Shipping lines are urgently scrambling to re-route US Gulf services unable to call at the port of Houston as Tropical Storm Harvey edges towards Texas and Louisiana again.The 6-ranked US container port by TEUs handled last year and the largest on the US Gulf Coast remained closed through Wednesday due to the impact of Hurricane Harvey which started to inundate the region with rain on Friday, before being downgraded to a Tropical Storm.An alert from the port earlier today said it was it was continuing to monitor weather conditions to determine when operations could safely resume.“At this point [there are] no indications from the US Coast Guard on when the Houston Ship Channel will reopen for vessel transits,” said the alert. “Updates will be provided as more information is available.”Some reports suggest that the Port of Houston may not allow sailings until Saturday, leaving several cargo ships still waiting out the storm in the Gulf of Mexico.Hong Kong-based shipping line OOCL told Lloyd’s Loading List earlier today that one vessel on its Trans-Atlantic ATG1 service, which was scheduled to call Houston on 25 August, had now been diverted to Tuxpan, Mexico. The carrier said export shipments for loading at Houston would be rebooked onto alternative ATG1 services, while imports for discharge would be reloaded at Tuxpan as soon as possible.Maersk Line’s latest customer update said its best-case scenario for a Houston call on its MECL loop was now 2 September.Cathy Roberson, founder and head analyst at US-based Logistics Trends & Insights, said the US port options for shipping lines were limited. “Container ships can be redirected to New Orleans, which is the nearest major port to the area, but that area and to the west of it in the Lake Charles area, is receiving rain from the tropical storm as well, and the potential for flooding in South West Louisiana is strong. So, the Gulf alternatives are Mobile, Tampa or, further afield, Miami.”She continued: “Maersk has a couple of ships waiting to dock in Houston and as of yesterday had said they were taking a wait and see approach. However, I expect Houston port is going to stay closed for the rest of this week because of the rains.”Many of the afflicted region’s roads and railways also remain impassable or clogged, while Houston’s two main airports – George Bush Intercontinental Airport and William P Hobby Airport – were closed again this morning.International and domestic airlines have cancelled hundreds of flights to and from the US Gulf, but two carriers are expected to suffer most harshly − Bush is the second-busiest hub for United Airlines, while Hobby is one of the top airports for Southwest Airlines.Areas of Houston have now received over 130 centimetres of rain since Friday and its mayor has imposed a night-time curfew following reports of looting in the US’ fourth biggest city, large parts of which remain under water.Harvey was due to make landfall for a second time this morning local time near the Louisiana/Texas border after picking up more speed in the US Gulf overnight. It is then expected to move up the Mississippi valley and into Tennessee, causing more damage and flooding but slowly losing power as it edges inland.