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00:00:00:10 – 00:00:17:19
Speaker 1
Welcome to today’s visit satellite session. And we’re pleased to have Chris Landsea from the National Hurricane Center to join us today and talk about, using satellite data to monitor African easterly waves. So with that, I will turn it over to Chris to lead the presentation.
00:00:17:21 – 00:00:41:12
Speaker 2
Okay. Well, thank you very much. Glad to help out today. Here. So every hurricane season, one of our task is to monitor African waves. Or we also call them tropical waves. Which can be a difficult task because they often can be a bit subtle and, and being able to monitor them. And so I’m going to discuss a bit about actually waves.
00:00:42:18 – 00:01:03:27
Speaker 2
A little bit behind the theory of them first, just to make sure everybody’s on the same page about what we’re talking about. And then go into the various tools that we have, that allow us to track, tropical waves. There are most interest because, they serve as the majority of, disturbances that form in the tropical cyclones.
00:01:04:15 – 00:01:40:20
Speaker 2
And, the vast majority of the ones that become major hurricanes. And. All right. So, kind of overview when we use the term tropical wave or African nation wave, we’re talking about these, large scale synoptic scale waves that propagate westward at low latitudes. Typically from about, say, the equator to 20 north, there, moving across, from West Africa westward across the Caribbean and Central America and, and some make their way into the eastern North Pacific.
00:01:41:12 – 00:02:01:25
Speaker 2
They’re interacting at the first with the, West African monsoon. And I’ll describe a little bit about the structure of that. Make sure that it’s clear, and it’s occurring during the, the rainy season. So, the peak tropical wave season at for numbers, frequency of waves corresponds with the peak rainy season for the West African monsoon.
00:02:02:06 – 00:02:28:18
Speaker 2
Typical scales, about 2000km. So we’re definitely talking synoptic scale, typical periodicity of 3 to 5 days. And, speed 7 or 9m a second. So typically we see them move about five degree 5 to 6 degrees longitude per day as they’re moving across the the, the Atlantic. So looking at West Africa, it’s important to understand why these waves occur.
00:02:28:20 – 00:03:02:24
Speaker 2
And it’s because of the unique configuration of the landmass of Africa. In conjunction with where the, the, the equator is, it’s on the upper left. It shows in general, the very hot conditions over the Sahara Desert and relatively mild, certainly not cold, but it’s quite a bit cooler in the rainforests along the Gulf of Guinea. Because of that, you end up having, bottom left, because of thermal in considerations, an easterly jet.
00:03:02:26 – 00:03:38:02
Speaker 2
And, as most of the time, as you’re moving poleward, you’re getting, cooler temperatures with latitude. So this westerly winds. But here it’s fairly unique because as you’re moving off the equator, moving forward, you’re getting distinct, change where it’s getting warmer. With latitude, bottom right. Because of that, you end up with, a potential vorticity, condition where it’s actually decreasing potential vorticity is going poleward.
00:03:38:04 – 00:04:13:28
Speaker 2
And that decrease of PV, is actually there tropical and very clinically unstable. And so that jet that’s a result of that reverse temperature gradient, breaks down into waves. And the upper right shows that climatology for the rainfall that occurs and the rainfall, in the dieback heat released contributes to the intensification of the waves. But the waves themselves are, due to the breakdown and the instability of the African easterly jet itself.
00:04:14:01 – 00:04:41:16
Speaker 2
So looking schematically over West Africa, and the zero latitude would be roughly about ten degrees north or so. So shaded blue, you have the monsoonal southwest release. And so they’re fairly shallow, and typically at about 15 degrees north latitude, you have the African actually jet. It’s a fairly shallow jet. And so it peaks at about 7 or 600 millibars.
00:04:41:28 – 00:04:54:17
Speaker 2
Farther north, you’re getting the typical mid-latitude westerlies, and farther south, higher up, you’re getting the response to the monsoonal circulation with the northeasterly return flow.
00:04:54:19 – 00:05:17:21
Speaker 2
So if we’re looking over West Africa, at this African easterly jet axis would be in, red. And as a wave develops along that jet axis, we’ll see the 700 millibar, which is typically the peak amplitude of the wave, start showing up in a, that, kind of at the trough axis showing up that way.
