Organizing Low Posted January 16, 2011 Share Posted January 16, 2011 cursory looks shows the GGEM was trying to do something similar to the NAM though not as robust intriguing, but fluid situatiion though..... Link to comment Share on other sites More sharing options...
cmichweather Posted January 16, 2011 Share Posted January 16, 2011 stebo patiently watching his snowpack melt away Link to comment Share on other sites More sharing options...
toronto blizzard Posted January 16, 2011 Share Posted January 16, 2011 Ugh When Philly's snow and you're rain, you know you've entered sucktown. Looks like a boatload of rain but its the RGEM so take it FWIW Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 What are some of the practical implications of this problem? Over-amplification? When the NAM does this, it is difficult to use for a variety of reasons. Some folks like to suggest simply "speeding" everything up a few hours, but that doesn't work very well mainly because feedback errors begin to amplify with time. In this case, feedback errors are likely, and beyond 48 hours, it is hard to give the NAM much credence overall with the height field pattern. Best use would be to hint at "potential" thermal fields, etc. When the NAM starts showing this ugly error, it becomes pretty useless overall beyond garnering a few details from it. Why does this ugly bias develop? I have no idea--I don;t think there are any concrete reasons why this occurs. Sometimes it lingers for multiple days on end--other times only a few runs. Monitor it though--if you see that ugly error popping up I would be more suspect of the NAM. Link to comment Share on other sites More sharing options...
Organizing Low Posted January 16, 2011 Share Posted January 16, 2011 Ugh When Philly's snow and you're rain, you know you've entered sucktown. well i think there would be ptype concerns for us, the question is whether we can get any backside snows. we are definteily wedged into the warm air stuck between the 2 systems i wasnt even going to pay attention to this until i saw the NAM this morning. Link to comment Share on other sites More sharing options...
snowyles25 Posted January 16, 2011 Share Posted January 16, 2011 Well 12z GFS looks like its trying to catch onto something to at 48hr. Low furthur south and wetter. Can tell looking at 500mb vortex its more amplified. Link to comment Share on other sites More sharing options...
Powerball Posted January 16, 2011 Share Posted January 16, 2011 12z GFS is SLIGHTLY cooler (slightly is the key word). Link to comment Share on other sites More sharing options...
snowstormcanuck Posted January 16, 2011 Share Posted January 16, 2011 Looks like a boatload of rain but its the RGEM so take it FWIW I was being overdramatic. It wouldn't start well per the RGEM, but it looks relatively similar to the 0z GGEM, which had us transitioning to snow late Tuesday. Per some of the AFDs I read this morning, I'd be surprised if rain was observed as far north as the RGEM is indicating. Link to comment Share on other sites More sharing options...
Stebo Posted January 16, 2011 Share Posted January 16, 2011 stebo patiently watching his snowpack melt away Captain always goes down with his ship Link to comment Share on other sites More sharing options...
snowstormcanuck Posted January 16, 2011 Share Posted January 16, 2011 When the NAM does this, it is difficult to use for a variety of reasons. Some folks like to suggest simply "speeding" everything up a few hours, but that doesn't work very well mainly because feedback errors begin to amplify with time. In this case, feedback errors are likely, and beyond 48 hours, it is hard to give the NAM much credence overall with the height field pattern. Best use would be to hint at "potential" thermal fields, etc. When the NAM starts showing this ugly error, it becomes pretty useless overall beyond garnering a few details from it. Why does this ugly bias develop? I have no idea--I don;t think there are any concrete reasons why this occurs. Sometimes it lingers for multiple days on end--other times only a few runs. Monitor it though--if you see that ugly error popping up I would be more suspect of the NAM. Thanks for the explanation. Notwithstanding the phase-shift problem, I wouldn't totally disregard what the NAM's showing this run as it does have some support from some other guidance (GEFS, GGEM). Just have to be careful not to fall in love with it verbatim, although that's always been a given with the NAM beyond 24 hours. Link to comment Share on other sites More sharing options...
