El Niño and La Niña are some of the main drivers of a long-range seasonal forecast. AccuWeather lead long-range expert Paul Pastelok explains.
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00:00Welcome to AccuWeather's Ask the Experts. I'm your host, Jeff Cornish. We go beyond
00:16the forecast to give you the how and why on all the cool and interesting things you've
00:20wondered about and wanted to ask in weather, space and science. And in this episode, we're
00:25talking about kind of a pair of weather phenomenons. They go hand in hand, opposite to one another,
00:30but they're integral in terms of long-range forecasting. We're going to break down El
00:34Niño and La Niña and how they influence the weather you feel during a particular season.
00:40So joining us to do that is Senior Meteorologist and Lead U.S. AccuWeather Long-Range Forecaster
00:44Paul Pastelak. Paul, we always love talking to you.
00:46Good to see you, Jeff.
00:47Well, thanks for making time for us here.
00:49Absolutely.
00:50Got a busy schedule, I know. But, you know, I think back to Chris Farley and Saturday
00:55Night Live with the El Niño character.
00:57Oh, yeah. I remember that. That was one of my favorites.
01:00It was great. It was great. Tassels, glitter, and he said that he was Spanish for the Niño.
01:06The Niño.
01:07We're going to talk about this. So in long-range forecasting, obviously, this is a critical
01:12thing that you look to.
01:14It is. It's one of the main drivers of our seasonal forecast that we do here. And it's
01:19kind of one of the first things that I look at. I look at a bunch of years. I put them
01:23down on paper. And one of the big things that comes out is El Niño or La Niña. Is
01:28that what we're looking at for the coming season? So definitely a heavily used driver
01:33in the meteorological world.
01:34And a lot of the time, long-range forecasting, we're looking at things that change very slowly.
01:39And water temperatures, big deviations compared to the norm, they're not going to change overnight.
01:44The thing about it is El Niño and La Niña, it's about the water temperatures initially.
01:51But we all know that water temperatures ends up affecting the upper atmosphere and the
01:56patterns that set up not just here in North America, but globally. And so that's why it's
02:01such a big deal. It's one of the things that we emphasize along with ENSO. All of the oceans
02:06really are taking the place when we look at seasonal forecasting.
02:09So fundamentally, what is El Niño and what is La Niña? Just kind of a weather 101.
02:15Well, the simple starting definition of El Niño and La Niña. El Niño is this warming
02:21of the water temperatures anomalies that are in the central eastern equatorial Pacific.
02:26So near the equator, from the date line to South America that we look at. And when those
02:32waters warm, we are in an El Niño when it gets by a certain criteria. Now, the opposite
02:38occurs on La Niña. The winds come out from east to west and they end up blowing a lot
02:43of that warm water across the ocean. And the upwelling takes place, meaning the cooler
02:48water that's down below comes up to the surface and the waters cool. So what happens is you
02:54get these water temperatures that are cooling off and then eventually they end up affecting
02:59the upper levels of the atmosphere. Replacement of high pressure areas and low pressure areas,
03:04upward and downward motion. So you get all that involved. It all has to come in sync
03:09for this to actually have a big impact on our weather forecasting. And we ultimately
03:14do if we have a big strong ridge of high pressure west of the west coast of the U.S. there will
03:18be downstream impacts and the atmosphere has these comfortable wavelengths that will affect
03:24things downstream across the whole globe in some form. It does. And I mean, it affects
03:30the jet stream patterns, the storm tracks that we look at specifically during an El
03:35Niño, a lot of times here in North America, the southern branch of the storm track is
03:40much stronger than the northern branch. So what does that mean? Well, we get bigger systems
03:44affecting places like maybe southern California in the wintertime or we get the southeast
03:49getting hit pretty hard. Then you look at La Niña, the northern branch of the jet stream
03:53tends to be a lot more active. And so you end up getting more colder air systems coming
03:57down and more storms like clippers in the wintertime, those fast moving systems out
04:02of western Canada that can bring quick hitters of snow. So you get different variations that
04:07take place, especially very highly correlated in the wintertime than the summertime. And
04:13one other note too, Jeff, is that when we talk about correlations, much stronger because
04:18the event takes near the equator, the closer you are to the equator, the higher probability
04:24that La Niña and El Niño will work to what it's supposed to do as opposed to going toward
04:30the polar regions as well as you get away from the El Niño, La Niña zone. So how long
04:33have we known about this and when was this first discovered? Well, you can go all the
04:37way back to the 15, 1600s when ships were going back and forth in that eastern Pacific
04:43zone and noticing these big significant wind changes and the speed of their ships could
04:49be, you know, directed at least the speed getting to destinations and slower or faster
04:55depending if you're in El Niño or La Niña. But you got to really, you really start to
04:59take place when you go back to the 1800s. The Peruvians, they're the ones that really
05:04kind of noticed it most for their fishery industry because during La Niña what happens
05:10is the upwelling, the cooling effect that takes place brings a lot of the nutrients
05:16that the fish feed upon. And so if the nutrients can get up to the surface during a cooler
05:21event during La Niña, the fish are able to feed and they stay there and their industry
05:27blossoms that season. But if it's El Niño, Tennessee is, the nutrients stay down below
05:34and the fish end up going somewhere else and they have a bad season. So they notice these
05:38cycles that take place. Fortunately, La Niña happens more than El Niño and that's a good
05:45thing because we have better seasons for fishery. That's very interesting and that does align
05:48with what you were saying about the closer you are to the equator, the more immediate
05:52and higher confidence the correlation is going to be. Absolutely. And it's in their backyard
05:56there and that's pretty cool. Yeah. I never knew that about the Peruvian fishing. Yeah.
