Decoding wonders of the weather
Exploring weather terms and phrases to help you better understand the weather around you.
Transcript
00:00Welcome to AccuWeather's Ask the Experts. I'm Jeff Cornish. Whether you nerd out on
00:17it or just want to know more about it, we talk to some of the best minds in meteorology,
00:21space and science to get answers on everything you've wanted to ask. So on today's show we're
00:27going to explore some weather forecasting phrases, weather terms, things you may have
00:31heard, but you might be unsure about a few of these. And we're going to kind of focus
00:35in on some terms that you may see or hear as we go from spring into summer. So joining
00:40us as our expert today is AccuWeather senior meteorologist Courtney Travis, who in addition
00:44to working as a forecaster and shift coordinator, she also leads training for our forecasters.
00:50So Courtney, thanks so much for being with us today. Absolutely. I'm happy to be here.
00:54Well, we're glad to have you here. Tell us a little bit about your journey and how you
00:58got to AccuWeather. Yeah, it's been a long journey at that. I started as a kid being
01:02really interested in the weather and then studied hard, went to Penn State and then
01:06I've been here now over a decade. All right. And where are you from? I'm from outside of
01:10Philadelphia, so not a far cry from State College, staying in Pennsylvania. But, you
01:16know, we've got some interesting weather here, that's for sure. Absolutely. And what, when
01:20you were growing up, really drew you into the weather? Was there a place you'd like
01:23to be, or a storm, or one experience that you had? Yeah, I don't know that it's all
01:27one experience, but certainly going down to the Jersey Shore, which was a very philly
01:32thing to do, go down to the Jersey Shore in the summer, certainly sparked some interest
01:35in that. Okay, that makes a lot of sense. I know the sea breeze can be fascinating,
01:40seeing snow at the beach, which is rare, but it can be... It happens. Yeah, I guess rare
01:45because for me, I typically find myself there only in the summer. Right. But it is cool
01:49to see if you happen to be there during the quote-unquote off-season. Well, we want to
01:53look at some weather scenarios and things that you could help us with, some of these
01:57weather setups, to explain words and phrases and what they mean. So the first one we want
02:02to begin with is a term we use especially in the spring and summer, and that is cold
02:07air damming, how cold air can get dammed somewhere. So where and when do we normally see this?
02:13Yeah, so we're really needing two important ingredients to get this to work. You need
02:17cold air, so you can't have this happening in the tropics or someplace that's warm year-round.
02:22And then number two is that change in elevation. You kind of need that so that the cold air
02:27can kind of get stuck and not able to overcome that elevation. Okay. I know that a lot of
02:33people often say that even when you're young and in science class, warm air rises. Yes.
02:38So what is that all about? I guess we have to talk about density to kind of break this
02:42down a little bit. Yeah, exactly. Cold air is more dense than warm air. So that's kind
02:46of part of the reason it can't overcome that elevation, is it kind of gets stuck and can't
02:51overcome that mountain. And then instead, we have the warm air that rises above it.
02:55Okay. And some of you who may live in a valley location, for example, not far from State
02:59College, we live in the Ridge and Valley region in Pennsylvania, and sometimes that cold air
03:04is very stubborn. We might have warm air streaming in overhead, but that cold air can really
03:09get stuck. So with the orientation of certain mountain ranges, are there areas where, at
03:15least in the U.S., we often see cold air damming? Yeah, we often see it across parts of east
03:19of the Appalachians. You'll see it. You can get it in the Rockies. Basically, any place
03:23that you can kind of get cold air to kind of get wedged in from the east. So what are
03:28some cities in the eastern U.S., east of the spine of the mountains, where we're especially
03:32prone to cold air damming? Yeah, you're talking about like Harrisonburg, Virginia. You talk
03:37about Roanoke, Virginia. You get down to Asheville in North Carolina, a really common place to
03:41see that. And sometimes we even see it as far east as maybe Charlotte. Yeah. Granted,
03:45it may not be as dramatic there. I know a lot of regional weather terms there sometimes
03:50refer to this as the wedge. Yes. So they're talking about kind of this three-dimensional
03:55view of things. And that's what we're showing here, this wedge of cold air near the ground.