00:05:20:02 – 00:05:53:25
Speaker 2
And at the surface or near surface, you may have, two vorticity maximums and one, farther north, which would be along the monsoonal trough over West Africa. Typically over in the Sahara Desert and one farther south, closer to the, about ten degrees north latitude, where the Gulf of Guinea begins. The northern one is often referred to as a northern, a dry vortex, because that may come off the coast and may be spinning a bit because but because it’s embedded in dry air and it’s over.
00:05:53:25 – 00:06:11:22
Speaker 2
Very cool water with the canary current that typically dies off. And so if the paisley wave does go on to develop in the tropical cyclone, it’s usually in association with the the southern vorticity maximum.
00:06:12:00 – 00:06:42:23
Speaker 2
When you look at the convection typically over West Africa, the convection would be maximum on the on the west side of the, the wave axis, looking at it by month. Typically the the most numerous or most frequent tropical waves are in June, July, August. That corresponds with the peak of the rainy season. You still do have, the African waves in September, October, they become less numerous, but, the maximum amplitude is usually September.
00:06:42:24 – 00:07:11:04
Speaker 2
You have the strongest waves coming off. You measure it by, by the vorticity of individual, waves. And I should point out, even outside of hurricane season December table, there are perturbations that are coming across. They’re just much lower amplitude, and they tend to be closer to the equator. So it’s more rare for us to track the waves and the National Hurricane Center during the off season.
00:07:11:04 – 00:07:42:28
Speaker 2
So they occur, but they’re much weaker and less consequential. So one aspect that, further complicates, African easterly waves is their interaction with the Saharan air layers and embedded in these are some distinct dust outbreaks that can occur. You can see them in the visible imagery. But also using, kind of a, a multiple window aspect to get a better definition of where the Saharan air layers are.
00:07:43:15 – 00:07:56:21
Speaker 2
And with a let’s call that that an aerosol tracking product developed by Jason Damian at the Hurricane Research Division.
00:07:56:23 – 00:08:30:28
Speaker 2
So often what we’ll see in this picture shows again, this Saharan air layer, imagery product, along with the blue lines or individual, trough axes. And I’ll get into how these are developed. The green lines are the 700 millibar jet axis. So that easterly jet axis that I mentioned earlier. And what is often seen is that the, the the maximum amount of the Saharan air layer and the dust and dry air is on the north side of the 700 millibar jet axis.
00:08:31:00 – 00:08:50:26
Speaker 2
And sometimes these waves can be embedded in these, very dry, dusty air. And it would make sense that when that occurs, it’s, more difficult for them to undergo Genesis. Or if it does undergo Genesis, further intensification.
00:08:50:29 – 00:09:17:16
Speaker 2
So a little bit about the thermal dynamics of these, Saharan air layers. They’ve done some experiments where they fly the Gulfstream for jet and drop, GPS based drops on the upper left. It shows, the imagery and, moist conditions are in this, orange in the very dry or in the blue and purple. The imagery is actually, total precipitable water imagery.
00:09:17:16 – 00:09:50:14
Speaker 2
So it’s derived from the low earth. Low Earth orbiting satellites and stitched together so it’s not a geostationary product. So a drop taken here on the edge of the Saharan air layer. And a bit east of where Tropical Storm Irene was showing. Temperature wise, fairly, Well pronounced. Very, strong. Excuse me.
00:09:51:00 – 00:10:08:07
Speaker 2
Very dry and very stable air. Starting at about 850 millibars. So you can see the relative humidity drops way off. And at the same time, you get a very pronounced, African easterly jet about, 25 to 30 knots.
00:10:08:10 – 00:10:31:17
Speaker 2
So let me go into a few tools that we use here at the hurricane Center to track the waves. Formal tracking is actually done by the the forecasters in our Tropical Analysis and Forecast branch. But certainly the hurricane specialist unit monitors them very closely as well. So one obvious tool to use would be the stationary satellite imagery.
