14 DAY TRIAL // Meteorologists are puzzled by the presence of lightings in some of this year's hurricanes: Rita, Katrina and Emily and they are trying to find a scientific answer for this dilemma.
Unlike storms, which are generally accompanied by lightning and thunderclaps, hurricanes are renowned for lacking them.
The only exceptions to this rule were Rita, Katrina, and Emily.
Richard Blakeslee of the Global Hydrology and Climate Center (GHCC) was one of a team of scientists who explored Hurricane Emily using NASA's ER-2 aircraft.
Flying high above the storm, they noted frequent lightning in the cylindrical wall of clouds surrounding the hurricane's eye.
"Both cloud-to-cloud and cloud-to-ground lightning were present, a few flashes per minute," says Blakeslee.
"Generally there's not a lot of lightning in the eye-wall region. So when people see lightning there, they perk up, they say, okay, something's happening."
Indeed, the electric fields above Emily were among the strongest ever measured by the aircraft's sensors over any storm.
"We observed steady fields in excess of 8 kilovolts per meter. That is huge--comparable to the strongest fields we would expect to find over a large land-based 'mesoscale' thunderstorm," Richard Blakeslee said.
Emily was the only hurricane researchers observed from the plane, but electrical discharges were also noticed for Rita and Katrina. In addition, a series of similarities can be identified: all three storms were powerful: Emily was a Category 4 storm, Rita and Katrina were Category 5, all three were over water when their lightning was detected; and in each case, the lightning was located around the eye-wall.
Richard Blakeslee says that the reason why hurricanes lack electrical discharges is that they don't have vertical winds.
The researcher also says that lightning has been seen in hurricanes before, but only when they made landfall in high altitude areas.
"Hurricanes are most likely to produce lightning when they're making landfall. But there were no mountains beneath the "electric hurricanes" of 2005, only flat water," he said.
One of the hypotheses is related to the intensity of the 2005 hurricanes, but the researcher says this explication is too simple. "There must be something else at work," Richard Blakeslee concluded.
