am19psu Posted January 9, 2011 Share Posted January 9, 2011 The NAM is already out, showing a monster east coast snowstorm. Again, it's physically possible, but an operational outlier at the time. FWIW, the 0z Euro ensembles showed very little spread at H5 compared to the ops. Link to comment Share on other sites More sharing options...
Paweatherguy1 Posted January 9, 2011 Share Posted January 9, 2011 The NAM is already out, showing a monster east coast snowstorm. Again, it's physically possible, but an operational outlier at the time. FWIW, the 0z Euro ensembles showed very little spread at H5 compared to the ops. I cantpost photos on my iPod, but the differences in the deep south storm between the nam and gfs have to be creating a forecasting nightmare. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 Through 36, there is very little difference between the new 12z GFS and the 0z run from last night. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 With very little spread in the combined members of the GFS/ECM, and everything being well sampled for multiple runs, it shouldn't be much of a surprise that the 12z GFS is tracking similarly to the 0z GFS. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 9, 2011 Share Posted January 9, 2011 The NAM is already out, showing a monster east coast snowstorm. Again, it's physically possible, but an operational outlier at the time. FWIW, the 0z Euro ensembles showed very little spread at H5 compared to the ops. I glanced at the ECM mean, it looked to me like it was stronger with the leading S/W wrt to the operational run. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 I glanced at the ECM mean, it looked to me like it was stronger with the leading S/W wrt to the operational run. There are 4 or 5 members that are really deep with it, but then they all come back together with the rest of the guidance by 54. There doesn't appear to be much model sensitivity to the southern stream, at least in terms of the track of the low. I suppose it could make a difference in the eventual final QPF. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 Through 72, the 12z GFS is a carbon copy of the 0z GFS and ECM. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 I guess the one difference is that the surface low is that the surface low is about 8mb weaker. That would like cause less deformation banding, but that's a mesoscale detail to be worked out at a later time. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 In terms of QPF, the Mid-Atlantic really gets robbed. Maybe 1-2 for VA and NC away from the mountains. All of PA basically gets 2-4, the 4-8 goes from N NJ to SNE. No big amounts on this run. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 This whole run is drier overall. The Plains and the South see less snow than had previously been progged, too. Link to comment Share on other sites More sharing options...
Rainshadow Posted January 9, 2011 Share Posted January 9, 2011 Neither model's initialization captured the southern low perfectly this morning, the nam looked poorer than the gfs, it looks more pinched, also the ridge axis is slightly stronger, slower in the northern plains. I'd call it even with the gfs and nam for the northern stream. Haven't gone below 500mb yet. Wes, We got mixed pcpn mentioned se of PHL, always get queasy with 850mb lows trundling into the Oh Valley, should I be reaching for more Tums? Link to comment Share on other sites More sharing options...
Typhoon Tip Posted January 9, 2011 Share Posted January 9, 2011 12z NAM looks like thunder-snowstorms for NYC-BOS.... In general, this is much less a Miller A modeled system and more of a NJ model low. What is going on here is complex - perhaps misleading to some degree. There is a lead S/W (now) over Texas that is giving the deep south headaches. The mid level support for that is attenuating, and will all but completely abolish by 00z Tuesday, but not before inducing a weak surface reflection that migrates eastward along the southern rim of the cP air mass, lopping overrunning snow and ice enough to through up warnings down there. However, this wave of low pressure gets orphaned by the said weakening governing dynamics. Meanwhile, a much stronger full trough ejection out of the west will be fully underway by 00z Tuesday. This next short wave has a very intense jet max(es) associated, enough to drill over 40 units of vorticity almost normal to the geopotential medium - all that is missing is moisture. This is where it gets really yucky. That leading southern stream impulse and weak juicy wave of low pressure is actually during the interim stealing moisture from the more polarward stream impulse. This is why there is only a weak amorphous area of low pressure moving ENE from the MV to the upper MA Coast over the next 36 hours. What happens next is intriguing. It eventually latches on to said vestigial circulation as it trundles calling for mommy off the southeast U.S. coast. The orphaned SE Coastal low gets pulled N and it is not until it's moisture supply gets involved do we see the surface wave more than less bomb moving ENE away from the NJ Coast. I see a track to this similar to 9 December 2005. Using the model blend, I suspect an intense thermal compression forms just S of LI with this cP air mass residing over the shelf waters S of LI. That region is likely to generate a very upright frontal slope as the nose of the jet max at mid levels enters the region and excites lift. The incoming lower level WAA responses will slam into this cP denser air mass and be tilted very proficiently skyward. This mechanically forced ascent, also having the benefit of the orphaned wave's moisture supply, will tap into the jet core at mid levels and that is when things rock 'n' roll. Immediately on the polar ward side of this baroclinic axis there will like be a band or parallel bands of -EPV and some impressive frontogenics at work. I see that QPF eruption in the NAM at 72 hours over much of NJ, going from a paltry 6-hourly .25" liq equiv to nearly 1.25" 6-hour equiv in a flash as being about equally synoptic driven but also convective in nature. This whole package of fun and games then lifts NE...bathing much of SNE with S+/S++ with occasional lighting as well. This entire evolution would probably limit the greater impact to region between PHL and NYC on up the coast, although some snow in DCA (thermal field depending) would take place. Link to comment Share on other sites More sharing options...
