OceanStWx Posted September 7, 2013 Share Posted September 7, 2013 I mentioned this before, but that storm has strong low level frontogenesis...not all from a CF, but in the 950-850 layer and this conv area was near the canal. Above that layer was an unstable layer with the dryslot. But, in my experience, you don't always get a precip max NW of the cstl front..you get a snowfall max. In fact, many times areas of SE MA will have the most QPF, but lack in snowfall. Really diving into the physics, I posit that it can't hurt to have marine influence being lofted over the coastal front and into the mid levels. Most notably would be sea salt, which if I'm remembering training correctly is pretty effective for ice nucleation. Link to comment Share on other sites More sharing options...
CoastalWx Posted September 7, 2013 Share Posted September 7, 2013 Really diving into the physics, I posit that it can't hurt to have marine influence being lofted over the coastal front and into the mid levels. Most notably would be sea salt, which if I'm remembering training correctly is pretty effective for ice nucleation. Yep, agree Sea salt is around -8C (I believe) for ice nucleation so yeah..certainly helps for better dendrites at lower temps. Many times you get that gravy train into SE MA and then up and over the CF so you go to pounding +RA to pounding +SN. I saw that a few times back in the '02-'03 winter. One thing I would like to read more about or perhaps a case study are the different types of CF enhancement. In some of those cases you literally have enhancement for only a few miles or so..but other times it's a much broader horizontal area. Clearly when you think about this, the vertical temp profile is the reason so it's not hard to deduce the type of profile for both..but it would be a cool little study. Of course sometimes radar doesn't even pick up on the enhancement going on since it may be too low level, so trying to separate enhanced snow vs what you would have normally received from synoptic snow would be difficult. Link to comment Share on other sites More sharing options...
ORH_wxman Posted September 7, 2013 Share Posted September 7, 2013 You can get dendrite growth in sea salt as warm as like -6C or even -5C if its dense....its very effective. I think it definitely plays a role in CF snowfall enhancement. Its not the primary factor, but I think it definitely helps some. Link to comment Share on other sites More sharing options...
OceanStWx Posted September 7, 2013 Share Posted September 7, 2013 You can get dendrite growth in sea salt as warm as like -6C or even -5C if its dense....its very effective. I think it definitely plays a role in CF snowfall enhancement. Its not the primary factor, but I think it definitely helps some. Probably more of a factor in snow character on the cold side of the coastal front. You're forming good dendrites at lower temperatures thanks to the sea salt, and they near freezing temps allow those to stick together better. So you flip from +RA to parachutes. Link to comment Share on other sites More sharing options...
CoastalWx Posted September 7, 2013 Share Posted September 7, 2013 Funny you mention that. Since I've had the tango with the coastal front in recent years, you definitely see different characteristics of post CF snow. Sometimes it's those parachutes for a few min before the lower levels cool off enough, but sometimes it's an immediate flip to better snowflakes...especially if it's cold at like 950-900mb for example. Link to comment Share on other sites More sharing options...
weathafella Posted September 7, 2013 Author Share Posted September 7, 2013 Some great analysis and discussion today. Thanks mets! Link to comment Share on other sites More sharing options...
OceanStWx Posted September 7, 2013 Share Posted September 7, 2013 Funny you mention that. Since I've had the tango with the coastal front in recent years, you definitely see different characteristics of post CF snow. Sometimes it's those parachutes for a few min before the lower levels cool off enough, but sometimes it's an immediate flip to better snowflakes...especially if it's cold at like 950-900mb for example. That's when I really love the job. Just geeking out at analyzing what the vertical temp profile is like based on the snowflakes falling. Link to comment Share on other sites More sharing options...
CoastalWx Posted September 7, 2013 Share Posted September 7, 2013 That's when I really love the job. Just geeking out at analyzing what the vertical temp profile is like based on the snowflakes falling. Ha, true though. Soon enough the soundings we'll be flying on this forum. Link to comment Share on other sites More sharing options...
ORH_wxman Posted September 7, 2013 Share Posted September 7, 2013 The observed snowfall rate tends to max out about 5-10 miles NW of the surface CF in my own anecdotel observations over the past decade or so of experience. Its probably where the lift maxes out in that 850-900mb region where its often cold enough to form good dendrites...and then perhaps fall through a marginal layer around 950-975mb before the lowest level is actually colder. That CF penetration often maxes out a bit above the surface due to friction/CAD. Link to comment Share on other sites More sharing options...
