Thundersnow12 Posted December 1, 2010 Author Share Posted December 1, 2010 Yeah, I know it's the NAM at 84 hours... showing a nice little first sticking snow event FWIW. a few inches from MSP to LAF Link to comment Share on other sites More sharing options...
Chicago WX Posted December 1, 2010 Share Posted December 1, 2010 Yeah, I know it's the NAM at 84 hours... Our margin for error is slim. Link to comment Share on other sites More sharing options...
AppsRunner Posted December 1, 2010 Share Posted December 1, 2010 FWIW... SREF: Link to comment Share on other sites More sharing options...
Hoosier Posted December 1, 2010 Share Posted December 1, 2010 Our margin for error is slim. Looks like it would be just cold enough. NAM seems like it wants to dryslot after that...close call, but probably not worth obsessing over at this point. Link to comment Share on other sites More sharing options...
Chicago WX Posted December 1, 2010 Share Posted December 1, 2010 Looks like it would be just cold enough. NAM seems like it wants to dryslot after that...close call, but probably not worth obsessing over at this point. It would probably be a front end 1-2" punch then dryslot and drizzle for us. But yeah I won't lose any sleep over the NAM at 84 hours...or any model for that matter. Link to comment Share on other sites More sharing options...
wxdudemike Posted December 1, 2010 Share Posted December 1, 2010 It would probably be a front end 1-2" punch then dryslot and drizzle for us. But yeah I won't lose any sleep over the NAM at 84 hours...or any model for that matter. Bet some of us would like to say the same "Oh, the Euro doesn't come out til 1:30am? Well.......I was gonna be up anyways......" Link to comment Share on other sites More sharing options...
Thundersnow12 Posted December 1, 2010 Author Share Posted December 1, 2010 FWIW.... Link to comment Share on other sites More sharing options...
Chicago WX Posted December 1, 2010 Share Posted December 1, 2010 Bet some of us would like to say the same "Oh, the Euro doesn't come out til 1:30am? Well.......I was gonna be up anyways......" Trust me, if it was looking like a big storm, I'm staying up for the Euro...work or no work tomorrow. That's part of the sickness. Link to comment Share on other sites More sharing options...
wxdudemike Posted December 1, 2010 Share Posted December 1, 2010 Trust me, if it was looking like a big storm, I'm staying up for the Euro...work or no work tomorrow. That's part of the sickness. For me it's classes, but I scheduled winter quarter classes to start at 10:30am so bring on the late nights Link to comment Share on other sites More sharing options...
cyclone77 Posted December 1, 2010 Share Posted December 1, 2010 Good to see the NAM joining the party. The little system still looks very vigorous. Could be some decent snow rates for a time wherever that main band sets up. Starting to look like we may be a bit too far south here, but we'll see. Link to comment Share on other sites More sharing options...
JoMo Posted December 1, 2010 Share Posted December 1, 2010 Do these bands usually end up farther NE than the models prog up that way? Down here, almost every clipper systems winds up farther NE than the models show it. Link to comment Share on other sites More sharing options...
JoMo Posted December 1, 2010 Share Posted December 1, 2010 More potent Link to comment Share on other sites More sharing options...
KokomoWX Posted December 1, 2010 Share Posted December 1, 2010 More potent But looks more west. hhhmmm....... Link to comment Share on other sites More sharing options...
Thundersnow12 Posted December 1, 2010 Author Share Posted December 1, 2010 0z GFS faster than the 12z run. 12z run at 84hrs at the H85 low on the MT/SD/ND border. 0z at 72 hours has H85 low center over ABR or a tad northeast of there. Link to comment Share on other sites More sharing options...
Chicago WX Posted December 1, 2010 Share Posted December 1, 2010 Do these bands usually end up farther NE than the models prog up that way? Down here, almost every clipper systems winds up farther NE than the models show it. Seems like they do...but that's not based off any scientific evidence. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted December 1, 2010 Author Share Posted December 1, 2010 Link to comment Share on other sites More sharing options...
Hoosier Posted December 1, 2010 Share Posted December 1, 2010 Seems like they do...but that's not based off any scientific evidence. I think it's mixed...I can think of events that went both ways... Link to comment Share on other sites More sharing options...
Chicago WX Posted December 1, 2010 Share Posted December 1, 2010 GFS really dampens it out as it moves east...but seemingly has kept the same area for the best zone of accumulating snows (central/southern MN, central/southern WI, northern IL, northwest IN). Link to comment Share on other sites More sharing options...
Hoosier Posted December 1, 2010 Share Posted December 1, 2010 GFS really dampens it out as it moves east...but seemingly has kept the same area for the best zone of accumulating snows (central/southern MN, central/southern WI, northern IL, northwest IN). The GFS seems like it's on the north end of the consensus at this point. Link to comment Share on other sites More sharing options...
cyclone77 Posted December 1, 2010 Share Posted December 1, 2010 The 18z and the new 00z GFS runs are way wetter and more dynamic with this system compared to the last several days. Good to see it come around and agree with what the GEM and Euro have shown for days. Link to comment Share on other sites More sharing options...
