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Old 06-22-2008, 12:34 PM   #1
This'nThat
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Default Tornado WARNING - Sunday, 1:30pm

Merideth is under a tornado warning right now. Baseball size hail has been reported. NWS: * Tornado Warning for...
northwestern Belknap County in central New Hampshire...
southern Grafton County in northern New Hampshire...
western Carroll County in northern New Hampshire...

until 1:45. Get in the basement, away from windows, under a table, bring a mattress, get under the mattress.
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Old 06-22-2008, 12:59 PM   #2
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Default any reports?

Any reports from the Moultonborough area?
Hope all is well up there...
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Old 06-22-2008, 01:00 PM   #3
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Exclamation The Warning - cut and paste, sorry it's all CAPS

At this time the Tornado Warning area appears to be the same as the Thunderstorm Warning area. The NWS release:

SEVERE THUNDERSTORM WARNING
Issue Date: 143 PM EDT SUN JUN 22 2008
Expiration: 215 PM EDT SUN JUN 22 2008

THE NATIONAL WEATHER SERVICE IN GRAY MAINE HAS ISSUED A
* SEVERE THUNDERSTORM WARNING FOR...
CENTRAL BELKNAP COUNTY IN CENTRAL NEW HAMPSHIRE...
SOUTHERN OXFORD COUNTY IN WESTERN MAINE...
CENTRAL CARROLL COUNTY IN NORTHERN NEW HAMPSHIRE...
* UNTIL 215 PM EDT
* AT 139 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING QUARTER SIZE
HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH. THESE STORMS WERE
LOCATED ALONG A LINE EXTENDING FROM CONWAY TO LACONIA...AND MOVING
NORTHEAST AT 45 MPH.
* SOME LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
FRYEBURG...OSSIPEE...EFFINGHAM...KEZAR FALLS AND HIRAM.
THIS STORM HAS A HISTORY OF PRODUCING DESTRUCTIVE WINDS AND LARGE
DAMAGING HAIL. SEEK SHELTER NOW INSIDE A STURDY STRUCTURE AND STAY
AWAY FROM WINDOWS!
PLEASE REPORT HAIL OR STRONG WINDS TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...1-877-633-6772...WHEN YOU CAN DO SO SAFELY.
LAT...LON 4400 7113 4417 7092 4409 7085 4409 7087
4405 7086 4404 7080 4397 7074 4387 7078
4386 7080 4382 7080 4379 7098 4374 7099
4344 7154
TIME...MOT...LOC 1743Z 236DEG 48KT 4395 7104 4358 7134

From This web site The area in RED on the county map shows Tornado Warning area. **edited to add updated info @ 2:20 PM. The link map no longer shows a Tornado or Thunderstorm Warning. At this moment. Conditions change fast.

Again, sorry for the CAPS. That's how the NWS sends their Warnings.

Stay safe.

Last edited by Skipper of the Sea Que; 06-22-2008 at 01:22 PM. Reason: Map in Link updates -
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Old 06-22-2008, 01:00 PM   #4
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Default Tornado Warning

Yes, interesting watching the storm clouds build and morph from the south side of the lake.

More warnings every few minutes -- now Severe Thunderstorm Warning for some areas.

Excellent place to see how it affects your location is through WMUR's interactive radar -- some may not already know about this sight. You can zoom in to your street...it's pretty intersting.

More storms forming as they move the Lakes Region....one coming up from our south right now...crack!

www.wmur.com

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Old 06-22-2008, 01:32 PM   #5
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In a Mac, create a dashboard with the WX radar and maps available.
Then your F12 key brings it up & then puts it away.

Only on a mac!!!
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Old 06-22-2008, 01:46 PM   #6
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Is this an accurate report or just a mistake?

A wind gust of 168mph at 1:34pm today, is reported on the Black Cat Weather Cam.

168mph....that's some gust....probably caused by a leaf blower accidentally aimed at the anamometer, or something?

