First hurricane to hit Texas coast in 12 years is called 'the new normal'?
Dr. Roy Specer a climatologist disputes the contention of the researchers with his analysis showing such storms are not that unusual. Other hurricanes have actually dumped more water. What made this one unusual is that it did not move over land as rapidly as past hurricanes which dumped more water.
'This is the new normal': Intense storms like Harvey are becoming more common due to global warming, warn scientists
Researchers are quick to say that climate change didn't cause Harvey in Texas, but they do note that warmer air and water mean wetter and possibly more intense hurricanes in the future.
...Spencer's piece is worth reading in full. He also describes previous floods in the Houston area before the population expansion that were actually much worse than Harvey.
There is no aspect of global warming theory that says rain systems are going to be moving slower, as we are seeing in Texas. This is just the luck of the draw. Sometimes weather systems stall, and that sucks if you are caught under one. The same is true of high pressure areas; when they stall, a drought results.