- 2 days ago
Category
🗞
NewsTranscript
00:00Well, we are tracking potential for severe weather later today, specifically a duratio event
00:05potentially for parts of southern Minnesota, South Dakota, Iowa, and these could be long-lasting
00:09moving into Illinois late in the night and bringing our second day in a row of possible
00:13severe weather to southern Minnesota.
00:25So you've probably heard the buzz about a potential duratio.
00:28These are long-lived squall line thunderstorms that produce some severe wind gusts.
00:33These are some of our most destructive type of severe storms in the Midwest and Northern
00:37Plains.
00:38Tornadoes get a lot of attention, but they tend to be short-lived and hit and miss, especially
00:41this far north.
00:42But these duratios can persist for hours and hundreds of miles, and that's what we're looking
00:47at the potential for later today.
00:49We've got a moderate risk for severe weather across southwestern and south-central Minnesota.
00:54That's where we're expecting the greatest risk of seeing those severe wind gusts.
00:59And then an enhanced slight risk all the way to the Twin Cities.
01:02That's a level three out of five.
01:03But moderate risk is pretty rare for us.
01:05I think this is only the second one we've seen so far this season in Minnesota.
01:09The first one was when Bemidji got hit by a pretty destructive microburst a little more
01:16than a month ago.
01:16So we are looking at some nasty conditions to potentially develop right now.
01:21It's pretty benign in North Dakota, but we've got a surface frontal boundary that's lingering
01:26around the area and also plenty of moisture, of course, though that front that came through
01:32last night has kind of pushed things a little further south, and that may save the Twin Cities
01:36from the worst weather.
01:37We will see.
01:38But I'm going to put on this surface streamlines here.
01:41This shows you the direction of those surface winds, and you can see that front across South
01:45Dakota, and then it kind of drapes around into north or west central Minnesota and then
01:49down to the south here across far southern Minnesota.
01:53And I'm going to pull up a screenshot that I did earlier to kind of visualize this more
01:58because what we're looking at is winds are kind of out of the east, southeast here in
02:02the Twin Cities and much of central and southeastern Minnesota.
02:04But if you look in southwestern Minnesota, those winds are out of the south and southwest.
02:09That's a clear sign that that frontal boundary is kind of sitting across southwestern Minnesota.
02:13And earlier, we saw a little bit of low cloud cover lining up with that surface front.
02:17And so that's why it looks like these storms that will develop somewhere in southeastern
02:22North Dakota, eastern South Dakota, will follow that gradient of the highest instability,
02:28essentially the gradient of the warmest temperatures and highest dew points.
02:33And then those storms will kind of dive south.
02:34That's their inflow.
02:35That's their food.
02:36They really need that in order to sustain themselves.
02:39We are looking at what's called a derecho, as we mentioned, and they are a unique storm
02:45in that they are long lived.
02:48And the key thing for any severe storm, and we talk about this all the time, you got to
02:52have shear to help organize the storm because your average thunderstorm grows and then kills
02:59itself because the rain cooled air chokes off the updraft, which fuels the storm with warm,
03:04humid air.
03:04But organized storms, whether it's a supercell or a derecho, is able to separate the cool
03:10downdraft air from the warm inflow air.
03:13And a derecho does that very efficiently.
03:14And one of the ways it does it is you get some strong, dry, mid-level winds, goes into
03:19the storm, that moisture evaporates, cools, and that pushes the air down.
03:23So it's a larger, more organized scale of what a downburst does in a thunderstorm anyway.
03:29And it's just able to keep going for hours because it pushes that warm, humid air, literally
03:33kind of plows it out ahead of it into the storm and separates the rain cooled air for a very
03:39long time, very efficiently.
03:41And so one of the things that we look at with that is the shear, as I mentioned, but specific
03:47to deratios, with the tornado, we want it to go in different directions, say it, whether
03:54they're converging at different levels or increasing speed and direction with height.
04:00But specifically, we want that with the deratio.
04:03And when we look at the soundings out here, forecast soundings in eastern South Dakota,
04:06we've got the ingredients in place.
