Closely watching the deep tropics, next storm likely to form soon

We just wrapped up a very quiet first half of hurricane season, and even now in the peak week of hurricane season there's one feature of interest to focus on, but no named storms.  A strong easterly wave exited the African coast back on September 8, and it's now centered about 800 miles east of the Leeward Islands.  Should it reach tropical storm status, the next name on the list is Fiona.  (Fiona was a new name introduced to this list in 2010 after Frances was retired in 2004.)

[UPDATE: this was upgraded to Tropical Depression 7 at 11am EDT on Wednesday]

It has been surrounded by dry Saharan air during its entire trek across the deep tropics so far, and that remains the case today and in the near future.  The longer-range outlook is complicated in terms of development because as it gradually escapes the dry air, the vertical wind shear is expected to increase.  The ocean temperature is plenty warm to sustain any amount of intensification.

Due to these competing factors, model guidance is expectedly diverse.  They agree on it reaching the Leeward Islands on Thursday as a tropical depression or tropical storm, but that's where the agreement ends.  If it remains further south (south of or over the Greater Antilles), it should also remain weak and disorganized.  But if it moves a little more to the north, the global model ensembles generally intensify it quite a bit and keep it going north.  Things can change of course, and the answer should be clear by Thursday.

Even as a disorganized tropical wave, it will bring very heavy rain to parts of the Leeward Islands and eastern Greater Antilles on Thursday-Friday... these are all islands that are infamously prone to deadly flash floods and mudslides.

If the northern set of ensemble members ends up being close to reality, it would be a case very similar to what we just saw with Earl: a slow-moving easterly wave that battled dry air in the deep tropics, turned north by 65-70°W, then strengthened into a hurricane after making that turn.

As far as the overall activity goes, the 2022 season has had 5 named storms, 2 hurricanes, and 0 major hurricanes so far.  Over the 1991-2020 "climate normal" period, the average by now is 8 named storms, 3 hurricanes, and 1 major hurricane.

The Accumulated Cyclone Energy, or ACE, is about 44% of the average value for this date, again using the 1991-2020 period as the baseline.  What makes this season really bizarre is that only 14% of the ACE was actually accrued in the tropics (Bonnie and a little bit of Earl)... the rest was all in the subtropics and extratropics.

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