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00:00Welcome to AccuWeather's Ask the Experts, I'm Jeff Cornish.
00:15We go beyond the forecast to give you the how and why on all the cool and interesting
00:19things you've wondered about and wanted to ask in weather, space and science.
00:24In the Northeast, the transition from winter to summer does not come quietly or with a
00:28slow steady pace.
00:30Wild temperature swings often take us from the 60s to wet snow, but gradually the tide
00:34of summer warmth wins out and it is this building warmth in the late spring and early summer
00:39that gradually fuels some of the region's most intense severe weather.
00:43He can also introduce some health and safety hazards as well.
00:46One man who has experienced all of this is meteorologist and long time leader at AccuWeather,
00:50AccuWeather Senior Vice President Evan Myers.
00:52Evan, thanks so much for making time for us today.
00:55Jeff, absolutely, but I always love these introductions.
00:57You talk about how, you know, basically, you don't say it, but you mean how old I am.
01:02So that's, I'm not sure how to take that.
01:05That's good.
01:06When Senior and Vice President are together, there's something there.
01:10Okay.
01:11I hear you.
01:12It's respect.
01:13It's nothing but respect.
01:14Right.
01:15Well, we want to get into this in weather forecasting.
01:17You've been doing this for a long time.
01:18Yes.
01:19We always want to recognize weather patterns that lead to extremes long before they happen.
01:23We want to provide the best forecast possible, do better than the models as well.
01:27And what are some signals that often flag things like record spring warmth in the Northeast?
01:33Well, it's kind of interesting.
01:34There you go.
01:35You go right to the warm weather, which is the thing that this time of the year folks
01:39are really interested in because they've had enough of winter.
01:41That's true.
01:42It's been cold long enough.
01:43There's been enough snow.
01:44There's been enough of any of that stuff.
01:46And so they want to know.
01:47And so what a meteorologist, as you say, what do we look for?
01:50Well, we look for a jet stream that's pulling northward up toward Canada and bringing and allowing
01:57for that void south of where that jet stream is to be filled by warmer air, more humid air out of the Gulf of Mexico, southern regions.
02:06But you don't really get the warm weather without the jet stream dipping southward somewhere else,
02:13because out ahead of that that dip is where you have that void I was talking about.
02:17But you have to have the jet stream pulling the warm air from somewhere.
02:21So it's got to be far enough south in some parts of the country to tap into that and then shoot it northward
02:27and into the northeastern states like we're talking about for the most part today.
02:30And also, I guess, we're going to talk about the Great Lakes a little bit, too.
02:33Sure.
02:33And we want to do better than the computer models.
02:35They're a helpful part of the forecast process.
02:37They are.
02:38But if we can consistently beat them, we can provide the best forecast out there.
02:43And there are some biases and sometimes some thumbprints of model error tied to this.
02:47So how can we outsmart the models in these weather patterns?
02:49You know, it's kind of interesting when you think about it, because it's one thing I've been talking about for,
02:54believe it or not, decades about how the computer models don't catch certain changes in the patterns and the trends.
03:00And you wonder why don't they if humans are aware of these things and humans make the models.
03:06And I don't really have a good answer for you.
03:09The other thing is that as we see perhaps some cuts in federal budgets,
03:13I'm not sure we're going to be able to look and tweak those things in the immediate future.
03:17But some of the things we look for, what do we look for?
03:20So this time of the year, in the springtime, first of all, the trees don't have very many leaves on them.
03:26And so that canopy of leaves in the summertime does act as a barrier, as an insulator to some extent,
03:34to keep the heat from pounding itself, the sun pounding itself on the surface of the ground,
03:40because heat radiates off the ground.
03:43And so therefore, if you have a lot of trees, you have a lot of leaves, you're not going to get the sun directly heating the ground.
03:51But in the springtime, you don't have as many leaves.
03:53And also, it tends to be somewhat drier.
03:55The grass is not fully green.
03:58There is moisture in that grass when it's all fully greened up and you get a little bit later in the spring.
04:05So you don't have the moisture, which actually causes temperatures to take their time heating up,
04:11because the sun's energy goes into evaporation.
04:15And you don't have the leaves that are kind of blocking some of the sun's energy.
04:19The sun just hits the ground and bakes it away.
04:22So that's one thing that really doesn't seem to be built into the models in the springtime, but should be.