Is a hurricane with 168mph winds rated as a force 5?
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Old 06-22-2008, 01:57 PM   #7
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I saw that as well. It was saying 51 MPH about 15 minutes before. Wondering if there is damage up there. Not so bad here in Concord.
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Old 06-22-2008, 02:10 PM   #8
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Default 3:10 Pm

Any report from anyone in Meredith area?????? Wife is there now, and can not reach her on cell.
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Old 06-22-2008, 03:07 PM   #9
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Default report from meredith

I was at Walters in holderness when it hit. the building was hit by lightning
and the fire dept. was in the bar with full gear. it was wild.
everyone moved into the center of the bar and watched it pass.
at 300 I was back in meredith to find riverbed remains all down my street and tree limbs all over my yard.
my screen porch looked like a fire hose had been sprayed at it.
right now it is light gray and calm.
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Old 06-22-2008, 06:24 PM   #10
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We were out off Bear when it got nasty...kind of snuck up on us! My son and I were to busy floating and enjoying the day! I haven't been stuck in rainlike that in a long time. We ended up leaving the Lake at 3ish and were soaked just from the run from the boat to the truck...and I have a covered slip!
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Old 06-22-2008, 08:42 PM   #11
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I doubt it hit 168 mph but it was the wildest weather I have seen since I've been on the island. My boat was beating up my 40' aluminum dock pretty good. I think if I was standing on the end of the dock I would have been thrown off from the jolts more than once. That's with snubbers and whips. For a while I was concerned that the aluminum might twist or even snap. Luckily it didn't but one of the bolts that holds the whip for the 15' whaler got pulled up from the pressure. I would say we were seeing consistent 3'+ waves and I have less than 2 miles of fetch to the north. I can't even imagine what it must have been like on the Broads side of Rattlesnake.
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Old 06-22-2008, 08:48 PM   #12
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We were at the Owls Nest having lunch and when we came out to their dock we could see the the wall of blackness coming in over the Meredith area. Needless to say we made very quick tracks back to the Glendale docks. We made it back with about 20 minutes to spare before the sky just opened up, just enough time to unpack the boat and head back to our RV. I'm glad I wasn't caught on the lake during this storm!

Dan
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Old 06-22-2008, 10:04 PM   #13
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Default Significant Wind Event

Of all the days I had to pick for some travel (which is now rare, thanks to high gas prices) it was now. My family is headed to the house at Black Cat now and should be able to see damage in daylight.

Here is what I have been able to learn about the wind event recorded by my (automated) weather station today, along with some other useful facts about this kind of weather, particularly as it relates to the lake.

Storm Prediction Center didn't seem too excited about today's severe weather threat when they made their prediction and I couldn't find any reason to predict much more than the "relaxation CD" style of thunderstorms we've had every other day this week. But then again, the weather is beyond mankind's control or prediction and it likes to assert that fact. Today was one of those days.

After a nice rare sleep-in, I logged on to check email but when my home page popped up I noticed it said "Tornado Warning."

There was no tornado watch in effect at the time, which usually is not the case when a tornado warning is issued by the local office. Usually the SPC in Norman OK is on top of it already by having issued a watch for the whole area. Not today. To their credit, the maps weren't showing anything hugely dramatic like they did when the heat wave ended earlier this month. I would expect to see more severe weather from that kind of situation than from a setup like today's.

Well, we had unstable air, and there was just enough of a trigger to get it to start rising rapidly, leading to the explosive development of the storms across the state today. Sometimes it happens like that.

My first thought was that the house had been destroyed and that the computer was still registering its last available weather readings which included the 168 mph. I remotely checked both the cam and weather station and found they were still live, still getting AC power (hadn't even switched to battery.)

So I threw out the 168 mph. I am calling that invalid for now. I do have a correction factor in the computer which corrects for the fact that there are trees with leaves in summertime. In winter the correction is not necessary except for one direction that still has trees. Today I got out a calculator and removed the correction factor to get the raw wind speed reading. It came out to 112 mph.

112 mph is still a very significant wind event, so my next step was to find any reason to doubt the equipment. I logged in remotely and checked it, and found it to have been working fine immediately before and after the wind event. Furthermore, I all the other major parameters (other than wind) that the station measures didn't feature any changes nearly as dramatic as the wind. For example, if the barometer, temperature, and other factors also experienced wacky, unbelievable changes at the same time as the wind, I could say the weather station or computer was acting up. But that wasn't the case.

