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00:00:00:03 – 00:00:23:24
Speaker 1
Joining us. So welcome to today’s visit, Satellite Chat. And the main focus of today’s satellite chat is this lake effect snow event that’s been occurring over the Great Lakes region and in particular downwind of Lake Erie. So, to begin with, an analysis of that, whenever you’re looking at lake effect snow, the one of your first questions is what’s the temperature of the lake?
00:00:23:26 – 00:00:48:16
Speaker 1
We’re relatively early in the season, so to speak. So the lakes are still relatively warm. So here’s the lake surface temperature. I’ll read off a couple of the Bui observations here as 46.9, 47.3 and 43.7 down here in the southwestern portion of the lake. But you can also see this little minimum here, this warm maximum right around 54, Fahrenheit.
00:00:48:16 – 00:01:15:29
Speaker 1
So quite warm. And then when you put that to a sounding here’s yesterday morning’s, buffalo sounding. First thing to note, very steep lapse rates, very deep, boundary layer that goes up to right around here at around 650 millibars or so. Very moist, nice, high relative humidity. Just note the surface base cape with that is, 18.
00:01:16:01 – 00:01:42:01
Speaker 1
And that’s obviously not representative of the parcels that originates over the lake. So what you would do is modify the zoning and can account for on a parcel that starts at the lake surface. So, so go ahead and put a parcel at the lake surface, which is right about seven Celsius. That’s 47, approximately 47°F that I use.
00:01:42:03 – 00:02:05:19
Speaker 1
This is your actual starting, parcel. So this would be your surface base cape, over the lake where the parcel starts off. And obviously, you would have a super adiabatic, layer very near the surface. And, your lake induced cape, as you call it, whenever you have this, surface parcel that starts from the lake, it’s called, lake induced cape.
00:02:05:21 – 00:02:23:02
Speaker 1
And then you come up with a number up here of, 1474 joules per kilogram. So that’s much more representative of the actual instability that we have over the lake. In other words, a lot of instability, given the cold air advection that’s occurring over the lake. And I think that I should. Yeah.
00:02:23:04 – 00:02:31:27
Speaker 2
Hey, what are you using for moisture, though? For your, as if it’s the lake. Wouldn’t you have to adjust that, too?
00:02:32:07 – 00:02:36:23
Speaker 1
Yeah, I did not, but, it would be in reality, a mixed out. It’d be.
00:02:36:23 – 00:02:38:10
Speaker 2
Yeah, exactly. Yeah. Yeah yeah.
00:02:38:11 – 00:03:01:15
Speaker 1
Yeah, that’s going to get to that. It’s in reality it’s, low level, mixed parcel that you’re using at some very lower level. So, the other thing I wanted to point out is that if you follow the lifted parcel up to the point where it intersects the temperature line, that’s your lake induced equilibrium level. That’s a very important parameter to look at as well, in terms of the depth of the boundary layer.
00:03:01:15 – 00:03:22:18
Speaker 1
The depth of the boundary layer can be as important as the, temperature difference between the lake surface and the low level, say, 15 millibars is a common, temperature difference to look at, but also the depth of the boundary layer. And you can see in this particular case here, it goes up to, around here’s 15,000ft right here, which is very deep.
00:03:22:21 – 00:03:48:18
Speaker 1
I was looking at Nam basket profiles and they had lake induced cape, those that were forecast around 1200 and, lake disequilibrium levels up around 16,000ft, quite, quite deep. Whenever you look at an an event like this here. So with that, here’s the, visible loop. Go ahead and, loop this, this is during the day yesterday.
00:03:48:18 – 00:04:27:00
Speaker 1
We’re zoomed in. Buffalo is right here. And you can see this, Long lake, single band here along the major axis of Lake Erie. We’re in a southwest flow right around 240 degrees or so. And, picking up the sensible and latent heat flux that didn’t draw a very good arrow there. I meant to just draw an arrow along the major lake X axis of the lake here and, picking up the sensible and latent heat fluxes, deepening the boundary layer, getting the convection going here, uniform, wind direction with height just nearly, in the lower levels here.
