Weather Blog: November in hurricane season

Tropical Storm Sebastien has formed in the middle of the Atlantic. It is weak and will dissipate within a day or two. (Spectrum Bay News 9)

TAMPA, Fla. – While we are at the end of the six-month hurricane season, we have another storm called.

Tropical Storm Sebastien formed in the middle of the Atlantic Ocean. It is weak and will disappear in a day or two.

November storms, while seem unlikely, are more common than you may think.

There’s a reason hurricane season includes November. Looking back on data from the past 50 years, 24 years even had at least one storm in November. So on average, a named storm occurs every two years in November.

When analyzing the data from the past 50 years, a number of things stand out.

First, there does not seem to be a connection between the incidence of a storm named November and the frequency of storms in that season. There have been very active seasons without the November storms. Consequently, there have been very quiet seasons with one or even two of the aforementioned November storms.

Also note that the vast majority of the named storms in November never affected the country. Most took place in the middle of the Atlantic Ocean.

The seasons that had called storms that struck the United States or Central America later occurred and frequency from October to November cold fronts. In other words, more than likely, there was less wind shear in the Caribbean and water temperatures in the Caribbean, West Atlantic and Gulf of Mexico were warmer and therefore able to support tropical development.

An interesting snack is the occurrence of “subtropical” storms. Before 2002, subtropical storms were not even given names. Before 2002, therefore, there were no named storms that would have been classified differently since 2002. But looking at the data, from 1969 to 2001, there was a subtropical storm in November in at least half of those years.

It’s just that they were mentioned no earlier than 2002. Also, as regards subtropical storms, there have been an average of two names each year since 2002, increasing the named storm averages in the long run.

There were some very notable absences from named storms in multiyear periods. There was a period of four consecutive years in the 1990s without a said November storm and eight consecutive years in the 1970s without one.

With regard to hurricanes in November, of the 24 years with a named storm or more in November, 14 of those years in November had at least one hurricane.

Finally some other facts. In two of the years without the aforementioned November storm, those seasons had named storms after the December hurricane season. And six of those years with a named storm in November had more than one. Those years were 2007, 2005 (which also had a storm in December), 2001, 1994, 1984 and 1980.