After having 20 named storms, the second-most on record through that date, before the start of October, it has been a historically quiet month of October in the Atlantic basin. Thus far, no tropical cyclones have formed in the month of October in the North Atlantic. The last year to have no tropical cyclones to form during the month of October in the Atlantic was 2015, which was a very strong El Niño year. What makes this inactivity even more surprising is that La Niña conditions have developed, which usually leads to increased activity in the Atlantic basin. Last year, also a La Niña year, saw a record-breaking 3 major hurricanes form during the month of October. The last year to have no tropical cyclones form during October during cool-ENSO conditions was 1983 – a very quiet season that featured a total of only 4 named storms during the cool Atlantic Multidecadal Oscillation era. 2021 will still end up as the third or fourth most active season on record in terms of named storms despite this lull in activity, but reaching the auxiliary list of names, which appeared very likely a few weeks ago, is now uncertain.

The primary reason this month has been quiet in the Atlantic basin is above-average vertical wind shear over the Caribbean Sea and subtropical Atlantic, typical hotspots for October hurricane activity. Even more surprising for a La Niña year is that the eastern Pacific has seen two hurricanes develop this month, Pamela and Rick, although both somewhat underperformed intensity forecasts.

There is still a chance that the Atlantic could have one named storm develop this month. Invest 94L,, a non-tropical area of low pressure, could acquire some tropical or subtropical characteristics late this week over the northern Atlantic. The National Hurricane Center (NHC) gives 94L a 10 percent chance of development within 48 hours, and a 40 percent chance within five days. 94L does not appear to be a threat to any land areas. There also remains a possibility that tropical cyclogenesis could occur in November; the month of November averages one named storm approximately 3 out of every 4 years. The most common hotspots for November tropical cyclogenesis are the subtropical Atlantic and southwestern Caribbean Sea. The vast majority of November tropical cyclones do not affect the United States.