24 June 2021

Attention shifts over to Africa... in June??

The large majority of strong Atlantic hurricanes have their origins as "easterly waves" over tropical Africa, and that season is typically August and September.  The waves tend to come off of the continent near the Cabo Verde islands, and we actually refer to that time of year as "Cabo Verde season".  It's quite rare to be paying attention to that area in June, but there's a wave of interest that has a shot at becoming the next tropical cyclone.  NHC is giving it a 40% probability within the next five days.

The European model's 50-member ensemble has been indicating a decent chance of this wave developing into at least a tropical depression in the coming days.  About 10% of the members develop it into a tropical storm, and a subset of those actually reach the Lesser Antilles.  We don't ever take a model run at face value, but the consistency of this has been notable, which gives forecasters some confidence that genesis is possible despite it being climatologically extraordinary.

Track density plot from the ECMWF ensemble out to ten days.  The area in the south-central Caribbean can be ignored... that's a quasi-permanent false alarm.

The map below shows the tracks of all tropical cyclones prior to July since 1851.  There are *2* as far east as this wave is now, so it would be truly remarkable if it developed in the next few days.  If you're curious, the two are a tropical depression that formed just north of Cabo Verde on June 30, 2000, and the other is a tropical depression that formed south of Cabo Verde on June 23, 1974.  You have to go wayyy over to 45.1°W in the central Atlantic to find the easternmost tropical storm formation, and that was in 1933!

Tracks of all known pre-July tropical cyclones in the Atlantic, 1851-2020.

Should this reach tropical storm status at some point, the next name on the list is Danny.  (The name Danny was introduced to the list in 1985 after David was retired in 1979)

1 comment:

  1. Brian, I've not completed repairs from Hurricane Sally. :-) Kindly tell all storms they must head north east along eastern seaboard for the year. :-) Thanks. Jill