The CIRA advected layer precipitable water (ALPW) product for Hurricane Harvey is quite interesting:
The loop spans from 12Z 23 August to 12Z 29 August. During that time period, we see the development of Hurricane Harvey in the western Gulf of Mexico. There are clear indications of moisture convergence in the vertical during the early stages which would add confidence to a forecast of a strengthening tropical cyclone. In the later periods of the loop, the system slows down along the coast of Texas. It is clear that abundant moisture exists over a deep layer in the vertical in the vicinity of the slow-moving circulation. High precipitation efficiency can be inferred from this imagery. Abundant moisture over a deep layer in the vertical, very slow movement and high precipitation efficiency came together and contributed to the significant flooding in the vicinity of the circulation over coastal Texas.