Fozz Posted February 8, 2017 Share Posted February 8, 2017 1 minute ago, WinterWxLuvr said: What are those things anyway? Just a higher ratio? I think it's some special algorithm that tries to take certain factors like predicted ratios and frozen precip types into account. Probably overdone for a storm like this. Link to comment Share on other sites More sharing options...
clskinsfan Posted February 8, 2017 Share Posted February 8, 2017 2 minutes ago, mappy said: Can we please stop posting the Kuchera snow maps? They are way overdone with this type of storm setup. Well. In this case the 10-1 map is even better!!! Link to comment Share on other sites More sharing options...
caviman2201 Posted February 8, 2017 Share Posted February 8, 2017 Just now, mappy said: all snow maps are overdone with this setup. i like posting them too but you can't take them at face value. look at temp profiles. DC is still at 34 when precip moves out of the area per 18z NAM. Do you really expect DC to pick up 1.3 of snow with that? I agree - just saying it does seem like Kuchera is 'doing its job' in this case... not just blowing up snow totals. I'm not suggesting we should take the maps verbatim. Link to comment Share on other sites More sharing options...
packfan98 Posted February 8, 2017 Share Posted February 8, 2017 how about snow depth = ground truth Link to comment Share on other sites More sharing options...
MD Snow Posted February 8, 2017 Share Posted February 8, 2017 I think the 12k seems to be a rational run. Doesn't really get any accumulating snow east of i 95 in md between the cities. Edit: Actually both the 12k and 4k took a pretty significant step back for accumulating snow south and east and even northeast of the cities. This is what we were expecting with the 18z suite and the warmer than forecasted temps. So far the NAM has picked up on it. We'll see if it makes a difference with the other models. I have to think it will. Link to comment Share on other sites More sharing options...
mappy Posted February 8, 2017 Share Posted February 8, 2017 3 minutes ago, WinterWxLuvr said: What are those things anyway? Just a higher ratio? I thought so, but seems Kuchera is lower than 10:1, at least per pivotalweather and their NAM snow maps. Either way -- no one should be relying on snow map outputs for this system. Link to comment Share on other sites More sharing options...
mappy Posted February 8, 2017 Share Posted February 8, 2017 2 minutes ago, clskinsfan said: Well. In this case the 10-1 map is even better!!! thanks smartass 1 minute ago, caviman2201 said: I agree - just saying it does seem like Kuchera is 'doing its job' in this case... not just blowing up snow totals. I'm not suggesting we should take the maps verbatim. I know you aren't, but we have a lot of people reading the thread who may or may not know what to take verbatim... 1 minute ago, packfan98 said: how about snow depth = ground truth yes, this I can get on board with Link to comment Share on other sites More sharing options...
caviman2201 Posted February 8, 2017 Share Posted February 8, 2017 I think this is definitely the type of system where the snow depth maps make a lot of sense to look at. If i understand correctly, a snowflake that melts on contact still counts as QPF "snowfall" even if it doesn't accumulate. If thats true, in a storm like this we could have a lot of snowfall which turns into very little or 0" of snow depth. Aka, its quite possible both the snowfall and snow depth maps are fairly accurate. Link to comment Share on other sites More sharing options...
ErinInTheSky Posted February 8, 2017 Share Posted February 8, 2017 Currently 62.5 degrees in my part off Gaithersburg. I'm actually coming in a little lower than the Weather Underground forecast for my particular weather station, in terms of temps. Link to comment Share on other sites More sharing options...
Fozz Posted February 8, 2017 Share Posted February 8, 2017 I think the 18z 4k NAM is realistic even at face value. Most of the others are not. Link to comment Share on other sites More sharing options...
clskinsfan Posted February 8, 2017 Share Posted February 8, 2017 Just now, caviman2201 said: I think this is definitely the type of system where the snow depth maps make a lot of sense to look at. If i understand correctly, a snowflake that melts on contact still counts as QPF "snowfall" even if it doesn't accumulate. If thats true, in a storm like this we could have a lot of snowfall which turns into very little or 0" of snow depth. Aka, its quite possible both the snowfall and snow depth maps are fairly accurate. Yep. The very definition of snow TV. 2 minutes ago, mappy said: thanks smartass Figured you would like that one. Link to comment Share on other sites More sharing options...