05:59It makes sense. So obviously with any atmospheric oscillation or long range pattern, sometimes
06:05there are big strong events, then there are weaker events and there's sometimes we even
06:09refer to La Nada where we're just kind of in the neutral zone. So talk about how the
06:14intensity of the ENSO, El Niño Southern Oscillation conversation plays out. Well, over years we've
06:20gotten more and more cases of what types of La Niña, whether they're weak, moderate
06:26or strong. And a lot of times there's been differences where it sets up. Where's the
06:31coolest waters? Where's the warmest waters? If they're closer to the dateline, we call
06:34it a Central Pacific based La Niña. And all these differences have had different outcomes
06:40on where the storm tracks can be. And a lot of it is related to what we call the Walker
06:44Circulation, the air going up and down globally across. And if you have downward motion, generally
06:51you're going to have better weather. OK. So if it's cooler water in the Central Pacific,
06:57the air is going down, but it's going up as you get over the land masses in North America
07:01and you have more activity. So it does depend on the strength and also the timing when this
07:08comes on as well. The thing about it is, Jeff, the weaker the signal is, the less reliable
07:17we've noticed to kind of go on ENSO. We've seen a couple of instances where we have a
07:23La Niña year coming up and then all of a sudden Southern California gets blasted with
07:29heavy rain when they're not supposed to get in in a La Niña. And if the La Niña comes
07:34in weak, there's other big drivers that take place. And so we have to take that in consideration
07:39when we're forecasting the strength and the timing that it comes on during the season.
07:44Things are never quite as straightforward as people would like when it comes to the
07:46atmosphere, whether it's a climate conversation, long-range forecasting or anything like that.
07:52What are some of the main effects of El Niño in the U.S.? I know that one thing that really
07:55put it in the media's eyes back in the 90s, excessive rain events in the 80s too in Southern
08:02California during a strong El Niño, for example. Yes, it can cause massive flooding.
08:07You can see heavy snow events, prolonged snow events in El Niño, especially across the
08:13Sierras. Definitely, we've seen that significance happen quite often. The thing about El Niño
08:21is that the patterns that set up in the Pacific, there's a split that goes on. And the storm
08:29track that goes pretty far south, even south of Hawaii, is what we call the subtropical
08:34jet stream. And when that's stronger, that feeds in over the Gulf of Mexico, which is
08:39generally warm most times of the year, and can really give a boost to East Coast storms.
08:47And that's why in El Niño winters, we always kind of look for the big bombers, the big
08:53storms, right? And so that's what we kind of look for when we get El Niños. We can
08:58see snow in big amounts in the East Coast, and generally that's what we kind of favor.
09:03The other problem, though, is the waters are warming so much, we don't have a lot of cold
09:07air around. It's tricky. People associate big snow with cold, but sometimes you have
09:11a milder than average winter, but you get that 25-inch event there for I-95, and it's
09:16just what everybody remembers. And, you know, and again, if the waters are too warm off
09:21the East Coast, it could push the storm track farther in, and so your folks in New York
09:26City and Washington, D.C., they're looking for these big storms, but they end up being
09:31rain more than snow, and they kind of miss out. And so that's a tendency that you see
09:36with El Niños.
09:37It's fascinating. This is what keeps us coming back for more year after year, though. There's
09:40a little bit of drama with the weather. Well, it is time for our first question, and this
09:44is from Doug in Alabama, writing, what is one of the worst examples of an El Niño or
09:49La Niña? Was there a particular year or season that jumps out to you?