04:28So when you see that jet stream pull northward and a strong southerly wind flow,
04:33usually that means that we can outsmart the models.
04:36And it gets warmer than the models indicate it's going to be.
04:39It's a pretty exciting time, too.
04:41There's, as you mentioned, high demand for that in the spring.
04:44And if we look at a difference in temperature kind of in a different context,
04:47without elevation playing a huge role, why is springtime the season
04:51when we get the greatest temperature contrasts in the northeast?
04:55Well, interesting, a lot of that occurs from what we would call a backdoor cold front.
04:59And the reason is that the ocean water temperatures are the coolest, really, of the year,
05:05because they've been cooling all winter long.
05:08And in the springtime, they're at their coldest point, believe it or not.
05:11Not in the middle of winter then. It's called seasonal lag.
05:14The warmest the ocean water temperatures are usually is in September for the same reason.
05:18So you have all this cool air sitting, all this cool water.
05:22And when the air passes over it, the cool water cools the air.
05:26So it gets pretty cool.
05:28Cool temperatures, cool air is much more dense.
05:31It's heavier than warm air. Warm air doesn't retreat.
05:35Cold air pushes it out of the way because it's much more dense.
05:38And so oftentimes that'll come in right in off the Atlantic Ocean and reach pretty far back.
05:45Places like New York City, obviously near the coast, even Philadelphia, which is, what, 70 miles, 60 miles inland.
05:51It reaches there. It can reach back into Baltimore and Washington, even into central Pennsylvania.
05:56With that backdoor cold front, it's called a backdoor front because usually cold fronts come from the northwest or the west.
06:02And this comes from the east or the northeast.
06:04And how do subtle shifts in the wind sometimes make a huge difference?
06:09There are certain cities where a lot of people live.
06:11And, you know, the report card might be the airport or the downtown temperature or something like that.
06:15Absolutely.
06:16Boston's tricky. Subtle shift in the wind, you can do really well or it can really go downhill fast.
06:20Well, and it's because of that, what we just talked about.
06:22You know, it's interesting because the same thing happens in Chicago.
06:25You know, people talk about how cold it is in Wrigley Field.
06:28But if you're in the western, because Wrigley Field is right near Lake Michigan, which is also cold from the winter.
06:33And in the springtime, you get the wind blowing off Lake Michigan and it cools it off.
06:37But you can go in the western suburbs.
06:39It can be 90 degrees in the western suburbs of Chicago.
06:43And it could be in the 50s at Wrigley Field.
06:46And people are like, what's going on here?
06:47It's all this micro, very localized climate that is caused by those temperature contrasts.
06:53And the water is actually cooling down the air, the Lake Michigan, the Atlantic Ocean.
06:59It happens in lots of places where the bodies of water are chilly.
07:02And on a broader scale, how do some of our bigger springtime, late spring severe weather outbreaks occur?
07:08Well, so we get thunderstorms, severe weather, and usually the most severe weather occurs in the springtime.
07:16And why is that?
07:17Well, at the surface, down where we all are, we get that warmer air that's coming up out of the south, out of Mexico, out of the Gulf of Mexico.
07:24That's already happening because the days are longer down there this time of the year, certainly.
07:30And so you get the buildup of heat.
07:32But yet, especially in the middle and upper reaches of the atmosphere, it's still cold from the leftover winter.
07:38It lags in the upper atmosphere like it does in bodies of water.
07:42And so you have a much greater contrast from the level of the ground where we are to the higher atmosphere.
07:48And the more temperature contrast you have, the greater difference in thermodynamics.
07:53We and I talked about that when we were talking about hurricanes.
07:57The greater difference that you have in temperature, the more instability you have and the ability you have for thunderstorms to form.
08:04So that's why in the springtime, it's way more likely.
08:07And it's interesting as the center of those severe thunderstorms start in the south Texas, the southern Mississippi Valley.
08:14But the frequency actually moves northward as things warm up.
08:18And so the frequency moves in the late spring into the northern plain states, the Dakotas, Nebraska, places like that is where the highest frequency is,
08:26as opposed to further south in the early part of the spring.
08:29Yeah, that jet stream, you can count on it.
08:32Every year it's going to migrate north and things get a little quieter near the Gulf Coast, at least for big types of your weather.
08:36Absolutely.
08:37So you lose that temperature contrast.
08:39But you also need that jet stream to inject some of the wind and some of the dynamics as far as the twist in the upper parts of the atmosphere to help some of that lift,
08:50to get the parcels of air to go up into the atmosphere and cool down and cause those storms.