cyclone77 Posted January 16, 2011 Share Posted January 16, 2011 Wow is it going to be a challenging forecast for eastern Iowa and northern Illinois. The GFS is continuing to be the coldest this morning. However, even it brings the snow/rain line to just north of the QC late tomorrow. Since the NAM and RGEM switch us to rain, I think it's safe to say we're going to get into the slop here as well. Right now it's looking like 2-3" of snow, followed by some rain, with flurries to finish it off. The rain may wipe out the snow that does fall, so this whole thing could end up being a wash. Looks like the Cedar Rapids to Dubuque areas will cash in on the best snows. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 Thanks for the explanation. Notwithstanding the phase-shift problem, I wouldn't totally disregard what the NAM's showing this run as it does have some support from some other guidance (GEFS, GGEM). Just have to be careful not to fall in love with it verbatim, although that's always been a given with the NAM beyond 24 hours. Right, sometimes a few details can be garnered from it even if it has that ugly phase shift issue. Other times it can wreck the forecast completely--especially when rapid positive feedback cyclogenesis is possible. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 Thanks for the explanation. Notwithstanding the phase-shift problem, I wouldn't totally disregard what the NAM's showing this run as it does have some support from some other guidance (GEFS, GGEM). Just have to be careful not to fall in love with it verbatim, although that's always been a given with the NAM beyond 24 hours. An incredible example where it can wreck the forecast. Remember this event? http://jasonahsenmacher.wordpress.com/2010/11/15/the-importance-of-model-timing-ohio-valley-and-se-rain-event/ Link to comment Share on other sites More sharing options...
snowyles25 Posted January 16, 2011 Share Posted January 16, 2011 An incredible example where it can wreck the forecast. Remember this event? http://jasonahsenmac...-se-rain-event/ Those maps look exactly like what is and might happen. Link to comment Share on other sites More sharing options...
ILSNOW Posted January 16, 2011 Share Posted January 16, 2011 anyone have the 12z GFS Bufkit for ORD?? Link to comment Share on other sites More sharing options...
michsnowfreak Posted January 16, 2011 Share Posted January 16, 2011 stebo patiently watching his snowpack melt away lol the snowpack may get dented, but next to zero chance it melts away. Link to comment Share on other sites More sharing options...
Stevo6899 Posted January 16, 2011 Share Posted January 16, 2011 Figures NAM finally looks good and of course the mention of errors have to rain on the parade. Link to comment Share on other sites More sharing options...
cmichweather Posted January 16, 2011 Share Posted January 16, 2011 Since I am not a model creator I do not have specifics to give but model algorithm calculations have been adjusted. Saying warm is a poor choice of words a more correct way of saying it is that algorithmic calculations have been altered to change the way they handle the whole physics of the atmosphere. I am not talking about one upgrade or a recent upgrade just a general schema. No model says "I am warm because I am told to do that" but the human or group of model interpreting calculations who put the physics behind it just seem to be running higher than the actual. Maybe it is just this winter and I am too quick to jump the gun but what has been spitting out usually ends up being under lately. This has nothing to do with GW or WARM CYCLE per se' but since it is an algorithmic calculation made by human inductive reasoning, the calculations change to try to make the model better and I believe those calculations were altered to try to adjust to the warming we have/had seen. A cheap example would be saying 2 + 2 = 4. Over time it came to figure out 2 + 2 = 5, so the people who do these things added an additional function to allow for that change. My question or debate lies in that area. Did scientists/physicists change their calculations due to a generally warming period to account for it because several years ago (how many I do not remember) models would run cold so they had to figure out a way to get them to sense more warmth? This has nothing to do with a particular storm or anything with that regard. This coming storm has no blocking and WAA will be prevalent and I am not debating that at all, my head scratching issue is are we getting to a point that a change in the algorithmic functions and calculations need to be reviewed. There has got to be a reason why models, in my opinion, are struggling terribly lately. All in all, I am using inductive logic to see if models continue to struggle mightily at times to come to a concrete solution that a review of some functions should be examined to help. Nothing will be perfect and maybe I am trying to delve too deep into something and over-analyzing something that is not worth it but the physics of the models are struggling so just throwing out a thought on the principle of trying to change some algorithms around to get a better grasp on the crazy physics of the atmosphere. Josh No one has changed the models to make them "warmer" based on the 2000's warmth. As you say they have upgraded and altered the models physics but nothing has been done to alter the warming we have seen. Take a look at the GFS vs. RGEM thermal profiles at hour 48 did the canadians alter their model to induce more low level WAA advection or does it simply have a a stronger 500 mb wave and stronger surface cyclogenesis to drive the warm air advection. If anything most models (especially the gfs) tend to miss WAA at the surface and will be to cold, you can cite certain cases were the models were in fact too warm for a certain situation but nothing funny has been done to the models in regards to unilaterally make them warmer. Link to comment Share on other sites More sharing options...