09:52You know, the 97-98 kind of was the changing of the guard as far as weather goes. It really,
10:02I think, promoted a big change in the water temperatures, which ended up feeding into
10:08weather patterns that followed 97-98. We went out of a phase of cooler waters in the Atlantic
10:15to warmer waters in the Atlantic, and so I think the 97-98 also we saw in the winter
10:22big storms on the West Coast and East Coast going on at the same time and caused tons
10:27of damage and much costly systems during that time frame. And so that was a really bad El
10:36Niño year.
10:37Well, we have a lot more to talk about, and we're going to continue our discussion here
10:40in just a few minutes. So coming up later, joint pain from the rain. It's a popular
10:45saying, but is this really a thing? We're going to look at that and other weather folklore
10:48coming up in our latest edition of WeatherWise.
10:51But next up, we're going to turn our attention to La Niña and show you how this weather
10:54pattern impacts the U.S. and the tropics and what makes it different from El Niño when
10:58Ask the Experts returns.
11:05Welcome back to AccuWeather's Ask the Experts. I'm your host, Jeff Cornish, and senior meteorologist
11:09and lead U.S. AccuWeather long-range forecaster Paul Pasilak is back with us. Familiar face
11:13here on the AccuWeather network. And Paul, you know, we were talking about El Niño and
11:18at one point I just briefly mentioned, I said Enso, El Niño, Southern Oscillation. There's
11:24an opposite to El Niño and this is not just the water that we're talking about. So what's
11:28Enso all about?
11:29Well, you know, Jeff, there is many years that people just thought there was El Niño
11:35and then nothing else. And so that's understandable. We just kind of stay with that topic, but
11:41it is related in the entire what we call Enso, you know, combination. And what the
11:49real easiest way to picture this is to think of blocks. If you have an El Niño, you have
11:54some very warm water. Warm air is going to rise from that warm water up into the atmosphere.
12:00The air is going to go up. But we know if air goes up, it's got to come down somewhere.
12:05And so think of it going up and doing these squares across the globe. Okay. So wherever
12:11the air is going up, generally you have showers and thunderstorms popping up and very active
12:16weather. Now, where the air is coming down, generally you have better weather. And so
12:21this is something that we found through Enso, you know, by Gilbert Walker, the person that
12:28did most of the research on this, discovered that. And eventually it led to something what
12:35we call La Niña. Okay. And so obviously El Niño, you said that the Peruvians had
12:41an inkling of this back in the 1800s and the opposite of that may have been bad fishing
12:46as you mentioned. When did we begin to kind of put a name on La Niña, the opposite of
12:50El Niño? That's why it was bad when they noticed it, right? El Niño was bad for the
12:55Peruvians. La Niña was good. And that's when they really didn't talk about it much when
12:59things were good. That doesn't make sense. But when you go back to the 1960s, Gilbert
13:04Walker had a friend, his name is Jacob, but I can't, I have a hard time, I apologize,
13:08I have a hard time pronouncing his last name, but he worked close hand with Gilbert Walker
13:14and they came up and looked back at some of the data from the past and discovered that
13:20La Niña was the opposite of El Niño where you have these stronger trade winds allowing
13:26the water to cool because it's upwelling from below and all the warm water ends up
13:31going across the Pacific onto the other side. And so you definitely get what you call a
13:36fast moving storm track in the north out of this situation because of the patterns that
13:40develop and also we've noticed, and this has been a general rule with tropical forecasting,
13:47that it lowers the frequency of vertical wind shear and you end up getting more tropical
13:53events to take place in the Atlantic Basin with the opposite happening because of the
13:57cooler waters in the eastern Pacific. Which is fascinating because it's 5, 6, 7,000 miles
14:02away but it makes a difference. It's influential. Water temperatures are so important. I mean
14:07they have such a big influence in La Niña and El Niño are the drivers. So what are
14:11the main effects of the La Niña weather pattern in the U.S.? We talk about the tropics, obviously
14:17the correlation with some more Atlantic tropical activity, but what else? Well we talked about
14:21in the last segment about a stronger storm track in the south, right? The winds are blowing
14:26the warmer water away from the eastern Pacific towards the western Pacific. It allows the
14:32southern track to kind of weaken a little bit so the northern track, it takes over.
