Well, the question is rather harder to answer than you could think, there's no straight yes or no answer for that one.
The thing about catastrophies, is that they always happen whatever the state of the climate may be. 5000 years ago, you already had tropical storms and tornados, and 5000 years from now, you will still have those.
Harvey is, with no doubt, a very extreme phenomenon: scientists have said it is a 1 in a 1000 years storm. Therefore, there is a chance that Harvey was just that, a 1 out of 1000 years event, and that nothing man does or did, caused it.
However, climate change isn't just about creating storms, it's mostly about having shorter time spans between cataclisms and the amplification of the damage they cause, two things that can apply perfectly to Harvey.
Let me explain: to understand what causes tornadoes, you need to know how these events are created. What happens is that the water in the Gulf is very hot, especially in summer. The heat provided by the sun evaporates gigantic ammounts of water to the sky, and when the air is saturated with water, aka when it reaches 100% humidity, it rains, a lot. That's mostly why tropical areas have a lot of water falling during summer. The ammount of water, and the energy provided by the heat, geting evaporated in the region formes depressions.
And when there's a lot more water and energy in the sky than usual, you have massive depressions that appear, and then puff you got your tornadoes.
That's an oversimplification of a very complex climatic system, but anyways.
So what Climate Change causes? It's mostly extra heat. The thing about ocean temperatures, is that the difference between a tropical rain and a tornado, is mostly a few extra degrees, and every time you add temperature, the worse a storm like Harvey becomes.
In addition to that, ocean temperatures take a lot more time to change than landmasses, so high temperature winters also affect the temperature of the water during summer. According to the NYtimes: "The daily surface temperature of the Gulf of Mexico last winter never dropped below 73 degrees." (which is 22,8 degrees in non-retard units). That is a very hot temperature for winter (first time ever recorded), if you know that the average temperature (AVERAGE!) of the gulf in January ranges from arround 55 to 65°F depending on the location.
So it's very likely that climate change caused Harvey, you can't say it for certain, because again, random events to exist, but it's a very high % chance that it did.
It is to forecast that events like this will probably keep continuing in the future, with increased intensity; at least that's what scientific models predict. Let's hope they are wrong about that...