Desnowlover Posted January 11, 2011 Share Posted January 11, 2011 Holy ****. I'm impressed. Well D*** What he said too! Said it in a manner laymen could understand as well! Thank you!!! Link to comment Share on other sites More sharing options...
famartin Posted January 11, 2011 Share Posted January 11, 2011 The Christmas bomb was a different beast than this with the initial surface low tracking through the GOM. Latent heat release and convergence in the GOM played a large role in the eventual development, and the GFS did well in the 3 day range because it was really the first keying in on the GOM role. As I had said back during that event, the early ECM runs lost the storm as the southern stream wave petered out once we came within 4-5 days of the event. All guidance lost the storm OTS because the configuration of the trough did not allow for rapid cyclogenesis early enough....and all solutions were OTS. GFS, by day 3, keyed in on the strength of convection in the GOM and the low level mass response/surface convergence and associated latent heat release via condensation in the lower boundary of the atmosphere. Moreover, the globals continued to trend towards a more amplified Rockies ridge and a deeper diving backside jet streak. The "capture" of that surface low in the GOM primed rapid feedback cyclogenesis over the Gulf Stream due to latent heat release in the GOM owing to the mass response/convergence to the developing convection. GFS was the first to key in on all those factors coming into play--and as a result--I think it is safe to say it "performed" the best within the day 3 range. As for that storm, development was also highly non-linear, but not nearly as non-linear as this system. Rapid feedback with that storm developed off SC coast with a much more amplified wave. This storm is bombing well N of Hatteras with a S/W ejecting over the Gulf Stream in a nearly W-E fashion. While the Christmas storm featured signficant non-synoptic scale development including the ridiculous ageo jet circulation, this storm features an insane dynamic tropopause and a large fold. We are talking deepening of 20-30 hpa in 18 hours with a compact low smaller than LI. The low itself is getting close to sub-grid scale for the GFS and its spectral wave ~ 25 km resolution. The GFS won't be able to handle that type of non-linear development like it did for the Christmas storm. A valid argument, ASSUMING the low is as small as you suggest. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 11, 2011 Share Posted January 11, 2011 May I ask a question? I understand mesoscale model. but what is non-hydrostatic? It means the model does not make the hydrostatic assumption--an assumption that vertical motions are mostly balanced by the vertical pressure gradient force. Works fine in synoptic scale motions, but it does not do well with mesoscale vertical motions--especially convection or where static stability is very low. It needs to be parametrized in hydrostatic models like global models. Link to comment Share on other sites More sharing options...
ORH_wxman Posted January 11, 2011 Share Posted January 11, 2011 Nice post, B_I. I think you know more about models than I do, so I'll defer to you here, but shouldn't the Euro be picking up on these processes as well, since its resolution is down to 15km? Or is it still hydrostatic and not picking up on some of the convective processes as a result? The Euro is still a hydrostatic model so it probably wouldn't treat the deepening of the low and convection the same way. I'll say this about these types of systems (well there really isn't a huge precedent)...but I had to forecast the 12/9/05 storm and the mesoscale models out performed the global models by a lot in that one. Even the Euro was way too east and not amped up enough. That doesn't mean the same thing will happen with this one, but it certainly could be a clue. I remember the mesoscale models having a few jumps too very close in...a run or two of the old ETA tried to bring the low W of BOS at one point. The ultimate solution was a track over Buzzards Bay just W of the Cape Cod Canal...the global models had it well SE of the Islands. I recall the Suny MM5 really doing well in that storm. Link to comment Share on other sites More sharing options...
Echo Posted January 11, 2011 Share Posted January 11, 2011 Leaving work in New Castle, De around 2, there were flurries and sunshine. The temp is right at 32. Link to comment Share on other sites More sharing options...
tcutter Posted January 11, 2011 Share Posted January 11, 2011 It means the model does not make the hydrostatic assumption--an assumption that vertical motions are mostly balanced by the vertical pressure gradient force. Works fine in synoptic scale motions, but it does not do well with mesoscale vertical motions--especially convection or where static stability is very low. It needs to be parametrized in hydrostatic models like global models. you should be a teacher!! Link to comment Share on other sites More sharing options...
