QLCS vs. MCS

[Jeff Duda]

What do you call it? From everything I've ever heard, QLCS is a child of the NWS. Thus I go with MCS.

 

[rdale]

Ron P is LSX is the expert on this, but a QLCS is a type of MCS (aka squall line, bow echo and sometimes derecho.) http://www.nssl.noaa.gov/users/brooks/public_html/papers/trappetal.pdf

A MCS can be a stationary long lasting major flood producing system (ask Iowa!) while QLCSs are a type of MCS that forms a line and moves with time.

http://www.stormtrack.org/forum/archive/index.php/t-18802.html

 

[Greg Blumberg]

To me, an MCS or Mesoscale Convective System (for those who don't know what the letters mean) is a rather general term that encompasses squall lines, quasi-linear convective systems (QLCS), Mesoscale Convective Complexes, and Line Echo Wave Patterns (LEWP). I always understood that a QLCS is a MCS that had developed 3-dimensional features like bookend vortices. I just went back and looked in my notes from Mesoscale last semester. I can't find a definition of a QLCS there or online. I wish I had my book.

 

[rdale]

QLCS: The Type II Vortex will represent those tornadoes that are produced by quasi-linear convective systems (QLCS), which is typically an MCS that has taken the form of a squall line or bow echo. The concept of a meteorological event known as the QLCS was first introduced by Weisman and Davis (1998) and the tornado climatology associated with QLCS was established by Trapp et al. (2005). Interestingly, the definition of the QLCS was not listed in the latest edition of the AMS Glossary of Meteorology (2000). The QLCS concept will include all "lines" of convective storms with features such as LEWPs, bows, BEVs, RIJs or any type of mesovortex event. The terminology used in this paper should not be confused with that presented by Gallus et al. (2008), as all nine categories of their storm morphologies basically equate to lines or cells. One in fact could argue that a "perfectly linear" system would not produce a Type II tornado, since each of the above features/events result in some kind of irregularity in the line. The "cold pool process" is typically fundamental in producing the tilting of horizontal vorticity, thus aiding in tornado formation. An example of a bow structure that developed within a line is shown in Fig. 2a. Also, the bow feature can often produce a BEV as illustrated in Fig. 2b. Further the mesoscale development of RIJs can add to the production of shear-induced mesovortices that form along the QLCS. As stated earlier, the Type II tornadoes can be as strong as most of the Type I tornadoes (but generally not beyond F4/EF4 intensity). Finally, another example of a QLCS with Type II tornadoes is shown in Fig. 2c, which contains a number of mesovortices that developed in association with tornadogenesis (a phenomenon that has been numerically simulated by Trapp and Weisman 2003)

http://www.eas.purdue.edu/mct/pdf/Proposed Taxonomy for Tornado Events.pdf

Looks like Weisman & Davis (NCAR) first coined it back in the late 90's.

http://journals.ametsoc.org/doi/pdf/10.1175/1520-0469(1998)055<2603:MFTGOM>2.0.CO;2

 

[John Wetter]

To me there isn't a choice here. The two can be completely different things... Or can be a specific descriptor of the other.

 

[Scott A. Kampas]

There is a fair amount of literature out there on this, including research by Jeff Trapp (academia) and Ron Przybylinski (NWS expert that works with academia), as previously shared and which I recommend reading. The term originates at least as early as rdale found. I should know but have forgotten. The term/concept has caught on: http://journals.ametsoc.org/doi/abs/10.1175/WAF1006.1 . Basically, a QLCS is a form of MCS, yes. A MCS is a generic term and was originally based on satellite observations of large convective cloud masses. Many of them are clusters or not organized as a continuous entity other than the satellite features, whereas QLCS are organized, exhibit linear structures, and tend to be forward-advancing. Now the difference between a QLCS and a squall line, that's where it gets fun. As it is, I cannot vote either option. NWS St. Louis (LSX) and Saint Louis University held a Bow Echo Workshop this past March: http://www.eas.slu.edu/CIPS/bowecho2.html .

 

[Jeff Duda]

I'm glad to finally be finding out this information. I had always operated under the assumption that QLCS was just a cool new name for MCS. Guess there are some differences. Thanks for the references.

 

[rdale]

Well it definitely is cool to impress the ladies with