July 31, 2024
The National Hurricane Center is still watching a tropical wave as it moves west across the Atlantic. Currently located over the Leeward Islands, the NHC gives this wave a 60% chance of development over the next 7 days. Conditions have just been marginal enough for this wave to remain a player but the environment is expected to improve as it continues west-northwest.
You can get an idea of the possible future of this system by looking at the orange triangle shape and for now that is all you really need to know so you can stop reading here if you want. I'll tell you what the consensus is and then I'll tell you my thoughts. The current consensus is to favor the Euro (which shows development along the East Coast) because it has been very consistent and picked up on the chance of development earlier. You can see this in that most of the triangle stays to the right and out of the Gulf. I am a bit leary of trusting the Euro this early and I'll explain why after I give you a few more details on what the models are showing.
Throughout the history of this system the Euro (both the operational model and the ensembles) have been much more bullish on development than the GFS suite. The Euro picked up on development first, with the GFS only showing development many days later. The Euro, again both the operational model and a majority of the ensembles, has also been consistent at developing a storm near the Bahamas with varying tracks along the East Coast. The GFS operational model on the other hand, which again jumped on board a bit later than the Euro, has been favoring solutions that wait until the wave is in the Gulf before development occurs. The GFS ensembles typically have only had a minority of members showing development with forecast tracks waffling between the Gulf and East Coast and sometimes split between the two. For what it's worth, the Canadian model has favored Gulf development, but it has had some solutions similar to the Euro. But the overall consensus, weighted by the Euro and its 51 ensemble members, favors an East Coast solution. I will say also that the details behind why the different models are showing different solutions favors the Euro as well, people smarter than me see the Euro's solution as the more logical one, so it's not just that they're jumping on board because of a strong model consensus.
Now my thoughts. I think I have explained before that until a center of circulation has formed the models are just sort of guessing at when and where development may occur. When and where the storm actually forms can make a huge difference as to its eventual track and intensity. So there is that piece that is always in play. Also, the Euro (and its ensembles) were wrong with Beryl's track for a long time, it wasn't until just a few days beforehand that they started to show a landfall along the upper Texas coast. It was locked into a more southerly track with Beryl into Mexico and southern Texas. It is a bit counter intuitive, but the lack of a diverse set of outcomes from an ensemble suite (underdispersion) is a bad thing. We know forecasts are uncertain, and when a 51 member model fails to show uncertainty, especially when we know the forecast is uncertain as we did with Beryl and as we do now, that is indicating some kind of bias towards one particular solution. Biases can keep a model from showing a range of possible outcomes or cause a model to favor one influencing factor more so than it should. My concern is that we may be seeing a bias again in this case. It's not that I think the Euro is forecasting the future environment incorrectly, I have no basis for thinking that. I'm just a bit concerned with the overconfidence this early, especially with the Euro's history with Beryl. The Euro's forecast of East Coast development may very well be correct, as I mentioned many people are leaning this way, but I'm not going to feel comfortable about that until other models start jumping on board, until we have an overall consensus. We should have better data in a few days when this starts to tighten up and/or when it's designated an invest and the suite of hurricane models start to run.
So that's a long read and hopefully it's helpful. I think we'll start to have a better idea of where this system may go over the weekend. Hopefully this stays out of the Gulf but it's too early to write that off.
Have a good rest of the week.
Chris
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