Blame El Nino for 2009 tropical season (Part 1)

This year has been a rather unusual year in the tropics from what I was expecting. Hurricane in the Atlantic peaked in 2004 - 05 and while activity has been fairly high in the years since, there have been very few landfalling storms with Gustav and Ike being major exceptions.

2009 was expected to be an average to slightly above average year with as many as 14 named storms. Before the season began the forecast was reduced by almost half to 7 - 11 storms. The end result was 9 named storms including 3 hurricanes, 2 of which were major.

Why such a mild season? Global warming alarmists have been saying for years that the number and intensity of hurricanes would increase as a result of increasing carbon dioxide concentration. A more scientifically viable theory is that we are still in the midst of an active period in the Atlantic Multidecadal Oscillation. The MDO is a regular, predicatable pettern of hurrricane activity in the Atlantic Basin. Activity was very high in the 30's and 40's and was high again in the late 90's and early to mid 2000's. But this year seemed to have unusually low activity.

The low tropical activity can be completely attributed to the presence of El Nino this year. El Nino occurs when the Central and Eastern Pacific Ocean become unusually warm, paricularly near the equator. As a result, wind shear in the Atlantic increases significantly. The end effect is a significant reduction in tropical storms in the Atlantic and an increase in storms in the eastern Pacific.

Colorado State: Atlantic Hurricane Season Quietest Since 1997 (Wall Street Journal)

NEW YORK (Dow Jones)--The Atlantic Hurricane season, which officials ends Nov. 30, will go into the record books as the quietest since 1997, due to the impact of the El Nino weather phenomenon, forecasters at Colorado State University said Thursday.

The season featured nine named storms, three hurricanes and two major hurricanes, with sustained winds of 111 miles per hour or greater. Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 major hurricanes per season.

In their far-forward December 2008 forecast, experts at Colorado State projected an above-average season, with 14 named storms and seven hurricanes.

The forecasters said the impacts of El Nino, unforeseen at the time, sharply reduced hurricane formation, and they reduced their storm expectations as the season progressed.

"Activity in 2009 was reduced considerably due largely to the moderate El Nino event that developed," said William Gray, who has been issuing forecasts for 26 years. "This event generated significantly stronger-than-average vertical wind shear, especially in the Caribbean and Gulf of Mexico."

The forecasters said five named storms dissipated over the open ocean this year, a fairly rare occurrence, caused by unusually high levels of vertical wind shear, caused by El Nino.

In the eastern and central Pacific, 17 named storms formed including 7 hurricanes. While the Pacific season is typically longer and more active than the Atlantic, the first half of this year was very active especially along the western coast of Mexico. The warmer water resulting from El Nino created conditions conducive to hurricane formation. Tropical activity was particularly high during the first half of the season.