tag:blogger.com,1999:blog-7478606652950905956.post1922373306477869976..comments2024-03-28T08:19:50.193-07:00Comments on Cliff Mass Weather Blog: Huge Gas Explosion Creates Pressure Wave over the Northwest PLUS a Powerful Storm Hits Our CoastCliff Mass Weather Bloghttp://www.blogger.com/profile/13948649423540350788noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-7478606652950905956.post-38240693637832386132016-03-10T16:50:40.349-08:002016-03-10T16:50:40.349-08:00"I think it's interesting to note the sho...<i>"I think it's interesting to note the shock wave produced by an explosion such as this actually travels supersonically. If it seemed like you felt the explosion last night before you heard it that was not your imagination. "</i><br /><br />It's rare, to the best of my knowledge, for natural-gas + air mixtures to actually detonate - that is, propagate supersonically. Even when such a mixture does, the resulting shock wave usually slows to subsonic in a fairly short distance, so the possible time lag is very short.<br /><br />Perhaps you're right, but I suspect the more likely reason some felt the explosion before they heard it is that lower frequencies, especially sub-audibles, are generally less attenuated by interactions with objects they encounter near the ground (like buildings and trees) - just like the bass from loud music is easier to hear in another room than the higher frequencies. In such case, the lower frequencies might make it to you by the shortest path possible and arrive first, but the higher frequencies might only make it to you by longer paths, such as by echoing off of thermoclines in the atmosphere.iamlucky13https://www.blogger.com/profile/11983645412851735508noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-83726242945843903212016-03-10T15:36:59.873-08:002016-03-10T15:36:59.873-08:00Cliff, now's as good a time as any to ask: Ho...Cliff, now's as good a time as any to ask: How do the models calculate wind gusts, and how were wind gusts historically predicted? Is it "simply" a matter of including turbulence in the models to predict statistical energy factors multiplied against the 'constant' wind speed from the pressure/temperature gradients, or is there something more basic (or complicated) in use? Did they have gust predictions in 1940 and, if so, was it anything more than "Oh the last time it looked like this the anemometer blew away"?<br /><br />Happy to ready any previous blog entries if this has already been answered. I tried simple Internet searching, but must admit I haven't spent hours looking for an answer.Brianhttps://www.blogger.com/profile/14433834468021679601noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-18331757257673071242016-03-10T10:21:08.313-08:002016-03-10T10:21:08.313-08:00Chris, here are three links to get you started
h...Chris, here are three links to get you started<br /><br /><br />http://tidesonline.nos.noaa.gov/geographic.html<br /><br />http://www.opc.ncep.noaa.gov/Loops/SURGE_NORTH_WEST/SURGE_NORTH_WEST_96_HR.php<br /><br />http://www.nws.noaa.gov/mdl/etsurge/index.php?page=stn&region=wc&datum=mllw&list=&map=0-48&type=both&stn=waseatZathrashttps://www.blogger.com/profile/17015108090179602410noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-59649677491083237712016-03-10T09:35:31.583-08:002016-03-10T09:35:31.583-08:00Cliff, Can you post a link to a graph or table sh...Cliff, Can you post a link to a graph or table showing the sea level change Vs atmospheric pressure? I was surprised this morning to see the high tide much higher than the predicted graph for our area. Thanks, ChrisAnonymoushttps://www.blogger.com/profile/01375751691233269779noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-2799348230482849002016-03-10T08:18:25.226-08:002016-03-10T08:18:25.226-08:00Some folks up here in Woodinville say they felt so...Some folks up here in Woodinville say they felt something too, such as a front door suddenly making a noise as if opening, a dog suddenly barking its head off at that time, and the like.Christina Wilsdonhttps://www.blogger.com/profile/02472802098557216513noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-48398780852063136922016-03-10T08:12:32.527-08:002016-03-10T08:12:32.527-08:00Western Skagit county is really windy this morning...Western Skagit county is really windy this morning. Fences and power down. An RV trailer blew over on westbound Hwy 20 just off I-5, blocking traffic. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-9798601487946276892016-03-10T06:34:42.966-08:002016-03-10T06:34:42.966-08:00It shook the picture on my wall and sounded like t...It shook the picture on my wall and sounded like thunder or an earthquake up in Lynnwood as well. I also checked USGS for seismic activity. Just wanted to chime in to say it was heard north of Shoreline, even (others heard it in my area as well).Sabrinahttps://www.blogger.com/profile/09229796078964070522noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-37968799541290611952016-03-10T01:12:34.513-08:002016-03-10T01:12:34.513-08:00It is interesting to relate this to sound pressure...It is interesting to relate this to sound pressure levels, for which 0dB SPL is defined as 0.00002 pascals.<br /><br />That means that your .17 pascals is about 20*log10(.17/.00002) or `79dB SPL, which is average speech level if it were in the same frequency range.<br /><br />Given that it's very low frequency, it is still, at that point, very nearly at the absolute threshold of hearing.<br /><br />http://www.sengpielaudio.com/calculator-soundlevel.htm has a set of converters from SPL to pascals, etc.<br /><br />This goes to show a couple of things, one of them the sensitivity of the undamaged human ear, which is 0.00001 pascals, give or take at the ear canal resonance, and also how small in terms of SPL a very loud sound is.<br /><br />I'll stop lecturing now. Hope this was interesting.audioskeptichttps://www.blogger.com/profile/13696374655495133407noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-21702263586682042802016-03-09T22:15:30.127-08:002016-03-09T22:15:30.127-08:00oh yea, woke me up at 5.5 miles north, in north ce...oh yea, woke me up at 5.5 miles north, in north central Shoreline.Wardhttps://www.blogger.com/profile/02414198550493495245noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-80524825694608776882016-03-09T22:14:35.194-08:002016-03-09T22:14:35.194-08:00Indeed. Shockwave. My bed shook, waking me up at 1...Indeed. Shockwave. My bed shook, waking me up at 1:45, after which, I heard the boom. I suspected a small earthquake. I quickly checked USGS for earthquake reports. Seeing none, I was a little confused. I knew something happened. But forgot about it until tonight, when I saw this on Cliff's blog. Thanks for the info-- it all makes sense now. Wardhttps://www.blogger.com/profile/02414198550493495245noreply@blogger.comtag:blogger.com,1999:blog-7478606652950905956.post-34382211708125887962016-03-09T21:17:46.650-08:002016-03-09T21:17:46.650-08:00I think it's interesting to note the shock wav...I think it's interesting to note the shock wave produced by an explosion such as this actually travels supersonically. If it seemed like you felt the explosion last night before you heard it that was not your imagination.seussnelsonhttps://www.blogger.com/profile/01057990148265860357noreply@blogger.com