What do warm Gulf temps have to do with our freak snowstorm? Maybe more than you think

It may seem illogical, but warmth may have helped feed the storm that dumped record snow on Louisiana, Mississippi and points beyond this week.

Unusually heated temperatures in the Gulf of Mexico may have contributed to the snowstorm, though the main driver of the event was a rare confluence of two other weather factors, said Jay Grymes, Louisiana’s state climatologist.

In recent decades, water temperatures in the Gulf have been increasing faster than average ocean temperatures across the globe, a result of heat-trapping greenhouse gas emissions and specific features of the region. That may have contributed to the intensity of the storm, Grymes said.

But Grymes cautioned that any influence from the warming Gulf would have likely been limited. The main factors at play involved cold air sliding south from the Arctic and a rainmaking storm system in the Gulf, which converged to create the record-breaking snow totals in some parts of the state.

“Those two colliding would have been a snowmaker regardless,” Grymes said.

The “freak event” that shut down schools, government offices and businesses was a result of an expansion in the polar vortex — likely the second-coldest air mass on record to hit the Gulf Coast, Grymes said — coincidentally meeting a storm system out in the Gulf. This is a very unique situation, he noted.

We not only got widespread record and near-record lows this morning, but yesterday we had widespread record and near-record snow totals, making this event arguably the record set for a winter storm event,” Grymes said on Wednesday.

‘An added ingredient to the equation’

At the same time, this is where the warming Gulf may have come into play: Warmer water temperatures mean more water vapor in the atmosphere, and more water vapor means more fuel to create snow.

A recent study published in the American Meteorological Society’s “Journal of Climate” found that water in the Gulf warmed at a rate double that of global ocean temperatures between 1970 and 2020. Rising ocean temperatures can exacerbate environmental risks such as damage to coastal wetlands, the “dead zone” in the Gulf, hurricane intensity and sea level rise.

“So I wouldn’t attribute the [snow] record to the fact the Gulf was warmer than normal, but I would certainly say that may have been an added ingredient to the equation,” Grymes said.

What about the polar vortex?

Amy Butler, a research scientist for the National Oceanic and Atmospheric Administration, said that some research suggests that changes to the polar vortex could be causing more cold extremes -- even as climate change is leading to more frequent heatwaves.

Changes in the Arctic air mass might occur when the polar vortex suddenly weakens, nudging the regular winter formation southward, “allowing cold Arctic air to spill into Europe and the U.S,” she said.

But, importantly, that’s not what happened this week.

“The vortex is actually stronger than normal and looks to strengthen further,” Butler wrote in an email.

What did happen this week is that the polar vortex elongated or stretched, a factor that has been tied to cold in North America. However, the cause and effect of the lengthened polar vortex and the weather is not scientifically settled.

“The vortex stretching could also just be a response to the weather pattern, rather than the driver,” she said.

Nazla Bushra, a professor in oceanography and coastal science at LSU, published a recent study on how the polar vortex has changed over time. She explained that the cold air mass from the Arctic could be reaching south more frequently in part due to warming temperatures in the Arctic itself.

“That means that the polar vortex, that boundary between the cold air in the [North] Pole and the warmer in the equator, is getting weaker,” she said. “They’re not distinctly different anymore because of this weakening boundary.”

And when there’s a weakened boundary, she explained, there’s a greater chance that colder air could reach regions as far south as Louisiana.

Bushra noted that global warming is shifting average conditions to the extreme, “so that we are seeing these weather events more frequently and more in a severe way.”