04:07Dry mid-level air, that's that gap between the green and red lines.
04:11That's the temperature in dew point that tells you the relative humidity there.
04:14That about 10,000 to 15,000 foot layer is pretty dry.
04:19So when you get those winds blowing through that layer into a line of storms, that's going
04:25to help produce more of that cool downdraft air to propel it and produce potentially some
04:30severe wind gusts.
04:31The other thing to notice is on the right side of this, these wind barbs.
04:34This is how we plot wind speed and direction.
04:37Each line is a greater speed and they are drawn into the direction the wind is moving.
04:44And while you can see at the surface, those winds are east-northeast, most of the winds
04:49from about a few thousand feet up are all almost in the same direction.
04:53But notice they increase speed with height until you get to the middle of the atmosphere
04:57and then the jet stream.
04:58So that is key for producing these long-lived storms because it will push that moisture out
05:05ahead of it as it grows and then allows that cool air to hit the ground and push that
05:11moisture, the low-level moisture out ahead of it.
05:14So we do have that ingredient in place here.
05:16This is a look at forecast relative humidity and winds at 18,000 feet, that very dry air
05:22there in the central part of South and North Dakota that will be moving in.
05:27And of course, we've got plenty of moisture.
05:29The dew points are pretty soupy here across eastern South Dakota and southwestern Minnesota
05:34in particular, 77-degree dew points, 70s in southwestern Minnesota.
05:38But you get into Twin Cities, and this is why I think we might be saved potentially.
05:44Our dew points are considerably dry.
05:46They're still muggy.
05:46It's in the 60s.
05:47But that really humid stuff is in southwestern Minnesota, and it's that gradient that these
05:52storms could follow here later in the day today.
05:55So we're looking at that.
05:57And then plenty of energy to work with here.
06:01The convective available potential energy, we call that CAPE.
06:05It's going to be very high here in eastern South Dakota.
06:08And again, we're looking at that gradient.
06:09Where's the tightest difference in that instability?
06:13And it's shifted a little further south, more into eastern South Dakota and far southwestern
06:18Minnesota, whereas earlier, if I can put on, let's see, the European model, this was the
06:25overnight run.
06:27It's a subtle difference, but it was a little further north.
06:30And now you look at a little bit of a shift to the southeast that could help to keep those
06:35storms maybe just a little further south, southeast.
06:37But that's why that is really in that moderate risk is following that CAPE gradient here in
06:43southeastern Minnesota.
06:44There is a slight risk of some tornadoes, too.
06:47We could see some isolated tornadoes.
06:48We tend to get these gustnadoes with these storms, which are literally spin-ups as they
06:53produce that bow echo, that line of wind.
06:56There you get a little vortex that can develop on either end.
06:58It's just literally, you think about when you paddle through water, you get little spin-ups
07:02on the edges of it occasionally, and that's what can happen.
07:05But we've got a hatched area of 45% risk of severe winds, particularly along the Minnesota
07:12River and southwest of it.
07:13Again, it goes up to the Twin Cities, so we're not out of the woods.
07:16But I do think that things are starting to point to a little bit of a shift maybe further
07:21to the south and southwest of us, and then far southern Minnesota into Iowa, and then
07:28eventually Illinois.
07:30And when we look at some of the parameters already, these are the live parameters, and
07:35this is, we specifically have lots of composites here, a list of them.
07:39You can make yourself dizzy looking at all these things.
07:41But one of them that we calculate is called the deratio composite.
07:45So this is specific to trying to track and analyze the potential for deratios, and you
07:49can see the highest values here are in eastern South Dakota, northeastern Nebraska, and then
07:54into western Minnesota.
07:55But then it does drop off as we head into eastern Minnesota.
07:57And then another way to look at where that surface front is here, again, these are the
08:01wind barbs.
08:02Notice the lighter, more southeast winds for us, more southerly into southwestern Minnesota,
08:06eastern South Dakota.
08:07That tells you that's where that warm, humid wedge is.
08:10And then the blue contours our surface vorticity basically helps to outline where that frontal
08:15boundary is.
