What is a nor'easter, bomb cyclone or an Alberta Clipper? Geoff Cornish breaks it down on this episode of Ask The Experts.
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00:00Welcome to AccuWeather's Ask the Experts. I'm Jeff Cornish. Here we go beyond the forecast
00:17to give you the how and why on all the cool and interesting things you've wondered about
00:21and wanted to ask in weather, space and science. And today we're talking about several weather
00:25terms that you may hear thrown around a lot. Some of these buzzwords, which like so many
00:30other words and phrases, have become what we call winter weather jargon. And specifically
00:35we're going to cover several of these terms and descriptors that you are bound to hear,
00:39especially in the winter, and explain them so you understand what they really mean, sometimes
00:44differently than how they are applied in the media. So joining us to help take some of
00:49the mystery out of these winter weather words is AccuWeather lead long-range forecaster
00:52Paul Pastelak. Paul. How are you doing, Jeff? Always good talking to you here. I am lucky
00:56to be on this segment. These are the big ones. This is what everybody likes to hear. We have
01:01a lot to talk about. Absolutely, yeah. And you've been here at AccuWeather for a long
01:04time, over 30 years. Started out as a general forecaster. Over the years you transitioned
01:09to more of a long-range forecaster, and now you run the show with that. So what made you
01:13make that transition to long-range forecasting? Well, it was kind of by default, but in any
01:18case I worked into it. I really liked looking beyond the 5-7. Actually, to be honest, I
01:25got kind of bored with the next 3 or 4 days. I got more excited by looking out 2 weeks,
01:303 weeks out and seeing what the next storm is going to be. Okay, that can be intimidating
01:34for most forecasters, but we want to get into some of these words and phrases that sometimes
01:39play a role in long-range forecasting and big picture things. Some of these phrases
01:43have been introduced to the public by meteorologists, and sometimes they are taken to kind of
01:48represent and describe parts of the weather that may be confusing. Sometimes they're
01:51misapplied by the media as well. So we're looking forward to this conversation here.
01:56And the first one that we wanted to talk about is a nor'easter. So what is a nor'easter?
02:00The nor'easter is a developing, intensifying, rapidly intensifying storm. But the thing
02:06about nor'easter is more defined by the wind and wind direction. The wind generally has
02:10to come out of the northeast direction. It's not about the precipitation, because it can
02:14be almost anything. You can have rain, you can have snow, you can have any type of precipitation.
02:19We can see a nor'easter at any time of the year, although prevalently they occur in October
02:24through May, because that's when the jet stream is so active. So again, these storms generally
02:30we find most of them on the east coast. That's where they generate. And they need warmer
02:35than average bodies of water. So when that system gets to the east coast and blows up,
02:41that's the intensification we see for a nor'easter.
02:43All right. Well, there are two types of nor'easters or classifications. And sometimes we talk
02:50about Miller Type A and Miller Type B. This sounds like, you know, very much inside baseball
02:55to the public, but they're very different storms. Some of you are going to probably
02:58recognize this, the earmark of a Miller A versus a Miller B. So what's this mean? How
03:03do we break this down?
03:04The Miller A type of system is generally a system that intensifies, either starts in
03:10the Gulf of Mexico or off the southeast coast, and rapidly intensifies either along a stalled
03:17frontal boundary or whatever, and then slowly comes up the east coast. And that generates
03:23a tremendous amount of precipitation over a wide coverage area. Generally, you can get
03:29rain or snow all the way down to the gulf coast with these kind of systems. And then
03:33in New England, you can get buried with these systems in snow. So generally originate from
03:37the gulf coast to the southeast coast.
03:39This is probably the more straightforward, iconic storm that many people think of if
03:43they just have, you know, one view in mind. But there's another storm that we see a lot
03:47of, and the Miller B comes in a little differently initially.
