Against the odds

[Steve M]

I have a question for the meteorologists of the forums. What is happening in the atmosphere that would allow a single or even a few isolated thunderstorms to develop when there is high pressure and subsidence abounds? Most clouds seem to struggle just to form but a few seem to make cumulonimbus stature in the midst of the harsh, cloud forming environment.

[Bill O]

Just because the air mass is sinking doesn't mean a thunderstorm can't push through that subsidence. When you talk about air sinking under high pressure its on the order of meters per hour or less. While a rising parcel of air in a thunderstorm is on the order of meters per second.

I'm guessing the isolated cells are caused by some sort of geographic feature. It could be a freshly plowed field, bare rocks above treeline, a dark evergreen forest. In winter, a relatively warm lake. Or it could be a cold pocket in the upper atmosphere that allows warm surface air to rise into.

If the atmosphere cools faster than a rising air parcel the parcel is going to keep ascending.

[Steve M]

So in the midst of an air mass there are micro air masses which can change over a very short period of time. That would explain why on radar you can see a storm or line of storms form and move 20 miles and then just dissolve before your eyes. I've seen that even in a tropical storm or hurricane, you think, ooh, were gonna get clobbered, but then it just falls apart right before it gets to you and it makes you mad.

[Bill O]

Of course, there are many micro and more likely mesoscale factors that control thunderstorms. Sea breeze and lake effect storms would be mesoscale.

Search the internet for "pulse thunderstorms". That might answer all your questions.

[Steve M]

Thanks for the info.

[Steve M]

Of course, there are many micro and more likely mesoscale factors that control thunderstorms. Sea breeze and lake effect storms would be mesoscale.

Search the internet for "pulse thunderstorms". That might answer all your questions.

Talking about pulse thunderstorms, we are about to get one here in about 10 minutes. Actually I'm not sure if it is a single cell or multi-cell storm. Can you tell the difference on radar?

[Bill O]

Talking about pulse thunderstorms, we are about to get one here in about 10 minutes. Actually I'm not sure if it is a single cell or multi-cell storm. Can you tell the difference on radar?

Those are pulse like, but its hard to tell with all that ground clutter showing up on radar. Which is typical on a clear evening.

To be more exact though, I think those storms are forming on an old outflow boundary. Basically the cold pool of air that came from an earlier storm over Georgia is acting like a cold front and causing storms to fire in FL.

[Steve M]

Those are pulse like, but its hard to tell with all that ground clutter showing up on radar. Which is typical on a clear evening.

To be more exact though, I think those storms are forming on an old outflow boundary. Basically the cold pool of air that came from an earlier storm over Georgia is acting like a cold front and causing storms to fire in FL.

That is cool. We just had a close lightning strike. Shook the dog up pretty good. I wouldn't call this storm severe, at least not where I'm sitting but it is a strong storm.

[Brad]

And I hope your computer is on a UPS so if the power goes out or surges, the computer will not be impacted.

I have the cable modem, wireless access point and Vonage box on a UPS also. So, computers and phone calls do not drop when the power goes out.

[Steve M]

And I hope your computer is on a UPS so if the power goes out or surges, the computer will not be impacted.

I have the cable modem, wireless access point and Vonage box on a UPS also. So, computers and phone calls do not drop when the power goes out.

That's a good idea, none of my computers, (5 total) my modem, router, printers are protected. We have had power outages and brown outs but thankfully never lost anything.