Saturday Morning Tropical Weather Update

July 25, 2020

This is a long one and I'm going to share a lot of images today, starting with the Atlantic 5-Day outlook. For a synopsis Hannah is the big story at the moment but I think we'll have something even more concerning next week. Gonzalo and Hannah flip-flopped with Hannah becoming the first 2020 hurricane and Gonzalo falling apart a bit earlier than expected.

Not to minimize the impact of Hannah on Texas, but the big story continues to be the new tropical wave now in the Eastern Atlantic off of the African coast. This product below is called day cloud phase with low clouds colored blue and high clouds pink. You can easily see the wave off of the African coast as well as Hannah in the Western Gulf and what's left of Gonzalo.

The NHC has designated this wave as Invest 92L which is helpful because we'll start seeing some of the specialized hurricane models take a look at this. Looking at the models the Euro was almost an outlier initially with the GFS showing no development and the other models in between, that is no longer the case. Over the last few days every major model has jumped on board with developing this system. Below I'm going to share several model products but I want to emphasize that none of these are a forecast. For one thing most of these are out seven days from now, which is a few days beyond what is considered to be reliable. Also, until a storm develops models have trouble getting a handle on exactly what is going on. What we can do is get an idea what the trend is if we sort of lump these together. It's not exactly scientific but it can give us some confidence looking at the longer term. I'm also showing a few different model products based on what is available and depending on what I think best shows the situation.

With that said, let's start with the Euro (ECMWF) and its 51-member ensemble (EPS). These are for the same time frame. You can see that the operational model (ECMWF) has a weak system in the Central Caribbean where the ensembles show some stronger possibilities to the northeast. It is subtle, but there are several weaker systems showing up in the Central Caribbean in agreement with the operational model. You can see this better on the spaghetti map which shows weaker tracks through the Caribbean and stronger tracks to the northeast, with maybe a few more southern tracks than northeast.

Now for the operational GFS and its 21 member ensemble (GEFS). This may be showing the opposite with the operational GFS showing a northeast track and the GEFS maybe weighted more to the south. I'm not sure that the GEFS spaghetti map is showing all 21 members so the MSLP heat map may better represent the GEFS in showing a majority of the members to the northeast. It could be that these northeast members are just stronger, washing out the weaker solutions.

Now let's look at the UKMET, Canadian operational model (CMC), and Canadian ensemble (GEPS). I only have access to UKMET products out to 144 hours but both Canadian products are at the same time frame as the Euro and GFS maps above. Both the UK and CMC are favoring the northeast track, but there's quite a bit of spread on the GEPS, maybe slightly favoring a more southern track. Not shown are the German ICON and Australian ACCESS models, which favor northeast and southern tracks respectively.

I think we can be fairly certain that we'll see some sort of development as 92L approaches the Lesser Antilles next week. To hazard a guess on a consensus, a track through the Northeast Caribbean right across the Greater Antilles looks favored at this time. This could end up being a good thing for the US as this may take the storm across some large mountainous land masses depending on the exact track. I think we can also say that a track more to the northeast favors a stronger storm, where a more southern track favors a weaker storm, at least out to about 1 week. One thing to note is that tracks through the Caribbean can favor weaker storms due to the general environment that exists there. A southern track would be more concerning for us on the Gulf Coast but a northeast track does not mean that 92L would not enter the Gulf. It could very well run up the east coast or it continue an east-northeast track north of Cuba right into the Gulf. I also don't want to discount the more southern track from the ECMWF just yet. It was the first to really pick up on 92L so it may be handling this the best even though it is a bit to the south of most of the other models. A possibility could be that we see a weaker storm move through the Caribbean that strengthens as it curves into the Gulf.

I wasn't expecting to send another update until early next week but with all the models jumping on board I decided to send one a little earlier. As we move into next week we will hopefully get a better idea on what 92L is going to do.

Have a great weekend and go stock up your hurricane kit if you haven't done so.

Chris