03:50Yeah, now the Miller A usually associated a lot of times with El Nino because you have
03:54a southern storm track generally with El Ninos. The Miller B storms are generally coming out
03:58of the Midwest Great Lakes area, kind of associated with La Nina, okay? And so when these systems
04:04are coming down, they look kind of innocent sometimes. They don't have a lot of moisture
04:08with them. But when they get to the east coast and they hit that warmer than average water
04:12temperature anomalies that set up along the Mid-Atlantic coast sometimes, they blow up.
04:16They intensify quick and they throw back moisture into the northeast and Mid-Atlantic. Generally,
04:21you don't get much support from the gulf coast or the southeast coast. But the Miller B storms
04:25can be very disruptive and they can intensify very quickly.
04:28And you can often see that transfer of energy here where the interior low begins to decay
04:32and the coastal low takes off. And sometimes, depending where you are, there's a spot kind
04:36of in the middle where you may get the dry slot and it can be kind of disappointing at
04:40times.
04:41I think the folks in central Pennsylvania know a lot about that.
04:44We have proclivity for sleet in State College with some of those storms as well.
04:48Exactly.
04:49Some people call it sleet college there. But what are some of the most famous or dangerous
04:53nor'easters that we've had in the past?
04:56There's a couple that stick out. The February 1978 blizzard in New England, I was eight
05:02years old and lived through that. And also the Superstorm March 93, both Miller A storms.
05:10And the 78 blizzard was the one that really stuck out to me because I lived in Connecticut
05:14during the time and Boston was just buried.
05:17And the thing about this was it was forecasted very well back in the 70s, 36 hours in advance.
05:25People were warm, except people ignored it. It was kind of strange and got stranded. And
05:30a lot of people were stranded in their cars in parts of eastern New England from that storm.
05:33That's pretty interesting. And I think a lot's changed with the media and the way storms
05:37are covered now and social media. There's this buildup of hysteria sometimes before a storm.
05:42I suspect it's a little less likely to happen the same way now.
05:45Yeah. And the 93 storm, I mean, that was one that really intensified quickly. I mean, the
05:50pressure drop with that storm was incredible. I think it was 30 millibars in 24 hours. And
05:56that's one of the characteristics you need for a bomb cyclone, which we'll get to shortly.
06:00But still a very, very intense system that brought us folks here in central Pennsylvania
06:07quite a bit of snow.
06:08Yeah. And I remember this one well. I was 12 growing up in the Philadelphia suburbs.
06:11And the one thing that sticks out to me is how wide the one foot accumulation plus band
06:16was about the width of Pennsylvania. Instead of it just being like multiple counties, it
06:20was really wide.
06:21And didn't it snow all the way down to maybe, I don't know if it was Florida or to Alabama
06:25with that system. It went all the way south.
06:27Birmingham had record lows behind this storm. It was just incredible.
06:30Tides, record tides, I guess, and everything, too.
06:33It was a wild storm.
06:34It was.
06:35Well, you hinted at this next one. And I think just the nature of the explosive terminology
06:40really lends itself to the media conversation. Now, bomb cyclone.
06:44Yes.
06:45What are we talking about here?
06:46Hey, when we talk about a bomb cyclone, it could be a storm that's just not along the
06:50East Coast. It could be over land as well. We've seen storms happen and intensify over
06:56the plains states. For instance, I think back in 2019 in March, Colorado, they saw a huge
07:02storm blow off the front range, several feet of snow and wind.
07:06And also a lot of these are more common in the Northwest as well. They can see big storms
07:11come in onshore there as well.
07:13We're talking about rapidly falling pressures, intensification of a storm. Generally, the
07:19rule is 24 millibars in 24 hours and lots of wind.
07:23And they can also influence the patterns after the storm goes by. It's incredible, causing
07:29blocking patterns. So the bomb cyclone is, like it said, it's scary. It's a very rapidly
07:35intense storm that can produce a lot of precipitation in a short period of time.
07:39And they can occur, as you said, in many areas. In the autumn of 2024, we had one that doubled
07:44the threshold and it didn't even come onshore. It lurked off the Northwest Coast, but it
07:49kind of drew this atmospheric river event on the south side that hammered parts of California.
