Ji Posted January 8, 2020 Share Posted January 8, 2020 We got lucky today 1 Link to comment Share on other sites More sharing options...
RedSky Posted January 8, 2020 Share Posted January 8, 2020 ^ Things only go wrong 99% of the time, you always have that 1% hiding in the shadows lol Link to comment Share on other sites More sharing options...
Ji Posted January 8, 2020 Share Posted January 8, 2020 ^ Things only go wrong 99% of the time, you always have that 1% hiding in the shadows lol If normal people only knew what million things have to happen for us to get snow.... Link to comment Share on other sites More sharing options...
jaydreb Posted January 8, 2020 Share Posted January 8, 2020 36 minutes ago, Ji said: We got lucky today Lol, if that NAO was any more positive it would look like a black hole on the map. Link to comment Share on other sites More sharing options...
psuhoffman Posted January 9, 2020 Author Share Posted January 9, 2020 On 1/7/2020 at 10:20 PM, Ji said: We got lucky today A little but it wasn’t that far off from the pna ridge/+AO/NAO composite look. We definitely got lucky that a nice vort was passing at exactly the right time given how transient the pna ridge was. Our window was like 12 hours. But there were only 6 of those type storms so it’s not a high probability look but not unheard of. Of course yesterday’s storm wouldn’t show up in my sample because it wasn’t significant in the cities. In our areas we can luck our way to some snow a lot easier in flawed setups. Link to comment Share on other sites More sharing options...
cbmclean Posted January 13, 2020 Share Posted January 13, 2020 On 12/31/2019 at 12:36 AM, psuhoffman said: I remember the exact conversation you are talking about. It is possible to get a ridge across the entirety of the EPO/AO/NAO domains...and yes that is commonly called a ridge bridge...and when it happens it is extremely good for our snow chances. But it is very rare. So the fact that there are not more snow events with both a -NAO and -EPO is simply because that combination is less common not that it isnt a good pattern. But the reason our absolute biggest storms are usually associated with a +EPO is mostly because they are also associated with the most anomalous west based NAO blocks. Typically a block that strong cut off over greenland makes it even harder to have a strong ridge in the EPO domain. Frankly if we did it would probably be too much of a good thing and might flood the CONUS with so much cold it would just be a uber cold dry look. Think January 1977 \ Brutal cold but not much snow. PSU (or anyone else interested in answering) I have been studying 500 HP trying to understand the correlation between them and surface temperatures. With a simple west ridge/east trough, it is very simple to see how the airflow brings cold air down from the norther latitudes and cools us down. But for something like the ridge bridge depicted above I have trouble visualizing how the gph anomalies lead to the conus getting flooded with cold air. Any wisdom to share? Link to comment Share on other sites More sharing options...
Bob Chill Posted January 13, 2020 Share Posted January 13, 2020 22 minutes ago, cbmclean said: PSU (or anyone else interested in answering) I have been studying 500 HP trying to understand the correlation between them and surface temperatures. With a simple west ridge/east trough, it is very simple to see how the airflow brings cold air down from the norther latitudes and cools us down. But for something like the ridge bridge depicted above I have trouble visualizing how the gph anomalies lead to the conus getting flooded with cold air. Any wisdom to share? Think of it like this. Even when northern Canada or the Arctic Circle temps are "above normal" that still means below zero. What all that ridging in the high latitudes does is it displaces cold continental airmasses southward into the mid latitudes. Above and below normal temps are relative to latitude. A +20 arctic circle airmass is -10 if it gets pushed over us. The panel you are looking at isn't big cold but it's below normal and that's all we need during jan/feb. 1 Link to comment Share on other sites More sharing options...
Lowershoresadness Posted January 14, 2020 Share Posted January 14, 2020 I have question for the class. Has the area ever seen a Becs and what would the chart look like to create a Becs? Link to comment Share on other sites More sharing options...
psuhoffman Posted January 14, 2020 Author Share Posted January 14, 2020 1 minute ago, Lowershoresadness said: I have question for the class. Has the area ever seen a Becs and what would the chart look like to create a Becs? It’s pretty obvious that storms like Feb 83, Jan 96, Feb 03, Dec 09, Feb 10, Jan 16 are roughly our max potential. (And a potential of 24-36” region wide is nothing to scoff at). There are lots of colder places that would be envious of our top end potential. The exact placement of the snow max will depend on meso banding but those storms were all examples of max potential around here. 2003 was the oddball in that it lacked blocking but it had a monster 50/50 to compensate. The rest had blocking. 2 Link to comment Share on other sites More sharing options...
