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Math/Met

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  1. Math/Met
    Obviously accumulations vary depending on the surface with these marginal temps and warm ground, but I have nearly an 1 inch on my car. Still coming down at a decent rate, but it’s having a hard time adding to the accumulation. It takes heavy snow rates to really add to the accumulation. The time of day didn’t help here either.
  2. Math/Met
    The Greeneville airport is down to 32 and reporting .25 visibility.
  3. Math/Met
    00z Euro has significantly improved for East TN. A step in the right direction.
  4. Math/Met
    Strictly in terms of precip totals, there was a decent jump in the right direction for East Tn on the 00z UKMET vs 12z.
  5. Math/Met
    I believe this snowfall output was from a weak inverted trough event. Totals increased at the last minute if I remember correctly.
  6. Math/Met
    When it comes to downslope winds in East TN, I would never say never. There are so many possible ways for it to happens. I assume that areas along the mountains of SE TN would have a slightly better chance of that happening, due to the surface winds being SE on the other side of the mountains in that area. I think areas farther to the northeast would be pretty safe from downslope in this situation. Just to be clear since there is some discussion about this now, this isn't a significant inverted trough. It is very subtle (mainly seen in wind field), but it maybe just enough to help us out a little. Especially in eastern counties. And the northerly flow down the valley could help areas further south with temps, as Jeff mentioned.
  7. Math/Met
    In these cases, the inverted trough is induced by the terrain. The air flow is different on either side of the mountains, so you can basically get a "pinching" (not a very technical way of describing it) between the two flows. Neither side has to deal with much downslope because it creates rising air in the low levels. It is a fixed feature because the mountains are a permanent feature. Hope that makes sense.
  8. Math/Met
    I always try to looks at small details for any event in East TN. Mainly because the terrain can cause things to go unexpectedly wrong or sometimes in our favor. Looking at the NAM, the thing I like about this system is that low level winds over WNC are from a more easterly direction during the start of the system, while winds over the ETN valley are more northerly. This typically happens when we get an inverted trough induced along the mountains, which helps provide some low level lift and often produces more precip than modeled. This current situation is more subtle, but the characteristics are still there. It’s something to watch to see if precip trends upward as we go.
  9. Math/Met
    Just got back from Camp Creek. The wind is pretty strong there tonight. I estimate that it was approaching 70mph where I was. I've definitely felt much stronger there in other events, but it was still worth the trip. Fairly consistent gusts.
  10. Math/Met
    I’ll move this to the main discussion based on Carvers suggestion. Just wanted to say that the wind event potential has trended a little stronger in my opinion. I thought the MRX discussion was very good regarding this potential.The NAM has slightly shifted the 850mb wind to more of a southerly direction, and that could be just enough to increase the mountain wave enhancement. You don’t really need a southeasterly flow at 850mb because the cross barrier flow is determined at lower levels based on statistical analysis. We often have a southerly or even slightly SW flow over the valley during a mountain wave event. This current event is right on the threshold, so it could go either way in terms of significant MW enhancement. Everything else is favorable. Regardless of MW enhancement, the LLJ is strong enough to potentially cause some tree problems in the mountain and foothills due to saturated ground conditions.
  11. Math/Met
    That’s definitely something to watch. There will be some additional strong winds... likely starting tomorrow afternoon. It doesn’t look like a strong wind event at this point, but enough for some concern. I don’t think it would take much to cause some downed trees at this point. If the LLJ trends slightly more southerly (versus SW), then the potential for higher gusts will increase.
  12. Math/Met
    It is a prolonged event, but wind gusts should pick up by Saturday morning and continue into the evening. The strongest LLJ winds move in later in the day. Sometimes there's a weakening of winds during the afternoon, and it gets stronger as the sun goes down.
  13. Math/Met
    I know Boulder, CO gets mountain waves too. My former advisor during graduate school wrote a paper on it. Strange coincidence that we both had interests in mountain waves.
  14. Math/Met
    That seems to match the graphic I posted.