07:53And like I said, it can influence other patterns, other places, not just the area that's getting
07:59hit as well. They're massive. And again, 2018, January 3rd, 5th storm that hit up the East
08:05Coast. Again, this one actually produced snow all the way down to Florida. I remember that.
08:10That's impressive stuff.
08:11Yes.
08:12That's good. Well, and I know that when we get these huge storms that can dislodge the
08:15weather pattern or whatever, this is where you guys really shine in the long-range forecast
08:19department because they can have downstream impacts half a world away.
08:23You know, I remember this term. This term actually was created, I think, back in 1980
08:27by two scientists, Fred Sanders and John Geichem. I think, I can't remember his pronunciation.
08:33But in any case, as we went along in time, I think people thought we were kind of playing
08:38it up in the media, this bomb cyclone. But in reality, these storms have really caused
08:43a lot of damage and some scary things.
08:46And there are some naysayers and skeptics out there that they love to kind of play a
08:50certain role on social media and say, well, this is all just hype or nothing.
08:54But there is a true definition to it.
08:55There is.
08:56And there's something explosive about it. And that's how it got its name.
08:58Yes. And again, these systems kind of act all similar to nor'easters and blizzards.
09:05They all kind of interact in some way. But the one thing about the bomb cyclones are
09:10the rapid intensification. And they act like hurricanes, developing rapidly, hurricanes,
09:16but on land sometimes. And like I said, you can see them in the plains, the West Coast
09:20or the East Coast.
09:21We have a quick viewer question now, Paul. This one comes from David in Wisconsin. And
09:24he writes, one phrase I've heard more than a few times in the news is Alberta Clipper.
09:28So what's an Alberta Clipper and how does this impact weather during the winter?
09:31This is a system that generally generates in Alberta, Canada. It starts over the, gets
09:36momentum coming out of the Canadian Rockies and really heads towards the southeast, gets
09:41a little bit of moisture pulled out of the Gulf of Mexico and causes intense bands of
09:46snow in a short period of time over a small area, not a widespread area, but a narrow
09:51area.
09:52But they can get to the East Coast. And like I said, if the water temperatures are right,
09:56if they're warmer than average, those can also turn into nor'easters.
10:00All right. And in the interior, we get a lot of nickel and dime type storms out of there,
10:041 to 3, 2 to 4 inch snow events, but they can cause a lot of problems. And again, it's
10:08not about the amount of snow sometimes, it's the intensity that it can come in.
10:12And lengthwise can cover a lot, but what width? Very narrow areas usually with Alberta Clippers.
10:18Sometimes just several counties.
10:19Yes.
10:20All right. Well, we are just getting started in our conversation about winter weather jargon
10:23with Paul Pastelak and we have much more to come. Coming up a little later in WeatherWise,
10:27we're going to answer some popular weather myths, like can loud noises really trigger
10:32an avalanche?
10:33We'll let you know in our Is This Really a Thing? segment.
10:37And after the break, Paul is sticking around to break down more winter weather buzzwords,
10:41especially one we seem to hear a lot in recent winters, the polar vortex.
10:45We're also going to answer more of your viewer questions when Ask the Experts returns.
11:04Welcome back to AccuWeather's Ask the Experts. I'm Jeff Cornish.
11:07Today we are diving into some of those terms and phrases you hear when we talk about winter weather.
11:12We want to help you understand what they really mean as you try to navigate through the winter season.
11:17And back to talk with us about winter weather jargon again is AccuWeather lead long range forecaster
11:22and expert, Paul Pastelak. And Paul, we want to demystify some of these terms.
11:27We've been doing this here for the past 15 minutes or so.
11:30One of the bigger buzzwords when it comes to the winter season is the polar vortex.
11:37Yes.
11:38So you've done a lot of research on the polar vortex. Absolutely.
11:41How can you help us understand this better?