All the other factors behaved as I would expect them to behave in a storm like this. The wind was the only odd child. If it had experienced something catastrophic like a lightning strike or physical damage, it wouldn't have gone back to functioning normally immediately after the storm passed.

I spent some more time checking and re-checking, looking at the storm itself, and waiting to see what sort of severe weather reports came in from the area itself.

I downloaded the entire 3-hour time lapse sequence and saw cloud formations that looked like they belonged to a tornado-producing thunderstorm, but I still didn't see what I needed to see: The funnel itself, or an obvious wall cloud (precursor to funnel).

Radar had indicated this storm to be a potential tornado-producer. There was no "ground truth" as forecasters call it, when human eyes actually confirm the presence of a funnel cloud (not touching ground) or a tornado. Sometimes a rotating wall cloud is good for confirmation also.

For those wondering how the radar works, it is relatively new (a few years old) and is capable of scanning at different tilts from horizontal as well as measuring the direction and speed of winds within a storm. This is how meteorologists find rotation within a thunderstorm. Before this radar was developed, they needed ground truth in order to issue a tornado warning. By the time the warning was out, often times the tornado had already killed people. This radar allows them to issue tornado warnings when it looks like one is about to form. This provides warning time that wasn't available before, so it saves lives. The drawback is that rotation within a thunderstorm doesn't always turn into a tornado. That's apparently what happened today - maybe.

It might have been a funnel cloud. More on that in a minute.

I put together what I had:

- The power at the house was still on.

- The webcam showed impressive clouds but still no ground truth. I would've loved to have seen some images saved from Gatto Nero's cam, or BearCam.

- I could find nothing malfunctioning in the weather station or its computer on a technical level.

- Wind speed shows an event well above 75 mph, which is the highest speed I've actually witnessed there (a couple years ago.) The trees survived that, and then 64 mph from the opposite direction ripped them apart during the April 16 2007 storm.

- Wind direction graph shows a steady east wind for an hour or so leading up to the main event, and then a total scatter-plot of all directions during the main event.

- I didn't have a way of seeing today's damage, and it's possible (based on past experience with high wind events) that any damage could look unremarkable to a non-scientific eye. Many years ago a near-tornado situation threw the heavy metal rowboat off the dock and through the air while leaving the trees untouched. It can do some odd things.

Here is the funnel cloud part, which is still unconfirmed:

I tried to answer the question: How could a wind gust of 112 mph hit the wind sensors at the house without at least knocking out the power?

Here's how: A funnel cloud doesn't affect what's below it. It's harmless to whatever it's not touching (when it touches down, it's a tornado.) That's why they tell you to get to the basement, or into the deepest ditch you can find. It is always safer to be below it. With this in mind, I asked the National Weather Service if it was possible that the very bottom of a funnel cloud touched the wind sensors, which are located on a tower well above the roof peak. He thought for a minute and said yes. Once again, if that happened, there would be other signs of that happening. I would expect to see damage to the far upper sections of adjacent trees, and the debris thrown about.

From past experience I also know that wind gusts don't always touch the ground. In January 2007 a thunderstorm passed with a wind gust of 65 mph. The air flow came down out of the cloud and immediately ascended. The gas grill with full tank got lifted enough to be pushed 10 feet, and from there the damage to the trees "downstream" occurred higher and higher up over a path of 1000 feet or so. The final victim lost its uppermost 10-foot section. With this event in mind, I will say it's possible that we had a similar straight-line but "diving & retreating" wind gust that reached the wind sensors but not all the way to the ground.

It is also possible that the weather station recorded one thing and the computer somehow misheard it, but this is very unlikely based on my experience with the equipment. If there's going to be a miscommunication it's usually the computer acting "deaf" to the weather station rather than "hyper."

Who knows. The Union Leader called after seeing the 168 mph reading on my site and I told them what I've figured out (and guessed) so far. It's like the weather was waiting for me to bite the bullet on the gas expense and go visit friends.

My family is at Black Cat now and will be able to see more in daylight. Hopefully I'll join them later tomorrow or Tuesday morning. For now, visiting friends is always more meaningful than this or anything else, in the long run.