michsnowfreak Posted January 16, 2011 Share Posted January 16, 2011 12z GFS is SLIGHTLY cooler (slightly is the key word). Best of all, 12z GFS picked up on the deform snow idea In "torch" scenarios, people always tend to think "theres such an expansive snowpack, the models are overdoing the warmth", when time and time again they get burned, and if anything the models sometimes underdo it. Hell, the one poster in IA saw his snow depth go from 14" to 0 in a few days with that New Years torch. HOWEVER....this is NOT a torch scenario, rather simply the models are bringing some milder moist air in for a brief stay. Now, I want to stay careful for fear of getting burned as I described in the torch scenario above, BUT, I can see this as being a time when so brief and certainly not excessively mild air IS tempered by a snowpack. Also, its so cold at the surface, could see freezing rain with a temp of 33 or even 34 (as we saw on Dec 30th). Link to comment Share on other sites More sharing options...
snowyles25 Posted January 16, 2011 Share Posted January 16, 2011 One thing for sure its not over yet. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 Those maps look exactly like what is and might happen. They aren't really comparable, but it could have been 3-4 days ago if the models were different on the timing of the southern stream waves. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 One thing for sure its not over yet. Definitely not over, just for some. Jackpot areas look to be around Lake Michigan on both sides--E and W. Chicago is definitely in some gray area. Canuck and those farther NE are also in some gray areas. Link to comment Share on other sites More sharing options...
snowyles25 Posted January 16, 2011 Share Posted January 16, 2011 I wonder if the 18z runs will pick up more on the wetter and furthur south low as it passes south of Chicago and develop a more organized deform band. Link to comment Share on other sites More sharing options...
cmichweather Posted January 16, 2011 Share Posted January 16, 2011 I wonder if the phase shift with the nam has something to do with the data assimilation that goes on with the model. I mean the nam and gfs are both fed the same soundings and other data but i wonder if while the nam is running if some extra data or most recent data like satellite data, radar data or something is given to the gfs which always makes it slightly faster than the nam in these situations. It really just looks like the nam is about an hour or so behind the gfs in the upper levels. Not really sure Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 I wonder if the phase shift with the nam has something to do with the data assimilation that goes on with the model. I mean the nam and gfs are both fed the same soundings and other data but i wonder if while the nam is running if some extra data or most recent data like satellite data, radar data or something is given to the gfs which always makes it slightly faster than the nam in these situations. It really just looks like the nam is about an hour or so behind the gfs in the upper levels. Not really sure I don't think so mainly because the initialized fields are almost always right on. The severity varies a lot--sometimes it is 6 hours behind only 24 hours into the forecast--other times, as you said, only a few 48 hours in. Ask Dr. Askelson--I wonder if he has any thoughts. I asked DTK here--the resident model expert since he works on the GFS data assimilation system, and he didn't have any answers. Link to comment Share on other sites More sharing options...
A-L-E-K Posted January 16, 2011 Author Share Posted January 16, 2011 I wonder if the 18z runs will pick up more on the wetter and furthur south low as it passes south of Chicago and develop a more organized deform band. I'll say this, prepare for rain, rain snow mix and a slushy inch. Link to comment Share on other sites More sharing options...
snowyles25 Posted January 16, 2011 Share Posted January 16, 2011 Whatever happened to DVN Justin? That met. Link to comment Share on other sites More sharing options...
cyclone77 Posted January 16, 2011 Share Posted January 16, 2011 Whatever happened to DVN Justin? That met. I think we scared him and Ocean away. Haven't been around for almost a month. Sucks because we can't afford to lose any posters from this area, let alone mets. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 16, 2011 Share Posted January 16, 2011 I think we scared him and Ocean away. Haven't been around for almost a month. Sucks because we can't afford to lose any posters from this area, let alone mets. I think the weenies scared away OceanStwx when they mocked the local office about their wind forecasting for the NP blizzard event. It was only a couple--but he hasn't been back since. I don't blame him. Link to comment Share on other sites More sharing options...
Chicago WX Posted January 16, 2011 Share Posted January 16, 2011 I think the weenies scared away OceanStwx when they mocked the local office about their wind forecasting for the NP blizzard event. It was only a couple--but he hasn't been back since. I don't blame him. Hmm, I don't remember this. I'll have to go back through that thread and take a look. I hope he isn't gone for good. Link to comment Share on other sites More sharing options...
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