dryslotted Posted January 9, 2011 Share Posted January 9, 2011 In terms of QPF, the Mid-Atlantic really gets robbed. Maybe 1-2 for VA and NC away from the mountains. All of PA basically gets 2-4, the 4-8 goes from N NJ to SNE. No big amounts on this run. Any thoughts why the NAM would begin deviating significantly from the gfs/ec? Link to comment Share on other sites More sharing options...
usedtobe Posted January 9, 2011 Share Posted January 9, 2011 Neither model's initialization captured the southern low perfectly this morning, the nam looked poorer than the gfs, it looks more pinched, also the ridge axis is slightly stronger, slower in the northern plains. I'd call it even with the gfs and nam for the northern stream. Haven't gone below 500mb yet. Wes, We got mixed pcpn mentioned se of PHL, always get queasy with 850mb lows trundling into the Oh Valley, should I be reaching for more Tums? It or depends. I do to and was suprised that the dc soundiings looked like snow through the entire event unless the cloud top temps get a little warmer than the minus 10 shown on the models. PHL looks OK but DOV looks dicey so yeah, reach for the tums. I'm not sure about your back yard. A lot still depends on how quickly the southern low deepens. The nam is pretty much a best case scenario. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 Any thoughts why the NAM would begin deviating significantly from the gfs/ec? I suspect because it is initially deeper with the southern low that eventually becomes the coastal. With a "pre-deepened" low, you can create stronger and quicker frontogenetic forcing. But that's a WAG. Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted January 9, 2011 Share Posted January 9, 2011 Well, the 12Z GFS looks a lot colder in the medium-longer range, whatever it's worth. At least compared to some of its previous cycles. Looks like it keeps the +PNA and perhaps hints at blocking/-NAO coming back? It still tries to do something interesting along the tail end of the cold front that goes through next weekend, it's done that at least a few times now recently. Not saying I buy it all, but some interesting developments. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 12z GEFS mean is right on top of the op and there remains little spread in the members at 72. Link to comment Share on other sites More sharing options...
Rainshadow Posted January 9, 2011 Share Posted January 9, 2011 It or depends. I do to and was suprised that the dc soundiings looked like snow through the entire event unless the cloud top temps get a little warmer than the minus 10 shown on the models. PHL looks OK but DOV looks dicey so yeah, reach for the tums. I'm not sure about your back yard. A lot still depends on how quickly the southern low deepens. The nam is pretty much a best case scenario. Wes, Thank-you for your input as always. Link to comment Share on other sites More sharing options...
usedtobe Posted January 9, 2011 Share Posted January 9, 2011 Wes, Thank-you for your input as always. In terms of QPF, I think the nam is a best case scenario and is probably overdone some up to the north. I'd go with the euro or a little more towards the gfs than the nam. I'm already tired of this winter since around here it's been forecast headach after headache with no pay off. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 12z Euro rolling... no changes through 24. EDIT: There is one difference - huge QPF bomb over N TX. If there is enough dynamic cooling, someone around the Metroplex is going to get a nice surprise. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 At 42, there is closed low off SC, just like the 0z run, which is not present on the 12z GFS. Probably just a minor detail. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 Still no difference through 54. As stated previously, this isn't a big surprise. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 Like before, the Euro is a little deeper with the sfc low than the GFS at 60. Will probably result in some more QPF for New England when it is all said and done Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 There is like zero difference between the 12z Euro at 66, the 12z GFS at 66 and the 0z Euro at 78, except the Euro is about 4mb deeper than the GFS. Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 By the way, the reason I'm not going into detail here is because you literally go look at the 12z GFS and get the same result if you live south of NYC. Like I said, New England is going to get more QPF, but that's about it. EDIT: Actually, NJ gets a bit more QPF here, too, but not a meaningful difference unless you are waffling between 6 and 8 inches for your forecast Link to comment Share on other sites More sharing options...
Paweatherguy1 Posted January 9, 2011 Share Posted January 9, 2011 By the way, the reason I'm not going into detail here is because you literally go look at the 12z GFS and get the same result if you live south of NYC. Like I said, New England is going to get more QPF, but that's about it. EDIT: Actually, NJ gets a bit more QPF here, too, but not a meaningful difference unless you are waffling between 6 and 8 inches for your forecast What about areas west of 95 and into thee Midwest? Same as gfs? Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 What about areas west of 95 and into thee Midwest? Same as gfs? Outside of the tri-state and New England, the QPF outputs are virtually the same nationwide. Link to comment Share on other sites More sharing options...
BDR Posted January 9, 2011 Share Posted January 9, 2011 Outside of the tri-state and New England, the QPF outputs are virtually the same nationwide. Well then, how's SNE look? Link to comment Share on other sites More sharing options...
am19psu Posted January 9, 2011 Author Share Posted January 9, 2011 Well then, how's SNE look? It's the same as 0z. Earthsat doesn't have well defined isohyets, so all I can say is >1". Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 9, 2011 Share Posted January 9, 2011 Some 12z Euro qpf amounts for PA: ABE: 0.45"-0.50" AVP: 0.40"-0.45" IPT: 0.30"-0.40" MDT: 0.30"-0.40" PHL: 0.50"-0.55" PIT: 0.35"-0.40" Link to comment Share on other sites More sharing options...
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