November hurricane outlook

November is here. What kind of activity can we expect this month from the busiest hurricane season on record? Historically, only about 5% of all Atlantic tropical storm activity occurs after November 1. Between 1871 and 2004, 57 tropical storms have formed in November. Of these, 28 became hurricanes, and four of these, major hurricanes. So on average, one tropical storm forms in November every other year, and we can expect a November hurricane about one year in four. Given that this is no ordinary year, the chances of getting a November storm are much higher than average. The Caribbean continues to be dominated by a deep layer of winds from the east from the surface to the upper Troposphere, conditions that mean low wind shear and a favorable environment for tropical storm formation. This deep easterly flow is forecast to continue for at least the next week, so we will have to watch all the tropical disturbances that may form in the Caribbean. There is a tropical disturbance just south of Hispanolia to watch today, but this disturbance is struggling with a lot of dry air being wrapped into it by an upper-level low pressure system just west of Hispanolia, and no tropical storm formation is likely through tomorrow in the Atlantic.

Farther north, in the Gulf of Mexico and Bahamas, strong westerly winds characteristic of the typical Fall weather regime over North America have settled in, making tropical storm formation unlikely in this area. As we can see from Figure 1 below, the central and southern Caribbean are the primary breeding grounds for November tropical cyclones in the Atlantic. Here, the ocean temperatures remain warmest the longest. The typical way a tropical storm develops in November is that a cold front pushes off the coast of North America, and its tail end remains over the southwest Caribbean. The remains of the cold front have a little bit of spin, and this area festers over the warm Caribbean waters for three to five days, and finally organizes into a tropical storm.


Figure 1. Preferred formation area and tracks for November tropical cyclones.

Historical November tropical cyclones
The most extraordinary November hurricanes was "Wrong-Way Lenny", which affected the northern Leeward Islands as a strong Category 4 hurricane with peak winds of 155 mph on November 17-18, 1999. Lenny was the first storm to have an extended west-to-east track across the central and eastern Caribbean Sea in the 135-year Atlantic tropical cyclone record, and was the strongest November hurricane on record. Hurricane Gordon was the deadliest November hurricane. It claimed 1122 lives in Haiti when it passed just west of the country as a tropical storm on November 13, 1994. Lenny claimed six lives in Costa Rica, five in the Dominican Republic, two in Jamaica, two in Cuba, and eight in Florida. Property damage to the United States was estimated at $400 million (1994 dollars), and was severe in Haiti and Cuba as well.

Three November hurricanes have hit the U.S.--an unnamed 1916 Category 1 hurricane that hit the Florida Keys, an unnamed 1925 Category 1 hurricane that struck Sarasota, Florida, and Hurricane Kate, which struck the Florida Panhandle on November 22, 1985.

Jeff Masters