Hurricane Harvey projected to be at least 2nd costliest storm in US history

— -- The cost to rebuild areas devastated by Hurricane Harvey is rising and already on track to shatter records.

All data is preliminary as officials struggle to assess the full devastation of the storm and its aftermath, but based on early economic models and simulations, Harvey is projected to be at least the second costliest storm in U.S. history, experts told ABC News.

Moody's Analytics puts the total predicted cost of Harvey at $108 billion in destruction and losses in output by the energy-rich region.

Texas Gov. Greg Abbott has said that the cost of Harvey could require federal support "far in excess" of $125 billion.

Ballooning these costs is the fact that Texas's critical oil and gas refineries are still struggling to get back online.

Even as ABC News Meteorologist Melissa Griffin confirmed "for the most part the worst is over," she noted that flood waters will take weeks to recede and downstream rivers are still rising in some areas.

Chuck Watson, director of research and development at Enki Research, said the computer modeling he has done shows the total damage from Harvey not yet breaking $100 billion.

Offering a more conservative prediction, Watson estimates Harvey's direct financial costs ranging from $72 billion to $85 billion.

"It’s easy to overestimate the long-term economic impact because a lot of the short-term losses are recovered in the months after a storm,” Watson told ABC News. “Our numbers represent what total costs will likely be looking back a year from now."

More than 185,000 homes have been damaged or destroyed as a result of Harvey, according to the Texas Division of Emergency Management.

Those numbers will certainly continue to "tick up," Tom Vinger from that agency told ABC News.

And approximately 80 percent of Texans lack flood insurance, according to data from the Texas Department of Insurance.

"There are 2.8 million residential policies in the counties on our list and 516,295 federal flood policies," Stephanie Goodman from the Texas Department of Insurance told ABC News. "These numbers start to give you a sense of how many homeowners in the area won't have coverage for most of the damage to their homes."

"That's the second wave of tragedy," Goodman added.

In terms of how Harvey stacks up against other storms, Harvey is still estimated to cost less than Hurricane Katrina, which caused $118 billion in damage when it hit New Orleans in 2005. But Harvey is projected to surpass Superstorm Sandy, which caused $75 billion in damage when it hit the eastern seaboard in 2013.

“Homeowners without flood insurance are eligible for FEMA assistance,” Goodman said.

About 440,000 Texans have registered for assistance from FEMA and the agency has approved more than $70 million in funds, Gov. Abbott said today.

Additionally, while most Texas do not have flood insurance, most homeowners are insured for wind damage. Texans have filed an estimated 100,000 windstorm damage claims and 100,000 auto insurance claims so far, according to Mark Hanna, a spokesman for the Insurance Council of Texas, a trade group that represents the state's insurers.