Sunday, September 10, 2023

 Nova Scotia·Weather

All eyes are on Hurricane Lee in Atlantic Canada

The hurricane may threaten Atlantic Canada late next week

Hurricane Lee is currently tracking westward in the tropical Atlantic.
Hurricane Lee is tracking westward in the tropical Atlantic. (NASA Worldview )

Hurricane Lee is a powerful hurricane slowly tracking through the Caribbean.

There is good forecast model agreement that Lee will continue to track west northwest over the next few days, tracking mainly north of the Greater Antilles.

Beyond that there is still a lot of uncertainty and many questions when it comes to the storm's eventual track.

Here are the five biggest questions we will need answered over the next few days.

There are many factors which will influence the track of Lee in the coming days.
There are many factors that will influence the track of Hurricane Lee in the coming days. (Ryan Snoddon/CBC)

When will the storm turn north?

We're seeing good model agreement that the storm will turn northward at some point in the middle of next week. However, there has been a recent small shift in the guidance, that the turn northward may occur a little earlier. This is important because even a slightly earlier turn will impact the forecast moving forward.

How quickly will the storm move northward?

Where we are seeing some of the largest disagreements between the forecasts is in the forward speed of the storm following its turn to the north. The image below shows the many different model ideas for where the centre of the storm may be on the morning of Sept. 15.

Uncertainty remains in many parts of the forecast, including the forward speed of Lee next week.
Uncertainty remains in many parts of the forecast, including the forward speed of Lee next week. (Tomer Burg/arctic.som.ou.edu)

This is important because the speed of the storm will determine how the storm will interact with a low-pressure trough over eastern North America.

How will the low-pressure trough impact the storm track?

Many of these questions are tied together. How Lee interacts with the trough over the Great Lakes will be critical to the forecast. The trough in question will strengthen over North America early next week as it slowly works toward the Eastern Seaboard.

The strength and placement will be important factors and remain uncertain at the moment. 

How will the high-pressure ridge impact the storm track?

Perhaps most critical to the forecast will be the strength and placement of the high-pressure ridge over Atlantic Canada and the northwest Atlantic ocean through next week.

A stronger ridge of high pressure in the early and middle part of next week will likely slow the storm, which will then have implications for how the storm interacts with the trough, and the eventual track.

A stronger ridge later in the week could push the system further west toward North America or, depending on its position, allow the storm an exit route offshore.

How will Margot impact the high-pressure ridge?

Finally, we have Margot. The latest named storm, which may become a hurricane over the next few days, will track northward through the middle of the Atlantic ocean over the next week or so.

This matters because Margot's track and strength will have implications for the high-pressure ridge over the northwest Atlantic, which will in turn have impacts on the track of Lee.

The track and strength of Margot next week may also have an impact on the track of Hurricane Lee.
The track and strength of Margot next week may also have an impact on the track of Hurricane Lee. (Tomer Burg/arctic.som.ou.edu)

So when will we know more?  

Unfortunately, with so many factors to consider, we likely will not know until early next week where Lee may eventually be heading.

Something to keep in mind next week is that while we will all be focused on the track of the centre of Lee, this will likely be a large storm and its impacts may expand hundreds of kilometres from the centre.

What we do know is that while Lee is currently a powerful major hurricane, the storm will begin to weaken as it tracks northwards next week into waters that are below the 26.5 C threshold tropical cyclones need to maintain strength. 

We will continue to monitor the storm over the next few days so be sure to stay tuned for updates.

Meteorologist Ryan Snoddon says Hurricane Lee is at least a week out from any potential impact in Nova Scotia.

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