00:10:32:11 – 00:10:55:22
Speaker 2
So the sort of picture of visible imagery. It turns out the visible imagery is at least useful for tracking, tracking, African easterly waves. Other imagery is much more powerful. We will use, quite a bit of infrared imagery and it shows a whole longer diagram, over about a week in time of tracking an individual wave.
00:10:55:23 – 00:11:26:03
Speaker 2
So, for example, this one that came off the west coast of Africa in this hard mode, molar goes from about ten north to 20 north, from West Africa to north South America and to the Pacific. So you can follow in the infrared imagery. So deep convection and it’s associated with a vigorous, African easterly wave. And then right behind it about three days later, 3 or 4 days later, another wave departs the coast and makes its way across.
00:11:26:05 – 00:11:50:21
Speaker 2
So it’s fairly typical to see these waves. Often they’re not nearly as convective active. So the amount of convective vigor depends a bit on the season as a whole. You know, if you have an East, an El Nino year like this here, they become more difficult to track because you tend to have more subsidence and less, less deep convection.
00:11:52:03 – 00:12:25:01
Speaker 2
So again, this is the hop, the diagrams and the shifted a little bit farther to the east. This one that came off the coast on the 23rd of July and kept track at, in the infrared, a little less convection with this one and reaches, the Caribbean, about six days later. And so, the impacts of the waves, even if they don’t become tropical cyclones, are, first felt by the folks in the Lesser Antilles, Barbados and the other islands there.
00:12:25:21 – 00:12:44:09
Speaker 2
And so they’ll have impacts from increased aerosol and dust. They actually have quite a bit reduced visibility. When you have a strong dust outbreak, associated with the initial wave, and then the wave itself may enhance convection as it’s coming across.
00:12:44:25 – 00:13:09:03
Speaker 2
Mentioned the tool that’s been used, more recently in the last, say, 4 to 5 years as the total precipitable water imagery. Turns out that when there is a bulge in the or a maximum and the TP p.w, usually the the wave axis is just to the west of that, TP maximum. And I’ll show some more examples of how we would use this.
00:13:09:09 – 00:13:38:10
Speaker 2
This last year’s hurricane season. We found that this is often our, our best tool. This polar orbiting provided total precipitable water imagery, is very helpful, even for relatively weak waves that have no deep convection. This tool is is often the only place you can can identify the waves, robustly. Another tool that’s useful.
00:13:38:21 – 00:14:06:24
Speaker 2
Right before the waves leave the coast would be to looking at the surface. Station pressures. Typically you’ll have, say 1 or 2 millibar pressure drop as a wave comes across. Strong ones, maybe even 3 or 4 millibars. And so this is very useful for, station based approach to help identify, a wave coming and progressing across.
00:14:06:27 – 00:14:36:00
Speaker 2
Another tool that’s been very helpful over the last decade as the, scatter ometer. So first off is the a quick scan, that NASA provided and more recently we’ve been using the, two European scatter orbiters, the a Scout, and there’s also a scatter ometer aboard the International Space Station right now. And so if a tropical wave has a, significant, surface signature, it’ll show up in a scatter ometer as as a as an open trough.
00:14:36:10 – 00:14:55:17
Speaker 2
Like this case shows. It’s not uncommon, though, for a wave to have a negligible, surface, reflection or surface condition to it. So that makes it difficult if we all see big waves in the scatter ometer data.
00:14:55:19 – 00:15:18:27
Speaker 2
Another very important tool for us to monitor the waves would be, using very wind signs. So, for example, here for waves from the car, in the Dakar soundings in Senegal, as well as, Sal, which is in the, the Cape Verde Islands. The red line would indicate, the wave axis or the trough axis for the wave.
00:15:18:29 – 00:15:46:12
Speaker 2
And, the colors indicate moisture and the barbs when the wind speed suppression is the total field. We’ll often break it up into anomalies. Make it even easier to see the waves coming and going. So, the upper panel shows a time series of rate one size 12 Z and zero Z from Dakar, Senegal. And it’s with the, the background, removed.
00:15:46:14 – 00:16:13:18
Speaker 2
So it’s just looking at a, day to day anomalies here for the for the wind and the moisture. The moisture shows up as, colors. Red indicates more moist, blue indicates, less moisture. And in this case, Guadeloupe is plot plot on the bottom. Guadeloupe is in the Lesser Antilles, and it typically takes a wave about, six days to reach across the Atlantic.