04:00Now, if temperatures are especially cold or borderline chilly, what can this do with precipitation?
04:06Yeah, the warm air kind of sitting on top of the cold air often can help create precipitation.
04:11And then you're, you know, thinking, oh, it's going to be a rainy day. But if that cold
04:15air is cold enough, now we're talking about ice, maybe even snow in a place that you wouldn't
04:19expect it. Okay. Fascinating stuff. And this is very relevant, especially in the spring
04:24sometimes, sometimes in the summer, though, too. Well, we want to delve into water spouts
04:28next. And these are really photogenic. But what is a water spout and where do they typically
04:33occur? Yeah, water spouts are just swirling columns of air that are developing over the
04:39water. So they're kind of pulling the water up, which allows us to see them. And it can
04:42really occur over any type of water, but certainly across the Great Lakes, Lake Michigan
04:47and Lake Erie, or across the ocean in the Gulf of Mexico. And we know that there are
04:52two classifications. There are fair weather water spouts and then tornadic water spouts.
04:58So what's the difference between these? Yeah, the fair weather water spouts usually don't
05:02occur congruently with thunderstorms. Instead, they kind of just stay put. They don't move
05:08very much. But then you're talking about the ones that do form in thunderstorms. And those
05:12are the ones that typically move and then can push over land and can be tornadoes and
05:17dangerous. Okay. And when they move over land, does their definition change or are they still
05:22a water spout? It moves to land spout. And again, the potential for a tornado. But they
05:28do usually dissipate quite quickly. But before that happens, certainly it's dangerous. Okay.
05:32We've been showing some really cool footage of various ones. They happen in Europe. They
05:36happen in the Black Sea as it could be anywhere. But in the Keys, the Florida Keys, you see
05:41a lot of them down there too. Another phrase that gets thrown around in meteorology, sometimes
05:45people say we're getting a backdoor cold front. So break this down for our viewers. What is
05:49a backdoor cold front? Yeah. So when you talk about how weather systems in North America
05:54move, usually we're talking about the moving from west to east, most storms at least. Well,
05:59when we're talking about a backdoor cold front, it kind of feels like the weather's moving
06:03in the opposite direction. And instead, you're seeing that cold air and new air mass move
06:07in from the northeast or the east. In this schematic, we have a cold front that would
06:11be moving from, say, eastern Pennsylvania into West Virginia, which may feel backwards,
06:16but that is the behavior that these things take sometimes. And what kind of experience
06:21would this be like in eastern New England? Yeah, it would definitely be cool and chilly.
06:26And again, compared to someplace on the other side of that front, it's going to be a huge
06:30difference. Are there any smaller scale kind of microcosms that are kind of parallel to
06:35backdoor cold fronts come to mind? I think that the one thing that we kind of touched
06:38on a little bit is at the beach, you're talking about a sea breeze. It's a nice warm afternoon.
06:42All of a sudden, the sea breeze kicks in and it gets chilly and cold. That's the wind moving
06:47that cold air over the water over to land, making that stark difference in temperature.
06:52All right. That makes good sense. And in some cases, this can really drop the temperature
06:56in a hurry in many areas. Well, another question we wanted to ask about, and this is where it gets
07:01a little bit more tricky sometimes, a little bit of thermodynamics, the difference between
07:06relative humidity and dew point. I know a lot of people in the public, they really love a zero to
07:12100 scale. Relative humidity is expressed as a percentage, but sometimes meteorologists,
07:17we kind of balk at that and we prefer the dew point. Yeah. So the dew point, again,
07:23meteorologists really prefer that. And there's a couple of reasons. One is that the dew point
07:27temperature is really the temperature you have to cool the air to, to be able to see precipitation
07:31or saturation. And really the good reason to use dew point is the higher the number goes,
07:38the more humid it feels. And that's not necessarily the case with relative humidity.
