September has turned out to be the calmest month for tropical storms or hurricanes in 13 years and or since 1997.

In September of 1997, only 1 named storm occurred. (Hurricane Erika)

This year,  2 named storms have occurred: Tropical Storm Erika and Hurricane Fred- during the month.

September is historically, the most active month for tropical activity. (hurricanes and tropical storms)

The month averages four named storms, including two hurricanes.

The most active September for tropical storms and or hurricanes since 1997 -was in 2002, when 8 named storms formed. (4 tropical storms and 4 hurricanes)

El Nino is the main cause of the unusually quiet month.

During El Niño years, wind shear increases across the Caribbean and the Atlantic, preventing tropical disturbances from developing and or strengthening into tropical storms or hurricanes.

Wind shear removes the heat and moisture the storms need from the area near their center.

Shear will also distort the shape of a hurricane by shearing it (blowing the top away from the lower portion), so that the vortex is tilted.

(WIND SHEAR ACROSS THE ATLANTIC BASIN DURING THE PAST 24 HOURS)

The last significant El Nino event occurred during the hurricane season of 1997  and only 7 named storms formed- during that year.

Hurricane season of 2009 is on a similar track with only six named storms, thus far.