal Atlantic Oscillation, which is “a natural cycle of fluctuating sea surface temperature that lasts for 20-40 years on average,” Matyas said. “The AMO has been linked to hurricanes in the Atlantic basin, as well as rainfall and temperature patterns. So the hurricane activity has occurred since 1995 in the Atlantic basin has been more active during the 1970 and 1980. ”
But wait, you wonder – if this hurricane production phase has been going since 1995, which explains the large year to year differences in the activity?
“There can be from year to year fluctuations in activity,” said Matyas. “Remember that in 2006, forecasters expect an active season on the heels of record for the 2005 season. However, an unexpected The child developed, and this condition is associated with reduced hurricane activity than normal in the Atlantic. ”
That is, the AMO has caused the hurricane season since 1995 to be more active than the average of the seasons before 1995, but within this general climate, factors such as El Ni?o? Or you can have a substantial effect on how many storms develop from year to year. This makes it difficult to predict with certainty how active hurricane season is coming.
“Due to the cycle of AMO, it is likely that hurricane activity will be more than normal on average during the next decade,” Matyas said, “but some years may still have a lower than normal activity within this time period. “
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