In the meantime, it's an unconfirmed report of 112 mph at Black Cat Island. If it was 112 mph, it was very localized, which has happened before. If it wasn't, then it was at least a very significant wind event on a par with the most intense thunderstorms I've ever witnessed around here.

NWS-Gray reports a chance of more severe weather across New Hampshire tomorrow (Monday.) This is from their latest discussion, written at 8 pm:

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
COLD FRONT APPROACHES THE REGION FROM THE WEST ON MONDAY. EXPECT
ANOTHER DAY OF SHOWERS AND THUNDERSTORMS WITH A THREAT OF SEVERE
THUNDERSTORMS MAINLY OVER NEW HAMPSHIRE. MARINE INFLUENCE SHOULD
ONCE AGAIN INHIBIT CONVECTION ALONG THE MAINE COAST.


UPDATE: I just had a good look at the station's minute-by-minute records during the height of the storm. I'll type them up when I'm more awake and no longer socializing, but for now here's what I see:

The peak wind speed (whatever it was) coincides with the maximum rainfall rate of 0.13" per minute (7.80" per hour) and also a rapid wind shift from NW to S to NE.

The rainfall rate had been sustained at 0.08" per minute (4.80" per hour) since 13:28. Immediately following the peak wind at 13:35 the rainfall rate dropped to 0.05" per minute (3 inches per hour.) At 13:36 the rate dropped to 0.01" per minute which is about the minimum for "heavy" and continued until 13:42. Heavy rain had begun at 13:15.

Temperature dropped from 75 to 65 between 12:55 and 13:10. Wind was calm or very light until 13:10. Winds approached 10 mph at that time, which is about the time NWS-Gray was preparing their tornado warning.

At 13:22, winds were averaging 10 mph (no correction for trees applied) and gusting to 32 mph. Direction was from the NW (where the closest trees are.) A raw reading of 32 mph from that direction in winter usually translates to an all-out hurricane on the lake in front of the house, and can be difficult to sleep through. Wind speed reached 20 mph (raw) from the NW at 13:27. Then a 98 mph gust comes (raw) also from the NW, and the rainfall ramps up big-time. Between 13:29 and 13:30 the barometer actually rises from 30.01 to 30.04.

At 13:34 the wind shifts to south and then to NE. Peak wind of 112 (raw) comes from the NE. It quickly dies off to 2 mph and then back up for one more gust to 96 mph (all NE) before ending at 13:44, also the end of the rain.

Since tornadoes usually occur in the rain-free part of the storm, I would be very surprised if this was a tornado/funnel cloud. A tornado-like phenomenon that often accompanies extremely heavy rain is a microburst. That's my guess for what this event was, for now.

Still need to see more. Now bedtime.

Last edited by CanisLupusArctos; 06-23-2008 at 12:48 AM.
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Old 06-23-2008, 07:15 AM   #14
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Great stuff CLA. Keep up the good work!
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Old 06-23-2008, 07:15 AM   #15
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Default Thanks for the lesson

CLA, back in the late 70's and early 80's, we lived in Bossier City LA, and saw our fair share of severe weather.

Yesterday, around 2PM or so, on our way back home from Farmington to Alton, right around the Alton/New Durham line on rte 11, looking across the Merrymeeting swamp, you could see tremendously heavier rain than that we were in. Rounding the left hand curve (heading west on rte 11), you could see on the road what looked almost like waves of water across the road, not from cars, but from the wind. Visibility dropped from a mile or more to an estimated 100-150 yards, and the sides of the road looked like streams. Wind was significant, but not shaking the Blazer. We were out of it by the time we reached Merrymeeting campground, back to just rain with a mile or more visibility.

