Gustav Weakens

Hurricane Gustav has weakened quite a bit during the night. As it crashed into Cuba Gustav was a Category 4 hurricane with winds of 150 mph, only 6 mph short of a Category 5! However, Cuba disrupted the eye of the hurricane during passage over the island and now Gustav has weakened all the way down to a low Category 3, or possibly now a Category 2. The latest Hurricane Hunter recon pass did not find flight level winds above 100 knots, indicating the surface is somewhere likely between 80-90 knots at best, or between 92-103 mph, or only a weak to moderate Category 2.

Why such the strong weakening? Well, first the passage over Cuba was much worse than expected. Earlier the models and forecasters were thinking Cuba would only reduce the winds a little bit (5-20 mph) and not completely disrupt the eyewall of the storm. Instead, Cuba broke down the eye allowing the pressure to come up from close to 940 mb at landfall to 960 mb now. Also, some shear (10-15 knots) has been influencing the system. Earlier the shear was not a factor because Gustav was located under an anti-cyclone which helped eject mass out of the top of the system, and because strong Category 3-4-5 hurricane eyewalls can protect the center of a storm from shear. Now, however, the eyewall has broken down some and the anti-cyclone did not follow the system into the Gulf. Thus, shear is impacting the storm more, not allowing it to go through rapid intensification while over the loop current. Actually, if this storm doesn't get its act together soon, we might not see more than a weak Category 2 hurricane at landfall, which would be great news!

Another issue that could come into play here is the building ridge to the north of the system. Now that it was weakened, the storm is less likely to plow through the ridge and should feel a bit more of a turn to the west. However, the ridge is now building in a bit weaker and the storm has sped up its arrival. Thus, the balance between these variables should be a wash and the storm looks to make landfall just about where the NHC track places it, to the south of New Orleans moving northwest. This still brings in the greatest surge to the New Orleans area, so any strengthening could lead to levee failures. If the storm stays as weak as it is right now (relatively, of course!) then the levees may hold. However, there are still weak points and it is definitely not the time to be in that city. One good thing, the system weakened as it passed over Cuba, so all the surge it had built up smashed Cuba but didn't continue into the Gulf. Hopefully Cuba was able to get everyone out of harms way.