Winnipesaukee Forum - View Single Post - Tornado WARNING

CanisLupusArctos · 06-22-2008, 10:04 PM

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.

06-22-2008, 10:04 PM	#13
CanisLupusArctos Senior Member Join Date: Jan 2007 Location: Center Harbor Posts: 1,049 Thanks: 15 Thanked 472 Times in 107 Posts	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.