08:16Because you can see in South Dakota, we've got strong north-northeast winds in the northern
08:19part of the state.
08:20Southern South Dakota has south winds.
08:22So there's a frontal boundary that is through that area, and so that's probably going to
08:26be this area of ongoing showers that are dissipating in North Dakota, moving into that
08:31boundary, peak heating of the day.
08:33We've got an upper-level disturbance coming in from the west.
08:36We put on the mid-layer contours.
08:39Here's this little X out here.
08:41That is a little shortwave, basically a little cool front's a loft that help to destabilize the
08:47atmosphere and get those storms firing later in the day.
08:50So when we look at the models, we'll take a run through them because they're kind of
08:55all over the place.
08:56The forecast models have not been particularly useful this season so far.
09:01There are many possible reasons why.
09:05I would be curious to see, it'll take a lot more research, but to see that the NOAA cuts
09:09getting rid of a lot of the weather balloon launches, which give us that picture of the
09:14middle and upper parts of the atmosphere to our west, which is where our weather comes
09:17from.
09:18When you eliminate that, it can't help anything.
09:21Forecast models need more data to be accurate, not less.
09:25But here's the evolution of the high-resolution rapid refresh model.
09:284 p.m., you've got some storms developing there in far southern South Dakota and then
09:32kind of expanding a little bit into southeastern South Dakota.
09:35But a lot of this kind of stays to the southwest.
09:38So that's the latest run.
09:39But if we go back to the morning run, which already looks different from just a few hours
09:44ago, it does build into the Twin Cities and then point south and east, but you can see
09:47that bowing structure here along the Minnesota-Iowa border pretty far south of us.
09:53So the morning model runs started to push these severe wind gusts further south.
09:59You can see a couple scattered ones up here in western and southern Minnesota.
10:03Again, the Twin Cities is on the edge of this, but each model run has been pretty different.
10:08So this is the previous hours model run, 11 a.m.
10:12You can choose another one, 10 a.m.
10:14model run.
10:15And then the latest one now, which doesn't go out far enough.
10:20Well, 2 a.m.
10:21I'm still kind of pushing through southern Minnesota.
10:23So generally, it's going to be that anywhere, eastern South Dakota, southern Minnesota, northern
10:28Iowa, basically where the Storm Prediction Center has outlined that moderate risk.
10:32But we are on the edge of it, so we will have to watch to see.
10:36It's all going to depend upon where those storms actually initiate.
10:39Another model that we look at is the rapid or is another one of NOAA's models, the rapid
10:45refresh forecast system model.
10:47This is one of the newer models that a lot of people are in love with.
10:53It's pretty good, but you need a whole slate of models, not just one to rely on.
10:58It has those storms developing farther north, but this is a model run from overnight.
11:03Things may be shifting.
11:04We have to look at a different...
11:07Let's look at some of the more recent updates here.
11:10So this is the 10 a.m. update of that same model.
11:15It's going to look a little different because it's a different website, pivotal weather,
11:19but we'll fast forward here to 2 p.m.
11:23and kind of go through what it is doing with the evolution of things.
11:28So here's 4 p.m.
11:29It starts to reignite stuff here in South Dakota.
11:32It's 5 p.m.
11:34It's a nasty-looking cell.
11:35And then going through time, 6, 7, 8, 9, 10.
11:50Here we go.
11:51Now we're starting to get activity into Western Minnesota.
11:5411 p.m., midnight.
11:58Not having a whole lot of bow structure to it.
12:00So there are some model runs now that are starting to point to maybe we won't get the
12:05deratio, maybe just some scattered downbursts, large hail, isolated tornadoes.
12:10But overnight runs last night were really starting to freak out forecasters because they were
12:16really pointing strongly towards deratio.
12:18And that's still very possible here.
12:21But some of these model runs are looking a lot more disorganized on that front.
12:26So we're talking about pretty late before anything would reach the Twin Cities area tonight
12:30regardless.
12:31So this is 1 a.m., midnight.
12:34It might be at midnight before we see it.
12:36The high-resolution rapid refresh model has it all coming in.