07:42Right. And most people are generally interested in how's it going to feel when I go outside. So
07:48that's why we have the accurate, the real field temperature and the dew point and the humidity
07:51are a big factor in that. But I think in popular discourse, people are not trying to have a heavy
07:56duty thermodynamic conversation. No. They just want to know, is it going to feel really, really
08:01humid out there or not? And the tough thing about relative humidity, if you have an air temp of
08:05four degrees and the dew point is four in February, it does not feel humid, but you're at 100%.
08:10Yeah. So it's a tough thing. So at what point does the dew point make it feel uncomfortable?
08:15Usually if you're in that forties to maybe 60 range, it feels pretty comfortable. But once
08:21you start to climb through the sixties, that's where it starts to feel a little sticky, a little
08:25more humid. And then certainly in the seventies and you get to the upper seventies, it really
08:31feels uncomfortable, but it really depends on what you're used to. Out in Arizona in the summer,
08:36it only gets into the upper fifties, but in New Orleans or Miami along the Gulf coast,
08:40it's in the seventies all summer. So it really depends on what you're used to.
08:43And sometimes in the West, it's just amazing. West Texas, New Mexico, during a wildfire danger
08:48setup, we can get to sub-zero dew points, a dew point of four below zero, but an air temp in the
08:53eighties or nineties at times. Yeah. So it can feel really different. And that's why a dew point
08:57is such a better gauge of that humidity level because the relative humidity could fluctuate
09:02so much even throughout the day and doesn't give you a good gauge of that. It is relative to the
09:07air temperature by definition. All right. Good stuff there, Courtney. Thanks for helping us
09:11understand a little bit more about that. We have a viewer question that we would like to hear,
09:16and this comes from Daniel in Texas. So Daniel writes, sometimes I hear my local weather person
09:21say bow echo when it's stormy out. So what are we talking about? Yeah, a bow echo is really just
09:26a line of thunderstorms and the bow part is really trying to characterize what it looks like. So
09:33instead of it being a straight line of thunderstorms, which you might see with a cold front
09:37coming through, the bow echo is going to instead have this little bit of a bulge that goes forward
09:42ahead of everything else. So really what you're looking for is just that shape. It's created when
09:48you actually get a downdraft, a super strong push of wind behind the storm, pushing it forward and
09:55bulging it forward in addition to creating some gusty winds. And where would the winds be strongest
10:00with a bow echo? You can really see them almost anywhere, but certainly in that central to lower
10:05part is really where you could see those strongest winds. Okay, so something to keep in mind. And it
10:10makes sense. It does look like a bow there. It's a curved line as opposed to a totally linear line
10:15there that you could place a ruler on and you wouldn't have any deviation from that. So thank
10:19you there, Courtney. And you know, at the end of our show in WeatherWise, we're going to show you
10:24three interesting things that you can see in the sky that have fun names, and we're going to talk
10:28about what they mean. But coming up next, what is an atmospheric river? How about a scud cloud or a
10:36derecho? All terms that you may have heard, but you need to understand better. And Courtney and I
10:41will help you to do that as we ask our expert, Courtney Travis, here when Ask the Experts
10:47continues.
