A handful of tropical storms and hurricanes have defied the odds and strengthened over land. Now researchers believe they have a better understanding why this occurs.
Tropical systems are expected to weaken while interacting with land, but if conditions are ideal, a land mass can feed these entities and act as a "brown ocean." A recently released study, funded by NASA and conducted by Drs. Theresa Andersen and Marshall Shepherd of the University of Georgia has found that abundant soil moisture can continue to feed a tropical storm or hurricane long after it has left the warm waters of an ocean.
According to Shepherd, 227 of the 3,254 storms from 1979 to 2008 met the criteria for landfalling tropical systems globally. Of those 227, 182 storms weakened after moving over land, but 45 maintained or increased in strength. Those 45 storms -- roughly 20 percent of all landfalling storms in the study -- became the subject of the team's investigation.
"This is particularly critical since a study by former National Hurricane Center deputy director Ed Rappaport found that 59 percent of fatalities in landfalling tropical cyclones are from inland freshwater flooding," Shepherd said in the report.
Tropical Storm Erin was one of those such storms in 2007. As it moved over moisture-rich Oklahoma, Erin picked up steam, forming an eye-like feature over the Plains.
"Erin's remnant in 2007 is forever burned in my mind," said weather.com senior meteorologist Jon Erdman. "I had never seen a tropical cyclone remnant that far inland behave like that."
During Erin, Watonga, Okla. recorded more than three consecutive hours of high winds, with a peak gust to 82 mph, during the overnight hours of Aug. 19, 2007, Erdman said.
NWS RADAR IMAGE
(MORE: The Storm That Killed 300,000)
In retrospect, Stu Ostro, meteorologist at The Weather Channel, wrote that the storm should have been reclassified by the National Hurricane Center as a tropical cyclone as it passed over Oklahoma.
These inland tropical cyclone maintenance and intensification events (TCMI) have been observed in the U.S. and China, butoccur in Australia most frequently, according to a LiveScience story on the report.
As hurricane season ramps up, researchers will be closely watching these "brown oceans" to see if they revive more tropical cyclones passing over our heads.
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