Maestrobjwa Posted January 18, 2020 Share Posted January 18, 2020 Thank you for making this, PSU. Ya know, maybe this is just my brain, but...sometimes when looking at these maps that show the -AO and all of those things...I have trouble visualizing the storm tracks while looking at them. Are there any vids that can show something like, say, an animation that illustrates a storm moving through/between these various atmospheric pieces? Link to comment Share on other sites More sharing options...
psuhoffman Posted January 26, 2020 Author Share Posted January 26, 2020 @Maestrobjwa CCB refers to the cold conveyor belt. I think to fully explain this I should do a quick overview of how most mid latitude cyclones work First of all low pressure typically forms along the boundary of cold and warm air...as air moves across the boundary to try to bring equilibrium to the imbalance. This movement of air creates lower pressure where the air is vacating faster than it is filling in. A low can really intensify when an area of divergence in the upper levels crosses over the surface area of lower pressure. These areas of divergence are typically found in front of either long-wave troughs or Rossby waves or smaller shortwave troughs embedded in the flow. This divergence aloft creates lift below it to "fill" the void and this lift (rising air) from the surface lowers the pressure as the lift outpaces the rate air is filling the surface void. On top of that the rising air cools and condenses causing precip but that process creates latent heat release which causes more lift (warm air rises). This creates a feedback loop that intensifies low pressure. Early in the life cycle of a developing low pressure area they are typically just waves along the temperature boundary Precipitation breaks out along the boundary where the flow ahead of the developing low pressure begins to cross the "boundary" to the north of the wave. The warmer air crossing the boundary has to rise over the denser colder air and this lift creates WAA (warm air advection) precipitation. (rising air cools and condenses creating precip) Showery precip usually exists along the cold front to the south of the low where cold air is undercutting the warmer air cause it to rise...but since this displacement happens much faster the precip there is sometimes more intense (thunderstorms or convective showers) but short lived. Many waves never make it beyond this stage if there are factors inhibiting their intensification. But if a low can amplify and deepen it will develop a circulation at several different levels As it develops this structure...the cold conveyor belt begins to bring moisture that is to the east of the low from the warm conveyor belt to the west of the low. As this happens the storm will begin to develop the classic comma head structure seen below. That precip to the west of the low track is often commonly called the "CCB" since it is a function of a healthy system developing precip in response to the cold conveyor belt transport of moisture west of the low track. Additionally the precip to the west of the surface low track is not driven by WAA as much as other forces and so can have a colder thermal profile, especially in marginal events. Seen above there the dry conveyor belt begins to cause the "dry slot" that you often get near the track of the surface low pressure. Below I have zoomed in on what is going on in the "CCB". This region in the "CCB" develops a deformation zone...a region where the atmosphere is being pulled in different directions at different levels. The convergence of the DCB, CCB, WCB, as well as the sheer at different levels created by the mid and upper level low pressures creates instability in this area. Where the moisture convergence from the CCB bringing moisture in off the WCB meets this instability you can get intense snow bands. This is what they call the "deform" band. One of the best examples of a deform band was from the February 2006 storm. This radar is from the NYC area but this same band impacted our area...I think the Columbia MD area got 20" because they were under this band for several hours. You can see on the radar loop the forces I described above at work. Later in the life cycle of a mid latitude cyclone, because the cold air often outpaces the advance of the warm air...the cold catches up and the low ends up cut off from the warm air advection...at this point we say it has occluded and it looks like this. At this stage the intensification period is over and the storm typically begins to weaken. But during this stage you can often see snowfall wrapped up even under the surface low instead of displaced to the NW of it. Hope this helped some. You can ask any follow up questions also...others feel free to add anything to this. 1 3 Link to comment Share on other sites More sharing options...
jaydreb Posted January 26, 2020 Share Posted January 26, 2020 1 hour ago, psuhoffman said: @Maestrobjwa Thanks so much for writing this up! Link to comment Share on other sites More sharing options...
