Boston/London: On Tuesday morning, disaster analyst Chuck Watson had pegged $42 billion as a reasonable estimate for the cost of destruction Tropical Storm Harvey would leave in its wake. By the end of the day, he’d added another $10 billion.

Harvey’s initial blast along the Texas coast as a Category 4 hurricane was bad enough, sending gasoline prices surging and crude futures plunging as refineries shut. Now the storm has returned, making landfall a second time in southwestern Louisiana, which was devastated by Hurricane Katrina in 2005.

The storm has brought torrential rain and the collapse of levees, dams and drains. That combination has analysts raising damage estimates by the hour and could easily push the catastrophe above the rank of Superstorm Sandy, the second-costliest weather disaster in US history.

“We’re on the verge of having cascading failures," said Watson, a Savannah, Georgia-based disaster modeler with Enki Research. “It is conceivable that we could get into the $60 to $80 billion range without that much effort."

Louisiana, including New Orleans, is familiar with apocalyptic storms. Hurricane Katrina killed at least 1,800 and caused $160 billion in damage. Sandy, which slammed into New York and New Jersey in 2012, claimed 147 lives along its path from the Caribbean, including 72 in the US. The damage was about $70.2 billion, according to the US National Centers for Environmental Information in Asheville, North Carolina.

The death toll from Harvey had reached at least 18 on Wednesday, according to the Austin American-Statesman newspaper. The New York Times cited Texas authorities as saying they believed Harvey caused at least 30 deaths.

A nighttime curfew, from 10pm to 5am, was imposed in Houston Tuesday night as the storm’s center drifted back toward the Gulf of Mexico. The storm made landfall between Port Aransas and Port O’Connor in Texas on Friday, stalled out further inland over the weekend and is now trekking eastward. It is expected to reach the Lower Mississippi Valley by Thursday.

The storm will be followed by tornadoes from Louisiana to Arkansas. East Texas could get another 10 inches (25 centimeters) of rain throughout the week.

“Harvey aligned perfectly to bring intense rain bands over Houston," said James Done, a project scientist and meteorologist at the National Center for Atmospheric Research in Boulder, Colorado. As it drifted along the coast on Monday and Tuesday, it also “perfectly aligned for Houston to get the peak rainfall."

Harvey also created a situation where Gulf of Mexico waters have kept drumming hard up against the coastline, preventing rain water from running off into the sea and backing everything up for miles around.

The ferocious arrival was tempered by high-pressure systems across the US, including a large one that pushed temperatures in California beyond 100 degrees Fahrenheit (38 Celsius), said Phil Klotzbach, a hurricane researcher at Colorado State University. Harvey became “a pebble in stagnant stream."

Predictions were that some areas east of Houston would witness 50 inches or more of rain by the time Harvey moved off into the central US. As of 3 am local time on Wednesday, the gauge at Mont Belvieu, east of the city, showed 51.88 inches had fallen since the start of the storm. That may be the most in recorded history for a tropical cyclone in the contiguous US, breaking a mark also set in Texas back in 1978.

The record for all 50 states in such a storm was set in 1950 in Hawaii -- 52 inches.

Harvey’s deluge was made all the worse because the ground was already saturated by heavy rainfall earlier in the season. “We have had roughly a year’s worth of rain in the last three months," said Wendy Wong, a National Weather Service meteorologist in Dickinson, Texas, a city that was evacuated.

Watson said disaster models just aren’t calibrated for a thing like Harvey. For instance, a typical scenario will assume infrastructure such as dams, levees and drainage systems will fail when stress rates reach 80 to 90 percent. “We are seeing failures at 60 percent," he said.

The pressure on the Addicks and Barker reservoirs west of Houston spurred the Army Corps of Engineers to release water, which flooded neighbourhoods that had been dry before. Now such deliberate flooding should be more calculated, Watson said.

“We’re starting to get into the apocalyptic -- this is what we don’t want to have happen," he said.

The Army Corps didn’t immediately respond to a request for comment, but said earlier on Tuesday that no decision had been made to increase discharge rates and that dam releases were expected to occur for several months.

Watson’s other concern is how slowly water is draining away from Houston. Done said the reason may be that Harvey’s surge is keeping up pressure on bays, inlets and the mouths of rivers, preventing runoff.

It could also be evidence that the pipes and drainage systems are failing, Watson said. That, of course, would increase the ultimate financial pain of the storm. The Army Corps said in a statement that the dams are operating “as expected."

‘Precarious Situation’

Now, New Orleans and the rest of coastal Louisiana are feeling the brunt of Harvey’s soaking rains, threatening yet another major US refining center. The hurricane center said 3 to 6 inches could fall across eastern Louisiana, including New Orleans. Mississippi, Arkansas and Alabama could soon get as much as 10 inches. Storm surge warnings, which means there is a danger of facing a life-threatening inundation of water, are in effect for much of the Gulf Coast.

The storm shut an estimated 3.9 million barrels a day of refining capacity due to flooding and port closures, according to Goldman Sachs Group Inc. analysts including Damien Courvalin. Buffalo Gas Plant at Stanton, Texas, reduced sale of natural gas liquids by 58 percent as fractionator plants in Houston were closed, while Targa Resources Corp. said damage to its facilities is minimal so far.

The infrastructure in New Orleans, “can barely keep up," Done said. “New Orleans is in a very precarious situation."

The forecast calls for the storm to continue into the central U.S., and it’s expected to become a tropical depression by tonight. And even then, Houston won’t be free from threats.

Rainfall over the state will eventually need to make its way into the Gulf, which means several more pulses of water could be coming the city’s way, Watson said.

“There is another train that is heading toward Houston," Watson said. “Behind every one of these dollar signs is a family that doesn’t have a house anymore." Bloomberg