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2009 Season in Review

Posted by Andy Johnson under Daily updates

The 2009 Atlantic basin hurricane season was more inactive than normal. Looking at the numbers of tropical cyclones does not tell the whole story. There were 9 named tropical storms, 3 hurricanes and 2 major hurricanes. This compares with the long term averages of 11 tropical storms, 6 hurricanes and 3 major hurricanes (winds greater than 110 MPH).

In addition, the strength and duration of the tropical systems was weaker and shorter than normal, respectively. The National Hurricane Center has an objective way of measuring the relative strength of the season. In 2009 the Accumulated Cyclone Energy (ACE) was only  50 which is less than half of the average which is 102.3. This is the lowest ACE since 1997. So, in addition to the fact that the total number of tropical cycloness was below normal, the total energy of the season was less than half of normal.

The primary reason that the season was so weak was the presence of  an El Niño , which produced stronger than normal shear especially in the Caribbean Sea. A secondary reason was drier than normal condition in the mid levels of the atmosphere throughout much of the areas that are usually favored for tropical storm development.

There were no named storms in June or July, 2009. The season did not start until Ana developed on August 15. We came very close to making it a later starting season than another El Niño year  - 1992. Even though 1992 was a generally weak season, the year is remembered for Hurricane Andrew which began on August 17.

Due to the fact that no hurricanes hit the United States and the strength of the total season was well below normal, fortunately loss of life was also low. The total direct death toll from hurricanes in 2009 was four.

The figure below shows the path of tropical storm Ana. Ana was a short lived storm that dissipated over an area where intensification ususally occurs. Tropical systems that weaken over warm tropical water, as opposed to, land or cold water are more likely to do so in an El Niño year. In fact, there were four other named storms that also dissipated over warm water regions.

The figure below shows the path of Hurricane Bill,which was the strongest hurricane of 2009. Bill was a classic Cape Verde type of hurricane . Bill reached Category 4 status on the Saffir-Simpson scale. Fortunately, for the United States, Bill recurved before making is as far west as the U.S. Bermuda was not so lucky and experienced some gusty winds. A place that is not normally associated with hurricanes, Nova Scotia, experienced gale force winds along the southern coast from Mahone Bay to Halifax. Bill was responsible for 2 deaths.

 The figure below shows the path of Tropical Storm Claudette. Even though the path does not indicate it, the precursor circulation of Claudette affected the lower and middle Florida Keys with heavy rain. Claudette was the only Florida landfalling storm and crossed the coast at Ft. Walton Beach on August 17.  

The figure below shows the path of Tropical Storm Danny. The map doesn’t tell the whole story, though. Danny was absorbed by an extratropical low and provided moisture and energy as the new system moved to the northeast. Eventually, ex-Danny caused strong winds once again to the south coast of Nova Scotia.

 Erika was another example of a tropical storm that weakened in an area that one would normally expect intensification in the middle of summer. Erika caused moderate rainfall totals in the Lesser Antilles but she was not responsible for any deaths or major damage.

Fred, shown in the figure below, started out as a very strong system in the eastern Atlantic but fizzled due to shear and dry air before even reaching the central Atlantic.  Fred was only the third storm on record to become a major hurricane eat of 35° West.  

Grace (shown below) started out as an extratropical system. She developed in relatively cool waters near the Azores Islands. Grace moved northeast towards Ireland before merging with another extratropical storm.

Henri always existed in a strong shear environment. The surprise with Henri was not that is dissipated so quickly but that it developed at all.

Ida (shown below) was the biggest surpise of the season. After persistent shear in the Caribbean throughout the hurricane season, oddly enough Ida developed in November. Ida created a few anxious moments along the Gulf coast as she strengthened to a category 2 storm in the Yucatan Channel. Ida succumbed to shear and cooler water temperatures in the northern Gulf before making landfall near Dauphin Island, AL as a minimal tropical storm. Even though it has been widely reported that Ida was the second latest tropical cyclone to make Gulf Coast landall, I count it as the 3rd latest Gulf landfall. A hurricane in 1925 crossed the coast near Brandenton on the night of November 30 and the morning of December 1. Also, Hurricane Kate struck near Apalachicola on November 21. In addition to Danny, Ida also provided energy to an extratropical storm. Even though the offical track does not show it here, ex-Ida went on to cause near record tidal flooding in Chesapeake Bay