Harvey: The Sequels

Harvey is the storm that just would not quit. It formed in the Atlantic and died in the Caribbean. It reformed in the Bay of Campeche and now threatens the middle Texas coast as a Cat 2, potentially Cat 3 Major Hurricane. If you live on the Texas coast, between Corpus Christi and Freeport, you need to be listening to local action statements and rapidly preparing for the impact of a potentially major hurricane. That means winds to 120 mph, a surge of anywhere from 12-15 feet, and rainfall amounts approaching three feet. This is no longer a potentially deadly situation but a probably deadly situation. Get out while you can!

So what about the rest of us? Well let’s recap what we know right now: Harvey at 9 am was located at 26.5 N 95.9W or about 135 SSE of Port O’Connor Texas. Max winds are 110 mph and climbing, it is moving NW at 10 mph and has a central pressure of 948 mb. This remains a quickly intensifying storm and it should be Cat 3 as it approaches the Texas coast. One way or another, our friends from Corpus to  Freeport are going to feel the brunt of a Cat 3 hurricane over the next 24 hours. And if this were a normal storm, it would push well inland and fall aprt with the remnants swept up to the NE eventually by the jet stream. Not Harvey!

The image to the right is what the hurricane center is thinking will happen. Quite frankly it is the best case scenario for the upper Texas and Louisiana coasts. It depicts a storm which comes ashore as a Major Hurricane early Saturday and by Sunday is about 60 miles inland as a hurricane and stalled. By early Monday it is back near where it made landfall, late Tuesday near Freeport as a Tropical Storm right on the coast, and Wednesday over Galveston as a Tropical Storm. Harvey, the storm that would not quit.

If this plays out as the actual path of the system, those of us on the Upper Texas and Louisiana coasts will get lots of rain, more on that in a bit, and some windy tropical storm like winds and conditions. All in all, not a bad outcome from a Cat 3 storm. But the problem is, as the NHC always tells us, don’t look at the path line itself, but rather the general motion. This is because the actual path is likely to deviate by as much as 60 miles, even in the short term. Therein lies the rub. The Hurricane Center has been shifting its products a bit to the east consistently over the past few days as the major models fight about the future course of the storm. The European model, arguably the best in the world has one idea and the US GFS model another.

Now is not the time to get into a discussion on the accuracy of various models. I will just say that the Euro has done a great job with Harvey so far and the GFS a good job. The major variance has been with what happens as Harvey approaches landfall. The Euro has consistently brought the storm barely inland, stalled it then kicked it out to the northeast back over the Gulf. The GFS wants to push it further inland towards San Anton io, then have it move eastward hugging the coast. Well except for yesterday when it took it towards Mexico?? In the end, we are not sure of where Harvey will go once it reaches the coast. The GFS and other models based off of its core model lie along the NHC track. The other half of the models follow the Euro, which has an intact system re-emerge over the Gulf before heading northeast early next week. What actually happens will mean a world of difference with regards to winds and tides for the are from Houston/Galveston to Berwick Bay.

This is why. This is a snapshot from the NAM model, the model used by the US Navy. It shows the position of the “remnants” of Harvey next Tuesday as a strong Tropical Storm due south of Cameron and heading to the NNE. The European Model depicts nearly the same scenario. Even the HRRR, the US tropical specialty model depicts something like this but maybe shifted west by 30 miles. The take away from all of this is we need to watch carefully and see how far inland Harvey’s center makes it. If it gets close to San Antonio, then the GFS is likely on the mark. If it makes it only to Victoria or so before stalling, the Euro camp is likely right. My gut right now lies with the Euro but it not with a great deal of certainty. What we absolutely do not want is Harvey to reach the coast and stall with it’s eye over water! Possible? Sure but not likely right now at least.

All that said, one thing is certain: Everyone from the Houston metro area well eastward into Louisiana is in for a lot of rain. And it really again depends on which of the model solutions verifies as to whether we talk in inches or a foot or more! The NHC has put out a rainfall prediction based upon the GFS course scenario which call for four or more inches of rain from Mobile to Brownsville, with a maximum of nearly three feet of rain near and around the area of initial landfall.

You can see from the image that the Berwick Bay region is predicted to be in the 10-15 inch swath, Cameron could approach 20 inches, and the Houston Mertroplex would be looking at 20-plus inches. Should the Euro/NAM solution be the right one, we would likely elongate the areas of heaviest rain farther to the east by say 75 miles. Bottom line, regardless of the winds and such Harvey brings us, we will be looking at lots of rainfall. Those in Houston who historically flood may need to be thinking about exit routes if waters begin to rise. Harvey will likely be known much more for his rainfall and flooding than his wind damage.

Look for updates over the next couple of days as the future track of Harvey becomes more certain. That will allow us to the north and east of the first landfall to prepare for Harvey Part III, whatever and where ever that may be. Until then, stay safe and stay dry!

Post a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.