11:43The thing about the polar vortex that I think most people get wrong is that they feel when the polar vortex is strong,
11:51that that's the time that we're going to be impacted with some really, really tough weather in the mid-latitudes.
11:59And so the polar vortex is in a large area of low pressure that's centered over the polar region.
12:05And the stratosphere comes and goes for half the year.
12:09The lower part of the atmosphere, it's there all year round.
12:13When it's strong, the winds are counterclockwise and it holds a lot of the coldest air over the polar region.
12:21And so the mid-latitudes, lots of westerly flow, generally milder conditions, doesn't much happen.
12:27The systems are moving fast west to east.
12:29But when the polar vortex is weaker, that's when we start to see the exciting weather patterns shaping up.
12:36Cold air escapes and then parts of the globe end up getting hit with some extreme type of weather, cold, storms, whatever.
12:45And so it's when the polar vortex is at a weaker stage, that's when you have a better chance of getting some exciting weather.
12:52I think it's an important distinction here because it is counterintuitive.
12:55People expect colder to mean stronger, but it's a weakening of the polar vortex.
13:00It becomes a little more wobbly and sometimes a lobe of that may wobble over us, at least the tropospheric one.
13:06And there's two levels, two types of vortexes that we're talking about.
13:09The lower level that we live in is called the polar jet stream.
13:13That directly affects us as far as weather systems go.
13:16Then there's another level in the stratosphere called the upper level polar vortex.
13:21And that is harder to disrupt.
13:23And what that has to happen is a lot of energy has to go up, down and up to get that to warm the stratosphere.
13:32When you warm the stratosphere, you weaken the polar vortex.
13:36The winds start to ease back, it becomes wobbly.
13:39So energy that comes from down below and up top.
13:43And a lot of times that's a better shot of doing that in the spring rather than in the late winter.
13:48Spring is when we have more solar heating taking place.
13:51Because in the fall, we lose the solar heating in the northern hemisphere.
13:54And so you have a better shot of disrupting the polar vortex in the late winter season than the early winter season.
14:00And we can't really be hit by the polar vortex.
14:03You can't touch it.
14:04No.
14:05It's a little more ambiguous or a little more removed from where we actually live than that.
14:10Exactly.
14:11And again, it's one of those things where things have to come together as well.
14:15It doesn't mean that North America is always going to get hit with a cold air mass or the effects of the stratospheric displacement that takes place.
14:24And that's another thing, too.
14:26There's many types of things that happen to polar vortex.
14:28They could split.
14:29It could be displaced.
14:30It could be stretched.
14:31And it makes all different reactions in the weather department for that to happen.
14:36Then there's other teleconnection, things that all have to come together to force that cold wherever on the globe.
14:42It not always comes here.
14:43It can go on the other side.
14:44So, again, there's a lot of things that are involved with the polar vortex.
14:48Another winter weather term that's maybe a little bit less difficult to talk about is graupel.
14:54But it's one of those things that people sometimes see, but they don't quite know what to call it.
14:58So what is graupel?
14:59Well, graupel is interesting because of the fact that what's happening in the process is that the liquid is being super cooled.
15:07And as it does, it attaches itself to other particles like snowflakes and snow in the atmosphere.
15:14And so it kind of gets that kind of crumbly feeling to it when you touch it.
15:19That's basically what the formation is going on.
15:22Now, it may look like hail, but hail is harder.
15:25It's more solid when it comes down.
15:27Yes, you can take it and crumble it in your hands.
15:29So that's kind of the difference between hail and graupel.
15:33It may look like hail, but it's not.
15:34It reminds me a little bit of Dippin' Dots.
15:36Yes, exactly.
15:37I know that there's like a slang term called soft hail.
15:40But it is kind of, you know, it's not really soft hail, but it is kind of ambiguously like that.
15:46Wouldn't it be cool if you can colorize it in the atmosphere somehow?
15:49Add some flavor.
15:50Right.
15:51Well, it is time for another viewer question.
