Electric Hurricanes

[lurkey]

Electric Hurricanes

01.09.2006

Three of the most powerful hurricanes of 2005 were filled with mysterious lightning.

January 9, 2006: The boom of thunder and crackle of lightning generally mean one thing: a storm is coming. Curiously, though, the biggest storms of all, hurricanes, are notoriously lacking in lightning. Hurricanes blow, they rain, they flood, but seldom do they crackle.

Surprise: During the record-setting hurricane season of 2005 three of the most powerful storms--Rita, Katrina, and Emily--did have lightning, lots of it. And researchers would like to know why.


Richard Blakeslee of the Global Hydrology and Climate Center (GHCC) in Huntsville, Alabama, was one of a team of scientists who explored Hurricane Emily using NASA's ER-2 aircraft, a research version of the famous U-2 spy plane. 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," he says. "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," says Blakeslee. "That is huge--comparable to the strongest fields we would expect to find over a large land-based 'mesoscale' thunderstorm."

The flight over Emily was part of a 30-day science data-gathering campaign in July 2005 organized and sponsored by NASA headquarters to improve scientists' understanding of hurricanes. Blakeslee and others from NASA, NOAA and 10 U.S. universities traveled to Costa Rica for the campaign, which is called "Tropical Cloud Systems and Processes." From the international airport near San Jose, the capital of Costa Rica, they could fly the ER-2 to storms in both the Caribbean and the eastern Pacific Ocean. They combined ER-2 data with data from satellites and ground-based sensors to get a comprehensive view of each storm.

Rita and Katrina were not part of the campaign. Lightning in those storms was detected by means of long-distance sensors on the ground, not the ER-2, so less is known about their electric fields.

Nevertheless, it is possible to note some similarities: (1) all three storms were powerful: Emily was a Category 4 storm, Rita and Katrina were Category 5; (2) all three were over water when their lightning was detected; and (3) in each case, the lightning was located around the eye-wall.

What does it all mean? The answer could teach scientists something new about the inner workings of hurricanes.

Actually, says Blakeslee, the reason most hurricanes don't have lightning is understood. "They're missing a key ingredient: vertical winds."

Within thunderclouds, vertical winds cause ice crystals and water droplets (called "hydrometeors") to bump together. This "rubbing" causes the hydrometeors to become charged. Think of rubbing your socked feet across wool carpet--zap! It's the same principle. For reasons not fully understood, positive electric charge accumulates on smaller particles while negative charge clings to the larger ones. Winds and gravity separate the charged hydrometeors, producing an enormous electric field within the storm. This is the source of lightning.

A hurricane's winds are mostly horizontal, not vertical. So the vertical churning that leads to lightning doesn't normally happen.



Lightning has been seen in hurricanes before. During a field campaign in 1998 called CAMEX-3, scientists detected lightning in the eye of hurricane Georges as it plowed over the Caribbean island of Hispaniola. The lightning probably was due to air forced upward -- called "orographic forcing" -- when the hurricane hit the mountains.

"Hurricanes are most likely to produce lightning when they're making landfall," says Blakeslee. But there were no mountains beneath the "electric hurricanes" of 2005—only flat water.

It's tempting to think that, because Emily, Rita and Katrina were all exceptionally powerful, their sheer violence somehow explains their lightning. But Blakeslee says that this explanation is too simple. "Other storms have been equally intense and did not produce much lightning," he says. "There must be something else at work."

It's too soon to say for certain what that missing factor is. Scientists will need months to pour over the reams of data gathered in this year's campaign before they can hope to have an answer.

Says Blakeslee, "We still have a lot to learn about hurricanes."


Authors: Patrick L. Barry and Dr. Tony Phillips | Production Editor: Dr. Tony Phillips | Credit: Science@NASA

[GulfHills]

Great article.

[Cookiely]

I saw a recent program and they mentioned control of the weather. This meterologist said that he had witnessed strange cloud formations in a grid like pattern that indicated someone was attempting to control the storm or create a storm. In my opinion it really didn't look like a normal cloud pattern. They introduced various experts and they gave their opinion on weather control pro and con. He discussed the possibility of controlling a hurricane and the economic impact it has. Could the lightning inside the hurricane be from someone trying to manipulate the core? Has anyone ever mentioned lightning in a hurricane prior to the last few years?

