As Tropical Storm Marco disintegrated near the southeastern Louisiana coast on Monday, meteorologists were already eyeing a second, more potent storm that is likely to come ashore midweek. Laura, currently a tropical storm thrashing Cuba, could explosively intensify into a major hurricane over the Gulf of Mexico on Tuesday and Wednesday, bringing the potential for widespread damage wherever it hits late Wednesday.

Or, it could peak at Category 1 or 2 status, sparing the coastline a more devastating impact, but still posing a risk of storm surge flooding, wind damage and heavy rains.

It’s a high-stakes forecast with implications for millions in the midst of a pandemic, which makes evacuation decisions even more fraught.

Currently, the National Hurricane Center is forecasting that Laura will make landfall near the Texas-Louisiana border as a high-end Category 2 storm, but the agency is closely eyeing data that favors a more bullish stance about the storm’s potential.

“There is an increasing risk of dangerous storm surge, wind, and rainfall impacts from the upper Texas coast through the north-central Gulf Coast beginning on Wednesday,” forecasters wrote.

Voluntary evacuations have already been issued for Galveston, Tex., while oil and gas companies are working to shut down operations at refineries and drilling platforms vulnerable to hurricanes.

What is rapid intensification?

Rapid intensification occurs when a tropical storm or hurricane’s maximum sustained winds increase by 35 mph or more in 24 hours. Often, the jump can be even more dramatic than that, and typically, storms that reach Category 3 intensity or greater undergo a period of rapid intensification. But this phenomenon has become more pronounced in recent years, having been observed in these prominent recent examples:

There is a chance that Tropical Storm Laura will rapidly intensify over the Gulf of Mexico on Tuesday and Wednesday, taking advantage of extremely high water temperatures and weak upper-level winds.

A volatile setting for hurricanes

Hurricanes feed off high sea-surface temperatures. Water temperatures in the Gulf of Mexico are well above average, approaching 90 degrees in some cases. That’s plenty warm enough to help a serious hurricane blossom but only if other conditions are met.

Among those other requirements? Little to no wind shear. Wind shear, or a change of wind speed and/or direction with height, can be disruptive to tropical systems by disturbing their vertical structure.

Tropical Storm Laura was combating some northerly mid-level wind shear on Monday that is forecast to persist into early Tuesday, which could hold its intensity in check. But then the shear is predicted to ebb.

In addition, clockwise-spinning high pressure over the Gulf of Mexico in the upper atmosphere may help Laura to evacuate its spent air at high altitudes away from the storm, thereby allowing the storm to ingest more air near the surface and become increasingly powerful.

A challenging forecast

There are plenty of things working in Laura’s favor, but it will take only a small inhibiting factor to prevent the storm from tapping into its overly ripe environment. Very few storms ever reach their maximum potential intensity.

How those interfering ingredients combine will determine Laura’s fate and, in turn, the outcome for millions of Gulf Coast residents. Researchers say that what happens overnight Monday into Tuesday is critical.

The sooner the storm develops its inner core of powerful thunderstorms arranged tightly around its low pressure center, or eye, the more likely it is that the storm will rapidly intensity, said Kim Wood, an assistant professor in the Department of Geosciences at Mississippi State.

“One thing we have to closely follow over the next 24 hours is what the vortex does south of Cuba,” Wood said. “Will the center stay offshore? Will it continue wobbling, following the deepest [shower and thunderstorm activity]?”

Wood said that computer models have been struggling to accurately simulate Laura’s future, since they haven’t resolved these all-important localized processes.

“It’s the nuances of what’s going on at the small scale,” Wood said.

Philippe Papin, an atmospheric scientist with the National Centers for Environmental Prediction, has also been observing Laura’s evolution.

“In order for rapid intensification to occur in the Gulf of Mexico, it will need its strongest convection [shower and thunderstorm activity] to persist within its radius of maximum winds and wrap around the center,” wrote Papin in a Twitter message.

Assuming Laura’s inner circulation remains relatively intact upon emerging over the Gulf early Tuesday, it would then begin the process of ramping up in strength shortly thereafter. A very toasty Gulf of Mexico Loop Current, which is relatively narrow current of water that moves into the Gulf from the Caribbean and eventually flows through the Florida Strait and into the Gulf Stream, may jump-start this process.

Some weather models indicate that Laura could peak at Category 3 or greater intensity over the Gulf of Mexico on Wednesday. A stronger storm would have a tendency to push farther west toward Texas, putting places like Houston and Beaumont and Port Arthur at a greater risk.

Climate change connection

Rapid intensification isn’t just a meteorological wild card. It’s also increasingly a staple of a warming world.

If Tropical Storm Laura does undergo rapid intensification, says Jim Kossin, a researcher at NOAA and the University of Wisconsin, “It’s very likely that climate change is playing some role in that.”

He said the unusually warm waters of the gulf are tied in part to human-caused global warming, since the vast majority of the heat trapped in the atmosphere by greenhouse-gas emissions ends up in the oceans. High water temperatures are a prerequisite for rapid intensification events, and right now, virtually the entire tropical Atlantic Ocean Basin is seeing unusually mild conditions.

“Rapid intensification events are more likely because of climate change,” he said in an interview.

Kossin co-authored a study published in Proceedings of the National Academy of Sciences in May that found a detectable increase in the occurrence of the most powerful hurricanes and typhoons. Such an increase had been predicted by computer models and explained using physical theories of how hurricanes form and intensify, but this was the first time a statistically significant trend had been observed.

“Our confidence continues to grow that storms have become stronger, and it is linked to climate change, and they will continue to get stronger as the world continues to warm,” Kossin said.