Jebman Posted February 8, 2017 Share Posted February 8, 2017 Temp 64 degrees, 37 dewpoints. Link to comment Share on other sites More sharing options...
yoda Posted February 8, 2017 Share Posted February 8, 2017 2 minutes ago, Fozz said: I think the 18z 4k NAM is realistic even at face value. Most of the others are not. The snow map or SLP path? Link to comment Share on other sites More sharing options...
KingJWx Posted February 8, 2017 Share Posted February 8, 2017 65 right now after hitting a high of 70 around noon. Link to comment Share on other sites More sharing options...
high risk Posted February 8, 2017 Share Posted February 8, 2017 2 minutes ago, caviman2201 said: I think this is definitely the type of system where the snow depth maps make a lot of sense to look at. If i understand correctly, a snowflake that melts on contact still counts as QPF "snowfall" even if it doesn't accumulate. If thats true, in a storm like this we could have a lot of snowfall which turns into very little or 0" of snow depth. Aka, its quite possible both the snowfall and snow depth maps are fairly accurate. that's pretty much on track. I've posted about it a few times today. If the NAM has 1" of liquid, and it thinks that the entire event is half snowflakes and half raindrops, it makes .50" liquid as snowfall. Apply the 10:1 ratio on those maps, and you have 5" of unrealistic snow. Link to comment Share on other sites More sharing options...
mappy Posted February 8, 2017 Share Posted February 8, 2017 8 minutes ago, caviman2201 said: I think this is definitely the type of system where the snow depth maps make a lot of sense to look at. If i understand correctly, a snowflake that melts on contact still counts as QPF "snowfall" even if it doesn't accumulate. If thats true, in a storm like this we could have a lot of snowfall which turns into very little or 0" of snow depth. Aka, its quite possible both the snowfall and snow depth maps are fairly accurate. Yup. I guess in my head when I see a snowfall map of 7-8" IMBY, I cut it in half, because I know that much will not accumulate given temps and ratios. Link to comment Share on other sites More sharing options...
Fozz Posted February 8, 2017 Share Posted February 8, 2017 I see a lot of nasty north shifts on the NAMs and the HRRR. This always required too many things to go exactly right from the changeover to the rates to the timing of the strengthening of the low, and had a high bust potential, so I'm not too surprised. Link to comment Share on other sites More sharing options...
BaltimoreWxGuy Posted February 8, 2017 Share Posted February 8, 2017 NAM stinks. Snow map is obviously overdone for what it shows. There isnt a changeover in DC until probably 6AM...By then the good stuff is beginning to pull east Link to comment Share on other sites More sharing options...
NorthArlington101 Posted February 8, 2017 Share Posted February 8, 2017 Link to the pressure change map for those who like to follow along: http://weather.unisys.com/surface/sfc_con.php?image=3p&inv=0&t=cur Link to comment Share on other sites More sharing options...
psuhoffman Posted February 8, 2017 Share Posted February 8, 2017 24 minutes ago, mappy said: Can we please stop posting the Kuchera snow maps? They are way overdone with this type of storm setup. The kuchera in this setup should actually be better as it will show lower ratios. It's the rain snow calculation that can be off like on wxbell where anything close defaults to snow. I'm not debating those maps aren't high just that the kuchera ones shouldn't be off more then the others. It's when we have cold temps and sometimes kuchera goes crazy with 20-1 ratios that I find it's high. Link to comment Share on other sites More sharing options...
high risk Posted February 8, 2017 Share Posted February 8, 2017 3 minutes ago, BaltimoreWxGuy said: NAM stinks. Snow map is obviously overdone for what it shows. There isnt a changeover in DC until probably 6AM...By then the good stuff is beginning to pull east just remember that the model isn't really showing all of that snow. Most of it in this case comes from the web sites interpreting snowfall as snow accumulation on the ground with a generic 10:1 ratio. Link to comment Share on other sites More sharing options...