[GulfHills]

I really don't see anything or anyone (other then God) being able to manipulate a hurricane.

[terstorm1012]

Someone posted during Katrina that unusual lightning might be due to the mineral content of the water south of the Mouth of the Mississippi...was it Nexrad? I don't recall exactly who....could be why...

[StormScanWx]

I really don't see anything or anyone (other then God) being able to manipulate a hurricane.

God is in control!


Very Very Good Article!

[Aslkahuna]

Katrina and Rita both showed a lot of lightning not only in the eyewall and outer band but also in the internal spiral bands (which is most unusual) during the explosive deepening phase of the storms when satellites were showing extremely cold (-85 to -90C) cloudtops in some of the bands and in the eyewall. In his long form video of Typhoon Omar, Jim Leonard not only got that close CG strike during the incoming eyewall but during the return wind phase recorded frequent lightning as the storm was still rapidly deepening as it moved away from Guam. We had thunderstorms during the eyewall of Typhoon Irma at Clark AB in 1974. The lightning during such explosive phases is indicative of the intense convective and dynamic activity going on but can it provide a clue as to what triggers these phases is the question.

Steve

[brunota2003]

But isnt the eyewall a ring of thunderstorms surrounding the eye??? so, if they are rapidily deepening, then it would get enough vertical lift to produce the lightning...right??? so, if the cloud tops were rapidly rising and cooling, then there should be lightning because there is alot of vertical lift going on...but when the hurricane is steady in intensity or weakening, then there isnt that vertical lift to produce the lightning because the clouds are staying the same height or collapsing...

[arkess7]

interesting

[Aslkahuna]

If you have ever seen a sounding from deep within an intense Tropical Cyclone, you will find that temperatures are very warm high up. Consequently, the ice crystals needed for charge initiation and separation will not be found until way up in the eyewall thus any lightning there is usually high up and weak. To have the amount of CG lightning that was observed in Katrina and Rita requires a tremendous amount of turbulent mixing to bring the charges centers down and hence more than the normal amount of convection typically found in the eyewall. Even more importantly was the lightning in the internal spiral bands of the storms since this is a very rare occurrence as the spiral bands are usually not high enough topped to be T-storms. Bottom line was that these storms were far more convectively active and dynamic than your usual hurricane. In some cases, a RIC might be anticipated if the storm is approach a trough where the flow may result in strong poleward outflow. But in the case of Katrina especially, the outflow was actually strongest to the south even to the point where it suppressed all convection beyond the storm as far as AZ. Another factor with these storms may have been the entrainment of Trade Air which has a different thermodynamic structure than pure mT air and which can release stored up Convective energy quick explosively (as I learned in the Philippines) when something forces it to.

Steve

[brunota2003]

ok, did you witness anything "usual" this season??? lol, it was just a thought i had, that seemed to of fit, and IMHO still does...

[btangy]

If the lightning was observed during the extreme intensifying phases of any of cyclones, the ageostrophic convergence due to the strong pressure falls would yield very strong vertical velocities. This is what you see in mid-latitude systems as well undergoing 'bombogenesis'.

[Aslkahuna]

Lightning has been observed before in typhoons undergoing RIC's so it's not really that rare insofar as eyewall lightning is concerned. What struck me was the lightning showing in the internal spirals. However, since we don't have the ability to detect lightning in typhoon RICs since, except for a few islands, those events usually take place far from any sensor sites we can't say for sure that a similar situation doesn't happen there as well though I never saw it recon reports on RIC typhoons when I was in the WPAC.

Steve

[Extremeweatherguy]

All I know is that when a hurricane is bearing down on you, the last thing you are going to be looking for is lightning or trying to hear thunder. Plus, any lightning will probably blend in with the thousands of transformers that are popping and making the sky blue...you won't know the difference. Also, with the roar of the wind...thunder would be very difficult to hear. Even if there was lightning, 99% of the people going through the eyewall would never notice.

[Terrell]

Very interesting article. The Electric Hurricanes does sound like a good name for a rock group.