An outflow-dominant storm is a storm whose downdraft has taken precedence over the updraft. Usually, outflow-dominant storms are characterized as "HP" storms, standing for High Precipitation. They are characterized by a large area of intense rain and hail, with virtually no visible updraft base.
An outflow-dominant structure is often one of the first signs to a classic supercell's demise. The updraft's power can be stymied if the storm moves into dryer air. Upper-level winds can also carry the downdraft right on top of the updraft, in turn choking it and creating an outflow-dominant storm.
It's important to note that the strong outflow of such storms can create lift nearby, in turn spawning new storms which may be hundreds of miles away from the original storm.
I guess I'll take a stab at this one. Often a subjective assessment, a storm which is described as outflow dominant is typically a storm where the gust front has completely undercut the storm's updraft. The 'cold pool' (rain-cooled air behind the gust front) of an outflow dominant storm often is much colder than storms that do not become outflow dominant, as a deep and large cold pool can often expand faster than the storm updraft, leading to an undercut storm. Additional factors at play that come to mind are the deep layer shear, which dictates the storm motion and spacing between the updraft and the main precipitation core; the height of the cloud base, as higher cloud base means lower relative humidity, more evaporational cooling and a stronger cold pool; low-level shear, as the surface winds, when opposed to the cold pool, can slow the rate of cold pool expansion (so you would want strong surface winds opposite the storm motion). While an outflow dominant storm can still produce significant severe weather, there is a lower probability of a tornado as the gust front surges well ahead of the updraft. As cells get older, the cold pools generally get stronger with time, so many storms will become outflow dominant later in life as the storm updraft starts to ingest more and more of it's own exhaust, and you may want to start looking for a new storm to chase.
An outflow dominant storm is also one that has gone from a possibly high tornado threat to more of a high wind threat.
If you watch supercells on radar, you may see them cycle a few times..... wrapping up, possibly producing tornadoes, sometimes multiple times. But sooner or later they lose that potential and start to gust out, or, become outflow dominant. Sometimes supercells will transition from tornado producers to bow echoes in rather short order.
And on the ground, it's noticeable as well. If you are standing in inflow, feeling those warm winds at your back being pulled into the storm, you know you are in business. But if in the same position you suddenly get hit by cool, outflow winds in the face, you know the storm has gone outflow dominate.
At least I hope I explained this in a manner it makes sense, based on my limited experience.
Good day everyone. Thanks for the info! Do you know of a site that would actually have photographs illustrating different terms used in storm analysis, chasing, spotting, etc? I'm a visual learner as well - I need pictures! LOL. Thanks to all and 73.
Originally posted by Christopher Madairy Good day everyone. Thanks for the info! Do you know of a site that would actually have photographs illustrating different terms used in storm analysis, chasing, spotting, etc? I'm a visual learner as well - I need pictures! LOL. Thanks to all and 73.