IsentropicLift Posted January 21, 2015 Author Share Posted January 21, 2015 15Z SREF's Link to comment Share on other sites More sharing options...
danstorm Posted January 21, 2015 Share Posted January 21, 2015 No matter what, there's certainly going to be mixing issues on the coast and possibly NYC during the early hours of the storm before turning over to complete snow as the system bombs out. That said, the system does not seem to close off completely according to the models. What are the chances it does? "Closing off" is completely overrated. When a storm closes off, the mechanisms responsible for vertical lift begin to weaken. Link to comment Share on other sites More sharing options...
robertgny Posted January 21, 2015 Share Posted January 21, 2015 Frontogenesis is basically lift due to rapidly strengthening thermal gradient... sharpening between temperatures on both sides of the low. This enhances mid level lift and precip rates. Sorry for the stupid question, maybe this belongs in the banter thread but what does the purple above nyc indicate? Link to comment Share on other sites More sharing options...
danstorm Posted January 21, 2015 Share Posted January 21, 2015 Sorry for the stupid question, maybe this belongs in the banter thread but what does the purple above nyc indicate? 700 mb frontogenesis. It is oftentimes a proxy for the location of a deformation band and can contain embedded CSI banding. Link to comment Share on other sites More sharing options...
ag3 Posted January 21, 2015 Share Posted January 21, 2015 I think people are getting a little carried away here. Especially for the coast (including NYC's boroughs). To me this looks like a 2"-5" front end, followed by a 3-6 hour period of sleet/mix/rain and then depending on where the 500mb low closes off, then the CCB will go from mix/rain to heavy snow for everyone. Euro has the 500mb low closing off just south of LI. In that scenario, the CCB would probably drop 4"-8" alone. If we can get the 500mb low to close off even further south, then we can be looking at higher amounts. But if it closes off too late, like the GFS at 12z did, then the CCB would be 2"-5" type of snow fall. A good early forecast, IMO, would be 4"-8" with rain/mix at the coast at the surface low's closest approach. While Jan. 26-27, 2011 scenario looks fairly similar, the 500mb low closed off well south of the area, allowing for the CCB to be well developed by the time it got here and thus dropping 8"-14" in that band alone. Link to comment Share on other sites More sharing options...
Superstorm93 Posted January 21, 2015 Share Posted January 21, 2015 Link to comment Share on other sites More sharing options...
Juliancolton Posted January 21, 2015 Share Posted January 21, 2015 Frontogenesis is basically lift due to rapidly strengthening thermal gradient... sharpening between temperatures on both sides of the low. This enhances mid level lift and precip rates. Strictly speaking, frontogenesis *is* the strengthening thermal gradient... Link to comment Share on other sites More sharing options...
danstorm Posted January 21, 2015 Share Posted January 21, 2015 700 mb frontogenesis. It is oftentimes a proxy for the location of a deformation band and can contain embedded CSI banding. That said, it is way too early to think about pinpointing such features. But the signals for a mature, strengthening CCB are certainly there. Link to comment Share on other sites More sharing options...
DTWXRISK Posted January 21, 2015 Share Posted January 21, 2015 100000% agreed I think people are getting a little carried away here. Especially for the coast (including NYC's boroughs). To me this looks like a 2"-5" front end, followed by a 3-6 hour period of sleet/mix/rain and then depending on where the 500mb low closes off, then the CCB will go from mix/rain to heavy snow for everyone. Euro has the 500mb low closing off just south of LI. In that scenario, the CCB would probably drop 4"-8" alone. If we can get the 500mb low to close off even further south, then we can be looking at higher amounts. But if it closes off too late, like the GFS at 12z did, then the CCB would be 2"-5" type of snow fall. A good early forecast, IMO, would be 4"-8" with rain/mix at the coast at the lows closest approach. While Jan. 26-27, 2011 scenario looks fairly similar, the 500mb low closed off well south of the area, allowing for the CCB to be well developed by the time it got here and thus dropping 8"-14" in that band alone. Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 21, 2015 Share Posted January 21, 2015 Its fairly rare to see snow to rain to snow events here, my guess is it ends up either all snow or rain to snow although as I said there is a chance it may do the former. Link to comment Share on other sites More sharing options...
Snowlover11 Posted January 21, 2015 Share Posted January 21, 2015 got it thanks Link to comment Share on other sites More sharing options...
Zynlamar Posted January 21, 2015 Share Posted January 21, 2015 Way to early in the game for all this type of talk. A major storm is on the table and I am happy with that. The fine details will be worked out as we get closer to the event (that will hopefully still be a factor in a few days) Link to comment Share on other sites More sharing options...