I haven't seen anything like that since LA. and look forward to your eye's inspection when you get home. Hope all is well there.
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Old 06-23-2008, 09:51 AM   #16
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Not being home is just not fair CLA.I would lean toward the microburst myself,which are associated with tornadic conditions.I've seen a couple at Cannon Mt that have done a huge amount of damage.Very large blowdown areas of around a couple hundred feet.All the trees layed down flat but no cyclonic pattern to the final position of the debris field.Great stuff though.No damage at your house I trust?
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Old 06-23-2008, 12:39 PM   #17
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I was at Black Cat during the storm. It was the worst I remember since we came in late 1960's. We face the northwest and there were incredible waves rolling into our cove. There was a lightning strike that I believe struck the island between our location and the bridge. It was the most powerful I have ever felt. I could actually feel the pressure wave. I don't know if that jolt could have affected your weather equipment but the heaviest rain immediately followed this strike.
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Old 06-23-2008, 04:00 PM   #18
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Default Microburts

About three years ago, late July, my wife called frantically around 9pm from our place on Long Island (NE side), screaming about high wind out front, with rain blasting sideways. With the front spotlight on, she couldn't see as far as the swim raft anchored about 75 feet out from shore. I packed a bag quickly and hit the road again. I arrived about 11pm, to complete calm. Power was out. The lower end of the Neck road had a few leaves and minor twigs on the pavement, but nothing notable otherwise. The driveway going in to the cottage, parallel to shore and about 60 feet back from the water, also had just some blown down leaves and minor twigs on it.

The inner half of my dock was ripped off the outer half, upturned, and substantially dismantled. The boat was still tied to the outer half, which was held down by a ballast platform loaded with rock. A neighbor had run a line from the boat to a tree on shore to keep the whole thing from drifting off.

In the morning I walked the shore, headed southeast. It appeared that whatever it was (microburst?) was exceedingly localized. It paralleled the shore, then, at a curve in the shoreline, it slammed into shore, snapping or uprooting upwards of a dozen large trees across two lots. We're talking about two feet and larger at the base. Just beyond those it veered off into the woods, leaving a similar path of destruction, then abruptly stopping. Further downshore there were a few other trees blown over.

I had never seen such destruction from a summer storm, or such localized destruction. The following week there wasn't any mention of this in the Meredith News. Too local, I guess. Too bad they missed such a great photo op.
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Old 06-25-2008, 08:38 AM   #19
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Default Any new news on the review??

CLA - Any new news on the review of the 112mph wind report? Just curious...
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Old 06-25-2008, 09:23 AM   #20
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Tornado's don't go up and down hills......the worst thing that could happen is a brief , isolated micro burst that would do the same damage as a tornado but only in a small area.Same with hurricanes...they break up rapidly once they get inland ,here in the north.
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Old 06-25-2008, 03:51 PM   #21
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Default All is well... sort of

Thank you all for curiosity, interest and concern.

Just a quick note because it's swim time and then more to do.

The basement was found flooded (now cleaned and drying), and the condition of the yard supports the incredibly intense rainfall rates recorded by the station.

However... I have seen more wind damage from the 40 mph events that we see regularly in normal thunderstorms and also in the wake of autumn-winter cold blasts. Yet eyewitnesses here all report incredible wind even if they couldn't measure it, and some of them have seen their share of bad storms.

The gust WAS recorded by the weather station prior to being picked up and sent out by the computer that monitors the weather station. Therefore, rule out computer issues.

I'm interested in the possibility of a lightning strike. The lake water temp monitor and a PC were both found with malfunctioning internet connections.

However...

- They were surge protected by battery backup, and so was the internet connection.

- The PC was off at the time.

- A second computer was on at the time, NOT surge protected, and shows no signs of damage.

- No other electronics on the same surge protectors, internet connection, or elsewhere in the house showed signs of harm.


Now the focus turns to wondering how to fund the replacement of the damaged components and in the meantime, if anyone feels like tackling the academic meteorology/engineering problem of "What happened?" it'll sure be interesting to piece it together.

Swim time.
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Old 06-26-2008, 07:47 AM   #22
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Lightning can travel in strange paths.I was hit a few years ago and lost 1 garage door opener but not the other and they were on the same circuit.2 tv's were fried but they were not on SP's.4 other SP's were fried but the tv's they were protecting were fine.I had a computer that was not protected and it survived.Go figure.
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Old 06-26-2008, 08:32 AM   #23
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Lightning can cause strange electrical probs. Two years ago, my next door neighbors house got hit. Specifically, it struck a tree, then his PWC trailers (yes, 2 different trailers), then it hit the nearby well head. OK I am not sure if that was the order the lightning hit, I just know it hit all of those things.
Anyway, his well pump got fried. Several pieces of electronics throughout his house did as well. TVs, radios, even battery chargers. Of course not every single one, but just some of them. Total cost was well into the thousands.

