Hurricane Harvey was the first hurricane to hit the Texas coast since 2008 when Hurricane Ike came through the Houston area and the first major (category 3 or better) hurricane to hit Texas since Bret in 1999. Hurricane Harvey started as a tropical wave off the African coast on August 13th and tracked westward across the Atlantic and on August 17th become a tropical storm which moved into the Caribbean Sea where Harvey become disorganized. Harvey was then downgraded to a tropical wave which entered the Gulf of Mexico on the 22nd.
On the morning of the 23rd, Harvey was upgraded again to tropical depression as the Bay of Campeche and the Western Gulf of Mexico had very warm waters. Over the next 48 hours Harvey would undergo a period of rapid intensification from a tropical depression to a category 4 hurricane. Harvey made landfall along the Texas coast near Port Aransas around 10 p.m. on August 25th as a cat 4 and brought devastating impacts.
As Harvey moved inland, it’s forward motion slowed to near 5mph after landfall and then meandered just north of Victoria, Texas by the 26th. Rain bands on the eastern side of the circulation of Harvey moved into southeast Texas on the morning of the 25th and continued through much of the night and into the 26th. A strong rainband developed over Fort Bend and Brazoria Counties during the evening hours of the 26th and spread into Harris County and slowed while training from south to north. This resulted in a rapid development of flash flooding between 10 p.m. and 1 a.m., as tremendous rainfall rates occurred across much of Harris County.
The morning of the 27th saw additional rain bands continued to develop and produced additional excessive rainfall amounts. As the center of Harvey slowly moved east-southeast and back offshore heavy rainfall continued to spread through much of the 29th and the 30th exacerbating the ongoing widespread and devastating flooding.
All of this rainfall caused catastrophic drainage issues and made rivers rise greatly. Only around 10 percent of the river forecast points in southeast Texas remained below flood stage due to the event, and approximately 46 percent of the river forecast points reached new record levels. Harvey maintained tropical storm intensity the entire time while inland over the Texas coastal bend and southeast Texas. After moving offshore, Harvey made a third landfall just west of Cameron, Louisiana on the morning of the 30th and brought more heavy rainfall to the Northern Gulf States. https://www.weather.gov/hgx/hurricaneharvey