  15. Math/Met
    Thought I’d give a quick update on the mountain wave event. Already getting some gusts of around 60mph at Camp Creek today, but this isn’t the main event. There are still a few things that could go hinder mountain wave development this weekend. As Jeff mentioned in the Severe Weather topic, the NAM has shown signs of wanting to keep 700mb winds more southerly. If that happens, then that could hinder the critical layer development (need SW winds at 700). Also, if there is any instability near the mountains, that could also decrease downslope potential. With that said, if everything comes together this could be a very significant wind event. The parameters are some of the best that I can remember. Just talking potential, because it’s impossible to say for sure when you are talking about wind speeds within stationary gravity waves. Here is one example of the Euro wind gust output. Not sure how reliable this particular product is, but models always underestimate winds with these events (along the mountains) so it caught my attention.
  16. Math/Met
    I know this doesn’t directly impact many people on this forum, but the 12z Euro is showing what would likely be a MAJOR mountain wave event this weekend for East TN. Details can change between now and then, but that looks like a very high end event currently.
  17. Math/Met
    Glad they did quality control and straightened that out. Are they saying 81mph was the peak gust today? Just wondering because it looked like there were legitimate gusts in the mid to upper 80's based on the plot. Not that it really matters at this point, just wondering if all recorded gusts were higher than actual winds.
  18. Math/Met
    I don’t want to post too much about the mountain wave event, but here is why I think the red data plots are incorrect. If you expand out to a 720 hour plot, you can see errors show up several times. The peak (green) is usually very accurate.
  19. Math/Met
    I haven't heard any major damage reports, but it looks like there are a lot of trees down in southern Greene County. WCYB Probably not the best idea to be standing there.
  20. Math/Met
    That’s unfortunate. It may end up being correct, but I would be VERY surprised. The near 90mph gusts seem legit. I have a full dataset for research purposes that goes back to 2008, and 123mph would be way above anything recorded there. I do think it’s possible for Camp Creek to gust over 100mph in mountain wave events. I’ve speculated that it was over 100mph in 2004, but there was no reliable data at that point.
  21. Math/Met
    https://oculus.atdd.noaa.gov/campcreek/
  22. Math/Met
    I think you are correct to ignore the red data on that chart. It is unreliable. The peak gust data (green) is probably accurate, so nearly 90mph.
  23. Math/Met
    About 30 minutes after posting that, Camp Creek switched to a SE wind and gusted to 53mph. It should continue to increase.
  24. Math/Met
    Everything still looks on track for a significant mountain wave wind event. It has taken awhile for conditions to become favorable. Even though VWP indicates 40kt SE winds at 4000ft, the cross barrier flow remains blocked. Camp Creek winds haven't really increased yet and aren't currently blowing from a SE direction. Conditions become much more favorable in the next few hours. HRRR is showing the enhancement right along the mountains and especially in the Camp Creek area by tomorrow morning. That's not the most reliable wind product, but it usually does a good job of showing areas of mountain wave enhancement (even if wind speed isn't accurate). The biggest question for me is how trees will hold up in areas with possible 75+ mph wind gusts and saturated soil.
  25. Math/Met
    Favorable conditions for mountain waves will be in place later tonight and especially tomorrow morning. MRX issued a High Wind Warning and mentioned the potential for downed trees due to saturated ground in the AFD. It could take a few hours for mountain waves to really get going tonight/tomorrow morning. Models show a very strong temperature inversion across the mountains later tonight and the 850mb flow has a bit for of an easterly component. So, it could take until early tomorrow morning to get the proper balance between cross barrier wind speed and stability (haven’t calculated the Froude number, just basing on past experience). The cross barrier flow could be partially blocked for part of the night and could prevent the downslope flow from being sustained. After the initial round of precip lifts north, the 850mb flow becomes more southerly and the temperature profile is more conducive. That’s when the conditions become very favorable for mountain waves. This could be a strong event, which will likely cause some problems with down trees along the mountains.
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