On an interesting note, the lighning went through the license plate on one of the trailers. Just a small round hole in the middle of the plate. On the other trailer, it hit the little metal hub cap and blew a hole in that as well. Cool stuff if you ask me!
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Old 06-26-2008, 11:21 AM   #24
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Lightning is slower than the speed of light. (A bit).
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Old 06-26-2008, 01:22 PM   #25
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Default Thanks!

This is great info to know! I never really studied "what lightning does once it lands" because I was always preoccupied with what's happening in the sky. Anyone else?

Slowly, I'm leaning towards the possibility that the lightning strike C Tucker mentioned might have been what fried the electronics (selectively) and that it might have introduced some voltage into the cable from the wind speed sensor.

But then I have the problem of "what speed was the wind?" I have witnessed a few events at or near hurricane force within the last 10 years and have seen the trees pushed to limits that I think plant biologists would want to study. Everyone seems to agree this event was far greater than anything that's hit in the last 10 years. So by that aspect, 112 mph is sort of in the ballpark.

If it happened, we have to answer the question, how did it happen without causing damage? There is no damage path on the island. Unless, as one of my family suggested, it started over the lake and literally ended at the house. It has to start and end somewhere.

There's also no way of knowing if the trees weren't at least fatally weakened by the wind until a gust of only 40 mph comes through and knocks down a bunch of them. I have seen trees survive big wind only to get knocked over by smaller wind a few months later.
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Old 06-26-2008, 01:44 PM   #26
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Some interesting reading, regarding lightning:

http://www.newton.dep.anl.gov/askasc...0/wea00030.htm

http://answers.yahoo.com/question/in...8082942AAQ6Kdf

http://www.peter-thomson.co.uk/tornado/Lightning.html
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Old 06-27-2008, 10:47 AM   #27
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Default Once at band camp

When I worked at Camp Lawrence, there was one of the usual quick popup storms. A group of us were sitting on the Dining hall porch watching the storm. The metal swim docks and the raft got hit, and then a bolt came down in the middle of the island. It hit the side of a cabin (made a hole), went though a pillow on a bed (made another hole), and then went down the antenna of a portable radio leaning against the bed (causing a small fire). A couple of seconds later another bolt came down on by west beach (Mark Island side of camp). It hit outside one of the cabins on the beach where some staff and campers had taken refuge during the storm. Two campers got a residual shock from the bolt. Not sure how the transfer happened, but the pillow that got hit in the cabin belonged to one of the kids that was shocked. Both campers were fine, and no one wanted to get on plane with the camper whose pillow got hit
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Old 06-27-2008, 12:53 PM   #28
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Quote:
Originally Posted by parrothead View Post
the pillow that got hit in the cabin belonged to one of the kids that was shocked. Both campers were fine, and no one wanted to get on plane with the camper whose pillow got hit
Interesting stuff! I would've asked that camper to pick my Powerball numbers and join me as I bought the ticket, then offer to split the winnings!

More serious note... strong thunderstorms are once again possible across the lake today. We are not in SPC's officially defined "severe threat" area but storms are becoming severe outside of it.

To our west, in Vermont, a storm is on a NW-SE path headed for Lebanon NH and radar has indicated weak rotation within it. Spotters have confirmed golfball hail from it.

Maybe it'll hold together and maybe it won't, but in any case, other storms are forming too. Keep your eyes to the sky this afternoon.

This stuff is becoming common in New England this summer, just as it has in the rest of the country, as the warmth of summer gets pushed around by the Canadian cool which is still out there. If the summer continues to be interrupted by cold fronts and Canadian disturbances, we can expect more severe weather.

Use this thread as a springboard for learning all you can about severe thunderstorms and tornadoes, or start a Q&A thread if you have specific questions.

