Hurricane Laura has intensified into a strong Category 4 hurricane in the Gulf of Mexico, and it’s forecast to get significantly stronger as it heads toward landfall near the Texas/Louisiana border late tonight. Unless there’s a miracle, it will be a catastrophic event for the cities of Port Arthur and Beaumont, Texas and Lake Charles, Louisiana, plus a wide swath of coastal communities near and well to the east of the landfall point.
Confidence is now high that the worst of the hurricane will miss metropolitan Houston. It was an extremely dicey situation yesterday. Many of the best computer forecast models were forecasting some version of a direct hit on one of the country’s largest population centers. But credit the experienced forecasters at the National Hurricane Center. They noted the trend in the models, but only nudged their forecast slightly in that direction.
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People that follow computer hurricane forecasts carefully know that they bounce around, and the prudent course is to only adjust the official forecast gradually because they often bounce back. This is why looking at models can be misleading. The best forecast is made by the NHC.
In addition, our government – NOAA and the National Weather Service, in this case – deployed every resource in their arsenal to precisely measure the hurricane and the surrounding environment. That data was inserted into all of the computer forecasting systems that are run around the world, which brought the outlying models into a tighter cluster. That gives us more confidence in the final forecast.
This is a good time to compare the two forecast cones that the National Hurricane Center issues. On the left is the traditional cone, which tracks where the center of the storm is most likely to track. Notice at the base of the cone there is an orange blob. That is the forecaster’s estimate of the area where winds of 40 mph or higher are occurring. You can see that it is much wider than the cone – meaning the bad weather almost always occurs outside of the cone’s boundaries.
We use 40 mph – or tropical-storm force – as a threshold because that’s about the wind speed that branches start blowing off trees, driving high-profile vehicles can become dangerous, and other things start to go wrong. It’s an estimate, but it works.
Since the area with 40-mph winds is much wider than the cone, the National Hurricane Center also produces the cone graphic on the right.
The cone with all of the colors shows the likelihood of certain areas getting 40 mph winds or higher. The purple area from Houston to the middle of Louisiana indicates the zone that is likely to get winds that strong, at least. Of course, the winds in some areas inside that zone will be much much higher than 40 mph.
In the green parts of the graphic, there is a chance of sustained 40 mph winds, but the odds favor more of a gusty day.
So the cone with the colors is designed to show the extent of the wind from the storm. But neither cone shows the extent of the storm surge likely to be pushed ashore by those strong winds.
The city of Lake Charles, Louisiana is 30 miles from the coast, but they are likely to experience storm surge. The Gulf water is forecast to be pushed 10 to 15 feet above the normal high-tide level south of Port Arthur, Texas and Lake Charles, with waves on top of that.
That huge mound of water will rush inland, up the rivers and over the islands that dominate that part of the coastline. Life-threatening storm surge will affect the entire Louisiana Gulf coast and the Texas coast from Houston north, at least. Even in Galveston Bay, just south of Houston, the surge is forecast to be 3 to 5 feet above normal high tide.
The map shows the storm-surge forecast numbers from the National Hurricane Center along the upper Texas and Louisiana coast.
Landfall is forecast for late tonight through the overnight, so people there will be encountering the storm in the dark. It’s going to be a horribly long night.
Elsewhere in the tropics, a disturbance is just moving off Africa that we’ll have to watch, but none of the long-range computer forecast models are indicating that it will organize at this point. So no development is expected through the weekend.