00:04:27:00 – 00:04:46:01
Speaker 1
So that helps promote, the organization here of these single bands that get going. And then you can see on the northern end of it, we have a pretty sudden clear out. And then on the southern end of it, it’s, more gradual, you see, more cloud debris on the southeast, flank of the snow band.
00:04:46:01 – 00:05:13:13
Speaker 1
So the question is, how’s that looking, radar? Scott Lindstrom at Wisconsin put together this nice radar loop. This is a long, radar loop. It goes, from 13 Z to the end of the day. So essentially all day yesterday into the evening hours. And two things to note. One, one, it’s stationary, just about stationary throughout the whole day, which obviously, helped to accumulate, large amounts of snowfall.
00:05:13:15 – 00:05:33:12
Speaker 1
And then also, as we saw in the case of indivisible imagery, we have this gradual tapering off to the band on the southeastern flank. And then on the northern flank of it, we see this very tight reflectivity gradient going from, essentially 35 to 40 DBZ to, to nothing, just a little bit, northwest of it.
00:05:33:15 – 00:06:10:24
Speaker 1
So the question is why? Why do we have that, tight reflectivity gradient? And also why is it, remaining stationary, for a long period of time? Well, if we go back to a, an old visitor training session, you’ll see this graphic that I have that talks about, thermal convergence zone. And essentially what you get is as the convection gets deeper here, whenever you have essentially, large enough temperature difference between the lake and lower levels, as well as a deep enough boundary layer, you get this deep convection that’s occurring, relatively speaking.
00:06:10:26 – 00:06:34:02
Speaker 1
And, you get these winds that converge here. This convergence gets stronger and stronger, and the wind speeds really pick up. And if it becomes intense enough, you can actually get winds in the vicinity of the band up to 90 degrees. In other words, perpendicular into the band, very close to the band. So what this sets up is this convergence zone.
00:06:34:02 – 00:07:08:15
Speaker 1
It pretty much locks the band into place here, and it becomes stationary for a long period of time. And basically the only thing that can change it is, a change in the boundary layer winds in terms of the direction usually, or sometimes the speed. You can assess that with an operational model like the Nam, for example, or some mesoscale disturbance that comes along, such as, these little eddies that can develop and these mesoscale low pressure systems that come along and, disrupt the band usually get a change in the convective mode when they come along and you get a change in the position of the mode.
00:07:08:15 – 00:07:30:27
Speaker 1
So usually those are the only two things. Otherwise, in the absence of those, you would expect the band to pretty much stay in place. And the tendency of the models, even the high res models, as they may move the bands too quickly. What’s happening is they’re not able to resolve these winds, which really change their direction in the vicinity of the band, right into the band here.
00:07:30:29 – 00:07:57:05
Speaker 1
So let’s go ahead and look at what happened yesterday. Here’s 21 yesterday. Here’s the band in the, radar. What I overlaid was the RTM, analysis of winds here. And you can see good frictional convergence across the the lake. Here’s the Buffalo radar. By the way, just to orient yourself. And here’s lake area. You can see good frictional convergence with relatively strong flow across the lake.
00:07:57:05 – 00:08:21:26
Speaker 1
And this, westerly direction and then more southwesterly over flow over here with lighter wind. So you can see, pretty well the frictional convergence as it, gets closer to the lake shore here. But the thing I want to point out is the surface observations. These are the key surface observations. There’s a buoy over the lake right here and also one at Port Colborne.
00:08:21:28 – 00:08:40:15
Speaker 1
And note how different they are than the analysis. And this comparison would be valid too. If you’re looking at a high res model like the of war for the her whatever, they would show a similar story here in terms of not picking up on the, wind speeds and also how weird they are. Notice that it’s more varied here.
00:08:40:15 – 00:09:06:08
Speaker 1
It’s, about westerly over the lake and then over here, Port Colburn. It’s actually northwesterly and, it’s moving right towards this, towards a snow band right here. So in reality here we have winds that are if I had to dry streamlines that are coming in almost like so, but very much local to the band. Because if you look further away note we still have southwesterly flow here.