HighStakes Posted January 26, 2020 Share Posted January 26, 2020 Great example bringing up the Feb. 2006 storm. Tremendous deform band. This storm demonstrates how getting into the CCB band can be a serious game changer and produce big time totals. I got 16 in Reisterstown. There were a few other spotters close by that measured 18. I believe Randallstown got 20 and like you said Columbia was 20-22. The storm was really slow to get going. When the first flakes started to fall most areas where well above freezing. Snow was rather light for most of the afternoon and didnt really start accumulating nicely until early evening. Even then rates never really got any better than moderate. Local mets didnt pick up on the deform potential and during the 11 o'clock news they pretty much thought the storm would wind down by 2 or 3 a.m. with maybe a couple more inches to come. I remember being exhausted and fell a sleep around 12:30 a.m. We had around 6 maybe 7 on the ground at that time. I woke up roughly 3 hours later. When I looked out the window I was shocked. S++. Easily 2-3 inches per hour. 10-12 inches fell in the area in just a 4-5 hour period. The deform band took this otherwise run of the mill decent type snowstorm and made it truly awesome. Had it been colder following the storm we would all remember it more fondly. On the other side of the spectrum you have several storms where the deform band underachieved and kept what could've been great storms rather pedestrian. The 2 late Feb. storms in 2005 come to mind. Classic Miller A's that both should've been 6-12 areawide ended up under producing only barely hitting low end warning criteria in most spots. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted February 24, 2020 Share Posted February 24, 2020 Link to comment Share on other sites More sharing options...
showmethesnow Posted February 24, 2020 Share Posted February 24, 2020 @psuhoffman Seeing as the mid/long range model thread has transitioned overnight into the Lawn and Garden thread I finally had a chance to look over this thread somewhat. Very nice work and very labor intensive I am sure. One thing I did notice with your Index breakdown for our storms is that what many consider the Holy Grail of our PAC look (-EPO, +PNA) for snow maybe isn't so much the look we really want to see for our best odds. Looking at the breakdown of the +PNA/-EPO regime we are only seeing 14 storms vs. 25 storms for a -EPO/-PNA regime. A +EPO/+PNA features 19 storms and even the polar opposite (+EPO/-PNA) is only marginally worse with 11 storms. But consider this. Maybe our ideal look isn't so much with what we see with the PNA index but more so on having an -EPO and where its placement is. Thinking it through I think if you looked at the -EPO storms in both a -PNA and +PNA regime we would find that a strong majority actually were very similar. And that is with featuring an eastern based EPO ridge that was encroaching into the PNA domain. What I often call a northern based +PNA over cutting troughing into the SW. Now if this is the case then many of these storms probably featured a weak +PNA or -PNA (close to a neutral state) depending on how far into the northern PNA domain the EPO was encroaching. Now I don't have your data so I can't really delve into this without quite a bit of effort but I was wondering if it was somewhat easy for you to do could you possibly throw up the number of storms we actually saw with a -EPO and a weak +/-/neutral PNA? Maybe a composite of those storms as well? One last thing. You didn't by chance get composites of the looks we were seeing 3/5/7 days in advance of these different regimes? If you haven't please don't spend the time. I will just make it a project over the summer when I get bored of tracking Fail after Fail with severe and tropical. Link to comment Share on other sites More sharing options...
psuhoffman Posted February 24, 2020 Author Share Posted February 24, 2020 3 hours ago, showmethesnow said: @psuhoffman Seeing as the mid/long range model thread has transitioned overnight into the Lawn and Garden thread I finally had a chance to look over this thread somewhat. Very nice work and very labor intensive I am sure. One thing I did notice with your Index breakdown for our storms is that what many consider the Holy Grail of our PAC look (-EPO, +PNA) for snow maybe isn't so much the look we really want to see for our best odds. Looking at the breakdown of the +PNA/-EPO regime we are only seeing 14 storms vs. 25 storms for a -EPO/-PNA regime. A +EPO/+PNA features 19 storms and even the polar opposite (+EPO/-PNA) is only marginally worse with 11 storms. But consider this. Maybe our ideal look isn't so much with what we see with the PNA index but more so on having an -EPO and where its placement is. Thinking it through I think if you looked at the -EPO storms in both a -PNA and +PNA regime we would find that a strong majority actually were very similar. And that is with featuring an eastern based EPO ridge that was encroaching into the PNA domain. What I often call a northern based +PNA over cutting troughing into the SW. Now if this is the case then many of these storms probably featured a weak +PNA or -PNA (close to a neutral state) depending on how far into the northern PNA domain the EPO was encroaching. Now I don't have your data so I can't really delve into this without quite a bit of effort but I was wondering if it was somewhat easy for