00:16:13:21 – 00:16:45:13
Speaker 2
So if a wave explains the coast of, Senegal, Dakar on the 25th, and you can see the rotation of the, the winds, especially 700 millibars or so, and, enhanced moisture on the backside and decreased moisture on the front side. In about six days, one would expect to see that same wave, reach, the Lesser Antilles as case did, quite a bit weaker in amplitude.
00:16:45:16 – 00:17:10:27
Speaker 2
So we can, show this for, for a few storms. A few tropical waves coming across. So on the top, it shows the moving time series for the car. And then on the bottom, it shows the same time series for Guadeloupe, but with a six day lag attached. So you can see individual waves that come off the coast of West Africa.
00:17:11:00 – 00:17:31:24
Speaker 2
They follow this one. Now, follow this one down here. So we can we can see these waves of all the way across the Atlantic. Even if there’s no convective signature. With there at the very once on information.
00:17:31:26 – 00:18:11:25
Speaker 2
Another tool in the last couple of years is developed by researchers at University of Albany. And, this is, a model based information. So it’s taking the global dynamical models, especially the 700 millibar wind flow and using that to help track the, the waves. The idea is that if you’re looking at, say, 700 millibar stream function over West Africa, as the waves develop, its waves may form in the eastern portion of West Africa and then reach maximum amplitude by the time they reach Senegal at 15 degrees west longitude.
00:18:11:28 – 00:18:40:18
Speaker 2
As you look at the stream function, it shows distinguish trough, ridge trough, ridge trough. So we can quantify that and and objectively provide troughs, as well as the the jet axis. So with the stream function, values being very, strong gradient here, that the African easterly jet would be right along here.
00:18:40:29 – 00:19:16:08
Speaker 2
So zooming in on it, this shows the 700 Millibar stream function in the non divergent land. And again, can visually pick out well there’s a trough and here’s a trough here with ridges in between. So if we quantify the relative vorticity again we can see well there is a trough here and trough there. But they’re, they’re kind of tilted a bit and, and it almost looks like there’s kind of, a, a peak of relative vorticity kind of going east west here as well as one here.
00:19:17:18 – 00:19:45:09
Speaker 2
So the idea is to split the vorticity into its shear and its curvature components. To better get out what is due to the wave itself versus what is due to the, shear component of the African actually, jet. So doing so it’s really, I think, helps. Nicely clarify what’s causing the the vorticity that you can associate with the trough.
00:19:45:11 – 00:20:10:06
Speaker 2
So the shaded parts here. That shows the curvature vorticity. And so the the wave axis for the first one is their wave access for the second one is here and the contours for the shear vorticity. So we can identify, if we use the zero contour of the shear vorticity that’s going to, lie right along the, the wind speed.
00:20:12:06 – 00:20:24:08
Speaker 2
Maximum where the African easterly jet is. So we want to better identify both where is the African actually jet and not where are the the waves that are feeding from that jet.
00:20:24:10 – 00:20:50:24
Speaker 2
So then one can, have the software identify where the troughs are in solid. And that shows, where the, in this case, that’s where the shear vorticity equals zero, where the winds are at least eight meters per second. So that shows the African jet and all these black lines show where there is that curve or tricity goes to zero.
00:20:51:07 – 00:21:19:12
Speaker 2
So you can further refine this and get rid of ones that are moving west east because we’re looking for easterly waves. When you do that, really helps to, provide an objective measure of where these African spin waves are. So that shows the 700 middle market and the solid line shows the individual African easterly waves. So I’ll show an example of how this was, used.
00:21:21:08 – 00:21:43:11
Speaker 2
When the, the developers from Albany first put this together. So we look at w13, which is a wave when it’s still over the West Africa. And the the dashed line again shows the 700 millibar jet axis and the, solid line shows the the wave axis. And again, we’re focusing on 700 millibars because that’s where the wave acts.
00:21:43:16 – 00:21:55:11
Speaker 2
The wave is strongest and easiest to track. So a day later, the wave is about to move off of the coast.