00:09:06:08 – 00:09:35:26
Speaker 1
So this is only very close to the band. So this helps to lock in the snow band into place. The models tend to struggle with this because they don’t pick up on the, wind circulation in the vicinity of the band. If you had a true analysis of the the MSP here, you would see an elongated area of a surface low right along the axis of the, lake effect snow band.
00:09:35:26 – 00:09:56:05
Speaker 1
But you would see a minimum central pressure, probably somewhere around here. So at the end of the snow band, where you have the deepest boundary layer, the deepest convection, relatively speaking, here. So you would have your deepest low right here. So you have a nice shallow component to the wind right here where you have those northwesterly is developing.
00:09:56:07 – 00:10:19:27
Speaker 1
That’s what’s causing the lowest pressure here. It’s helping it to maintain itself. I mean, it’s it’s almost like a positive feedback. As that convection gets deeper, it helps to maintain itself that way. If we look at a zoomed out perspective here, the thing to note here is those two key observations right here with the more veered winds going right towards the, snow band here.
00:10:20:01 – 00:10:42:24
Speaker 1
But then the thing to note is, if you scale back some, you see that we’re in the South. We maintain ourselves in a southwesterly flow around it. So it’s just very close to the snow band here that we see that. And like I said, it helps it maintain its, stationary. This keeps it stationary here. So if we look at the forecast, this is the 16, the rock.
00:10:43:26 – 00:11:04:18
Speaker 1
I can show the, this a wharf, which I’m not going to show here, but there’s other high res models that had pretty much the same story, and the models had a tendency to, move it southward during the day. There’s the forecast valid at 21, and there it is valid at 22. And then here’s 23.
00:11:04:25 – 00:11:25:10
Speaker 1
So they have they had a tendency to move it southward during the day. And also with the shorter fetch kind of changing, the structure to the band itself, with not as much fetch to work with here. So that was the tendency in the models. Why? Because it didn’t pick up on the strong, winds that were almost 93 degrees coming into there.
00:11:25:10 – 00:11:47:07
Speaker 1
In other words, the lack thermal convergence on the kinematic structure around the band. How did it, look at 23? See, in reality, here it is. Did not move to the south. It continued to maintain itself. And the reason you had that tight reflectivity band on the northern edge here was a very strong winds coming in from the northwest and west here.
00:11:47:07 – 00:12:07:03
Speaker 1
So you had a very strong convergence, right into this region right here. And then you had your southwest release here. How did it look in terms of a picture? Imagine here’s your, westerly or north westerly winds coming in. And then you have your southwest is right here where the snow is. So you have very strong convergence.
00:12:07:03 – 00:12:37:11
Speaker 1
This is your tight reflectivity, gradient that you would see, with these, updrafts right over the lake. And then obviously precipitating, the snowfall here right into that region where we have the convergence. If we look at the, perspective from a little bit further to the north, you’d almost think this is something that you might see along the dry line or something in the high Plains where you have, so dry southwesterly winds coming into a squall line here, and you have a nasty thunderstorm here.
00:12:37:14 – 00:13:05:22
Speaker 1
Very similar thing going on. We have, very strong convergence just west of that would be strong, divergence field. And then we would have our, westerly northwesterly winds quite strong coming into this really helping to, maintain that convergence right into the snow band here. Any questions before I turn it over to Scott Lindstrom? Actually, one more thing I wanted to show before I turn it over to Scott.
00:13:05:24 – 00:13:27:23
Speaker 1
A nice, picture show. The Scott will show some more, pictures here, but I like this one. This is the morning of the 17th, and this is the morning of the 18th, from Lancaster, where they reported, over 60in of snow, with this and, the snowfall rates here were just phenomenal. 3 to 5in, per hour for a long period of time.
00:13:27:26 – 00:13:47:11
Speaker 1
This is actually a swimming pool here. And you can see in the after picture, it’s right at the top of the fence of this, swimming pool. So it’s kind of, an interesting, perspective. So now at this point, I’ll take any questions or comments before we turn it over to, Scott Lindstrom.
00:13:47:13 – 00:13:49:02
Speaker 2
Yeah. Hi, Dan, it’s Tony.
00:13:49:05 – 00:13:50:15
Speaker 1
Yeah. Hi, Tony.