There are many myths and truths associated with this sort of weather, and the discussion on this thread should give you an idea of what it can do and how odd it can be when it wants to.
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Old 06-27-2008, 01:54 PM   #29
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Default Just a short distance away

We are not very far from CLA but face east. Although we recieved a lot of rain on Sunday, the wind was minimal. We had some leaf clusters blown down but no branches and we didn't have to close any windows.
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Old 06-28-2008, 03:47 PM   #30
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Default Minute by Minute

BlackCatIslander's account makes this weather event even more interesting. There are now two accounts from the west side of the island describing a horrible storm, and BCI's account from the east side. This weather is consistent with the way the strongest thunderstorms are known for behaving: Totally lashing one location, while leaving the adjacent neighborhood almost unaware.

Here, finally, is the minute-by-minute data from the station. Note the wind shift as the storm passed directly over. NW winds become South and then quickly NE... no wonder the NEXRAD radar detected rotation within the storm. What I wonder is, can the radar tell the difference between an actual rotation and a localized area where there's a lot of difference in wind direction for some other reason? It seems to me that the two would look similar in the graphic display.

Time rain (in.) ... Wind (degrees/mph)... Remark
1255 --- --- Temp 75

1310 --- CALM Temp 65 Lgt Rain

1315 .04 --- Tornado Warning issued

1321 .04 304 at 16 G21
1322 .04 297 at 16 G49
1323 .02 283 at 21
1324 .02 295 at 18
1325 .03 300 at 18
1326 .03 316 at 25
1327 .05 326 at 31 Lightning strikes island (time approx - source: C Tucker)
1328 .08 292 at 13
1329 .08 296 at 98 Baro 30.01
1330 .09 307 at 100 Baro 30.04
1331 .08 293 at 96
1332 .08 312 at 98
1333 .12 343 at 94
1334 .13 180 at 94 G113 Rain rate 24.00”/hr (0.40”/min)
1335 .05 065 at 112
1336 .01 025 at 96
1337 .01 024 at 82
1338 .02 029 at 3
1339 .02 056 at 96
1340 .01 043 at 66
1341 .00 045 at 4
1342 .01 027 at 4
1343 .00 008 at 102
1344 .00 009 at 1 Baro 30.04
1345 .00 006 at 1 Baro 30.02
1346 .00 180 at 0
1347 .00 009 at 0

Rainfall is a minute-long accumulation ending at time of observation.

Rainfall rate of 24" per hour was mathematically calculated and recorded by the weather station and does not represent an actual accumulation of rain. The rate was probably sustained for no more than 15 seconds or so.

Barometric pressure readings are provided where changes took place.

Wind direction is in degrees. For a full explanation click on the wind direction number on the WeatherCam site, or ask a pilot or sailor.

Peak wind gust as recorded by the weather station (Davis VantagePro 2, cabled version) was 113 mph from the south. The 112 was what the monitoring software saw. The two machines read decimal points differently.

--------
Additional Note:

After spending some time looking at the trees, we discovered that many look like overgrown krummholz trees like you see at treeline in the Whites... especially above a certain height. Their branches grow a lot bigger on the southern and eastern sides. Many trees lean toward the southeast (annual dominant wind direction here is NW). It's visibly clear that they have grown in accordance with the wind speeds that blow at 40+ at least once a month at this location, especially winter when 50+ is common. Makes me wonder if it's possible for them to survive a 112-mph event however localized. My sister, whose academic studies have included a lot of trees, told me they perform much better with quick gusts (as in a severe thunderstorm) whipping back and forth, than they do with steady stress from sustained high winds (arctic blasts, hurricanes, blizzards, etc.) One more aspect to think about. And if it's true, one more thing to be amazed at.

Last edited by CanisLupusArctos; 07-01-2008 at 10:06 AM. Reason: change typo in wind direction from 393 to 293
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Old 07-11-2008, 05:31 PM   #31
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Default 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!
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Old 07-11-2008, 07:03 PM   #32
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Default Timing is everything!

It's got to be driving you nuts to have missed this severe weather occurance.
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Old 07-15-2008, 11:32 PM   #33
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A few years ago I saw a flagpole about 70 feet from me get struck. It was by far the loudest thing I ever heard. It was like firing a large caliber gun without ear protection. It felt like someone took a hammer and hit me in the head, then I heard just ringing...


But it was REALLY cool!
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