11 September 2019

Tropical wave heading for Bahamas, Florida, then Gulf coast

Although there are no named storms in the Atlantic today, there are a few disturbances and waves of interest.  The first is over the far eastern Bahamas and will have an impact in the Bahamas, the Florida peninsula, and then likely the northern Gulf coast in the coming days.
Map with surface wind flow denoted by white lines, moisture (precipitable water) in background shading, and an "x" marking the center of the three features of interest. (earth.nullschool.com)
Significant development is not expected at this time, especially while over the Bahamas and by the time it reaches Florida on Friday.  Those areas will experience rainy and breezy conditions -- even in the very slim chance it becomes a tropical depression or low-end tropical storm in the near future.  But as you can see from the satellite loop below, it is broad and disorganized.

Seven-day rainfall forecast (in inches), valid from today through next Wednesday. (NOAA/WPC)
But after crossing the Florida peninsula, some development is likely, as favored by the majority of models.  The most recent European model ensemble guidance is shown below, and it is fairly consistent with the past few runs.  It shows the track and intensity of any low detected in the member forecasts, from today through Monday, every six hours. In this run, all members remain well below hurricane intensity, but largely agree on a track into the northern Gulf coast.  If this does reach tropical storm status at some point, the next name on the list is Humberto.

The other two areas of interest are in the deep tropics, east of the Lesser Antilles. Neither is likely to develop in the foreseeable future, but will be watched very closely of course -- after all, it's mid-September and they're African waves.  However, they are both battling dry air and wind shear.  The western one would reach the Lesser Antilles sometime around Monday, and the one south of Cabo Verde has a long way to go to be a concern (see map at top of the post).

The ACE (Accumulated Cyclone Energy) is at 115% of the average for this date, using the past 50 years as climatology.  Unless a named storm forms soon, 2019 will slip behind the average again on Sunday. This time of year is climatologically active, so every day without something is anomalous.  Of the seven named storms so far this season, Dorian alone contributed 82% of the total ACE!

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