00:13:50:17 – 00:13:56:03
Speaker 2
Yeah, I’m looking at, her run. I was just trying to, Which time where you, compare in there?
00:13:56:06 – 00:14:06:27
Speaker 1
This is the 16 Z run. I did see it in some earlier runs as well. And I also looked at the ness of war. So just a sample of some some of the high res models that I was looking at.
00:14:06:29 – 00:14:25:14
Speaker 2
Okay. Yeah. Because that one is still available online. So I pop that up real quick and I can see that earlier in the run it didn’t have the band. But look at her. But yeah, with time you can see it’s slowly pushing it to the south and line and even breaking it up a little bit. It’s yeah, yeah, yeah.
00:14:25:16 – 00:14:52:09
Speaker 1
That was the picture. Let’s go ahead. And that, that was the tendency in the models I was looking at. I didn’t look past the 16 Z run. I thought that was a fairly reasonable thing, but the missile war front that I looked at, they they all had the tendency to move the band to the south, and that is, known bias as a as I pointed out in this, training session, back in the lake effect snow one, session, something to watch for.
00:14:52:11 – 00:15:06:21
Speaker 2
Okay. Hey, Dan, is that, wanted for a couple of things, but first of all, that know, single versus more than than one band. Are there ever any hints as to what you’re going to get or, or.
00:15:06:23 – 00:15:09:05
Speaker 1
In terms of, single versus, multiple.
00:15:09:05 – 00:15:10:20
Speaker 2
Or sometimes you get multiple.
00:15:10:20 – 00:15:37:05
Speaker 1
Bands? Oh, yeah. Yeah. In terms of the, directional shear that’ll, that’ll dictate. Also, you tend to get single bands along these, I’ll say relatively narrower lakes compared to, say, Lake Superior where it’s, it’s larger. I mean, you can see them there, but the, the geometry of the lake plays a critical role here as well.
00:15:37:05 – 00:16:02:08
Speaker 1
So if you look over Lake Michigan, for example, over the short axis of the lake, they’re in westerly flow and you’ll typically see these multiple bands. Not quite the intensity in terms of the snowfall rates. So, so yeah, the, wind shear, the directional shear plays a role with more shear favoring, multiple bands, but also the geometry of the lake itself.
00:16:02:14 – 00:16:13:15
Speaker 2
Yeah. And this, this, convergence you’re talking about, is it a consequence, kind of a feedback from getting this stronger band, stronger updrafts.
00:16:13:15 – 00:16:20:18
Speaker 1
And yes, it builds itself. Really. So if the model doesn’t adequately represent that in terms.
00:16:20:19 – 00:16:22:15
Speaker 2
Exactly. I said I’m wondering about, yeah.
00:16:22:20 – 00:16:43:06
Speaker 1
It’s got to get the deeper boundary layer. It’s got to continue to grow, you know, get the deeper boundary layer, maintain that strong instability which is driving it. If it if it’s missing out on any of those, it’s it’s not it’s not going to get this. This is the key that you have to if you don’t see this in the model, if you see this in the observation.
00:16:43:06 – 00:17:02:26
Speaker 1
So that’s your tip off. That should be your tip off that that band is going to stay locked in for a long period of time. Like I said, until you see something on a larger scale, larger scale, come along in terms of a change in the boundary layer winds or a mesoscale disturbance that sometimes you’ll see, with the satellite radar.
00:17:02:29 – 00:17:38:04
Speaker 2
Very, very good. Dan. Okay. And then Dan, one more. Yeah. You’re what you’re circling there is particularly important. I think I remember seeing this, actually, they did, when they were doing, her analysis back over the summer and there was, a big flood event. I don’t know if you guys recall, over Long Island, and I think it was, you know, very different nature, but still, you know, when you have just maybe only a couple large, helping to you know, not a key feature like that.
00:17:38:15 – 00:18:00:00
Speaker 2
The one is, you know, is that really being picked up in the Dan analysis and actually being picked up it into the model? Or maybe the model actually loses it, right? With your simulation? I don’t know that if you my I well, I would like take a closer look at the models, but perhaps it also loses it just because, as Dan said, maybe it maybe it doesn’t.