12:41Yeah, same time, about 1, 2 a.m.
12:43So even later before we'd see some activity with the latest runs.
12:49Some of the runs earlier were as early as maybe 10, 11 p.m.
12:53But this is not going to be a daytime thing for us.
12:56If we go back to the early morning run, it had some stuff in central Minnesota in the
13:03evening, kind of random.
13:05And then, yeah, some midnight to 1 a.m. stuff.
13:07So this is going to be late.
13:08I encourage people to have a way to get alerts and warnings because I'm assuming you're going
13:14to be in bed at that time and you want to stay abreast of conditions.
13:18But, yeah, that's what we're looking at here.
13:21Probably a late-night scenario.
13:22Twin Cities will be probably on the northeastern edge of it.
13:26Let's just look at some of the wind gusts in here, see what it's doing.
13:32Back it up a little bit.
13:34Back to this RRFS model.
13:37These aren't wind gusts, but these are sustained wind speeds at the surface.
13:46Not a lot of detail, but we can get the general idea.
13:50This looks like a pretty nasty line coming in to the west metro.
13:53Again, that's midnight.
13:54So, yeah, we'll animate it.
14:00That's better.
14:07Loading.
14:08Loading.
14:10This site has a lot of windows and junk.
14:13Sorry.
14:13Or not.
14:23There we go.
14:24Yeah, so basically reiterating the same thing we've been talking about.
14:28Twin Cities on the northern and eastern edge of these potential strong winds.
14:32But if you're in south-central, southwestern Minnesota, northern Iowa,
14:35really got to be on the lookout here because that could definitely be
14:39the most probable part of this here.
14:43I'm just going to make an animation of these winds
14:47so that you can kind of see a similar scenario playing out.
14:55So these are wind gusts swaths,
14:57keeping the past ones on with the future ones.
15:00And, yeah, you can see a similar scenario.
15:03We're on the northern edge, similar to this model,
15:07with southern Minnesota and northern Iowa really seeing the worst of it here.
15:12So let's see if I can go back to here.
15:18So, yeah, moderate risk.
15:20Mankato, Montevideo, Marshall, almost to Rochester.
15:25And then the Twin Cities on that outer band there in the enhanced risk.
15:28Again, we are on kind of the northern edge of it.
15:30So got to watch out for that.
15:33And then we will be rewarded with nice weather after this.
15:37We're looking at highs that will start to already be cooler tomorrow,
15:40but the big drop in humidity Wednesday.
15:42Two points will be in the 50s for the rest of the week into Sunday,
15:46with highs maybe struggling to reach 80 degrees.
15:48So if you have not been a fan of the steamy weather and severe weather,
15:52we get a nice break here because that drier air will definitely calm things down.
15:56So hot, humid still today.
15:58We are put into the heat advisory in the Twin Cities.
16:02I can actually show you that here.
16:04But we're on the northern edge of that.
16:06Of course, the biggest thing everybody's worried about is those potential severe storms.
16:12So there's, again, the metro, all of southern Minnesota, and that heat advisory for today.
16:15But that'll be the last one of those.
16:17And then we are headed for potential severe storms this evening.
16:22Again, here's the southern Minnesota.
16:30Yeah, southwestern Minnesota.
16:31So heads up, again, have a way to get some alerts because it could be dicey later on.
16:35But right now, it looks like the Twin Cities could be on the northern or eastern edge of that.
16:39But it will all depend upon where these storms initiate here,
16:42which isn't going to be until the evening hour, very late afternoon, evening hours in north and south Dakota.
16:47And then they will migrate north and east.
16:49The further north those storms develop, better chance of the Twin Cities getting nailed.
16:53If those continue to develop further south, then a better chance that it stays more into southeastern South Dakota,
16:58far southern Minnesota, and northern Iowa.
17:02So that's what we're looking at.
17:03Stay safe, everybody.
17:05Hopefully we don't have to deal with massive power outages and damage.
17:10But late summer is our time of year for these types of storms.
17:14So good luck.
17:19We'll see you next time.
Recommended
5:04
|
Up next