00:21:56:10 – 00:22:21:10
Speaker 2
One day later, it’s, approaching the, the Cape Verde Islands. Another day. It’s kind of moving a little toward the west northwest. That’s usually not a good sign for something developing, because it gets in the cool water at higher share pretty fast. And embedded along the, the jet axis at 700 millibars. And one more day, it’s it’s looking at there and here.
00:22:21:11 – 00:22:32:00
Speaker 2
So you can see it moving across the Atlantic, at about 5 to 6 degrees longitude per day.
00:22:32:03 – 00:23:03:19
Speaker 2
So lastly, I wanted to show, how for this hurricane season, we are tracking it, using a combination of all these different things together. So this is from, the 15th of August this last year. And the Orange lines depicts where, human analysts. That would be me put a, African easterly jet. I’m sorry. The, the wave axis here and and circling where there was, cyclonic vorticity associated with that particular wave.
00:23:03:21 – 00:23:30:03
Speaker 2
So some waves are fairly narrow in extent and some of them are quite a bit wider. The colors again are the total precipitable water. The red, wind barbs are from, kind of rain wind sites. And occasionally they’ll be drop zones from the Gulf Stream for jet and the, the blue vectors are the 700 millibar analyzes from the, the GFS.
00:23:30:05 – 00:24:00:17
Speaker 2
And so as an example, this wave in the Caribbean, shows up fairly nicely with, rain, one sort of from San Juan showing southeast winds on the left side of it shows, more easterly flow, shown up by the Kingston, Jamaica. And very once on there’s a bulge and total principal water in a tree on the east side of the wave axis, which is expected because it be affecting, moisture from, the IPCC hubs northwestward.
00:24:00:19 – 00:24:26:00
Speaker 2
So if we move forward in time following that, that that wave, a day later, it’s becoming a little more indistinct. One more day later. Again, it’s a bit hard to concern. A little bit about maximum in the total precipitable water imagery. But it reaches the East Pacific, and it’s, I put a wave access there.
00:24:26:01 – 00:24:46:10
Speaker 2
There’s a little bit of turning at 700 millibars. According to the GFS, but as often is the case, they become very difficult to, to monitor. And once they reach the East or Pacific, the last one, still a little bit of curvature apparent there. Let’s go back and let’s look at another one over, West Africa.
00:24:46:13 – 00:25:15:23
Speaker 2
Follow that line. So there’s a wave that had come off the coast, a day or two before, a little bit of curvature here. A little bit of curvature still, but it’s in very dry air. So this is, example of a wave that is certainly not going to develop, following it along that further. Still, a little bit of a bulge and DPW on the east side of the wave axis.
00:25:16:23 – 00:25:40:06
Speaker 2
Sometimes they’re, intensify in this case, we’re seeing more, moisture on the east side of the trough axis. And again, a little bit more moisture on the trough axis. A little bit of a hint of curvature from the, I think that’s from the Martinique, reference on the and again, the wave showing up there.
00:25:40:08 – 00:26:01:28
Speaker 2
So it’s fairly typical. Often these waves are, a challenge to monitor. So we’re putting all of the different tools that we have available, whether it’s the Albany diagnostics. Looking at the, the GFS analysis, the one signs and again, more recently, the total price of water inventory.
00:26:02:01 – 00:26:39:14
Speaker 2
So just to finish up and I wanted to mention how we depict, provide wave information on our products here at the National Hurricane Center. So we include on our surface analysis the tropical waves. So this is done every synoptic time. And, we include them even if there’s no significant surface, component to it. And we’ve had discussions of whether to, divorce wave analysis from the surface map when there’s occasions where there’s a wave, 700 millibars, but really not not much at all at the surface.
00:26:39:15 – 00:27:03:19
Speaker 2
So we’re we’re still considering that for the future. Another way that we include, tropical wave information is in our tropical weather discussion. It’s again issued every six hours. And so every wave that’s depicted on our map, there’s a discussion about, how it’s being monitored, how much convection is going on, and if it’s associated with, a feature in the tropics.
