Smoke from distant fires intensified devastating tornado outbreak, says study
Meteorologist/Science Writer
Tuesday, February 10, 2015, 4:40 PM - Back in April 2011, a devastating tornado outbreak killed hundreds of people and causing billions of dollars in damages, and researchers have found that the strength of this outbreak was intensified by smoke blowing in from forest fires over a thousand kilometres away.
When a total of 122 tornadoes spawned on April 27, 2011, the US National Weather Service counted the outbreak as "one of the deadliest in the country since systematic tornado record keeping began in 1950." This assessment was partly for the number of tornadoes and the number of exceptionally powerful tornadoes - 15 that ranked as EF4 or EF5 - but also for the over 300 fatalities caused and the estimate of between $6 billion to $11 billion in damages wrought in just that one day.
The combination of conditions that went into the outbreak were fairly typical, with a mixup of dry flow from the west, moist flow from the Gulf of Mexico to the south, and a strong upper-level trough that tracked across the Southern Plains to the East Coast to focus all the resulting energy.
RELATED: However, one added factor came into play which had gone unnoticed until now.
Researchers from the University of Iowa examined the flow of particulate matter - smoke from fires set to clear agricultural land in Central America - into the region of the outbreak, and found that it had a significant effect on the intensity of the storms and the strength of the tornadoes that spawned from them.
Credit: Brad Pierce, NOAA Satellite and Information Service Center for Satellite Applications and Research.
The above satellite image, from April 27, 2011, includes tornado tracks from April 26-28 added as solid red lines, with yellow dots showing the locations of fires. The swath of colours over the Gulf of Mexico, and behind the bank of clouds that spawned the tornadoes, represents the concentration of smoke particles in the atmosphere. The highest concentrations are indicated in red, with the lowest concentrations in purple.
The fact that this outbreak occurred in a region of the United States that allowed for a great number of scientific instruments to be brought to bear in recording it meant that researchers had a vast array of data to use in modeling the event. That's exactly what co-leads Gregory Carmichael and Pablo Saide, along with their colleagues, put to use in their study, adding in additional data gathered by satellite that detailed the amount of smoke trapped in the flow off the Gulf.
According to what the researchers wrote:
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| Numerical experiments indicate that the presence of smoke during this event leads to optical thickening of shallow clouds while soot within the smoke enhances the capping inversion through radiation absorption. The smoke effects are consistent with measurements of clouds and radiation before and during the outbreak. These effects result in lower cloud bases and stronger low-level wind shear in the warm sector of the extratropical cyclone generating the outbreak; two indicators of higher probability of tornadogenesis and tornado intensity and longevity. |
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"These results are of great importance, as it is the first study to show smoke influence on tornado severity in a real case scenario. Also, severe weather prediction centers do not include atmospheric particles and their effects in their models, and we show that they should at least consider it," Carmichael said in a University of Iowa press release.
"We show the smoke influence for one tornado outbreak, so in the future we will analyze smoke effects for other outbreaks on the record to see if similar impacts are found and under which conditions they occur," Saide added. "We also plan to work along with model developers and institutions in charge of forecasting to move forward in the implementation, testing and incorporation of these effects on operational weather prediction models."
Sources: NWS, Carmichael, Saide, et al., UI News.
RELATED VIDEO: Meteorologist Jaclyn Whittal describes one of the more unusual, and spectacular 'weather' events - the fire tornado.
