I wanted to take some time to lay out some scenarios for everyone as it relates to Laura’s path. While the path is going to determine the strength and vice-versa, and we can estimate some things from the eventual path, this breakdown isn’t going to focus on intensity as much as “where” this storm may go – and why. And what to look for in the next 24 hours to determine if you (where ever you are) need to take action.
First things first, I really want to point out that this forecast is coming into better focus now that Marco is out of the way, but there ar still a few pieces of the puzzle that aren’t “locked in” and so there is a bit of uncertainty with the current forecast from the National Hurricane Center – in both track and intensity.
From the NHC
So! Here is the 1AM forecast for Laura from the National Hurricane Center:
A breakdown
And while I can’t speak from the NHC, here is a look at some of the current conditions and the ‘pieces to the puzzle’ meteorologists are tracking to come up with the forecast for Laura. As well as a breakdown of what those pieces mean and where they may go and why it matters.
On the map we have Laura (L), the ridge of high pressure (H), the upper-level Low (UL), the direction of each (white arrow) and the mid-level winds (blue arrow). There is also the black lines indicating the alleyway for Laura to the north, given the pattern in place, and the purple show the general path of the forecast from the NHC.
Notice that both the UL and the H are moving west. They are doing so at a slightly slower speed than Laura is moving. In fact, the UL is currently nearly stationary and barely drifting back to the west.
The space between the two, where the winds in the mid-levels converge (blue arrows) is the alley to the north. That is where there is a weakness between the ridge to the east and the one (off the map) to the west… AND the place there the flow around the mid-level low is directing Laura.
So the current – as of this writing – alleyway north It runs from about Houston, Texas to the mouth of the Mississippi River. Where Marco just died.
But that is just right now. And Laura is just now entering the Gulf.
So the eventual alleyway north is going to move between now and the time that Laura makes it to the center of the Gulf, and then shift again as it moves toward the coast, and then shift again after it makes landfall.
Option 1: Little-to-no movement
This scenario shows no real movement in the H or the UL. And, thus, the alleyway is relatively unchanged, too.
If anything, the ridge shows a bit more assertion into the Gulf, but the UL doesn’t really budge. This thins the alley north to – generally – along the Louisiana coast and extreme eastern Texas.
Sort of.
If there is very little movement, as shown in this model, there is still a chance that Laura could push further west before feeling enough of a tug from the Coriolis Effect to move north. So that alleyway, despite having a westward edge on the east side of Houston, would likely be on the west side of Houston.
Now the final track inside of that alley will be dependent on the strength of Laura. In this case, a stronger storm would take a more southerly track and make it further west before making the turn north. Meaning it would glide up the western side of the alley. A weaker storm would likely gain latitude a bit faster in this scenario, and take a route up the eastern side of the alley.
Why? Because a stronger storm with deeper convection should feel the push of the ridge a bit more as the deeper cloud deck would be more susceptible to the mid-level and upper-level winds.
Option 2: Everything moves West
In this scenario, the H and the UL both jog west a bit. Teh H moves a big more. And that forces the alleyway to shift closer to Texas.
This may also allow for a more robust development for Laura. It would have more access to warmer water. At the same time, though, the closeness of the ridge, nudging it along, would also limit the ‘exhaust’ on the east side of Laura with the pressure of the wind blowing into the system.
The same rules as the last scenario would apply here. A stronger storm would continue to trek further west and a weaker storm wouldn’t feel as much of a push to the west and could make the turn north a bit sooner. This puts places further west along the Texas coast in the potential path.
Option 3: Super assertive ridge
In this scenario the ridge, H, really gains strength and pushes itself halfway across the Gulf. This is actually a pretty reasonable scenario. This H has been following Laura for a while now and the modeling has continued to under-estimate how far west it will build each model run.
In this case, the UL in Texas isn’t as well-defined and the flow on the east side of it isn’t as strong. That leaves the west side of the alleyway without a wall. Now the question about Laura’s track will be answered by Coriolis around the edge of the extra-strong ridge.
This is probably the most head-scratcher option because now we aren’t given an “alley” for Laura to use. And the final track is dependent on two grey areas, Laura’s strength and the ridge’s strength.
Which option is the most accurate?
It could be argued that the last one – based on recent history – may be the most accurate. Where the ridge is more pronounced into the Gulf and the upper-low isn’t as strong. This opens the door for a further westward track, too. So places like Houston, Corpus Christi and places near by and between need to keep close tabs on Laura, even if they are not currently in the cone.
The interesting part is that each one of those options eventually put Laura making landfall within 75 miles the Sabine National Wildlife Refuge by Thursday morning. So while the alleyway may look pretty wide – stronger storm vs weaker storm, stronger ridge vs weaker ridge – the final path when putting all the variables into the pot may eventually shake out with a pretty similar outcome.
And that outcome lines up with what the NHC is predicting.
A couple of notes about intensity and wind field
Since this storm has a pretty large wind field right now after scraping by nearly every island in the Caribbean, it may take it some extra time to wrap itself up and intensify. But any delay in that, will not be the limit to its top-end eventual strength. So, please know, that if in 24 hours it is still a Category 1 Hurricane, that does not mean that it will – for sure – stay that way.
It may take a little extra ‘umph’ to get the ball rolling on intensification, but once it is rolling, the only limit will be how much time it has over the Gulf before landfall and how it eventually interacts with the UL and the H.
And once the storm does intensify, that wind field will continue to grow, so this may be a pretty massive storm – from a wind perspective, by the time things are all said and done.
Could it make landfall along the Mississippi Coast?
At this point it looks unlikely, but not impossible. If it did, it would need to be a much weaker storm system that was moving much faster.And the ridge to the east would need to weaken. Adn the upper-low to the west would need to move east into the Gulf.
So sure, it could happen. But it is highly unlikely.