08:56Yeah.
08:57Well, we want to get to our first viewer question here, Evan.
08:59How can gardeners prevent themselves from being fooled by early warmth?
09:03When is it actually safe to plant?
09:05Aha.
09:06Well, that's interesting.
09:07And I say aha is because it depends.
09:09In some ways, it's almost personal preference.
09:11So some people say, well, after the average date of the first freeze, it's okay to plant.
09:17The problem is that's an average date.
09:19And I don't go by the first freeze or the last freeze, rather.
09:24I go by the average date of the last frost because if tender vegetation, tomato plants, for example, things like that,
09:32you've got to watch out for the fact that even if the low temperature only drops to maybe 34 or 35,
09:40right at the surface, it could be a few degrees colder and you get a frost to form or you get it to form on the plants and that's deadly.
09:47So the best thing to do is to check out when that average date is and then wait maybe either as well.
09:53I do a week or two past that.
09:55The other thing is plant things like peas, which can take a frost, whereas tomato plants, you can't do that.
10:03You know, they'll die off.
10:04So really take a look at the things you're planting and take a look at those average dates of first freeze, rather last freeze, last frost, and go with that too.
10:14And we often kind of land on 36 degrees is something close to the final frost producing cold night.
10:19Exactly.
10:20Great conversation so far, Evan.
10:22We're going to have much more coming right up here.
10:24And coming up a little later in weather wise, we'll explore one type of severe weather event that's often found near the edge of a late spring or summer heat dome.
10:33Highly destructive to ratios.
10:35But up next, we'll continue our conversation about the Northeast wild warm season weather as we transition to the summer heat.
10:41How can it be dangerous and what can you do to keep yourself protected?
10:44Welcome back to AccuWeather's Ask the Experts.
11:07I'm Jeff Cornish.
11:08We're talking about the wild warm season weather in the Northeast and that transition from spring into the summer.
11:13And back with us again to give us more insight is AccuWeather Senior Vice President Evan Myers.
11:18And earlier, Evan, we were talking about the spring warmth and severe weather behavior into the summer months.
11:23And that does kind of land us into the hottest time of the year.
11:26So how does extreme heat set the table for volatile weather?
11:29Well, it's kind of interesting because it means you have even greater contrast, not only from the surface of the upper atmosphere, which is what we talked about a few minutes ago, but over distance and time.
11:41So you get cold air that's moving rapidly into warm air.
11:46At the same time, you have a lot of spin in the atmosphere.
11:48So that cold air is being pushed by the jet stream moving and changing with changing with its speed with height.
11:57And so you have basically what's a vortices occurring in the upper atmosphere.
12:02You have that much greater contrast.
12:04And that helps actually spawn that change with as you go up in the atmosphere with over over time and space.
12:11And so that that's one of the reasons why in the in the spring you have that much greater contrast in the fall.
12:18You don't have the same contrast because in the upper atmosphere, it's not as cold.
12:21It takes, you know, till you get to midwinter to get almost as cold as it is in the spring as you go up 18,000 feet or so and above.
12:29So that's one of the reasons why in the spring you have that that opportunity to have a lot more severe weather.
12:35And we're in the business of informing the public so they can stay as safe as possible and take action and and be safe.
12:41A lot of the time, you know, we show compelling video of tornadoes, damaging winds and flooding and so forth.
12:46But sometimes the deceptive dangers in life, they certainly include those things.
12:50But extremes in temperature may not be as visually compelling.
12:54They can be very dangerous.
12:55They can indeed.
12:56You know, it's interesting.
12:57You and I were talking about this a couple of weeks ago.
13:00I was down for a wedding in Florida, northern Florida, and it was in the 80s, the low 80s.
13:06And the humidity wasn't hot, but it seemed hot.
13:08Well, why was that?
13:09Because we were coming.
13:10My wife and I were coming from the north and it had been in the 50s.
13:14And just that big temperature contrast, if it was the middle of the summertime and our bodies had gotten used to it,
13:20I don't think, I think we would have felt very comfortable.
13:23But that's what happens.
13:24It takes, just like if you exercise.
13:26If you hadn't exercised at all and you go out and start running sprints, you're going to pull some muscles.
13:31And so if you haven't become used to warm weather and you go outside, it's going to put a lot more stress on your body than if your body has become used to it.