11:05Welcome back to AccuWeather's Ask the Experts. I'm Jeff Cornish, and joining us today, we are
11:10joined by Courtney Travis as we talk about weather terms and phrases that you sometimes see and hear
11:15that may not make a whole lot of sense until you get a little more acquainted with the weather. So
11:20we're giving these more context with senior meteorologist Courtney Travis here, and she has
11:26been very helpful here through our first block. So let's just continue on into number two. And
11:31Courtney, there are certain weather terms and phrases that start getting used more and more
11:35over time. I think the media might gravitate towards some of these. A little bit. Right. And
11:40one of these is atmospheric river. Yeah. Yeah. So what is an atmospheric river? It's really just a
11:47narrow, long column of air in the atmosphere that gets used as kind of a transport for air
11:54and for moisture. It'll really take moisture and the water vapor from a more tropical wet region
12:02into something that's not necessarily wet. So we'll necessarily see that transport. And in
12:10addition, we end up with a lot more precipitation in some places that might not normally see it. And
12:15this is a really broad thing vertically within multiple levels in the atmosphere. So what parts
12:22of the United States, for example, would be more likely to see an atmospheric river? Yeah, there
12:27could be a lot of places, but because these atmospheric rivers tend to happen over water
12:31where it can pick up that tropical moisture, we're talking about like the west coast of the U.S.,
12:35even western parts of Canada can really see that long band of wind start to pull up the river and
12:42bring precipitation. And when I was first learning about meteorology, I graduated in 2004. The term
12:48was the Pineapple Express. Yeah. I know that's a subset of what we now call atmospheric rivers. So
12:54how does this relate to atmospheric rivers as a whole? It really isn't a type of atmospheric river,
12:59just kind of narrowing down where the location is. And the Pineapple Express is an atmospheric
13:05river that starts out in Hawaii and then kind of transports that moisture all the way to the
13:12northwest. And you see heavier precipitation, but it's called the Pineapple Express because of the
13:16pineapples that they grow. I'm on board. And you can see the scale of what we're talking about,
13:20multiple thousands of miles, maybe two or three thousand miles. And this could be a really robust
13:25game changer here for moisture. So what's the experience like for this example, if you were
13:31sitting in Olympia, Washington? It's going to be a wet one. It's not going to be a dry experience.
13:37So instead, you're going to feel that humidity that we talked about earlier, that moisture in
13:41the air in the west coast, again, where sometimes it can get quite dry. Okay. And I'm beginning to
13:46hear this in public discourse a little bit more for the eastern U.S. at times, not your typical
13:51storm setup, but it's being used to describe weather patterns in more areas I've noticed
13:57lately. Yeah. And sometimes the generic form and word that we'll use for an atmospheric river is
14:03tropical connection. There's tropical places all over the globe. So if you think about the east
14:08coast, we have that tropical connection that comes from the gulf up into the east coast,
14:12even from the Atlantic. The difference in the east coast is because of that west to east transport
14:17of storms, it kind of gets pointed out over the water. So you don't see that ringing out of
14:22moisture like you would on the west coast, but it's still there. It's still a tropical connection.
14:26Okay. Switching gears to scud cloud. Sometimes during severe weather conversations, people
14:31might say it looks like a tornado, but it's actually a scud cloud. So what are they talking
14:36about? What is a scud cloud? Yeah, a scud cloud is really a cloud that just kind of forms at the
14:41base of the rest of the clouds. It's irregularly shaped, it's wispy in view, and again, it looks
14:49like it's sitting kind of below things, which makes sense of why it could be really easily
14:52confused. Usually a funnel cloud before a tornado starts is also sitting below like the deck of the
14:58cloud. Scud itself is actually an acronym for a type of cloud. It's stratocumulus under deck,
15:04and deck is kind of that level of the clouds that meteorologists use. Is there one thing that's kind
15:09of like the litmus test that determines is this a funnel cloud or not? I think that the shape and
15:16kind of what it looks like is one, that it's not going to be irregularly shaped when you're talking
15:20about a funnel cloud. It's going to be more dense, it's going to be really narrow, but instead it's
15:24going to be swirling too. A scud cloud is usually going to kind of float along instead. With a
15:28little bit of imagination, a lot of clouds can look scary, but if you don't see clear-cut rotation,
15:34then it's probably not a funnel cloud. Yep. It might be scud. Well, this is good stuff. We have
15:39Drew joining us from Pennsylvania, and Drew, we would love to hear your question. So what would
15:44you like to ask the experts? Hey, Jeff. Hey, Courtney. One phrase I hear a lot on the news
15:50is duratio. I think I'm pronouncing that right. Some might confuse that with a tornado, but they're
15:57very different. Can you break that down for us? Yeah, absolutely. That's a great question, Drew.