Jebman Posted February 8, 2017 Share Posted February 8, 2017 10 minutes ago, mappy said: Yup. I guess in my head when I see a snowfall map of 7-8" IMBY, I cut it in half, because I know that much will not accumulate given temps and ratios. The last snowstorm, one map showed 6 inches for Dale City. I halved it. I ended up with 2.8 inches with that storm. This storm the models show a trace for me, so I just halved it. Link to comment Share on other sites More sharing options...
mappy Posted February 8, 2017 Share Posted February 8, 2017 1 minute ago, psuhoffman said: The kuchera in this setup should actually be better as it will show lower ratios. It's the rain snow calculation that can be off like on wxbell where anything close defaults to snow. I'm not debating those maps aren't high just that the kuchera ones shouldn't be off more then the others. It's when we have cold temps and sometimes kuchera goes crazy with 20-1 ratios that I find it's high. shhh you Link to comment Share on other sites More sharing options...
MD Snow Posted February 8, 2017 Share Posted February 8, 2017 19z HRRR at the end of it's run. I'm just rooting to see some flakes flying as precip tapers off. Link to comment Share on other sites More sharing options...
TSG Posted February 8, 2017 Share Posted February 8, 2017 18hr Hrrrrrrrrrrrrrrrrrrr.... Not sure why anyone is putting much stock in whatever it's showing at that range, good or bad. Link to comment Share on other sites More sharing options...
psuhoffman Posted February 8, 2017 Share Posted February 8, 2017 26 minutes ago, mappy said: shhh you You were right those numbers are overdone I just wanted to clear up the difference with the kuchera. The trend is more important then the number. The 12k nam actually trended slightly better. The way the calculate snow is based on metrics that do matter so even though the number is bogus you still want it to go up. For us it went from 4" to about 6". The bad news is both the 4K and 3k got way worse. 4K went from about 8" to 3.5". Slower flip and less organized precip after the flip. The nam has been running the warmest all along but then seemed to cave at 12z and came in line with the euro and rgem and gfs which all converged on a consensus compromise. Since that compromise was pretty good for us (3-6" looking from 12z guidance) I hoped that would lock in. But now the nam reverted to its warmer look of yesterday. Hopefully it's a hiccup and not the start of one last minute jump north that screws us over. Link to comment Share on other sites More sharing options...
MD Snow Posted February 8, 2017 Share Posted February 8, 2017 7 minutes ago, TSG said: 18hr Hrrrrrrrrrrrrrrrrrrr.... Not sure why anyone is putting much stock in whatever it's showing at that range, good or bad. Not putting any stock in it. This is an observation thread. I use the HRRR to observe trends from run to run and compare with current surface trends etc. Isn't that what this thread is supposed to be about? I'm not going to get any accumulating snow south of baltimore. However, I am interested to see if I actually flip over to snow and how much snow areas north and west of me get. I use the HRRR to look at short term trends. Link to comment Share on other sites More sharing options...
psuhoffman Posted February 8, 2017 Share Posted February 8, 2017 The wrf and nmm look good but their from 12z. They update late Link to comment Share on other sites More sharing options...
Fozz Posted February 8, 2017 Share Posted February 8, 2017 4 minutes ago, psuhoffman said: You were right those numbers are overdone I just wanted to clear up the difference with the kuchera. The trend is more important then the number. The 12k nam actually trended slightly better. The way the calculate snow is based on metrics that do matter so even though the number is bogus you still want it to go up. For us it went from 4" to about 6". The bad news is both the 4K and 3k got way worse. 4K went from about 8" to 3.5". Slower flip and less organized precip after the flip. The nam has been running the warmest all along but then seemed to cave at 12z and came in line with the euro and rgem and gfs which all converged on a consensus compromise. Since that compromise was pretty good for us (3-6" looking from 12z guidance) I hoped that would lock in. But now the nam reverted to its warmer look of yesterday. Hopefully it's a hiccup and not the start of one last minute jump north that screws us over. IIRC, both October 2011 and early Feb 2014 had last minute jumps to the north. I don't know what this storm will do, but the NAMs and HRRR aren't looking very encouraging, not to mention temps today ended several degrees warmer than what many of the "good" 12z runs predicted, which will make a difference for those of us on the edge. At this point, I have no idea whether to trust the short term/mesoscale models or the usual global models. Link to comment Share on other sites More sharing options...
cae Posted February 8, 2017 Share Posted February 8, 2017 The 18z RGEM is also coming in warmer. Let's hope it's an 18z blip. Link to comment Share on other sites More sharing options...
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