"The Death Ridge"

[mw174620]

To start, I know this term is possibly "unliked" on this forum. I have seen some higher level users post that this gets posted every year, usually along with, "the season is over."

My question is, what is it? Why does it happen? Why does it signify a decrease in severe storms? Does it happen every year?

 

[David Wolfson]

Broadly speaking, seasonal heating over higher terrain of northern Mexico and the intermountain west equates to ridging which both limits any significant flow at higher altitudes to the northern Plains and causes what flow there is to tend generally from the northwest, which limits moisture above the surface.

 

[Skip Talbot]

what is it? Why does it happen? Why does it signify a decrease in severe storms? Does it happen every year?

Here's a brief intro to troughs and ridges:
http://www.theweatherprediction.com/habyhints2/457/

The meteorologists can give you a better answer on the fundamentals of what a ridge is, how it works, and why it happens. A blocking pattern will keep a ridge in place over the great plains:
http://www.theweatherprediction.com/habyhints/144/

They're also common in the summer time, when the plains transition from springtime troughs with storms to summer time ridges with hot temperatures and dry conditions. Chasers call a persistent ridge a death ridge because it can shut down the chances for severe weather across the great plains, meaning no chasing over the central plains. We see ridges and persistent ridges every year, usually during the summer months. Usually there is some some ridging in the middle of severe weather season, but persistent ridging from April through June often means we have a very quiet year without many great plains tornado chases.

Even with a death ridge over the central plains, that doesn't mean no storm chasing anywhere. Storms chasers can often have great chases on the high plains in Wyoming and Colorado chasing upslope flow events. A ridge over the plains, often means troughing way up to the northwest such as in Montana, Alberta, and Saskatchewan, or northwest flow events over the Midwest. Each area can produce photogenic supercells and tornadoes, while Kansas and Oklahoma have only blue skies.

 

[Tim Supinie]

The "Death Ridge" is a bubble of warm air at the surface and aloft that parks itself over the central US during the summer. This is typically manifest as a region of high 500 mb heights (a simplistic way of looking at this is that the warm air takes up more space than the cooler air around it, so it "pushes" the heights up). It signifies a decrease in severe storms because the warm air aloft stabilizes the atmosphere and eliminates the chance for convection (which requires cool air aloft). The "warming aloft" part happens every summer, but a classic "Death Ridge" doesn't happen every summer.

This is what the "Death Ridge" looks like at the 500 mb level (see the central US).

And this is a sounding from the middle of that ridge.

 

[mw174620]

The "Death Ridge" is a bubble of warm air at the surface and aloft that parks itself over the central US during the summer. This is typically manifest as a region of high 500 mb heights (a simplistic way of looking at this is that the warm air takes up more space than the cooler air around it, so it "pushes" the heights up). It signifies a decrease in severe storms because the warm air aloft stabilizes the atmosphere and eliminates the chance for convection (which requires cool air aloft). The "warming aloft" part happens every summer, but a classic "Death Ridge" doesn't happen every summer.

This is what the "Death Ridge" looks like at the 500 mb level (see the central US).

And this is a sounding from the middle of that ridge.

Could a short wave still manifest within this ridge and cause convection/severe weather?

Excuse me if I use incorrect terminology here, I am still in the early learning stages, but this ridge, if it were to develop a jet streak, would have anticyclonic flow? So would the storms develop on the left-rear quad, as opposed to the right-front quad we see during the Great Plains tornado season?

 

[Mark Blue]

Usually in the summertime the ridge will become dominant over the plains and most convection will occur on the periphery of the high pressure in what is commonly known as the ring of fire (queue up Johnny Cash now). There are shortwave impulses, as well as others that bump up against the periphery of a dome of high pressure and cause convection, but in terms of jet streaks those are associated with troughs (both long and shortwave) versus ridges. Those links Skip provided are the fundamentals and should be read thoroughly as they are key to understanding the basics of ridges, troughs, and jet streaks. Are you trying to understand anti cyclonic tornadoes perhaps?

 

[mw174620]

Usually in the summertime the ridge will become dominant over the plains and most convection will occur on the periphery of the high pressure in what is commonly known as the ring of fire (queue up Johnny Cash now). There are shortwave impulses, as well as others that bump up against the periphery of a dome of high pressure and cause convection, but in terms of jet streaks those are associated with troughs (both long and shortwave) versus ridges. Those links Skip provided are the fundamentals and should be read thoroughly as they are key to understanding the basics of ridges, troughs, and jet streaks. Are you trying to understand anti cyclonic tornadoes perhaps?

Mark,

Thanks for the response. I read the links from Skip on Jeff's website. Seeing that it is called the omega block, helps me find much more information on it. I am just curious if sever storms still initiate with this blocking feature in place, and if so, what their characteristics are. I am just guessing, from little experience, that if convection were to occur along the ridge, it would be along anti-cyclonic flow. (edit: I guess my confusion is that the overall flow is anticyclonic, not the area of convection. That is the inexperience talking.)

 

[Mark Blue]

The short answer is no. If you want to see severe thunderstorms it will be associated with a variety of other surface features and conditions, but not underneath the influence of a ridge of high pressure. When the a Death Ridge arrives it signals the arrival of summer and most notably drier conditions. The zone between a trough and a ridge can light up as mentioned before, and in the example from Tim you'd have convection on the west and east coast regions but not in between (where the high pressure resides). Here are a couple more Haby Hints along the same lines that discusses the jet stream and so forth: http://www.theweatherprediction.com/habyhints/256/

This one is more detailed, I hope it helps: http://www.theweatherprediction.com/charts/300/