00:18:00:02 – 00:18:18:09
Speaker 2
Maybe the mechanism that’s driving that isn’t a isn’t a large scale mechanism. So if it doesn’t pick up on the smaller scale, you know, it’s going to lose it again. Was saying maybe it’s not picking up on the intensity of the overall convection. And right. So I, I looked at only that feedback mechanism. Yeah. Yeah. Look at a later Ryan.
00:18:18:09 – 00:18:38:15
Speaker 2
It was interesting. It didn’t totally lose it you know. So we were saying earlier it does kind of move it off to the south. But then later on it actually almost re develops the fan and actually aligns it up pretty well. So you may want to look at a couple later on that was looking at like 20 a and look look how it actually redeveloped that feature.
00:18:38:15 – 00:18:41:04
Speaker 2
So yeah very interesting case. Thanks.
00:18:41:06 – 00:19:03:06
Speaker 1
Yeah. This kind of comparisons is what you’d have to look for. Compare your available surface UVs with whatever your model or in this case RTM is. If you see that difference, especially in the speed and the direction here, if you see that difference, that’s your that’s your clue that you have a locked thermal convergence zone. And and if there’s a difference there, then you know the models are going to struggle with it.
00:19:03:09 – 00:19:09:25
Speaker 1
Okay. Let’s see, unless there’s any other questions, I’ll turn it over to Scott Lindstrom at Wisconsin.
00:19:09:27 – 00:19:29:04
Speaker 2
Okay. And I’ll be showing you once I take control here. I will be showing you some. First. I’m just going to show you, you know, what you can get from the satellite data for sea surface temperatures, even. This is from this morning. So even though there is this picture going on, it’s still showing around the edges, some fairly warm temperatures.
00:19:29:04 – 00:19:53:12
Speaker 2
So you can infer some still some pretty warm temperatures. Over Lake Erie in Lake Ontario, those lighter cyan colors are temperatures close to 50. So, there is a forecast for this mechanism to kick in again tomorrow night. And these lake surface temperatures are still just as warm. Well, maybe they’ve caught up just a little bit as they were with this immediately past event.
00:19:53:12 – 00:20:18:01
Speaker 2
So, look for the snow machine to start over. So what I’ve, what I’ve made is, sumi npp flew over this region, actually saw it four times in the last two nights. So it’s favorable geometry for scanning. So what we have here is from just before seven on, not last night, but the night before. So you’re looking at the date night band.
00:20:18:10 – 00:20:42:13
Speaker 2
And then the 11.45 is in here. The 3.74, and then the one with the orange is the, brightness temperature difference between, 11.45 and 3.74. So what what was what is sometimes called the fog product. And I like this because it shows up the day night that even though there is really no lunar illumination right now, we’re very close to a full moon.
00:20:42:15 – 00:21:12:18
Speaker 2
I mean, you can still see the the edge of the clouds, both at 60. I’ll show you a little bit later as well. You see, the development of the, fairly high cloud tops. So those, when we’re looking at the 11.45 and the 3.7 for those, goldish colors are -33. Now, that’s just about where the modified cursor that Dan showed was that was passing through the soundings.
00:21:12:18 – 00:21:52:04
Speaker 2
So it’s consistent with the sounding at Buffalo. So this is the seven Z. And it’s over 90 minutes later. Here we have 833 Z. And you’re starting to see a very sharp edge to the, a very sharp northern edge. So maybe the development now, maybe this is when, if you’re looking at the Artemia, comparing it to the, those two observations, the ten circles, maybe this is when the wind starts to become a little bit more convergent, as observed, and maybe not as shown in the, in the Artemis, but you’re seeing a very nice development at a single band along the, along the Great Lakes.
00:21:52:06 – 00:22:16:25
Speaker 2
And then that continues most of the day. Then the day night band from last night. So this is from six, 635 this morning. You’re still seeing really pretty much the exact same, picture. It looks like the northern edge of the band of Spencer pushed just maybe a couple miles to the south. It looks a little bit clearer in the day night band than it did on the previous night.
