Tropics Update, 6 Sept 2023

As expected the former invest area AL95 became Tropical Depression 13 and is now Tropical Storm Lee – by this afternoon it should be Hurricane Lee. Conditions are really favorable for continued intensification, but at the moment while the track is on a path that skirts the Leeward Islands (who should “monitor”) and freaks out Florida (not that it takes much to freak out Florida), at the moment it is not expected to be a direct threat to land. Here are NHC’s Key Messages regarding Tropical Storm Lee (en Español: Mensajes Claves).

The 5am forecast wasn’t terribly different from the previous runs; here is the impact swath using my TAOS/TC model, based on the 5am NHC track:

click any image to embiggen.

On this path the Leeward Islands would be on the fringes – swell (waves) mostly, but no direct impacts. The concern with such a powerful storm is if it goes a bit south then you start to quickly get impacts, so while things look OK for the moment, it certainly makes sense for those in the islands to be watching and ready to act if the forecast changes and warnings are required. The models are, in the words of NHC, “very aggressive” on the intensity forecast, with many spinning up Lee to a Category 5 hurricane within the next 72 hours (!). NHC is “only” forecasting at strong Category 4.

On this track, the usual suspects in the Southeastern US are freaking out and/or gleefully checking their ad revenues. Should they? Probably not freak out, but this weekend will be good for the hit counters. While the straight line of the current NHC forecast is not what you would want to see, it should start to develop a rightward hook – the longer range models (and the meteorological reasoning) at the moment show a pretty radical shift in the steering in about five days. Here is what the major track models are showing at the moment …

If you look at the ensembles, they too are mostly favoring the sharp northward turn in about five days, just after the storm passes the Leeward Islands. Here is just the GFS ensemble tracks. Remember, the main forecast is the blue line – the cloud of gray lines are individual ensemble members, and can’t really be pulled out of context on their own. But the scenarios almost all show the turn:

So what’s the TLDR? Lee is going to be a powerful storm, but all signs are it is not going to have significant impacts in the Caribbean or US other than waves and swell (and therefore rip currents) on the US. We’ll have to see if the storm impacts Bermuda, or potentially even Nova Scotia and Vinland (also called Newfoundland by some revisionists). But that’s a problem for next week and way too early to speculate about.


  1. Truly, thanks, Chuck … a great and professional forecaster / scientist!

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