Interesting Weather: Sioux Falls Heat Burst

**pthebutcher** · 08-04-2008, 10:58 AM

Convective Heat Burst moves across Sioux Falls

The temperature went from the lower 70's at 410 AM this morning to 101 degrees by 425 AM with winds gusting at 50 to 60 mph. The link has a more in depth explanation for the phenomena, but basically, a dying thunderstorm forces warm air in the mid-levels of the atmosphere to the ground. As this warm air sinks it experiences compressional heating due to the greater pressure near the ground and heats up very fast.

Ames actually experienced a heat burst in the summer of 2006. I think the temperature then went from the 60's to the 80's in matter of about 10 or 15 minutes with a gust of around 60 mph in Ames. The gust actually knocked out power at Biolife while I was donating plasma and the backup generators failed. So I was sitting there with a bunch of my blood just sitting outside my body thinking...this can't be good.

**cstrunk** · 08-04-2008, 10:59 AM

It's a very fascinating weather phenomena, it would be wild to experience one of these while out camping.

**Cyclonepride** · 08-04-2008, 11:15 AM

Wow........that sounds kinda cool. I've certainly experienced the other side, when a front comes through and the temperature drops like a rock.

**brianhos** · 08-04-2008, 11:19 AM

That would be really cool to be camping and feel that.

**jdoggivjc** · 08-04-2008, 11:20 AM

Hey Wx - wanna explain this one in further detail for us?

**pthebutcher** · 08-04-2008, 11:44 AM

Originally Posted by jdoggivjc

Hey Wx - wanna explain this one in further detail for us?

I have a weather background so I think I'm qualified to take a stab at this one ;) Really, there isn't much more to it than what I gave in my quick explanation in my first post.

Essentially what you need is a very dry atmosphere in the middle to upper levels and typically a dying thunderstorm. The dry atmosphere allows for any of the precipitation falling in this layer to be completely evaporated (the dying thunderstorm creates a situation where there isn't too much precipitation, so that all the water can be evaporated). The evaporation process 'sucks' up a bunch of the heat from this air and causes it cool and become more dense than its surroundings. Since this air is more dense it begins to fall towards the ground. The pressure of the atmosphere is greater as you get closer to the ground, so as the air falls, it gets compressed and is forced to heat up (ideal gas law). Now one caveat is that this air must fall towards the ground very very fast, because as the air heats up, it will become less dense and want to rise in relation to its surroundings. If the air doesn't fall to the ground fast enough, it will just become buoyant and rise back up in the atmosphere without ever reaching the ground..

Hope that helps :D

**DJK15** · 08-04-2008, 11:47 AM

Originally Posted by pthebutcher

The gust actually knocked out power at Biolife while I was donating plasma and the backup generators failed. So I was sitting there with a bunch of my blood just sitting outside my body thinking...this can't be good.

Wow...that could have been bad. How long was the power out?

**pthebutcher** · 08-04-2008, 11:50 AM

Originally Posted by DJK15

Wow...that could have been bad. How long was the power out?

The power was still out when they finished up with me about 20 minutes later. They had to go around to each person and hold the packet of blood up above you so gravity would slowly drain it back in. I would guess they had a bunch of employees with sore shoulders hehe.

**jdoggivjc** · 08-04-2008, 11:51 AM

Originally Posted by pthebutcher

I have a weather background so I think I'm qualified to take a stab at this one ;) Really, there isn't much more to it than what I gave in my quick explanation in my first post.

Essentially what you need is a very dry atmosphere in the middle to upper levels and typically a dying thunderstorm. The dry atmosphere allows for any of the precipitation falling in this layer to be completely evaporated (the dying thunderstorm creates a situation where there isn't too much precipitation, so that all the water can be evaporated). The evaporation process 'sucks' up a bunch of the heat from this air and causes it cool and become more dense than its surroundings. Since this air is more dense it begins to fall towards the ground. The pressure of the atmosphere is greater as you get closer to the ground, so as the air falls, it gets compressed and is forced to heat up (ideal gas law). Now one caveat is that this air must fall towards the ground very very fast, because as the air heats up, it will become less dense and want to rise in relation to its surroundings. If the air doesn't fall to the ground fast enough, it will just become buoyant and rise back up in the atmosphere without ever reaching the ground..

Hope that helps :D

Actually, I'll rephrase - MrsWx - wanna take a stab at this one

**MrsWx4Cy** · 08-04-2008, 11:55 AM

Originally Posted by jdoggivjc

Hey Wx - wanna explain this one in further detail for us?

Here's the technical explanation:

The rapid and temporary rise in temperature and drop in dew point is a classic signature. These events are often caused by rapidly decaying thunderstorms producing a downward rush of air that warms as the pressure increases. This air hits the ground and spreads out over a limited area producing high winds with hot and dry conditions.

**Clone9** · 08-04-2008, 12:01 PM

I think I experienced one of these in high school. I went into the movies and it was about 60 or 65 degrees outside, and 1.5 hrs later came out and it was in the 90's. And this was from 9-11 pm, which it should be getting cooler. It was one of the most bizarre weather experiences of my life, and finally I have a potential explanation.

**jdoggivjc** · 08-04-2008, 12:05 PM

Originally Posted by MrsWx4Cy

Here's the technical explanation:

The rapid and temporary rise in temperature and drop in dew point is a classic signature. These events are often caused by rapidly decaying thunderstorms producing a downward rush of air that warms as the pressure increases. This air hits the ground and spreads out over a limited area producing high winds with hot and dry conditions.

It all makes so much more sense now...