CoastalWx Posted September 7, 2013 Share Posted September 7, 2013 Hopefully I can substitute -5C 850 temps with my E-NE winds this winter. I don't care what winds do if temps aloft are like that. Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted September 7, 2013 Share Posted September 7, 2013 what a winter thread this is. sickness. Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted September 7, 2013 Share Posted September 7, 2013 You can get dendrite growth in sea salt as warm as like -6C or even -5C if its dense....its very effective. I think it definitely plays a role in CF snowfall enhancement. Its not the primary factor, but I think it definitely helps some. yeah that's why you can get OE with such marginal temps aloft Link to comment Share on other sites More sharing options...
free_man Posted September 7, 2013 Share Posted September 7, 2013 Yeah that area got ripped in the Dec '08 icestorm...one of the few low elevation areas in MA that did in addition to further northeast like Chelmsford/Tyngsboro/Andover/Haverhill....there was a distinct line for the ice in those low elevation spots right from like Littleton to Carlisle to Tewksbury. That line is very frequently a line of significant ice (say >0.2" accretion) versus just marginal glaze in a lot of the CAD events...you notice a big jump to the N and NW of Littleton. There are a few sets of sw/ne running hills near Harvard/Bolton etc. where that jump happens, I-495 area. I'm sure you know the ones. Does that help a bit with low level cold air, to the west? Link to comment Share on other sites More sharing options...
weathafella Posted September 8, 2013 Author Share Posted September 8, 2013 FYI....the annual thread on the main page has been launched. http://www.americanwx.com/bb/index.php/topic/41113-and-we-begin/ Link to comment Share on other sites More sharing options...
CoastalWx Posted September 8, 2013 Share Posted September 8, 2013 The euro seasonal is interesting. So it starts out with some ridging over the east in the NDJ timeframe with a ridge centered along the coast of western Canada. However the 850 temps are not very warm at all around here in terms of anomalies. Closer to normal. They are warmer down by the Mid Atlantic. As we go out in time, some anomalous higher heights hang over the east but weaken with time heading into DJF. Also, the ridge over coastal western Canada trends stronger ( a good thing). The ECMWF tries to develop an Aleutian low as well which is almost more Nino like. I see signs of a -NAO, but nothing that sticks out to me. Some higher heights over the AO region so that's good So all in all that's a pretty decent patterh for us I think. The higher heights over the east may mean a storm track close by and the ridge in western Canada is always a plus. Link to comment Share on other sites More sharing options...
weathafella Posted September 8, 2013 Author Share Posted September 8, 2013 The euro seasonal is interesting. So it starts out with some ridging over the east in the NDJ timeframe with a ridge centered along the coast of western Canada. However the 850 temps are not very warm at all around here in terms of anomalies. Closer to normal. They are warmer down by the Mid Atlantic. As we go out in time, some anomalous higher heights hang over the east but weaken with time heading into DJF. Also, the ridge over coastal western Canada trends stronger ( a good thing). The ECMWF tries to develop an Aleutian low as well which is almost more Nino like. I see signs of a -NAO, but nothing that sticks out to me. Some higher heights over the AO region so that's good So all in all that's a pretty decent patterh for us I think. The higher heights over the east may mean a storm track close by and the ridge in western Canada is always a plus. Ironically similar to expected h5 anomalies with current ssta. Thanks for the update! Link to comment Share on other sites More sharing options...
ORH_wxman Posted September 8, 2013 Share Posted September 8, 2013 Conflicting signals on there...SE ridge like a Nina but the -EPO/+PNA like a Nino. Could be quite a gradient over the region. Link to comment Share on other sites More sharing options...
CoastalWx Posted September 8, 2013 Share Posted September 8, 2013 Conflicting signals on there...SE ridge like a Nina but the -EPO/+PNA like a Nino. Could be quite a gradient over the region. Can you recall something similar? I feel like it's one or the other...feel like wavelengths may not support a ridge out west and over the SE unless perhaps it's feeble. Link to comment Share on other sites More sharing options...
JBG Posted September 8, 2013 Share Posted September 8, 2013 Conflicting signals on there...SE ridge like a Nina but the -EPO/+PNA like a Nino. Could be quite a gradient over the region.Can you recall something similar? I feel like it's one or the other...feel like wavelengths may not support a ridge out west and over the SE unless perhaps it's feeble.2008-9? Link to comment Share on other sites More sharing options...
weathafella Posted September 9, 2013 Author Share Posted September 9, 2013 Can you recall something similar? I feel like it's one or the other...feel like wavelengths may not support a ridge out west and over the SE unless perhaps it's feeble. What an 2 months.... Link to comment Share on other sites More sharing options...