Chicago WX Posted December 1, 2010 Share Posted December 1, 2010 I think it's mixed...I can think of events that went both ways... I always think back to our most recent "successful" clipper, 2/6/07, and I believe it started out north on the models...trended to our south, only to come back north a bit at the last minute. The rest was history. Link to comment Share on other sites More sharing options...
cyclone77 Posted December 1, 2010 Share Posted December 1, 2010 I predict the new GEM will lay down 8-12" in a 300 mile wide swath from Minnesota to Indiana. Link to comment Share on other sites More sharing options...
Stebo Posted December 1, 2010 Share Posted December 1, 2010 I predict the new GEM will lay down 8-12" in a 300 mile wide swath from Minnesota to Indiana. Come on now, lets be real its the GGEM... it will show 12-18" Link to comment Share on other sites More sharing options...
cyclone77 Posted December 1, 2010 Share Posted December 1, 2010 Come on now, lets be real its the GGEM... it will show 12-18" That is true. Hopefully it does trend wetter again though. This morning's run was drier than the last few days. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted December 1, 2010 Author Share Posted December 1, 2010 0z NAM images Link to comment Share on other sites More sharing options...
cyclone77 Posted December 1, 2010 Share Posted December 1, 2010 The new GEM is back to being wetter again, much like the last few days. The track looks similar to what it's been showing all along as well. Link to comment Share on other sites More sharing options...
Hoosier Posted December 1, 2010 Share Posted December 1, 2010 I always think back to our most recent "successful" clipper, 2/6/07, and I believe it started out north on the models...trended to our south, only to come back north a bit at the last minute. The rest was history. That event had a much more impressive thermal gradient, but I believe you're correct that it did creep north at the last minute. That is one of my favorite smaller snow events...gonna post more about it in the past snowstorms thread in a few minutes... Link to comment Share on other sites More sharing options...
Thundersnow12 Posted December 1, 2010 Author Share Posted December 1, 2010 That event had a much more impressive thermal gradient, but I believe you're correct that it did creep north at the last minute. That is one of my favorite smaller snow events...gonna post more about it in the past snowstorms thread in a few minutes... had to go back and look at a radar loop of that system for myself since I forgot what it looked like. Link to comment Share on other sites More sharing options...
cyclone77 Posted December 1, 2010 Share Posted December 1, 2010 The new GEM maintains about the same track as it has shown the last 3-4 days. This places the best band of snow a bit further south than the NAM and especially the GFS. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted December 1, 2010 Share Posted December 1, 2010 Do these bands usually end up farther NE than the models prog up that way? Down here, almost every clipper systems winds up farther NE than the models show it. An interesting question. It is strongly dependent on the strength of the upper level wave and upper level cold front. Clippers are mostly low amplitude upper tropospheric shortwaves interacting with a rather sharp thermal gradient (baroclinic zone). From a standpoint of cyclogenesis, what you have is a "wave" in the upper atmosphere and a tight low level circulation. This results in rapid frontogenesis as the thermal gradient "tightens" with the progression of the low amplitude wave. Frontal banding along the frontal circulation aloft becomes the dominant forcing mechanism (mesoscale) with synoptic forcings generally playing a much smaller role than larger cyclones. These clippers are so challenging to forecast both because of the small scale upper wave, the rapid speed of the wave (low amplitude waves propagate much faster, so timing is a challenge), and small changes in the thermal gradient and placement of the polar front can make huge changes. Look at our snow pack across the northern plains and intermountain west: http://www.nohrsc.no...05_National.jpg For instance, this data is ingested into the numerical models, and exactly how they model both this data and how much snow will potentially melt can have a large impact on where the thermal contrast develops and where the eventual wave develops. Also, this is a phase event over the Pacific: http://www.atmos.was...1_x_500vor+///3 Note how the weak shortwave phases with the upper low around the Aleutians, deamplifies over the Rockies, then weakly phases again with the polar branch over the Dakotas. There is a lot of variability right there, and depending on how far south the wave takes will influence the strength of the cross barrier flow across the Rockies and subsequent lee troughing and moisture/thermal transport (note the lee trough the models develop after 48 hrs). Getting back to what I said earlier though, with clippers, what generally happens is stronger upper shortwaves develop strong frontogenesis aloft. Because the frontal boundary is tilted over cold air (static stability), this results in qpf that generally ends up farther N. Here is a "model" cold front to help you visualize a typical orientation of a cold front using a vertical cross section: If the upper level shortwave aloft is weaker, this usually results in stronger frontogenesis in the lower levels closer to the surface, which results in a farther S track. As you can see, clippers are usually quite tough to forecast and I have seen many times where the snow band is off kilter by 50-100 miles within the final 24 hours of the forecast. Small scale errors with how models simulate the development of a clipper grows FAST with time. As others have said, I think it is a "wash" from a climo standpoint. If you feel the wave is potentially going to be more intense and or/of greater amplitude, possibly shift the track a tad north. if you feel it will be weaker and/or of less amplitude, shift the track a tad south. This of course does not take into account the placement of the baroclinic zone. if you feel that may be farther N or S, also take that into account when forecasting the track. Also, stronger waves usually support deeper frontogenesis and slightly wider snow bands, so take that into consideration as well. Link to comment Share on other sites More sharing options...
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