00:27:03:19 – 00:27:29:21
Speaker 2
Weather outlook would be a little discussion on, on, what the likelihood is that it could develop into a tropical cyclone. We also include tropical waves on our, wind wave products, in particular as our surface forecast graphics. In this case, you see, four different waves depicted on the, the 24 hour surface product map here.
00:27:30:00 – 00:27:57:22
Speaker 2
And lastly, the waves will show up in products from a hurricane specialist unit when there is a non-zero likelihood that they could develop into a tropical cyclone. Because again, about, you know, a little more than half of all the tropical cyclones originate in Africa makes the waves. And the vast majority of major hurricanes, begin their their life cycle as a, as an African wave in the deep tropics.
00:27:57:25 – 00:28:16:25
Speaker 2
So I hope that was helpful to get an idea of some, what what is an easterly wave? What are the factors that go into causing it? How what are some of the tools that we use to monitor African initial waves and the products that we provide on a, on a routine basis there? Thank you very much.
00:28:17:06 – 00:28:44:29
Speaker 2
Are there any questions? I just have a, comment. Very good talk. This short couple, since formerly was working at, and there’s this SRB. I retired in August. How do you look at the, the normal, TBWA imagery that may kind of enhance things a little bit, in the sense of these easterly waves that come off of Africa.
00:28:44:29 – 00:29:12:21
Speaker 2
And, also on our web page here, there are sectors so set up for, Europe, which go down to, Northern Africa and also, over Africa, which the northern portion of it, includes the, the tropical portion over, Africa. Just, I’d say yes. Information. Yes. Certainly. Some of our forecasters take a look at the percentage of normal of TP.
00:29:13:25 – 00:29:48:05
Speaker 2
But because there’s such huge variability, it shows up because of where the Saharan air layer is, respect to the African wave. Most of the time, though, the the actual amounts make it very apparent of where the waves are. Another aspect is that we have the p.w, imagery within R and A with the National Advanced Weather Interactive Processing System, and that allows us to, as I showed in the last few examples, put other data sources on the top.
00:29:48:08 – 00:30:23:07
Speaker 2
So it really helps us out because that’s, that’s our main, analysis tool is, is and equips. And there’s also this experimental layered sip of water product that, Sierra has been, producing for the last two years. And, and so, has a grant from the G.P.S., program that, should be pretty helpful for, looking at different layers of the atmosphere for, for moisture, as there’s, I guess, ways that come off of Africa as well.
00:30:23:10 – 00:30:44:06
Speaker 2
Yeah. You’re right. That’s, some imagery when we started getting experimentally here as part, I think it was our proving ground. And to me, that may have, even more utility, because the tip tends to be dominated by what’s going on in the, in the boundary layer, whereas the African East, the waves are maximum amplitude of 700 millibars.
00:30:44:09 – 00:31:02:00
Speaker 2
So so you’re right that that, layered approach, may provide even more information for us about the the waves and potential impacts of the Saharan earlier on tropical cyclones. Okay. Again, very good to thank you.
00:31:02:03 – 00:31:23:23
Speaker 3
Okay. And this is, Bernie Connell. And I was wondering, you were looking at soundings. Have you tried looking in any of the new cap soundings that are starting to become available? I’m not sure if they’re available there, but that might be a newer thing. And Scott Lindstrom can give a little bit background on those.
00:31:23:25 – 00:31:47:25
Speaker 2
Yeah. So so so so maybe I could get more information from you. So they’re from semi NPP. It’s a blend of the Chris and the HMS. So it’s you know two per day. And you can usually get that from climate from class and probably get them. I mean I know they’re in a I don’t know if they’re and they were so good.
00:31:47:28 – 00:32:07:07
Speaker 2
Well, the good news is, in the next year or two will be, fully migrating to a combined ellipse to that, whatever observations are in one are going to be in the other. The, the for from our perspective. So that’s that’ll be good to take a look at that.
00:32:07:09 – 00:32:31:03
Speaker 2
Any other questions or comments? Hey Chris, this is Bob out in Honolulu. How are you doing? I’m doing well. Bob, how are you doing today? Great. I had a couple of questions for you. You showed a graphic that showed surface pressure falls. So you’re tracking pressure falls over, you know, as the as the waves come through, what time period is that?