SP Posted January 11, 2011 Share Posted January 11, 2011 The Christmas bomb was a different beast than this with the initial surface low tracking through the GOM. Latent heat release and convergence in the GOM played a large role in the eventual development, and the GFS did well in the 3 day range because it was really the first keying in on the GOM role. As I had said back during that event, the early ECM runs lost the storm as the southern stream wave petered out once we came within 4-5 days of the event. All guidance lost the storm OTS because the configuration of the trough did not allow for rapid cyclogenesis early enough....and all solutions were OTS. GFS, by day 3, keyed in on the strength of convection in the GOM and the low level mass response/surface convergence and associated latent heat release via condensation in the lower boundary of the atmosphere. Moreover, the globals continued to trend towards a more amplified Rockies ridge and a deeper diving backside jet streak. The "capture" of that surface low in the GOM primed rapid feedback cyclogenesis over the Gulf Stream due to latent heat release in the GOM owing to the mass response/convergence to the developing convection. GFS was the first to key in on all those factors coming into play--and as a result--I think it is safe to say it "performed" the best within the day 3 range. As for that storm, development was also highly non-linear, but not nearly as non-linear as this system. Rapid feedback with that storm developed off SC coast with a much more amplified wave. This storm is bombing well N of Hatteras with a S/W ejecting over the Gulf Stream in a nearly W-E fashion. While the Christmas storm featured signficant non-synoptic scale development including the ridiculous ageo jet circulation, this storm features an insane dynamic tropopause and a large fold. We are talking deepening of 20-30 hpa in 18 hours with a compact low smaller than LI. The low itself is getting close to sub-grid scale for the GFS and its spectral wave ~ 25 km resolution. The GFS won't be able to handle that type of non-linear development like it did for the Christmas storm. Nice write up.... Dynamic Tropopause....... We need to get you and Typhoon Tip into a chat room!! Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 11, 2011 Share Posted January 11, 2011 Nice post, B_I. I think you know more about models than I do, so I'll defer to you here, but shouldn't the Euro be picking up on these processes as well, since its resolution is down to 15km? Or is it still hydrostatic and not picking up on some of the convective processes as a result? The ECM is a head scratcher to me--I like how some of the NWS folks went with the 0Z instead--seems more realistic. The GFS op is an even bigger head scratcher--it is even E of its own mean. SO it does seem it can simulate this storm, but for whatever reason, the GFS op and the ECM op have been slow to react to changes in their own height field with this storm. Even 4-6 days out, the ops were stalwarts in remaining flat and weak in the height field, and when they did make changes, it took 2-4 runs for those surface changes to manifest themselves. Look how long the GFS was OTS with this storm threat, for instance. If anything I would be going GFS mean if I were to bother with the GFS at all. The mesoscale models with their non-hydro assumption will have a huge advantage here though--considering their initial conditions are decent. Through 18Z it seems like the 12Z NAM is about right with the coastal track. Link to comment Share on other sites More sharing options...
famartin Posted January 11, 2011 Share Posted January 11, 2011 Since we are making comparisons to 12/9/2005... I'll point out that that system was already significantly better developed by the time it arrived in this area than the current system appears to be. This means little for New England... but much for this region. Link to comment Share on other sites More sharing options...
WeatherQ Posted January 11, 2011 Share Posted January 11, 2011 Cheer up bluehens, that weird finger of total precip on the NMM brings ~ 1.0 in. qpf to our local and keeps us in the PHL/Southern Chester County snow zone. Interesting to see if it verifies. Godd to see the radar echos increasing SW to NE in VA Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 11, 2011 Share Posted January 11, 2011 Since we are making comparisons to 12/9/2005... I'll point out that that system was already significantly better developed by the time it arrived in this area than the current system appears to be. This means little for New England... but much for this region. I am not saying the 06Z NAM will verify, but the GFS will be pulling a major coup if it does considering it is already well off with the coastal--and it has been putrid with the plains/OV low from the start. Don't get me wrong though, this will be fun to watch. I am not 100% sure how this will verify out--I don't think nobody is. Link to comment Share on other sites More sharing options...
NaoPos Posted January 11, 2011 Share Posted January 11, 2011 My buddy works down Edgewood, Aberdeen proving grounds, says light steady snow falling.. Time for an ons thread? Link to comment Share on other sites More sharing options...
bluehens Posted January 11, 2011 Share Posted January 11, 2011 I think Mt. Holly just downgraded ILG to 2-4" from 5-8"....at least it appears that way in the text of the forecast. This is going to be a repeat of 12/26 for us as everything is sliding east. Just looking at the radar returns you can see the trend of everything sliding to the SE. Almost all of the precip forecasts have been shifting east. I got 4" combined this past Friday and Saturday from a clipper/ULL passing by and I now think this storm will be lucky to match that. Just reading between the lines of what the red taggers are saying I think hopes are fading. Tony/Mike....any of the Mt. Holly guys care to chime in on what they're thinking for ILG? I already saw that the NWS offices further SE towards BWI have cut back on their forecast totals. Link to comment Share on other sites More sharing options...
am19psu Posted January 11, 2011 Author Share Posted January 11, 2011 NMM Clown map Two runs in a row now with that weird finger back through Philly and along the M-D line. Makes me think there is a good chance it could be real. Maybe not in QPF, but at least in relative snow amounts. Link to comment Share on other sites More sharing options...
