Gulf Coast states brace for Tropical Storm Harvey

The governor of Texas has declared a preemptive state of emergency in 30 counties as the state prepares for catastrophic rainfall and coastal flooding from Harvey.
3:40 | 08/24/17

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Transcript for Gulf Coast states brace for Tropical Storm Harvey
We want to get right to that hurricane watch. It's happening on the gulf coast. Take a look at this image from nasa. That is tropical storm Harvey from space. It's massive. And it is gaining strength right now. Evacuations under way in some parts of Texas preparing for the worst stocking up on supplies. We want to go right to ginger tracking the storm. Good morning. They are right to prepare for the worst. This will be a heavy rain event and flooding that could impact life and property. We could lose both this weekend. Let me take you to tropical storm Harvey that formed overnight or redeveloped and you can see it's about 300 miles south and east of Brownsville, max sustained winds right now, 45 miles per hour, moving north at 10 miles per hour. There are hurricane watches, tropical storm warnings and a hurricane warning for a large area but this flood watch extends to San Antonio for up to 20 inches of rain. We have to get to the track in a couple of moments. But first our Matt Gutman standing in water in corpus Christi. Matt. Reporter: Hey, good morning, ginger. Right, water is the major story now. Check this out. The water here off corpus Christi is like a bathtub. 87 degrees which is great if you want to go swimming, very bad for a storm. It's basically turbo charging Harvey and all morning long our phones have been buzzing with hurricane warnings, Texas is very much on its toes this morning. This morning, Texas declaring a state of disaster with city as long a 600-mile stretch of the gulf of Mexico bracing for catastrophic rainfall. We need people to be aware. Reporter: Harvey churning toward the Texas gulf coast upgraded to a tropical storm overnight. Major cities including Houston and San Antonio forecast for a deluge of over a foot of rain from this storm, plus potentially devastating storm surge. We're going to have coastal flooding. All of our bayous and creeks would be potentially a problem. Reporter: Residents there emptying chefs. Many stores selling out of basics including water. Some of the essentials. Water and food and batteries. Just getting ready for it. Reporter: City offs and emergency responders preparing for the worst this morning. Local law enforcement practicing for potential helicopter rescues. College campuses under mandatory evacuations and drivers warned to avoid the roads as main thoroughfares are shut down. Now, 12,000 students could potentially be locked out of the local university here. There's sandbagging operations all over town and their concern is as far away as New Orleans, 550 miles away that the pumps there won't be able to handle that massive deluge, ginger. Matt, thank you. So much to talk about here. We have to go to the track and the timing. I know that's important to everyone so as it gets going the next 24 hours we should sky this become a category 1 hurricane and makes landfall sometime early Saturday morning, just south of Corpus Christi in this latest track. Then it sits around and that's going to be the problem. It does not move much and that's where you'll end up getting significant rainfall. Some of the warnings have up to 25 inches locally. A wide swath of 8 to 15 inches and you can see it goes all the way as Matt was saying up through Louisiana. Storm surge, two to seven feet. Huge waves that we will talk about in just a bit and, guys, this is going to be a big storm, not just because of the storm surge but because of that rain, much like tropical storm Alison. Look at these images from 2001. This was only in quotes a tropical storm but if we remember, there were $5 billion in damage, more than 20 people dead. 30,000 homes in Houston lost because of the rain, George.

This transcript has been automatically generated and may not be 100% accurate.

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