Backing Winds

[David Williams]

I'm watching Mike's Storm Structure 101 DVD, and he is talking about the four way intersection of a low, warm front, dry line, and moisture line. He mentions backing winds along the warm front and dry line in addition to directional shear. Can someone please explain to me what backing winds are and how they effect storm development?

 

[rdale]

http://stormtrack.org/forum/showthread.php?t=16448&highlight=backing+winds

 

[Darren Addy]

If I could expand on the original question: Is there a difference between "backing winds" and the inflow? If you are standing under the beaver tail, are you feeling inflow, backing winds, or both?

 

[Patrick Marsh]

If I could expand on the original question: Is there a difference between "backing winds" and the inflow? If you are standing under the beaver tail, are you feeling inflow, backing winds, or both?

Backing winds refers to what is happening to the direction of the winds. Not a type of wind or the location of the wind. To answer your question it's inflow.

 

[Greg McLaughlin]

Backing winds is a term to describe the direction the wind has changed. When winds back they turn to the right. For example, if you begin with a south wind and it turns to the southeast you have "backing" winds. Veering winds are the exact opposite. If you start with a south winds and the direction changes to the southwest, you have "veering" winds. Winds tend to back ahead of a front or low, and veer with the passage of a front or low.

Typically surface winds tend to back ahead of a surface low, or along/ north of a warm front. Surface winds also tend to back in response to an approaching mid-level disturbance. Often you will also see a rise in dewpoints with backing winds.

Backing winds can play an important role in forecasting tornadoes as low-level helicity is often maximized where low-level winds are backed.

 

[David Williams]

So, is the term backing winds referring primarily to wind direction change on the ground?

Also, you said, "Backing winds can play an important role in forecasting tornadoes as low-level helicity is often maximized where low-level winds are backed." In order to talk it through so I understand it better, are you saying that low level backing winds are usually beneficial to tornado/supercell development because with winds moving to the right (south to southeast) better directional shear with height (850 mb south winds, 500 mb southwest, and 300 mb west) can be established? Helicity being the change in wind direction with height, right?

 

[David Draun]

Backing winds also refers to a counterclockwise turning in the wind with height. A backing wind profile from the surface to 500mb is indicative of cold air advection (CAA). Warm air advection (WAA) creates a veering profile, or a clockwise turn with height. When winds back at the surface, they become more easterly, allowing a stronger veering profile from surface to upper-level, more supportive of our favorite convective phenomena.

 

[Greg McLaughlin]

So, is the term backing winds referring primarily to wind direction change on the ground?

Also, you said, "Backing winds can play an important role in forecasting tornadoes as low-level helicity is often maximized where low-level winds are backed." In order to talk it through so I understand it better, are you saying that low level backing winds are usually beneficial to tornado/supercell development because with winds moving to the right (south to southeast) better directional shear with height (850 mb south winds, 500 mb southwest, and 300 mb west) can be established? Helicity being the change in wind direction with height, right?

That is the textbook wind profile found with supercells and tornadoes, however all of that is relative. Helicity is directly related to the change in wind speed and direction with height.