Harbourton Posted January 11, 2011 Share Posted January 11, 2011 The Euro is still a hydrostatic model so it probably wouldn't treat the deepening of the low and convection the same way. I'll say this about these types of systems (well there really isn't a huge precedent)...but I had to forecast the 12/9/05 storm and the mesoscale models out performed the global models by a lot in that one. Even the Euro was way too east and not amped up enough. That doesn't mean the same thing will happen with this one, but it certainly could be a clue. I remember the mesoscale models having a few jumps too very close in...a run or two of the old ETA tried to bring the low W of BOS at one point. The ultimate solution was a track over Buzzards Bay just W of the Cape Cod Canal...the global models had it well SE of the Islands. I recall the Suny MM5 really doing well in that storm. This may not be the case for long. The ECMWF Workshop on Non-hydrostatic Modelling will be held from 8 to 10 November 2010. The workshop will bring together leading experts in the field of non-hydrostatic modelling to discuss recent developments in this area and to provide recommendations on how to prepare ECMWF’s Integrated Forecasting System (IFS) for global atmospheric modelling at future high to ultra-high resolutions. It will consider the strengths and weaknesses of different approaches taken in the development of non-hydrostatic dynamical cores and exchange ideas about efficient ways of testing the performance of these models at all scales. Workshop attendance is by invitation only. Link to comment Share on other sites More sharing options...
soadforecaster Posted January 11, 2011 Share Posted January 11, 2011 Two runs in a row now with that weird finger back through Philly and along the M-D line. Makes me think there is a good chance it could be real. ive been noticing that as well, seems like it wants to develop a band of hvy snow between the two systems. it would be great it this were to verify. Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted January 11, 2011 Share Posted January 11, 2011 Two runs in a row now with that weird finger back through Philly and along the M-D line. Makes me think there is a good chance it could be real. Maybe not in QPF, but at least in relative snow amounts. that 20" is insane Link to comment Share on other sites More sharing options...
bluehens Posted January 11, 2011 Share Posted January 11, 2011 Why do you think that model keeps putting that finger out there? Very odd. Its been there now on a couple of runs but the last run it was further north. I would cry tears of joy if it verified because it runs right through my backyard. Two runs in a row now with that weird finger back through Philly and along the M-D line. Makes me think there is a good chance it could be real. Maybe not in QPF, but at least in relative snow amounts. Link to comment Share on other sites More sharing options...
am19psu Posted January 11, 2011 Author Share Posted January 11, 2011 Why do you think that model keeps putting that finger out there? Very odd. Its been there now on a couple of runs but the last run it was further north. I would cry tears of joy if it verified because it runs right through my backyard. The only thing that even makes sense to me is a CSI band, but I'm not looking at any cross sections or anything, just postulating. Link to comment Share on other sites More sharing options...
SmokeEater Posted January 11, 2011 Share Posted January 11, 2011 NAM coming in even drier than 12z. Link to comment Share on other sites More sharing options...
goombatommy Posted January 11, 2011 Share Posted January 11, 2011 So, basically because of one or two model runs, and a "right now its looking like poo..." radar returns, people are jumping off the deep-end? Good Lord people, settle the heck down. This thing could easily come west and surprise many of us. Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted January 11, 2011 Share Posted January 11, 2011 . Link to comment Share on other sites More sharing options...
SmokeEater Posted January 11, 2011 Share Posted January 11, 2011 . That's what's worrying me, that primary is gonna hold on too long, and screw us. It shows no sign of dying out. And the NAM isn't dying it out until around midnight. Not a good sign. Link to comment Share on other sites More sharing options...
Ralph Wiggum Posted January 11, 2011 Share Posted January 11, 2011 Mix of snow, sleet, graupel in Wildwood, NJ attm Link to comment Share on other sites More sharing options...
SmokeEater Posted January 11, 2011 Share Posted January 11, 2011 Light snow just started here. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 11, 2011 Share Posted January 11, 2011 Nice to see the precip shield breaking up over OH. Makes me believe the energy transfer has begun. Link to comment Share on other sites More sharing options...
Voyager Posted January 11, 2011 Share Posted January 11, 2011 So which NAM would be the closest to verifying? 0, 6, 12, or 18z? Light snow and graupel here as well. Link to comment Share on other sites More sharing options...
SmokeEater Posted January 11, 2011 Share Posted January 11, 2011 Nice to see the precip shield breaking up over OH. Makes me believe the energy transfer has begun. It's not breaking up, in fact over W PA precip is blossoming. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 11, 2011 Share Posted January 11, 2011 It's not breaking up, in fact over W PA precip is blossoming. what you are seeing is the low unraveling and enhancing precip away from the actual low center which is what we want to see. Link to comment Share on other sites More sharing options...
atownwxwatcher Posted January 11, 2011 Share Posted January 11, 2011 To my knowledge NO model has showed what is currently happening.. HPC has the low tucked close to the coast (been shown) but as of 18 Z down to 1012 MBS... Even the NAM @ 6z at that time only had it at 1013 MBS.... Link to comment Share on other sites More sharing options...
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