ORH_wxman Posted September 9, 2013 Share Posted September 9, 2013 2008-9? '08-'09 had an Aleutian ridge...not like what the Euro seasonal is showing. Link to comment Share on other sites More sharing options...
nzucker Posted September 9, 2013 Share Posted September 9, 2013 '08-'09 had an Aleutian ridge...not like what the Euro seasonal is showing. Didn't we see some weak SE ridging in 08-09 though with frequent SW flow events like 12/19/08 (8" here in Westchester), 12/21/08 (2" here but you got hammered), and then 1/28/09 (7" here but more up at Middlebury)? That could be similar to what the Euro is showing.. Link to comment Share on other sites More sharing options...
ORH_wxman Posted September 9, 2013 Share Posted September 9, 2013 Didn't we see some weak SE ridging in 08-09 though with frequent SW flow events like 12/19/08 (8" here in Westchester), 12/21/08 (2" here but you got hammered), and then 1/28/09 (7" here but more up at Middlebury)? That could be similar to what the Euro is showing.. Yes we did. The Euro is showing a +PNA though which is the opposite of those patterns you listed. The SE ridge is common but the PNA is opposite signs. Its a weird analog...maybe something like Feb 2003 sort of shows up where you have a +PNA and also a bit of a SE ridge...but its more muted than what the Euro shows. Link to comment Share on other sites More sharing options...
weathafella Posted September 9, 2013 Author Share Posted September 9, 2013 ENSO areas warming... Full speed ahead. Is the obscenely warm area south of the Aleutians migrating west? Link to comment Share on other sites More sharing options...
forkyfork Posted September 9, 2013 Share Posted September 9, 2013 that is a lot of warmer than normal water. wow Link to comment Share on other sites More sharing options...
mitchnick Posted September 9, 2013 Share Posted September 9, 2013 Full speed ahead. Is the obscenely warm area south of the Aleutians migrating west? Seems like the N PAC is cooling as a whole vs. a migration of GOA warmth westward http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/anim_full.html Link to comment Share on other sites More sharing options...
Typhoon Tip Posted September 10, 2013 Share Posted September 10, 2013 that is a lot of warmer than normal water. wow Yeah, but how deep is the thermocline. Actual integrated oceanic heat content is what matters to the longer term forcing in the weakly coupled, oceanic/atmospheric model. Intra-seasonal SS stressing from winds can pile warm water into the area where the Aleutian low would otherwise up-well. Point is ... these can give the illusion of + or - PDO tendencies, but may or may not match with the longer term. We all know this ... just sayin'/remindin' What I think is interesting is the lack of tropical system activity all over the Globe. Even the west Pac region is involved in the deficits. TC's play a vital role in the over-all thermal engine/regulation of the planet. They are veritable chimneys for heat ... liberating the oceans of burden, and supplying the greater Hadly cells yadda yadda yadda. But, the deficit on-going means that the oceans at deeper latitude are not liberating large stows of thermal energy. It opens a lot of questions from the 50,000 foot view. Like, would this potentially accelerate/enhance the warm ENSO that's slated to be weak, next spring? When we think about easterly propagating Kelvin wave phenomenon that is usually preceding warming in the NINO 1+2 and 3.4 regions, what happens when/if such a wave does so with a larger than normal oceanic heat content because of a lack of preceding normalcy with the frequency of TC ?? What does that mean for winter as the hemispheric gradient seasonally steepens. One may be inclined to intuitively leap to a stormy conclusion, but ... uber fast ambient flow regimes don't really produce big storms. You really want midland velocities acting on strongly curved surfaces. If the AO goes actively negative, and the dump is fairly evenly distributed, than the ambient flow everywhere may speed up. huh Link to comment Share on other sites More sharing options...
weathafella Posted September 12, 2013 Author Share Posted September 12, 2013 Full speed ahead. Is the obscenely warm area south of the Aleutians migrating west? Cooling in areas but most prominently south of Aleutians. NAO areas look awful truth be told. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted September 12, 2013 Share Posted September 12, 2013 i don't think the Atlantic SSTs are all that bad Jer'. That's at least a weakly tripolar layout, which correlates with -NAO Link to comment Share on other sites More sharing options...
Ginx snewx Posted September 12, 2013 Share Posted September 12, 2013 Cooling in areas but most prominently south of Aleutians. NAO areas look awful truth be told. Jerry here is a Neg Nao tripole ideal setup, compare with what you posted, not bad warm cold warm Link to comment Share on other sites More sharing options...
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