15:53We want to hear from Drew in Pennsylvania.
15:55Drew, what do you want to ask the experts?
15:58I've got a question about thundersnow.
16:00I've never experienced it, but I've seen videos online where it's occurred.
16:05Is it a rare occurrence?
16:07Does it happen often?
16:09All right.
16:10Good question there, Drew.
16:11So what do you think?
16:12Well, I mean, it's two separate things that come together.
16:16It's a term that, you know, you have thunder and you have snow.
16:20And what it is is basically you can get revved up.
16:25The air can rise very quickly, like it does in the spring,
16:29causes these strong cells that form inside, you know, a bigger playing field,
16:36and you can get convection called thunderstorms that do develop.
16:39And then it's so super cool that takes place on the backside in the wintertime
16:44that you can get any precipitation to stay all snow all the way down the ground,
16:47and the visibility can get down to less than half a mile most of the time with thunderstorms.
16:51It's amazing.
16:52We've seen these in big storms like the March 93 storm.
16:55We saw a lot of thunderstorm snow.
16:57It can happen.
16:58It does happen.
16:59People hear it.
17:00It's just basically just intensifying of the storm itself can produce these kind of events,
17:06and you can get three, four-inch-an-hour rates as far as the snowfall goes.
17:11And if you're tuned in, you're probably into the weather to some extent here,
17:15and it's a pretty exciting juxtaposition of a warm-season phenomenon
17:18that we usually associate with thunderstorms and snow,
17:21so it does get a lot of attention, and rightfully so.
17:23It does. It does.
17:24All right.
17:25Well, we really want to thank AccuWeather lead long-range expert and forecaster Paul Pastolak.
17:28Paul.
17:29Hey, thanks.
17:30Great stuff. We always appreciate your insight and all that you do here.
17:32He's the wizard when it comes to the long-range forecast.
17:35And don't forget, when you have a question about weather, space, or science,
17:39you can write us or send us a video question at asktheexperts at accuweather.com.
17:43You can also call us at 888-566-6606.
17:47And coming up soon, we've got answers to some popular weather myths,
17:51like can a loud noise really trigger an avalanche?
17:54Find out in our Is This Really a Thing? segment when we come back.
18:04It's now time for weather-wise in our segment Is This Really a Thing?
18:08First up, can noise trigger an avalanche? Is this really a thing?
18:12It's a popular myth that gunfire, shouting, or screaming,
18:16or lots of noise from any source can cause an avalanche.
18:19But as it turns out, it's really just a movie-perpetuated myth.
18:23It's not really a thing.
18:25So to put this in perspective, according to the Guinness Book of World Records,
18:28some 70,000 screaming Kansas City football fans at Arrowhead Stadium
18:33set a record back in 2014 for the loudest crowd roar at a stadium.
18:38And this was measured at over 140 decibels.
18:42Even that would not be enough to trigger an avalanche.
18:45So in comparison to tremendous amounts of noise, by a wide margin,
18:49a much less significant weight of people or animals traversing the mountainside
18:54creates a potentially deadly release of slabs of snow and ice
18:58in well over 90% of avalanche disasters.
19:01Next, what about the popular saying, no two snowflakes are alike?
19:05Is this really a thing?
19:07Well, it turns out that it really is a thing.
19:09Snow crystals are sensitive to temperature and dew point,
19:12and they're going to change shape as they bump into one another, falling to the ground.
19:16They're exposed to fluctuating temperatures at different levels of the atmosphere.
19:19So to have two snow crystals or flakes with precisely the same history of development
19:24is indeed virtually impossible, and therefore no two snowflakes are alike.
19:29That is a thing.
19:30Thanks so much for being with us here on AccuWeather's Ask the Experts.
19:33I'm Jeff Cornish.
19:35Whenever you have a question about weather, space, or science,
19:37you can write us or send us a video question at asktheexperts at accuweather.com.
19:41You can also call us at 888-566-6606.
19:46Thanks for being with us. Have a great one.