Gulf Coast Hurricane Tracker

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Sunday, June 27, 2010

Will TS Alex turn away from the oil?

There is rightfully a great deal of concern regarding whether Tropical Storm Alex will affect the oil in the Gulf of Mexico or if the storm track will take it away from the spill.

Throughout this week, the computer models were very divergent. After crossing the Yucatan Peninsula, the individual model tracks scattered across the Gulf spreading between Louisiana and Florida. As the week progressed, the model predictions focused on two areas for potential landfall - southeastern Louisiana and deep south Texas/Mexico Gulf coast. Many news articles were pointing to doom and gloom stating that the storm was coming close to the oil.

By Saturday, all models were converged on a Mexico landfall as shown in the graphic to the right (source: Examiner). This is the best possible location for a storm that is going to enter the Gulf of Mexico with regard to interaction with the oil slick. So does this mean that there is nothing to worry about with regard to the interaction of the storm with the oil slick? Absolutely NOT!

Models change with new data

Computer models are only as good as the data that are supplied to them. As conditions change, the models change to accommodate the new information. Within a day, model tracks were again showing the potential for landfall in southeast Texas or Louisiana. While the most likely pathway for this storm is towards Mexico, there is a potential that a more northerly route could be taken.

The more north the storm travels, the more that it will affect or impact the area of the spill. Even if the storm track keeps Alex in the western Gulf, the possibility of increased wave action could make an already difficult task even more so. As the storm track takes the storm more to the northern portions of the gulf, the edges of the storm will moves more eastward resulting in heavier surf and stronger winds.

The fact that the oil spill is located in essentially the central Gulf of Mexico, there are few areas in the Gulf where the presence of a storm of any size won't have an effect.

The graphic to the left shows the model tracks as they exist mid-day Sunday. (source: http://www.spaghettimodels.com/). While the vast majority of the storm tracks are showing landfall just south of Brownsville, TX, two are indicating the storm track to pass over Galveston Bay while a third brings the storm to southwest Louisiana.

We should also note that the storm tracks showing landfall in Mexico and Texas are significantly further north than a day earlier. As the steering currents fluctuate, the projected tracks will change accordingly.

Steering Currents

So, the million dollar question is: "Where is Alex going to go?"

One place to look is at the barometric pressure over the southern region of the US. As the diagram shows (source: Golden Triangle Weather Page), there appears to be a ridge of higher pressure over the southeastern US.

The pressure from Tennessee to the Eastern Gulf is 1012 mbar. Lower pressure of 1006 mbar extends from Oklahoma and the Texas Panhandle down into north central Mexico. I assume that even lower pressure is in place further south in Mexico. Also a Bermuda High is developing off the eastern seaboard.

These high pressure regions will tend to push Alex towards the west. However, we must keep in mind that the map above is a snapshot frozen in time. We do not know how long these higher pressure areas will remain in position or if the pressure is high enough to form a blocking high that prevents Alex from drifting more eastward. The further east that the pressure moves, the more that Alex will be able to drift to the east and closer to the oil.

The forecast for Alex is that his forward motion is expected to decrease while crossing land and may even slow further or remain stead while over water. The slower Alex moves forward, the more time is available for the steering currents to shift. As long as Alex is over water, he could change direction and head towards the oil.

Conclusion

Is hurricane tracking just a guessing game? No it is based on science with a bit of art. But the science is of a chaotic system that defies a clear, finite model. Probabilities determine where the storm will go. Looking at the current situation, the probability is that Alex will strengthen to a Category 2 hurricane and will head in a northwesterly direction making landfall somewhere near or south of the Texas-Mexico border. This is the most likely scenario as conditions currently exist.

There is a chance that Alex could become stronger than a Cat 2 or remain as a tropical storm. In my opinion, this will depend on his forward speed. If the forward speed increases and Alex heads straight for southern or central Mexico, then there may not be enough time for further development. I do not think that this is likely.

If Alex slows down and remains in the warm Gulf longer, further development is not only possible but likely. Wind shear appears fairly non existent in the southwestern Gulf, but is strong from Texas through Florida and over to the Bahamas along the coast. This means that the best chance for strengthening is for Alex to languish in the area where he is currently predicted to go - southwestern gulf.

If the storm heads north, it could break apart from the wind shear, but not before considerable damage is inflicted with regard to the oil. As the models show, there is a chance that Alex could head to the north. It is not the favorable path at this time, but weather conditions are continually changing.

We are currently 4 - 6 days out before final landfall of Alex. The best odds are that he will hit northeastern Mexico. But it is not a given. A storm in the Gulf can be a very fickle thing.

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