14:37It becomes the bully and that ends up coming across western Canada down into the eastern
14:43U.S. But most of the moisture a lot of times with La Niña is dumped into the northwest
14:48and western Canada. So most times and often that's where you see the above average precipitation
14:54and the above snowfall is in the west. Southern California, you kind of miss out. The south,
14:59you kind of miss out as well. So that's generally as far as that goes. As far as cold goes,
15:06yes, you get a little bit more cold air masses that come down because our air masses are
15:10coming out of Canada. But a lot of other things depend on snowpack and things like that. How
15:14about like lake effect snow? Oh yeah, definitely La Niña is the time to get lake effect snow
15:20because that's when you get the Arctic air masses in. El Nino, we have a hard time getting
15:24that kind of cold infrequently and so you have less snowpack from lake effect. If you're
15:28a fan of snow, the Great Lakes are fun because you don't really need that more warm moisture
15:34coming up from the south. The lakes are there. They're going to provide the moisture. One
15:37more thing about La Niña is we've noticed after big events of La Niña that significant
15:42drought situation set up and we saw that in California in the 2016-17 time periods
15:49and led to big fires that took place in there as well. So definitely drought is a major
15:54factor that follows a La Niña cold season and can be very significant and impactful
16:01to many things. Okay, we want to get to another viewer question. This one comes from Trent
16:05in New Jersey, New York City I should say. And Trent, what would you like to ask the
16:10experts? Why is one winter so different from another? Well, you can, I don't even think
16:20we have enough time for this one. But you know, you look at the ENSO changes that take
16:25place. We've gone over all that. But water temperatures are so important. If the waters
16:30are warmer in the Northeast Pacific, it could have a different result of what storms and
16:35the tracks that go in there. Also snowpack, the building snowpack in Canada. If it builds
16:40faster, we get cold air faster, we get more cold air coming into the United States. Also
16:47the water temperatures in the Atlantic, setting the stage up to where the storm track's going
16:51to be. Is it going to be too far off the East Coast or is it going to be right along the
16:55coast? Things like that have a very big influence on why the winters change from time to time.
17:02You've got to look at the stratosphere. The stratosphere can have a big impact. The polar
17:06vortex, we've talked about the polar vortex so often in the media. It could get moved,
17:12it could get pushed around. That could have a big impact on one winter to the next on
17:16how cold it can get. There are other shorter scale oscillations that we don't have time
17:21to address, particularly the MJO and other things. So there's not just one driver most
17:25of the time. It's amazing how much stuff we have to look at before the season starts,
17:29I tell you. You're a busy man for that reason and you do a great job. Senior meteorologist
17:33and lead long range forecaster, Paul Pastelak. Paul, thanks so much. We appreciate the fruits
17:37of your labor here at AccuWeather and you help all of our viewers understand this stuff
17:40better as well. Thanks, Jeff. Thanks, Jeff. Good stuff. Well, coming up, can pets predict
17:44the weather? I don't know. Paul may have opinions on that, but can you really smell rain? See
17:49if there's any truth to some of these statements that you often hear in our weather-wise segment.
17:53Is this really a thing? When Ask the Experts returns.
18:00Welcome back to AccuWeather's Ask the Experts. It is now time for weather-wise and our segment
18:09is this really a thing? Where we reveal if popular sayings about the weather are fact
18:13or fiction. So let's start with the premise. Can pets predict the weather? Is this really
18:18a thing? Well, we know that dogs have a heightened sense of smell and that may play a role in
18:22their ability to detect changes in barometric pressure before weekend. Experts say cats
18:28are even more sensitive to sights and sounds than dogs. So a cat's inner ear will not only
18:33detect a drop in atmospheric pressure, but they also hear the distant rumble of thunder
18:37earlier than weekend. So yes, it is really a thing that cats and dogs may sense a storm
18:41coming before weekend. Next up, can you smell the rain? Is this really a thing? So that
18:47earthy smell that so many people describe as the rain is starting is called petrichor.
18:52These are oils and bacteria from plants. They get trapped in rocks and soil over time
18:57and they're released by high humidity right before it rains or as the rain is beginning.
19:03So in this case, you're not specifically smelling the rain, but it is closely associated with
19:08the arrival of rain beginning. And finally, can weather cause joint pain? Is this really
19:13a thing? We use a barometric pressure to measure the weight of the atmosphere above us. And
19:18when the pressure is low, weather is often cloudy with rain, snow, and sometimes stormy.
19:23This can cause your body's joints to expand just a little bit, causing aches and pains.
19:27So yes, it is really a thing that bad weather can indeed cause joint pain. Thanks so much
19:32for joining us here on AccuWeather's Ask the Experts. I'm Jeff Cornish. Don't forget, when
19:36you have a question about weather, space, or science, you can write us or send us a
19:40video question at asktheexperts at accuweather.com. You can also call us at 888-566-6606. Thanks
19:48for being with us. Have a great one.