2011-04-14 DISC: OK/KS

[Warren Faidley]

I found a previous ST discussion about gravity waves here:

http://www.stormtrack.org/forum/showthread.php?15689-Gravity-Waves-Make-Tornadoes

W.

 

[Steve Miller TX]

You can get a gravity wave pretty much anytime you have a strong inversion of potential temperature and a source of excitation. Gravity waves are everywhere, but they're hard to see when there's nothing to mark them. Clouds can mark gravity waves. I thought maybe that line was a gravity wave, but something about it is keeping me from wanting to call it one: its propagation speed appears to be too slow to be a true internal gravity wave. It still may be some kind of bore feature, though.

Yeah, the stationary aspect had me dismissing it as a gravity wave at first and still bugs me as far as a true gravity wave as you mentioned. But, could a wave propagating like that with the wave axis (roughly NNW to SSE) being parallel to the boundary layer flow have anything to do with it? I'm thinking more in terms of an undular bore where perhaps the wave inertia is dampened somehow.

 

[Jeff Duda]

Yeah, the stationary aspect had me dismissing it as a gravity wave at first and still bugs me as far as a true gravity wave as you mentioned. But, could a wave propagating like that with the wave axis (roughly NNW to SSE) being parallel to the boundary layer flow have anything to do with it? I'm thinking more in terms of an undular bore where perhaps the wave inertia is dampened somehow.

It could, but I don't know. The wave may not have even been a fully PBL-based feature. What can be said is that there was something causing downward motion and/or heating to evaporate the clouds along that line. It could've been associated with a boundary aloft that resisted flow from the west, causing it to divert both above and below the boundary. Looking back at SPC RUC mesoanalyses from yesterday, there was a moisture/thermal gradient running along the line of clearing with west winds behind it and S/SSE winds ahead of it.

 

[Steve Miller TX]

I found a previous ST discussion about gravity waves here:

http://www.stormtrack.org/forum/showthread.php?15689-Gravity-Waves-Make-Tornadoes

W.

Awesome find Warren. Ever since the Jarrell, TX event in 1997 where a pronounced gravity wave propagated SW along the SSW/NNE oriented boundary and triggered those violent storms as it did, I pay close attention to such phenomena as it pertains to significant tornado events. In fact, Alan Moller mentioned one of the studies by Texas A&M where they ran a simulation without the interaction of a gravity wave and the violent storms did not occur...just regular thunderstorms. Not presenting that as scientific evidence, but definitely something worth noting and in my mind and experience seeing even the most subtle of boundaries or features aid in tornado development...the satellite feature I posted definitely caught my attention regarding the Tushka monster. I hope some scientific minds in the research community can expand on this in more detail and analysis than I could ever hope to come close to achieving on my own.

 

[mikegeukes]

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
420 PM CDT FRI APR 15 2011

..PRELIMINARY SURVEY RESULTS FOR THE APRIL 14 2011...TORNADOES
http://kamala.cod.edu/offs/KOUN/1104152127.nous44.html

 

[mikegeukes]

PUBLIC INFORMATION STATEMENT...UPDATED
NATIONAL WEATHER SERVICE TULSA OK
937 PM CDT FRI APR 15 2011

..TORNADO DAMAGE SURVEYS ONGOING FOR 14 APRIL 2011 EVENT

..7 TORNADOES CONFIRMED AT THIS TIME

http://kamala.cod.edu/offs/KTSA/1104160237.nous44.html

Updated with pics:
http://www.srh.noaa.gov/news/display_cmsstory.php?wfo=tsa&storyid=66688&source=0

 

[Chris Nuttall]

I had actually been watching that wave propagate through TX/OK all day Thursday. I thought it might be a gravity wave...especially with the way the low clouds that persisted most of the day ahead of that line were cleared out behind it by subsidence. I thought those might be horizontal convective rolls behind the wave and extending back to the dryline. All bets are off when gravity waves get thrown into the mix.