A low pressure area is spinning its way northwestward over the warm waters of the Gulf of Mexico. On its eastern flank, massive thunderstorms tower to heights of 40,000 feet or more, dumping rainfall at rates of greater than two inches per hour.

This storm may soon become tropical storm Bill, but even if it does not develop fully, it is making a beeline for the Texas coast, between Houston and Corpus Christi.

This couldn't come at a worse time, considering that Texas just had its wettest month of any month on record during May, as did Oklahoma, which will also be affected by this storm. Flooding in these states, and others, killed more than three dozen people in May. Any new heavy rainfall is likely to result in flooding.

The National Weather Service in Houston issued a special weather statement on Monday warning of a "dangerous flood threat for parts of southeast Texas." The statement mentions the potential for up to 10 inches of rainfall in some areas. "Rainfall totals this high will lead to flooding," the NWS added.

In a fascinating but unwelcome twist, the record wet month of May — and more recent rains in June — may give rise to a rare meteorological event, known as a "brown ocean" storm.

In short, the tropical system trying to organize over the Gulf of Mexico may defy the common knowledge about hurricanes and tropical storms. The storm may actually intensify as it moves inland, rather than fall apart.

Exceptions to every rule

Computer model projection of the tropical weather system as it moves over North Texas on June 17, 2015. Image: WeatherBELL Analytics

The vast majority of tropical storms and hurricanes feed off heat and moisture from warm ocean waters, and weaken once that source of heat and moisture is lost after crossing a coastline. But a tiny minority of storms don't weaken over land, or do so very slowly. Even fewer actually intensify as they move inland.

How wet soils can intensify/maintain tropical cyclone via Andersen&Shepherd 2014, Andersen, Shepherd,Radcliffe 2014 pic.twitter.com/dArxjLYKnu — Marshall Shepherd (@DrShepherd2013) June 15, 2015

There are exceptions to the rule because these storms can feed off unusually moist soil, which provide the necessary heat for tropical weather systems, according to studies by University of Georgia meteorologists Theresa Anderson and Marshall Shepherd.

A 2013 study published in the International Journal of Climatology found that of 227 inland tropical cyclones examined, 45 maintained strength or increased their intensity inland. Not all remained purely tropical weather systems; just 16 remained "warm core" storms, which includes tropical storms and hurricanes (non-tropical systems have cold cores).

The tropical weather system will bring a plume of unusually moist air into Texas, Oklahoma and all the way to the Ohio Valley (reddish hues). Image: WeatherBell Analytics

These 16 storms occurred in northern Australia, eastern China, India and the U.S.

The poster storm for this phenomena in the U.S. is 2007's Tropical Storm Erin, which made landfall in coastal Texas, but proceeded to intensify as it moved inland, even forming an eye over Oklahoma.

That study, and another study published the same year in the Journal of Applied Meteorology and Climatology, found that three conditions are especially crucial to maintaining a tropical cyclone's intensity or strengthening it when it moves inland. Low-level temperatures must be relatively uniform, as they are over the tropical oceans; soil moisture must be unusually high before the storm arrives in order to sustain a high rate of evaporation, which is a source of heat energy for the storm, technically known as latent heat; and the amount of latent heat released from the soils must be at least 70 watts per square meter for storms to maintain strength or intensify over land.

Computer model projection for the storm over Oklahoma on June 18, 2015, showing an even stronger system at that point. Image: WeatherBELL Analytics

The latent heat from the ocean averages about 200 watts per square meter, according to a press release.

The evaporation of high amounts of soil moisture is a phenomenon that Andersen and Shepherd call the "brown ocean."

"The land essentially mimics the moisture-rich environment of the ocean, where the storm originated," Andersen said in a NASA press release.

via @MichaelRLowry soil moisture ahead of what could be TS Bill, so that is why I am watching for brown ocean effect pic.twitter.com/pWerjDR0S7 — Marshall Shepherd (@DrShepherd2013) June 15, 2015

There is little doubt that the soil moisture in Texas, Louisiana and Oklahoma is abundant enough to maintain or even boost a tropical weather system beginning on Tuesday morning, lasting through Wednesday and into Thursday.

Five-day precipitation totals, showing a plume of heavy rains from Texas to Massachusetts. Image: National Weather Service

Storms that intensify as inland tropical cyclones have the potential to bring much more rainfall than storms that weaken as they move inland, and this does not bode well for Texas and Oklahoma this week.

Currently, the National Weather Service is warning of widespread rainfall of five inches or more across central and eastern Texas and into Oklahoma and western Louisiana through Thursday, but the exact placement of the heaviest rains is unclear at this point.

In anticipation of the heavy rain and higher than usual tide levels, Galveston County Judge Mark Henry ordered a voluntary evacuation order for residents of the Bolivar Peninsula near Houston.