00:32:31:03 – 00:32:56:02
Speaker 2
Are you looking at 24 hour pressure falls or 12 or. Yeah, 24 is great because then you don’t need to worry about the diagonal variability. Right. Which of course this is fairly large in the tropics there. So so yeah that’s something that we’re able to routinely park Florida. And and they were in the 24 hour pressure changes. And that that’s actually a picture right from an ellipse for one of these waves.
00:32:56:04 – 00:33:21:24
Speaker 2
Okay. And then another question I had was I know you said that you used scatter ometer, but, the maximum amplitude of the waves is typically a little higher, up by 700 millibars. Have you had much luck using, ghosts or medium sized atmospheric motion vectors to to look at wave amplitude or weight axes? Yeah. Yes. That that that’s helpful as well.
00:33:22:24 – 00:33:51:26
Speaker 2
Certainly because if you get the low level vectors, from the visible imagery, that’ll help you with, you know, the wind flow, say, at 850 or 900 millibars. So, yes, that’s that’s a component as well. You know, eventually as the global model data simulation continues to improve, you know, and they’re able to capture small scale details and you know, whatever observations we’re looking at should be available within the global models.
00:33:51:26 – 00:34:26:12
Speaker 2
And, and, and certainly it appears that, the global models representation, both in the analysis and the forecast fields have improved dramatically over the last ten, ten years or so. Yeah, that’s that’s great. You know, we see we see wave axes out here in the Pacific as well. Sometimes the orientation is a little different, whether they extend, north to south or whether they extend southwest to northeast.
00:34:26:14 – 00:35:00:05
Speaker 2
And, you know, the vertical extent in the atmosphere is different, but it sometimes seems like some of these waves in the deep tropics originate from something, you know, other than than just, you know, then I think the classic Genesis mechanism is the African, you know, the Genesis mechanism that you that you showed. But it seems like sometimes you have waves that generate that are, say, southeasterly surges across, you know, equatorial surges that are coming in.
00:35:00:05 – 00:35:32:23
Speaker 2
And there may be other genesis mechanisms, perhaps at least out here. Yeah, I think that’s the case. And indeed there is there’s a secondary, jet, in the West Caribbean that also can break down and cause waves. So occasionally we’ll see an easterly wave that we really can’t track back to Africa. But some, you know, in the, in the Western Caribbean, you may have a, you know, a secondary, easterly wave formation area.
00:35:33:07 – 00:36:03:26
Speaker 2
And there’s been studies, for example, Shiller, a few years ago at CSU said that, you know, the IPCC in the eastern Pacific by itself can cause that reversed, theta e theta, great. If any gradient. And they’re clinically better than notable people. Yeah. So yeah, you don’t necessarily have to have, well, you certainly don’t, need West Africa to explain all the waves.
00:36:03:26 – 00:36:16:16
Speaker 2
The waves can, can form in other parts of the world as well. Sure. Yeah, I think I think that’s an ideal Genesis area. But it’s interesting that you see those across the tropics.
00:36:16:18 – 00:36:42:02
Speaker 2
Well, that was a great talk, Chris. Really appreciate it. Glad to help. Oh, one other thing I thought might be interesting is, you guys were talking about the layered, layers of moisture layered TB w we’re pretty excited about, you know, with Goes-r and Himawari being able to look at that lower level water vapor band.
00:36:42:14 – 00:37:09:06
Speaker 2
I guess it’s I think it’s been ten. And that might be helpful for everybody to track these things. Yeah. I mean, when we get these new capabilities, you know, it’s I think it’s going to be a learning curve to really get a great understanding of how they can all be used. There’s going to be some, I think, really neat surprises about, capabilities that they weren’t thought of before.
00:37:09:07 – 00:37:19:27
Speaker 2
So, so, yeah, we’re looking forward to Goes-r being launched. Soon as it can. Yeah. For sure.
00:37:20:00 – 00:37:26:06
Speaker 1
Oh. Are there any other questions for Chris?
00:37:26:09 – 00:37:35:03
Speaker 1
Okay. Well, if not, we want to thank Chris for leading the discussion together today. And, wish everybody a good day. Thank you. Thanks, everybody.