you to do could you possibly throw up the number of storms we actually saw with a +EPO and a weak +/-/neutral PNA? Maybe a composite of those storms as well? One last thing. You didn't by chance get composites of the looks we were seeing 3/5/7 days in advance of these different regimes? If you haven't please don't spend the time. I will just make it a project over the summer when I get bored of tracking Fail after Fail with severe and tropical. Thank you. 2 thoughts wrt what you noticed (I noted it also). First it's hard to draw conclusions about that because what those numbers don't show is the frequency of those patterns. If a pattern is more rare it might be the best pattern but have less instances of snow simply because there were less opportunities compared to a more common but less productive pattern. That said, I do think there is also a bit of "too much of a good thing" going on with a -EPO/+PNA full latitude ridge. In a vacuum a -EPO/+PNA/-AO/-NAO are the best phases of each of the 4 major indexes. But when in combination it's not always that simple. When we have a really strong -NAO for instance, some of our biggest snowstorms happened with an unfavorable PNA/EPO combo, but in reality that "unfavorable" pattern out west trying to force ridging into the cold locked into the northeast is what created the big storm. Without that we would have been cold/dry with a weak wave running off the southeast coast. Time of year also matters...we typically need the epo/pna more early in the season and the nao more late. Without any NAO help...by far our best look is that east based EPO ridge nosing over the top creating a broad flat trough under it across the lower 48. The NAO changes the equation. The more blocking (especially later in winter) the less we need EPO/PNA help. Enough blocking later in the season and we actually dont want a big wester ridge. So there really is no one perfect look that is universal across the whole winter season. That study I did was just step one is a larger plan. Right now I have no time for anything. My less frequent posting lately is not just because the weather sucks... its more that this is a busy time of year for me. December/January I have a lot of free time. Between Holidays, end of semester and PD breaks there, and testing I have a solid 2 months with not much going on other than my normal teaching duties and even those...I only have a normal class to plan for or stuff to grade about half the time. Right now is one of the times of year I am slammed with observations, curriculum planning meetings, summer school planning, bridge project scoring, Test prep planning, debate events... I just don't have time. But I have way more in the plans. I just found out I might be getting a rather significant increase in my responsibilities wrt to my summer position so I may not get to all of this but I should still have more time to at least start this list. In addition to what I did in December, I want to do a similar study for our area. Then I also want to look month by month and break down the dominant patterns from 1950 on to see the frequency of each pattern. I also want to break down those splits by month to confirm which patterns work best by each month. Once done I would be able to determine what the odds of snowfall in any given pattern are (roughly) by month. That would make what I posted here a lot more useful. But that will take a lot of time I don't have right now. If I don't get it finished this summer I probably will next December during my next "down time" period. 1 Link to comment Share on other sites More sharing options...
snownut Posted February 24, 2020 Share Posted February 24, 2020 21 hours ago, Eskimo Joe said: Really cool map. Maybe that is why the PNW snowpack seems so durable and long lasting. Dense and thick ( see photo from 1 week ago at 8,000') there will be snow at that spot well into August. Noticed flying over the intermountain west in the summer that most of the summits are melted out while Cascades hang on. Washington State seem to always have a nice solid snow cover much of the year. Anyway, very dry February out here so getting nervous about fire season?? Link to comment Share on other sites More sharing options...
psuhoffman Posted December 20, 2020 Author Share Posted December 20, 2020 4 hours ago, Ji said: Why are their cutters on the gfs The first storm after Xmas (the only one in range of worrying about yet) doesn’t cut. It gets shredded them redevelops as a miller b that misses us. Problem is the NS wave runs out ahead of the SS and gets shredded but it also flattens the heights and squashes the SS until it phases and comes together too late. We need the SS out in front so the NS can phase in to our south. 1 hour ago, snowman19 said: It’s an EPO problem too, troughing over AK Look at the h5 for most of our big snows (it’s on the climo thread) there is a trough near AK usually. Link to comment Share on other sites More sharing options...
yoda Posted December 20, 2020 Share Posted December 20, 2020 Thanks for bumping this thread back up @psuhoffman... very informative thread 1 Link to comment Share on other sites More sharing options...
nj2va Posted December 20, 2020 Share Posted December 20, 2020 For those wondering the differences between a west or east based block, the link below is a great read: https://climate.ncsu.edu/climate/patterns/nao 1 1 Link to comment Share on other sites More sharing options...
