Why Are Hurricanes Like Dorian Stalling, And Is Global Warming Involved?

| Educate!

Above Photo: Hurricane Dorian’s eyewall, with the storm’s most damaging winds and intense rainfall, stalled over Grand Bahama as the storm pounded the island. “We are in the midst of a historic tragedy in parts of our northern Bahamas,” Prime Minister Hubert Minnis said. Credit: NOAA GOES satellite imagery

Hurricanes Harvey and Florence also stalled, leading to extreme rainfall. Research shows it’s a global trend.

Hurricane Dorian’s slow, destructive track through the Bahamas fits a pattern scientists have been seeing over recent decades, and one they expect to continue as the planet warms: hurricanes stalling over coastal areas and bringing extreme rainfall.

Dorian made landfall in the northern Bahamas on Sept. 1 as one of the strongest Atlantic hurricanes on record, then battered the islands for hours on end with heavy rain, a storm surge of up to 23 feet and sustained wind speeds reaching 185 miles per hour. The storm’s slow forward motion—at times only 1 mile per hour—is one of the reasons forecasters were having a hard time pinpointing its exact future path toward the U.S. coast.

With the storm still over the islands on Sept. 2, the magnitude of the devastation and death toll was only beginning to become clear. “We are in the midst of a historic tragedy in parts of our northern Bahamas,” Prime Minister Hubert Minnis told reporters.

Recent research shows that more North Atlantic hurricanes have been stalling as Dorian did, leading to more extreme rainfall. Their average forward speed has also decreased by 17 percent—from 11.5 mph, to 9.6 mph—from 1944 to 2017, according to a study published in June by federal scientists at NASA and NOAA.

The researchers don’t understand exactly why tropical storms are stalling more, but they think it’s caused by a general slowdown of atmospheric circulation (global winds), both in the tropics, where the systems form, and in the mid-latitudes, where they hit land and cause damage.

Hurricanes are steered and carried by large-scale wind flows, “like a cork in a stream,” said Tim Hall, a hurricane researcher with NASA’s Goddard Institute for Space Studies and author of the study. So, if those winds slow down or shift direction, it affects how fast hurricanes move forward and where they end up.

How that slowing is connected to global warming is still an area of debate. There are different mechanisms at work in the tropics and mid-latitudes, but, “in the broadest sense, global warming makes the global atmospheric circulation slow down,” said NOAA hurricane expert Jim Kossin, co-author of the June study.

He said scientists suspect the overall slowing of winds is at least partly due to rapid warming of the Arctic. The temperature contrast between the Arctic and the equator is a main driver of wind. Since the Arctic is warming faster than lower latitudes, the contrast is decreasing, and so are wind speeds.

“There is a lot of evidence to suggest this is more than just natural variability,” Kossin said.

In a 2018 paper, Kossin showed that the increase in tropical cyclones stalling is a global trend. The magnitude varies by region but is “generally consistent with expected changes in atmospheric circulation forced by anthropogenic emissions,” he wrote.

The Fifth Category 5 Hurricane in Four years

Rising global temperatures also influence storms in other ways: A warmer atmosphere holds more moisture, which means hurricanes can bring more rain, and warmer oceans provide additional energy that can make them stronger.

Hurricane Harvey dumped 60 inches of rain on parts of Texas in 2017 and stalled over the Houston area for days. Hurricane Florence stalled in 2018, flooding parts of coastal North Carolina. Kossin said Hurricane Sandy, in 2012, also took an unusual path that may have been affected by shifting global wind patterns, turning west and slamming into New Jersey instead of being carried eastward, out to sea and away from land, by prevailing westerly winds.

“Stalling hurricanes wreak much more havoc than those that blow through quickly,” said Hall. “Dorian definitely fits the pattern that we found in our paper.”

Dorian is the fifth Category 5 hurricane in just four years in the Atlantic, and only the 35th on record going back nearly a century.

Scientists have seen a trend toward stronger hurricanes in the Atlantic, but not an increase in the total number of storms, said Kevin Trenberth, a climate scientist with the National Center for Atmospheric Research.

“The environment for all such storms has changed because of climate change. The oceans are warmer, especially in the upper 100 meters, which is most important for such storms,” Trenberth said. “This makes available more energy via water vapor for the storms and makes for more activity: more intensity, bigger and longer lasting storms, with heavier rainfalls.”

“The case can readily be made that all storms are affected but each responds differently. For example, Michael (2018) was a very intense Category 5 but moved fast. The slower storms can become large,” he said.

Leading Edge of the Science

Scientists are still working to understand the ways that global warming affects hurricanes and tropical storms, including its influence on wind patterns.

Karsten Haustein, a climate researcher with World Weather Attribution and Oxford University’s Climate Research Lab, said there might be other dynamic factors at play, such as changing land-ocean temperature contrasts, but since models don’t show such things, it is hard to know for sure.