LongBeachSurfFreak Posted January 21, 2015 Share Posted January 21, 2015 Do you honestly believe that 1.25" liquid is likely with those dynamics? Should have been closer to 2". Then give me 12:1 ratios and you have 24". I don't see how that's out of the question. I'm not giving out a public forecast, just speculating.You would be right somewhere if the current euro verified verbatim. Super strong and dynamic storms have areas of enhanced precip that aren't going to show on a long range global. Not an analog but 12/10 and 2/13 both exhibited that trait. Now let's see what really happens. One run of one model. Odds are high that the met area sees it's first 6+ of the season though Link to comment Share on other sites More sharing options...
USCG RS Posted January 21, 2015 Share Posted January 21, 2015 "Closing off" is completely overrated. When a storm closes off, the mechanisms responsible for vertical lift begin to weaken.Yes, but to my understanding, if you're in the correct position when it closes off, you get rocked. But yes, closing off means it becomes vertically stacked and therefore it begins to fill. United States Coast Guard Rescue Swimmer Link to comment Share on other sites More sharing options...
SnowGoose69 Posted January 21, 2015 Share Posted January 21, 2015 If anyone ever wants an example of a storm where a -NAO may have screwed us, this is it right here. Link to comment Share on other sites More sharing options...
robertgny Posted January 21, 2015 Share Posted January 21, 2015 Wait a second 500 mb low closing is 100% a key to getting a ccb. How do you get precip to expeand to the west and nw of a low. You need mid level spin to the west of the surface low ( surface low yielding colliding air along the front ) to carry precip back to the west and nw. So the premise it's not the case is wrong. Link to comment Share on other sites More sharing options...
Rtd208 Posted January 21, 2015 Share Posted January 21, 2015 Once again, its a little to early to get into the specific details. For now the 6"-10" amounts that DT mentioned seems fine and that can always be increased or reduced later since we are still 2.5-3 days away from this event. I am just excited to see a major storm on the models for us and the potential of seeing a plowable significant snowfall is rather high. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 21, 2015 Author Share Posted January 21, 2015 The 18z NAM is probably going to be West of 12z. Like the Euro the trough axis is West of the prior run. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 21, 2015 Author Share Posted January 21, 2015 The NAM is also more amped up at hr 60. This might be one of those old fashioned NAM runs that shows like 40" of snow. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 21, 2015 Author Share Posted January 21, 2015 992mb 75 miles SE of ACY. A little weird to see it less enthusiastic than the Euro, but the long range NAM is known for having whacked out solutions. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 21, 2015 Author Share Posted January 21, 2015 987mb south of the benchmark. It's colder for the coast than the GGEM and ECWMF but the best dynamics are offshore. Funny how the trough axis was West and yet the surface low ended up further southeast. Link to comment Share on other sites More sharing options...
PB GFI Posted January 21, 2015 Share Posted January 21, 2015 Looks good to me Link to comment Share on other sites More sharing options...
robertgny Posted January 21, 2015 Share Posted January 21, 2015 Neg tilt...never closes off. And it still closes off south of Long Island just like the Euro. I'm going to say toss the QPF. Link to comment Share on other sites More sharing options...
swamplover56 Posted January 21, 2015 Share Posted January 21, 2015 Wonder why the best stuff stays offshore with that track Link to comment Share on other sites More sharing options...
WaPo Posted January 21, 2015 Share Posted January 21, 2015 And it still closes off south of Long Island just like the Euro. I'm going to say toss the QPF. Toss the QPF? As in wait til we get closer to the weekend? Link to comment Share on other sites More sharing options...
Stormlover74 Posted January 21, 2015 Share Posted January 21, 2015 Toss the QPF? As in wait til we get closer to the weekend? Too soon to worry about that. Track looks fine. Link to comment Share on other sites More sharing options...
SnoSki14 Posted January 21, 2015 Share Posted January 21, 2015 Wonder why the best stuff stays offshore with that track Because it's the Nam at 72 hrs. The fact that it resembles the other models this far out is a miracle. Link to comment Share on other sites More sharing options...
baseball0618 Posted January 21, 2015 Share Posted January 21, 2015 987mb south of the benchmark. It's colder for the coast than the GGEM and ECWMF but the best dynamics are offshore. Funny how the trough axis was West and yet the surface low ended up further southeast. less northern stream interaction depicted here until it's already at your latitude. but not sure why you'd take the nam at face value outside of it's useful range anyway. Link to comment Share on other sites More sharing options...
IsentropicLift Posted January 21, 2015 Author Share Posted January 21, 2015 I stand corrected, the NAM does not close off the 500mb low. That could be another reason why it doesn't have as much expansion on the NW side. Link to comment Share on other sites More sharing options...
Doorman Posted January 21, 2015 Share Posted January 21, 2015 http://www.hpc.ncep.noaa.gov/wwd/day3_psnow_gt_04.gif http://www.hpc.ncep.noaa.gov/qpf/fill_99qwbg.gif?1421873810296 http://www.tropicaltidbits.com/analysis/models/gfs-ens/2015012112/gfs-ens_apcpn24_us_15.png Link to comment Share on other sites More sharing options...
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