16:02Thank you, Drew. It's good to hear from you. Yeah, so when you're talking about a duratio,
16:06it's really easy to confuse them for a couple of reasons. Reason number one is they occur in
16:11stormy weather, and they cause a lot of damage. So it's really easy for them to be confused
16:16together because of that. But there are some significant differences, like you said, and one
16:21is that duratios are usually much wider scale. We're talking about something that is hundreds
16:27of miles wide and causes damage paths that have to be over 400 miles long for them to even be
16:32classified as a duratio. And you're going to see strong winds, but they're straight line winds,
16:37so they're all kind of pushing the same direction. That's pretty interesting stuff. I know that
16:42sometimes during a squall line type event, there's often a conversation, is this a duratio or not?
16:49So the damage needs to be pretty consistent. There can't be big gaps without damage in between these
16:54points. Yeah, exactly. It has to be consistent, and you have to see a lot of damage, and there's
16:59criteria for that. But one is that damage width path, and like you said, no breaks. I remember back,
17:04it was a Friday, June 29th of 2012. Some of you remember from near Chicago to D.C., just a
17:09tremendous duratio tore through a big chunk of the Midwest and into the mid-Atlantic states with just
17:14millions without power. Yeah, absolutely. And instead with tornadoes, they're much smaller, so they can
17:20cause a lot of damage. Same amount of wind, but it's much smaller scale and fortunately not 400
17:25miles long. Okay, well that's certainly a big difference there. Drew, thank you so much for
17:30taking time to ask the experts and dialing in. Well, that'll wrap up our question and answer
17:34segment. I want to thank Courtney Travis for joining us. Courtney, thank you so much. Absolutely.
17:38When you have a question about weather, space, or science, you can write to us and send us a video
17:43question at asktheexperts at accuweather.com. You can also call us at 888-566-6606.
17:52Up next in WeatherWise, three interesting things. Ask the experts returns after a quick break.
18:12When you have a question about weather, space, or science, you can write to us
18:16and send us a video question.
18:18Absolutely.
18:25Welcome back to AccuWeather's Ask the Experts. It is time for WeatherWise,
18:29and in today's segment, we showcase three interesting things we can see in the sky.
18:34Atmospheric optics are a cool part of meteorology that involves sometimes surprising or amazing
18:39scenes resulting from the interaction between light and the atmosphere. First up, we have
18:44halos. A halo is a circle that forms around the sun or the moon. Halos are more common in the
18:49winter because a halo occurs when light refracts or bends off ice crystals inside cirrus clouds,
18:56thin clouds that are high in the sky. So, halos are most often a bright white ring,
19:00but they can also have color and they can be a harbinger of bad weather as moisture
19:05increases upstairs. Second, let's talk about sun dogs and moon dogs. These are bright
19:11spots you can see on either side or sometimes on both sides of the sun and the moon. Again,
19:17more apt to be seen in colder weather because they are interactions with sun and ice crystals often
19:22within thin cirrus clouds. They're called dogs because they look like either the sun or the
19:28moon is walking a dog. In other words, the spot appears to be on a leash or on one side or the
19:33other. Sun dogs are seen in the day, moon dogs at night. Like halos, these spots can be bright white
19:40or they can also have hues and color resembling a rainbow. Finally, the most familiar atmospheric
19:46optic is, in fact, a rainbow. Many of you may have been on board with this here. Guess that
19:52rainbows occur when the sunlight hits water droplets usually near the edge of a downpour
19:56and the light scatters through the water and is refracted or bent in different colors,
20:00revealing the full visual spectrum of light. All the colors of a rainbow. Hey, thank you so much
20:05for joining us on AccuWeather's Ask the Experts. I'm Jeff Cornish. Remember, when you have a weather
20:10question, you can email us at asktheexperts at accuweather.com or call us at 888-566-6606.