Satellite image of Tropical Depression 16 over the southwest Caribbean Sea. (NASA)

Hurricane season in the Atlantic Ocean typically ends on Nov. 30. It’s not that storms don’t form past that date — it went beyond December in 2005 — but on average, the tropics are cooling off by this point. Which is why it’s strange so see a tropical depression in the Caribbean on Nov. 21, let alone one that could strengthen into a hurricane by Thanksgiving.

Tropical Depression 16 formed early Monday morning in the southwest corner of the Caribbean, and it’s probably going to become this season’s 15th named storm, “Otto.” If 15 named storms sounds impressive, it should; the last year we had so many storms was 2012, and the average total by the end of a season is 12.

The storm will track slowly west over the next few days and arrive in Nicaragua by Thursday. It is currently stationary over very warm water, and as the vertical wind shear relaxes over the next couple of days, it is forecast to become a tropical storm very soon and possibly a hurricane by midweek.

The last storm to be named in this region was Ida, and that made landfall on Nicaragua as a Category 1 hurricane on Nov. 5, 2009.


(NOAA)

The western Caribbean is a climatologically-favored region for late season development, but by this late in the hurricane season, very few storms have ever formed.

Going back to 1851, we found 35 storms that reached tropical storm intensity on or after Nov. 15 — that’s an average of about once every five years.  The most recent was Melissa in 2013, and the strongest was Kate in 1985. Roughly half of the storms shown on the map below went on to reach hurricane intensity.

Hurricane season officially ends next week, so stay tuned for our season summary!


Tracks of 35 tropical cyclones that reached at least tropical storm intensity on or after November 15. The white dots indicate where the storm first reached that intensity. (NOAA and B. McNoldy)