How Intense Will Storms Get? New Model Helps Answer Question

How Intense Will Storms Get? New Model Helps Answer Question

ScienceDaily (July 9, 2008) — A new mathematical model indicates that dust devils, water spouts, tornadoes, hurricanes and cyclones are all born of the same mechanism and will intensify as climate change warms the Earth's surface.

The new equation, developed by University of Michigan atmospheric and planetary scientist Nilton Renno, could allow scientists to more accurately calculate the maximum expected intensity of a spiraling storm based on the depth of the troposphere and the temperature and humidity of the air in the storm's path. The troposphere is the lowest layer of Earth's atmosphere.

This equation improves upon current methods, Renno says, because it takes into account the energy feeding the storm system and the full measure of friction slowing it down. Current thermodynamic models make assumptions about these variables, rather than include actual quantities.

"This model allows us to relate changes in storms' intensity to environmental conditions," Renno said. "It shows us that climate change could lead to increases in how efficient convective vortices are and how much energy they transform into wind. Fueled by warmer and moister air, there will be stronger and deeper storms in the future that reach higher into the atmosphere."

Renno and research scientist Natalia Andronova used the model to quantify how intense they expect storms to get based on current climate predictions. For every 3.6 degrees Fahrenheit that the Earth's surface temperature warms, the intensity of storms could increase by at least a few percent, the scientists say. For an intense storm, that could translate into a 10 percent increase in destructive power.

Renno's model is what scientists call a "generalization" of Daniel Bernoulli's 18th-century equation that explains how airplane flight is possible. Bernoulli's equation basically says that as wind speed increases, air pressure decreases. It leaves out variables that were considered difficult to deal with such as friction and energy sources (which, in the case of a whirling storm, is warm air and condensation of water vapor.) And in certain idealized situations, omitting that information works fine.

But by including these additional variables, Renno was able to broaden Bernoulli's equation to apply it to more general phenomena such as atmospheric vortices.

"The laws of physics are generally very simple," Renno said. "When you make assumptions, you are not representing the simple, basic law anymore. If you don't make assumptions, your equations have those simple, basic laws in them. It gets a little more complicated to get to the solution, but you don't introduce error, and you answer is more elegant, more simple."

Renno's work bolsters studies by others who say hurricanes have grown stronger over the past 50 years as sea surface temperatures have risen. This effect has not been extreme enough for humans to notice without looking, scientists say. Hurricane Katrina and Cyclone Nargis were not the most intense storm to hit land in the past half century. Other factors contributed to the devastation they caused.

This new model helps explain the formation of spiral bands and wall clouds, the first clouds that descend during a tornado. It's clear now that they are the result of a pressure drop where the airspeed has increased.

Renno says unifying convective vortices from dust devils to cyclones will help scientists better understand them.

"This is the first thermodynamic model that unifies all these vortices," he said. "When you unify them, you can see the big picture and you can really understand what makes them form and change."

A co-investigator on NASA's Mars Phoenix Lander mission, Renno has used his new model to calculate the intensity of dust storms in Mars' polar regions. He found that at the Phoenix landing site dust storms can have winds in excess of 200 mph.

Renno is an associate professor in the Department of Atmospheric, Oceanic and Space Sciences. Andronova is a research scientist in the Department of Atmospheric, Oceanic and Space Sciences.

WEATHER NOTE

Spotting Storms?

This is from a Wisconsin storm spotter/chaser on June 27, 2008. Talk about an unusual radar target!

"My bother called from Antigo to say he has been watching three triangular shaped UFO's flying a little north of Antigo the past hour. I don't have time to look outside but check out this radar loop from Green Bay.."

You never know......

World weather expert says El Nino, La Nina outlook mild

The World Meteorological Organisation said Tuesday that 2008 was proving a year of respite from natural climatic phenomena identified by scientists as causing havoc with weather patterns.

The effects of El Nino and La Nina, respectively the warming and related cooling of Pacific sea surface temperatures, are felt in many parts of the globe, and have been blamed for a lengthy drought in Australia, flooding in the Horn of Africa and Bolivia, and more severe winter monsoons in South Asia in 2006-2007.

However, WMO official Rupa Kumar Kroll said that effects over the coming months are expected to be mild.

"Near neutral conditions are considered the most likely outcome for the middle part of the year and shortly thereafter," Kroll said, adding that La Nina "gradually weakened from its peak strength in February."

"Rapid development of El Nino or re-development of La Nina is not considered likely for the middle part of the year," he said.

The expert nevertheless cautioned that other factors which also influence seasonal climatic patterns could still trigger extreme weather conditions.

MARITIME NOTE

Riverdance ferry contractors praised after Cleveleys clear up

The contractors charged with cutting up the stricken Riverdance ferry have been praised for their work in keeping the beach clear of oil.

Nearly all of the oil has now been removed from the ship by Hancock’s Contractors Ltd and sub-contractor PGC Demolition Ltd, and the firms have been congratulated for their work.

Hugh Shaw, the secretary of state's representative for the operation, said: “The progress that has been made during the operation has been excellent and we are delighted that the beach has been kept free of oil.

“The contractors have gone to a great effort on the environmental side of things and they deserve full credit for that.”

Work is set to start soon on the removal of the engine and the remaining fuel tanks from the vessel, which ran aground just south of Cleveleys on January 31.

Cruise West already under Coast Guard watch
FLEET OPERATOR: Ships are being inspected and crew members questioned.

By JAMES HALPIN

The number of mishaps aboard Cruise West vessels so far this season has landed the company on a special program to review the ships' safety and maintenance procedures, according to the U.S. Coast Guard.

Seattle-based Cruise West ships have so far suffered three mechanical failures and two groundings, including the most recent that took place Monday morning when the Spirit of Glacier Bay ran aground in Tarr Inlet near its namesake bay.

The Coast Guard began talking to the company about the trend after its ships suffered the second mechanical failure of the season, said Capt. Scott Robert, Coast Guard sector Juneau commander.

Mechanical problems are common on ships, and the Coast Guard in Alaska responds to hundreds of such calls each season, he said. But the number specifically on Cruise West ships this season prompted the extra attention, he said.

"After the third mechanical failure and the (first) grounding is when we started to take a very proactive approach on looking at the safety systems on board those vessels," Robert said. "These safety stand-downs are above and beyond what we, the Coast Guard, typically do with this industry."

The Coast Guard frequently holds surprise spot inspections and evaluates vessels at the beginning of the season, Robert said. The "safety stand-downs" are an added layer of oversight to promote safety and prevent serious accidents, he said.

As part of the plan, all of Cruise West's ships are being inspected by Coast Guard personnel, who are examining safety plans, equipment and maintenance policies, Robert said. The boardings also entail talking to crew members to improve their awareness of safety conditions, he said.

Cruise West officials are working in partnership, with its vice president "actively participating" in the stand-downs, Robert said. The boardings are scheduled in advance and take about two or three hours on average, he said. They are being held wherever the ships are -- in Alaska and elsewhere.

"This is a Coast Guard-wide issue," Robert said. "This is a combined, overarching look (at) Cruise West across the entire Coast Guard."

The agency plans to continue with the stand-downs until it is convinced Cruise West vessels are being operated and maintained safely, Robert said.

Jerrol Golden, spokeswoman for Cruise West, which operates nine small cruise ships, would not comment on the Coast Guard program, though she said safety is a top priority for the company. She stressed none of the incidents this season involved any injuries.

"Each incident is different, and there's definitely lessons learned immediately," she said. "There's no doubt the management system is under review by us, for sure."

She would not elaborate.

Have a really great weekend!

RS