Q&A of the Day – What Determines Where Hurricanes Go?
Each day I feature a listener question sent by one of these methods.
iHeartRadio: Use the Talkback feature – the microphone button on our station’s page in the iHeart app.
Today’s Entry: Brian, I’ve listened to you for many years including during hurricane coverage. You seem to have a knack for being able to infer what storms we need to be concerned with and even at times where they will go preceding forecasting. For example, you began talking about the Big Bend communities that would be impacted by the direct impact of the hurricane when Tampa was still inside the cone for Idalia. I’d like to learn more about this rather than just looking at models when they come out. How is it that you go about studying systems?
Bottom Line: I love next level questions like these and though I’ve received many hurricane related questions over the years I don’t recall ever fielding this one. The way I go about studying tropical systems is much the same way I imagine most meteorologists do as well with a wrinkle or two added into the mix. The bottom line in determining where any tropical systems will go comes down to which way the winds are blowing – around the system itself. You’re probably familiar with terms like prevailing winds or trade winds, wind fields and steering currents. They’re ultimately responsible for determining whether a tropical disturbance is able to develop into a storm and a storm into a hurricane and so on. They’re also responsible for where those systems will go. Some of them are natural, for example, standard Atlantic trade winds pull towards the west, which is why almost all systems which develop in the Atlantic move towards the west. Some are influenced by climate patterns like La Nina and El Nino – which we’re currently in. All of those factors, and the strength of those factors at any given time, come together in producing the myriad of models that you see and the cones that the National Hurricane Center produces. Like you I’m interested in knowing what’s behind the models, what’s behind the forecasting, and it’s my perception of them which colors my analysis on occasion, like with Hurricane Idalia as well.
Hurricane Idalia produced the most predictable forecast track of any hurricane I’ve covered (in my opinion). That’s the reason I first highlighted it as a concern for the Big Bend when it was still a disturbance in the Pacific and why I spoke of specific communities at a point of impact in the Big Bend two days before impact. The steering currents through the Gulf of Mexico were working like a tight conveyor belt pulling the system directly through the Big Bend with a lot of conviction from the time the disturbance crossed over from the Pacific. That’s why the National Hurricane Center quickly put Cuba and Florida on notice, prior to the storm having even developed. But the key isn’t always what’s happening right now with the winds and the currents around disturbances, it’s what will happen next with them. That’s where all of the science becomes especially tricky and where all of the different models are derived.
The bottom line is that there is always an awful lot happening atmospherically at any given time, especially in the tropics during hurricane season and especially, when you have something other than a neutral climate pattern in place. That’s why at any given time tropical storm and hurricane models may show systems going in vastly different directions. If you study the patterns enough, like anything else, you’ll have a better sense of what’s likely to happen next. As for what I tend to lean on when studying systems... The Cooperative Institute for Meteorological Satellite Studies Space Science and Engineering Center at the University of Wisconsin. They provide complete wind and steering analysis tools that are dynamically updated. Rather than cherry picking computer models to follow (which is unnecessary anyway because that’s what the National Hurricane Center does best), I watch those patterns to see what the winds are doing and to try to infer what influences might impact where a system may go. The less conviction there is in the weather pattern, the harder it is to try to guess where a system may go. The greater the conviction, the easier it is to tell. And that’s for two reasons. First, if a system hooks up with strong steering currents, as was the case with Idalia, its pulled straight along a path. Second, is that strong winds and steering currents effectively block paths for where a system can go. That’s the scenario we’re currently in with Lee in the Atlantic.
The strongest steering currents moving from the east to the west are currently in the South Atlantic pulling towards the Gulf of Mexico (well south of where Lee is). The Gulf, and right now Texas, Louisiana, and Mississippi in particular, are the most vulnerable to the impact of a tropical system if one forms in the South Atlantic or Carribean Sea. In our case, on the east coast of Florida, we’ve consistently benefitted from El Nino influenced upper-level winds over Florida which have been pushing out into the Atlantic. These have effectively operated as a barrier protecting Florida’s east coast from systems being steered directly towards us. The question is if that will continue and what happens next. And that’s where it gets tricky. In the case of Lee, it’s a guessing game about what will happen 8-10 days from now in terms of any potential impact to the eastern United States including Florida. Based on the patterns we’ve seen throughout this hurricane season, and with El Nino intact, it looks very likely that those winds will remain intact creating a strong wind barrier well off of our coast which should push the system towards the north – which is what most longer range models are showing too.
So that’s the story behind the story of how this stuff works and how I go about studying and covering these systems. And for those of us on the east coast of Florida, may the winds continue to be our friends.