May 28, 2024
I hope you all had a great holiday weekend and that the rain stayed away enough for you to enjoy it. The North Atlantic hurricane season begins this Saturday on June 1st and I wanted to give you an idea of what we may be in store for this season. To start with, you should prepare the same for every hurricane season. All it takes is one storm to impact you for it to be a busy season for you. That being said, if the early seasonal forecasts are correct we may be in for a rough time. If you stop reading here, do this one thing and watch this video from Dr. Levi Cowan. He does an excellent job explaining the possibilities for the coming season. I recommend subscribing to his channel as well. He doesn't produce too many videos but when he does they are usually something you want to pay attention to.
Now for the season outlook...The Barcelona Supercomputing Center (link) compiles the forecasts for over 20 different agencies and groups that provide seasonal hurricane forecasts. The current compilation is below.
You can see that most forecasts are in the red zone, showing a strong consensus that we can expect above normal activity this season. Note that the above is for hurricanes, not named storms, which could easily be double what is shown. One of the most well known seasonal forecasts is the one from Colorado State University (CSU). Their preseason forecast this year, which they describe as "extremely active," is the highest from them on record! They are forecasting 23 named storms, 11 hurricanes, and 5 major hurricanes. The 1991-2020 average for these is 14.4, 7.2, and 3.2 respectively. Along with the expectation of a high number of storms from CSU is higher than normal landfall probabilities for every part of the US. Their probabilities for at least one major hurricane making landfall is 42% for the Gulf Coast (Brownsville, TX to Cedar Key, FL), 34% for the East Coast (Cedar Key south to the Keys and then north up the East Coast), and 66% for the Caribbean (averages are 27%, 21%, and 47%). NOAA's forecast is similarly high if you'd like to look at it. While higher activity does not always mean a high number of landfalls, generally more storms equates to more landfalls. Early things I'm reading indicate storm formation locations and expected steering current patterns will favor quite a few landfalling storms but we'll have to wait and see what happens.
So what is driving these high forecast numbers? One of the main factors is that we are transitioning from El Nino to neutral conditions with La Nina conditions expected later in the summer. A neutral ENSO (El Nino Southern Oscillation) or La Nina state favors tropical development due to lower wind shear in the Atlantic basin. One of the other factors (the primary factor according to CSU) is that sea surface temperatures (SSTs) across almost the entire North Atlantic are well above normal and this is correlated with a greater number of storms as well as the potential for stronger storms. Below is the current SST anomaly map (difference from the 1981-2010 average). That is quite a bit of extra energy stored in the ocean compared to a normal season and with the forecast being for this anomaly to persist it is expected that there will be plenty of fuel for tropical cyclones.
So what might the season look like? Storms can and do form almost anywhere anytime, but here is the typical pattern. Here in late May and early-mid June we're in the part of the season where we may see homegrown storms form in the Caribbean, off the East Coast, or even in the Gulf from energy left over from a passing cold front or a Central American Gyre (CAG). There have been a few hints of a storm in the Caribbean or off the East Coast but no strong signals so far. Later in June and into July activity in the tropics tends to stay at a low level with maybe a storm or two forming in the Caribbean or Gulf. Activity starts to ramp up around the 1st of August as we get into the part of the season where storms start forming in the deep tropics from tropical waves moving off of Africa. These are the long track storms we sometimes watch for a week or more as they move across the Atlantic. This activity potentially continues a few months with the peak of the season coming on September 10th on average. During this time some tropical waves have to travel farther to find a favorable environment which leads to some storms forming closer in in the Caribbean or off the East Coast. After the September peak activity slowly decreases and storm formation shifts back to the Caribbean as we head into October and early November. From what I have read I think we'll see most of the activity during the normal peak lasting maybe later into the fall. For more details on seasonal norms with lots of maps and charts see this link.
Don't wait to prepare and think about how a storm may impact summer travel plans. If you need a refresher, below are a few good links on how to prepare. I'm far from an expert but I'm always willing to answer any questions or point you to a good resource.
https://www.redcross.org/get-help/how-to-prepare-for-emergencies/types-of-emergencies/hurricane.html
I'll probably send out tropical weather updates every two weeks or so and of course more frequently as warranted. I am way behind putting together a summary of our extended severe weather season, which I really hope has come to an end finally, but I'll do that soon.
Chris
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