00:22:17:19 – 00:22:43:00
Speaker 2
But we still have fairly cold temperatures there, about -30, so that has remained the same. But there’s a big change between this image, and, and the following. Well, maybe not. It’s a big changes back over the central part of the lake where we have it looks like there’s some indication of a some kind of mesoscale features coming along that’s going to shift everything up to the north.
00:22:43:00 – 00:23:12:00
Speaker 2
And that is actually what happens. So you have a much bigger mass of lake effect clouds. I would say north of Cleveland. And that’s going to propagate down the, down the band and affect exactly where it’s going on shore. So even though we’re just even though this is just looking at polar imagery, because of some favorable orbit geometry from last, from the last two nights, you actually had some nice temporal resolution for the polar, polar data.
00:23:12:00 – 00:23:36:13
Speaker 2
So every 90 minutes, twice. So around 17, around 833 for the past two nights. And it really highlights, the single banded nature and the very strong convergence into the northern part of this band. So you have a very sharp northern edge to the band, and the southern edge is a little kind of more pleats off to from cloudiness and to clear.
00:23:36:13 – 00:23:43:14
Speaker 2
So, are there any questions on this?
00:23:43:16 – 00:23:44:21
Unknown
And if not, I will just.
00:23:44:21 – 00:24:08:06
Speaker 2
Throw it back to Dan. Yeah. This is up again. I have a question. Okay. So, on the, on the, for some part of Michigan, you see something coming out? I’m not sure what what bay that is that you’re seeing at Saginaw Bay. Yeah, I was going to say Saginaw. So, what do we have there?
00:24:08:08 – 00:24:29:11
Speaker 2
It’s it’s trapped all over east. Where? Across the lake is. Is that a big snow band and which direction? I mean, the wind should be fine. Yeah, I would, I would assume that the winds there are southwesterly. So you had a long fetch because of the of Saginaw Bay? I’d say kind of has cooled off pretty rapidly.
00:24:29:11 – 00:24:58:10
Speaker 2
I’m guessing that the temperatures there are probably, surface temperatures there have probably cooled off pretty close to down to 40 degrees now. So, that is going to reduce things. But yes, I mean, I can’t imagine that. I mean, if there’s no patch, on the western side of that. So, it just looks it’s at well, I would say there is a southwest wind that blows right along the length of stay in our bay, then out into the, then out into the lake.
00:24:58:16 – 00:25:21:09
Speaker 1
And it’s got one other thing to add is you can see, bands set up there a little bit more enhanced just because of the geometry of the bay. Like I said earlier, when you when you have a geometry of the lake or in this instance, the geometry of a something like this where it’s close, you can actually sharpen up the convergence more easily than it would be, as if it was a wider bay or a wider lake.
00:25:21:09 – 00:25:28:27
Speaker 1
So. So yeah, it’s definitely a band that’s setting up in there in the geometry of the Bay. Actually, enhances it to an extent.
00:25:29:00 – 00:25:51:14
Speaker 2
Yeah. Let me see. Let me go to the earlier it’s there at 66, 630 the as well. So you can see it’s setting up between those two polar passes. I’d like to talk a little bit about that. So after the reporting is stop. Yeah. Okay.
00:25:51:17 – 00:26:01:14
Speaker 1
Okay. Let me, bring it back to my screen here. Just,
00:26:01:16 – 00:26:22:03
Speaker 1
And, go to the snowfall reports to. So you can see, how much snow fell here. And one of the more interesting things that I thought here was, the max at Cheektowaga for South Cheektowaga, 65in. And then on the other side of town. So if you assume that’s for south and that’s three north seven miles away.
00:26:22:14 – 00:26:36:06
Speaker 1
Two inches. So that’s the kind of gradient you can see. They were pretty much right along the edge of that high reflectivity gradient here, just several miles away. You have this enormous difference in terms of, how much snow fell. So.
00:26:36:19 – 00:26:38:15
Speaker 2
From two inches to two yards.
00:26:38:17 – 00:26:53:04
Speaker 1
Yes. This, this, this enormous, difference. So, we’re just about out of time. So any other questions or comments?
00:26:53:06 – 00:26:55:15
Speaker 1
Okay. Well thank you everybody and have a great day.