Tropical Storm Laura begins her journey towards the Gulf of Mexico

by Jordanna Sheermohamed of Weather Forecast Solutions

Tropical Storm Laura has created quite the headache for meteorologists this week, with so many of the difficulties being able to pinpoint where the actual center of the system was located. After all, you can’t forecast the direction of a system when the center keeps shifting/relocating! It’s a two-fold problem with tropical weather forecasting; track and intensity.

The system struggled to align several times over the last days, appearing first as an elongated wave which could have produced the center along the more southern side or northern side. The low-level and mid-level centers of the system didn’t seemingly want to cooperate, which is necessary to locate the ACTUAL center of a hurricane, and thus determine its potential track and intensity (again, located over open waters or mountains).

The vertical tilt of a hurricane requires it to lean from SW to NE like this: “/”. This is an indication that the wind shear increases with height just the right amount: not enough to blow the high level clouds too far downstream from the system therefore destroying it’s vertical integrity, not too little to force the system to choke itself, but just the right amount to allow it to vent it’s heat at the adequate rate it could replenish itself. The system struggled to identify itself as it underwent a tug-of-war situation between the low-level and mid-level center, with each attempting the force the other to reestablish itself accordingly.

Then became the land interaction game, otherwise known as “hurricane bowling”. Would it slide over Puerto Rico or Hispaniola and get torn apart by the island’s rugged terrain? Would the low level center remain to the south of the Greater Antilles, over the warm luxurious Caribbean waters? Would the system “thread the needle” and remain to the north of the Greater Antilles, again allowing full access to warm waters and a direct one-way ticket to the Bahamas and Florida. Laura continued to tout multiple options in the short term track, each one making the long-term forecast that much more difficult to narrow down to potential outcomes.

Then she went south, with Puerto Rico and Hispaniola offering little in the way of destroying the system because Laura’s low level center appeared to reinforce its’ presence south of the islands, allowing for convection to occur, clouds to build, and storms to explode.

Next up to bat today was Cuba, in which we saw Laura skirt just far south enough to keep the convection engine churning. The overall hopes was that the island chains would disrupt or weaken it before it entered into the Gulf; one last fight! It didn’t. So Laura will indeed enter into the Gulf with some strength under her belt. Nothing in the way between her and landfall but vast open warm water. The fuel is there, so now it becomes important to understand the “where”.

Think back to that required “Goldilocks” level of wind shear described above. Would Laura continue with a forward speed that would put the system in the wrong place at the right time, shearing off the upper levels to help keep the intensity in check? Or would the system move at just the right speed, to align with an incoming Gulf of Mexico ridge, with minimal shear, giving Laura all the necessary infrastructure to rapidly intensify into a major hurricane before landfall.

Notice I haven’t mentioned hurricane models once. Yet. Because the truth is that they can be VERY helpful when you observe a trend and when the models are able to simultaneously sniff out the obvious options. Laura wasn’t playing nice and gave those models a real run for their money over the last few days. But it’s also important to consider the fact that because so many options appeared, it meant that any option could have been possible. Now that the system is passing the island obstacles, they are becoming into better alignment with potential outcomes. There is little in the way to think that this system wouldn’t intensify before landfall. Even more unfortunate is that there wasn’t much to destroy the system’s integrity before it entered into the Gulf of Mexico. The puzzle pieces are beginning to fall into place.

As to where it will go, systems are driven by what’s going on in the big picture of the atmosphere. You have to look upstream, downstream, north and south, to figure out exactly what players are present and how much they will affect the big picture. It’s like throwing ball into a turbulent lake, and deciding which waves will ultimately determine the ball’s final location. You can determine a likely outcome (this is the National Hurricane Center’s official cone), you can determine the locations that are ruled out (the areas that are well outside the NHC cone), but there’s always those areas that in the maybe’s (areas just outside the cone).

The large scale picture continues to indicate a more westerly track before the northwest turn towards the NW Gulf of Mexico. This means Central Texas to Louisiana finds itself more likely in the cone than anywhere else. This doesn’t safety exists outside of the cone. As per the NHC’s PM ET advisory, “storm surge, wind, and rainfall hazards will extend well away from Laura’s center along the Gulf Coast”.

The next 12-24 hours will help close the gap on potential outcomes, with some location along the Gulf being the unlucky recipient of Laura’s arrival.

For some of you still wondering:

No, an erratic detour isn’t an option, i.e. Florida – The ball in the lake doesn’t suddenly fight against the waves to move at its own discretion.

and

No, Laura will not help resuscitate Marco from the dead to become Storm2020saurusRex.