Winnipesaukee Forum - View Single Post - Tornado WARNING

CanisLupusArctos · 07-11-2008, 05:31 PM

The 112-mph wind gust from June 22 is being downgraded to (and officially recorded as) 75 mph. The cause for the abnormally high readings has been ruled a lightning strike.

C Tucker's report of the lightning strike was the turning point in this, as were the other witness reports from Black Cat during the storm, and emails from others on this forum (like DRH and others) who gave me enough stories about "the odd things we've seen lightning do at our house" so that I was able to make lightning a prime suspect and form a hypothesis that the weather instrument manufacturer just confirmed.

According to Tom Raymond of the technical support dept. at Davis Instruments, the cause for the high wind speed reading was most likely static electricity from either a nearby lightning strike AND/OR a statically-charged environment created by the direct overhead passage of a severe thunderstorm. The static entered the wind speed cable and caused the weather station's main console to think that the wind speed was higher than it actually was. This condition lasted for several minutes and then dissipated, allowing "normal" readings to resume.

When discussing this hypothesis with Mr. Raymond he concluded that if the damage wasn't consistent with 112 mph but there is damage from lightning at the location (the water temp monitor was a casualty) then he believes the hypothesis is most likely what happened.

As for the 75 mph reading, I am basing that on the reports of Gatto Nero, C Tucker and a renter on the island, in comparison with a previous, similar thunderstorm during which I measured 75 mph. The trees survived that thunderstorm although they were weakened by it, and they did their breaking in lesser winds during the weeks to follow.

Similarly, the most tree damage in the April 16, 2007 Nor'Easter occurred a few hours after the storm's peak wind. Last week we had a wind gust to 60 mph from the south in a thunderstorm that took down a lot more branches than the June 22 storm (I found most of them a couple hundred feet north of the trees they came from.) They were probably pre-stressed from the June 22 storm.

The other readings from the station on June 22 (such as the incredibly heavy rain) are being considered accurate because there was plenty of physical damage, and witness reports to confirm them.

The storm was a very turbulent one (hence the NWS issuing a tornado warning for it) and turbulent thunderstorms generate a lot of static - lots of lightning. Based on the minute-by-minute data (posted above) I would say it passed directly overhead. The whole place was probably awash with static electricity for several minutes. I certainly wouldn't have wanted to be standing around in that one - or near any plumbing or electrical stuff inside.

So, to conclude: The June 22 thunderstorm at Black Cat Island generated a 75 mph wind gust that the weather station recorded as 112 mph due to static electric interference in the sensor cables due to lightning and/or statically charged environment.

Many thanks to all who offered reports and info to help solve this!

07-11-2008, 05:31 PM	#31
CanisLupusArctos Senior Member Join Date: Jan 2007 Location: Center Harbor Posts: 1,049 Thanks: 15 Thanked 472 Times in 107 Posts	The verdict is in The 112-mph wind gust from June 22 is being downgraded to (and officially recorded as) 75 mph. The cause for the abnormally high readings has been ruled a lightning strike. C Tucker's report of the lightning strike was the turning point in this, as were the other witness reports from Black Cat during the storm, and emails from others on this forum (like DRH and others) who gave me enough stories about "the odd things we've seen lightning do at our house" so that I was able to make lightning a prime suspect and form a hypothesis that the weather instrument manufacturer just confirmed. According to Tom Raymond of the technical support dept. at Davis Instruments, the cause for the high wind speed reading was most likely static electricity from either a nearby lightning strike AND/OR a statically-charged environment created by the direct overhead passage of a severe thunderstorm. The static entered the wind speed cable and caused the weather station's main console to think that the wind speed was higher than it actually was. This condition lasted for several minutes and then dissipated, allowing "normal" readings to resume. When discussing this hypothesis with Mr. Raymond he concluded that if the damage wasn't consistent with 112 mph but there is damage from lightning at the location (the water temp monitor was a casualty) then he believes the hypothesis is most likely what happened. As for the 75 mph reading, I am basing that on the reports of Gatto Nero, C Tucker and a renter on the island, in comparison with a previous, similar thunderstorm during which I measured 75 mph. The trees survived that thunderstorm although they were weakened by it, and they did their breaking in lesser winds during the weeks to follow. Similarly, the most tree damage in the April 16, 2007 Nor'Easter occurred a few hours after the storm's peak wind. Last week we had a wind gust to 60 mph from the south in a thunderstorm that took down a lot more branches than the June 22 storm (I found most of them a couple hundred feet north of the trees they came from.) They were probably pre-stressed from the June 22 storm. The other readings from the station on June 22 (such as the incredibly heavy rain) are being considered accurate because there was plenty of physical damage, and witness reports to confirm them. The storm was a very turbulent one (hence the NWS issuing a tornado warning for it) and turbulent thunderstorms generate a lot of static - lots of lightning. Based on the minute-by-minute data (posted above) I would say it passed directly overhead. The whole place was probably awash with static electricity for several minutes. I certainly wouldn't have wanted to be standing around in that one - or near any plumbing or electrical stuff inside. So, to conclude: The June 22 thunderstorm at Black Cat Island generated a 75 mph wind gust that the weather station recorded as 112 mph due to static electric interference in the sensor cables due to lightning and/or statically charged environment. Many thanks to all who offered reports and info to help solve this!