40westwx Posted December 21, 2020 Share Posted December 21, 2020 On 12/30/2019 at 2:00 AM, psuhoffman said: I will do some more profiles tomorrow... others feel free to ask questions or add information to this thread. Goodnight I remember when the Weather Channel was actually good and they did the "look ahead".. it was at 50 past the hour and it was obviously snow weenie stuff.. They would start out every one with the ten day progression of the jet stream.. without knowing any of this above, after a while I could recognize what the jet stream would look like when there would be a corresponding snow storm in our area.. I realize now that they were showing the jet stream because it was how they use pattern recognition to sniff out snow storms in the long range.. its the same thing we do now.. we just have a lot of fancy acronyms that end in O. Link to comment Share on other sites More sharing options...
mattie g Posted December 22, 2020 Share Posted December 22, 2020 On 12/21/2020 at 1:56 PM, psuhoffman said: It's too far east to get a HECS probably but we can get a good old regular snowstorm with blocking there. We focus way too much on the HECS look. That look is super rare...happens only a handful of times a decade and if were lucky a couple hit. But MOST, by a LARGE %, of our snowfall comes during good but not PERFECT patterns with slight flaws. I think this is the best place to put this... I think the reason that there have been so many comments about the progged look not being ideal is because there are many of us (me included) who can recognize that classic look but who can't recognize a general good pattern in which we can score. There are other (like you, psu) who can recognize those "workable" patterns because you've researched them over the years, but the rest of us can't recognize or don't understand the nuances of those decent looks. If we don't see a ridge on the west coast, a 50/50 low, and a big, red blob in the NAO domain then we assume that it's not a good enough look for snow...or it's a look in which we are very likely to fail. Anyways, thanks for the work you put into this. Your skills as both a hobbyist and a teacher really come through when explaining what does or doesn't constitute a pattern that can bring us snow. Link to comment Share on other sites More sharing options...
mattie g Posted January 7, 2021 Share Posted January 7, 2021 Question: If a block is supposed to slow down the flow and, in theory, make it easier for models to "understand" what's going to happen, then why do we have so many fast-moving vorts flying all over the place right now, thus leading to model chaos? Link to comment Share on other sites More sharing options...
WinterWxLuvr Posted January 7, 2021 Share Posted January 7, 2021 5 hours ago, mattie g said: Question: If a block is supposed to slow down the flow and, in theory, make it easier for models to "understand" what's going to happen, then why do we have so many fast-moving vorts flying all over the place right now, thus leading to model chaos? I think that’s a great question Link to comment Share on other sites More sharing options...
nj2va Posted January 7, 2021 Share Posted January 7, 2021 8 hours ago, mattie g said: Question: If a block is supposed to slow down the flow and, in theory, make it easier for models to "understand" what's going to happen, then why do we have so many fast-moving vorts flying all over the place right now, thus leading to model chaos? I thought WxUSAF hit on this earlier today in the model thread....weak west coast ridging so I think it means there's a lot of s/w flying all over. I'm a dummy with weather so who knows if this is right but perhaps that changes when we get better WC ridging later this month. Link to comment Share on other sites More sharing options...
Cobalt Posted January 14, 2021 Share Posted January 14, 2021 Since we're on the topic of snowless periods.. how does the early 14/15 winter pattern compare to what we're going through right now? Obviously the pattern we're in has for sure been serviceable, but I'm mainly contrasting that winter and this one because it seems like Feb '15 essentially flipped a switch after a super dormant period with not much domestic cold. I know that was a PAC based shift, but before that from late Nov to late January (outside of the fluke warning level clipper), it was basically a snowless pattern for 60 days, going all the way into what would be the peak climo of late January. What went into that big shift? Link to comment Share on other sites More sharing options...
Cobalt Posted January 14, 2021 Share Posted January 14, 2021 Perhaps 17-18 is more fitting, given how scorched North America was in February Link to comment Share on other sites More sharing options...
Lowershoresadness Posted February 7, 2021 Share Posted February 7, 2021 can someone explain the dynamics when its snowing at 40 degrees. Thanks Link to comment Share on other sites More sharing options...
MN Transplant Posted February 7, 2021 Share Posted February 7, 2021 2 hours ago, Lowershoresadness said: can someone explain the dynamics when its snowing at 40 degrees. Thanks Simply put, it the snow doesn't have the time or opportunity to melt on the way to the surface. It is generally going to be a shallow (and relatively dry) warm layer when it snows at 40. 1 Link to comment Share on other sites More sharing options...
psuhoffman Posted February 10, 2021 Author Share Posted February 10, 2021 On 2/7/2021 at 2:29 PM, MN Transplant said: It is generally going to be a shallow (and relatively dry) warm layer when it snows at 40. Or a really wild 40th birthday party 1 Link to comment Share on other sites More sharing options...
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