“What we do know is that warmer ocean waters intensify storms if all other conditions remain constant,” Haustein said. “In that sense, the simplest attribution experiment would be one in which ocean and atmosphere have warmed as observed. In the case of Dorian, this would probably translate into an increased rainfall amount of at least 5 percent over affected areas. We found up to a 14 percent increase in case of Harvey.”

Penn State University climate scientist Michael Mann said that while there are uncertainties about what causes hurricanes to stall, some trends are becoming more clear.

“We are definitely seeing a trend toward stalling of these systems after they make landfall, and there may be a climate change connection, though this is really at the leading edge of the science and is still being debated,” Mann said.

Climate models can’t precisely identify the atmospheric changes that cause stalling, he said, “so it is possible that those same models are not capturing how climate change in influencing this particular aspect of hurricane behavior.”

  • rgaura

    Dane Wigington posted an explanation yesterday, with weather maps that I recommend folks view. These storms can be manipulated with powerful microwave transmissions. Note that the Chinese were developing some kind of base there. (It also may be relevant that Epstein/Wexner´s trafficking went through the area; drugs, arms, and humans and human organs, this required a lot of boats and aircraft, and warehouses. Much of this infrastructure and records has been destroyed.) They go way back to Iran-Contra, and so does Wm. Barr. This is weather warfare, via geoengineering. This has been practiced for 70 years, and there are dozens, if not hundreds of patents on these technologies.

  • Greeley Miklashek

    Hurricanes generally slow and weaken over land due to simple increased friction/wind resistance and the entire course of Dorian over the Bahamas was essentially over land, as the Abacos and the Bahama Bank are only covered by 20′ of water. Remember Occam’s Razor?

  • chetdude

    That does NOT explain the Cat 5 hurricane that sat near where I live in the Pacific and threatened my home for 3 days last year…

    It’s primarily the side-effects of fossil-fueled Capitalogenic Global Warming…

  • D Turgeon

    To quote Greeley, above: “Remember Occam’s Razor?”. I didn’t think so.

  • rgaura

    Occam´s razor is generally in reference to scientific matters, and used because the simplest theory is most easily testable. To apply it wholesale to matters involving the complexities of human societies may defy logic. Go to Dane´s site. He starts every podcast with a chilling recording of Lyndon Baines Johnson raving like the murderous sociopath he was. He crows about weather warfare, and says, `he who controls the weather will control the world´. Really chilling.
    I’m afraid, dear Turgeon, that there are more things under heaven and on earth than resides in your philosophy (apologies for the approximate quote).
    The Chinese port under construction is surely ruined.

  • D Turgeon

    The complexities of human society are surely no greater than the complexities of nature or the universe.

    Speaking of complexity, LBJ was probably one of the most complex Presidents of modern times. To dismiss him as a sociopath based on a single angry rant speaks to the simplicity of your philosophy, not to mention you’re paranoia. Robert A. Caro’s multi-volume, as yet unfinished biography of LBJ attests to his many complexities.

    Lord knows, there’s plenty of real conspiracies to be paranoid about without inventing more. Global warming will surely take care of the destruction of the climate without LBJ’s or your efforts.

  • rgaura

    The global warming campaign is simple, and innacurrate. It is used to push native peoples off their lands, and create investment vehicles and generally, to keep the energy industry in control.

    LBJ was a complex human who surely caused the violent death and destruction of millions, ecocide, the rise of the MIC, as well as the murder of President Kennedy. He was a vile mobster. Maybe he loved his dog. On balance, one would have to judge him harshly, despite hagiographies.

  • D Turgeon

    If you think Caro’s biography is a hagiography, either you haven’t read it or you don’t know the meaning of the word. Judge LBJ harshly yes, by all means, but the man did have his better moments which is more than I can say for those who came after.

    As to your conspiracy theories regarding man-made global warming, they are no better or worse than the theories of the more run-of-the-mill climate change deniers. They all serve to divert attention from the worldwide, man-made crisis that the psychopathic oligarchs would like us all to ignore.

  • rgaura

    Actually, my statements are based on science. You have accepted a theory based on a model of something which scientists do not understand. It is a vastly complicated, interactive, living, conscious, system. The simple model employed in the carbon based global warming is constantly revised as some of its base assumptions have been disproved. For example, they miscalculated the effects of cloud cover cooling, also of calving glaciers cooling effects. They did not take into account cosmic particles, or solar weather or the emerging understanding of electromagnetic aspects of climate. These are the kinds of discussions I find interesting. One propaganda technique that has been employed is the One Cause (much like the Bad Man reason to go to war). Blaming carbon is not the one aspect we need to monitor and understand. If we did, we would be building soil and planting trees. Now that the methane is being released from the tundra, that’s huge. Also, scientists who limit the data to what they can measure and/or control miss a lot. Gaia has amazing feedback and rebalancing abilities. So much we have yet to understand. I´v been reading about ice cores since the 70´s. I respect scientific data and theories. I think there is a lot being covered up and diverted in the carbon hysteria. Why not be hysterical about particulates in the air, glyphosate everywhere, chemicals in our children’s bodies? We need a systems shift, based in a view of deep respect for all of life.