13:40And you're also used to coping with it better because you've been doing it for a number of weeks or months.
13:45So you drink more fluids and those types of things stay in the shade more.
13:49If there is in the spring, there isn't as much shade.
13:52So when it first turns warm, your body is under a lot of stress.
13:55And that happens even more.
13:57It becomes exacerbated even more in the springtime when you're just not used to it.
14:01Of course, in the height of summer, when you get real extreme temperatures, it turns very deadly for a lot of folks.
14:08And we've seen some heat waves.
14:10Notably, I think the one in Chicago in, I think it was 1995, almost 1,000 people died directly as a result of the heat wave.
14:18But probably many more did because of health-related things that occurred after that.
14:23And there could be a cumulative effect.
14:25If you can't cool your place down in the middle of the night, in the early morning, it just builds day after day.
14:30And I think that was the problem with some of that.
14:32We've also had extreme heat in the Northwest in recent years.
14:35Yes, indeed.
14:36With offshore winds, and we don't have air conditioning in many spots there.
14:38Right, places that don't have that kind of air conditioning.
14:40And, you know, dating myself again, but before the advent of air conditioning in the Northeast, for example, in a lot of places,
14:48people tried to do things, you know, they would fill up their bathtub with cold water and sit in it.
14:53They'll cool off.
14:54They would find a place, they'd go to the movies if they could.
14:57Sure.
14:58And not everybody could do that.
14:59And so open the windows more.
15:01But if it stayed really warm at night in that great Chicago heat wave in 1995, even though there was certainly a lot of air conditioning,
15:09the temperatures oftentimes didn't drop much below 90.
15:12Well, it's not going to cool off very much if that's the case.
15:16And so then the next morning, obviously, the temperatures were off to the races.
15:20And it doesn't really give your body an opportunity to cool down at all.
15:24Are there any memorable Northeast heat waves or maybe even before that predate us that jump out to you in history?
15:31In 1911, we had a tremendous wave.
15:33Yes.
15:34There was a great heat wave in 1911 in the whole Northeast.
15:38I've seen some depictions, maybe not some photos, but of folks in New York City in some of the tenements,
15:46opening the windows and sleeping out on fire escapes or on roofs and places like that.
15:51Any place they could to try to escape the heat, try to sleep in a park on grass, things like that.
15:57There's all kinds of ways that folks have tried to cope with that.
16:00Obviously, the advent of air conditioning has not only made that a little more healthy,
16:04but has allowed some of our cities in the southern part of the country in the southwest to explode in populations.
16:11Well, we want to get to another viewer question here.
16:13And this one comes to us from Sam in New York.
16:16Sam writes, how are we improving our resilience to heat and what are other cities doing?
16:21What are cities doing to mitigate the problem?
16:23Well, the idea of resilience to heat is some of it is getting getting more used to it,
16:27being being more aware of medical things like hydrating yourself and, you know,
16:32not to stop if you're doing something and getting overheated.
16:35But a lot of cities have gone to try to green up their cities to provide more trees, more grass,
16:41things like that that will help lower the temperature.
16:45Over time, if you look, there's something called the urban heat island effect.
16:49And you have all the concrete, all the macadam.
16:51You have all the buildings that are heating up even faster than a lawn would be with all that grass.
16:59And so it's actually hotter in the cities just because of the concrete and the streets and so on
17:05than it would be out on the countryside even a few miles away.
17:09So a lot of cities are starting to move to kind of green up some of their highways
17:13and really encourage folks to plant more trees, things like that that might help that.
17:18All right.
17:19Pretty fascinating stuff.
17:20Well, we do want to thank AccuWeather Senior Vice President Evan Myers for joining us today.
17:24Evan, thanks again for making time.
17:25My pleasure. All the time, anytime.
17:27Well, we appreciate talking to you and it's, you know, you have a wealth of knowledge.
17:30You've been doing this for a long time.
17:31And coming up next in WeatherWise, we're taking a look at the danger of deratios.
17:41We break down some of the most destructive deratio events of the past 20 years.
18:05Welcome back.
18:06It is now time for WeatherWise.
18:07And today we look at powerful storms called deratios.
18:10While a tornado is a rotating column of air, a deratio is a fast-moving straight-line storm
18:15with wind speeds of at least 58 miles per hour and often much stronger wind gusts
18:19that can create damage in a path extending more than 400 miles.
18:23So here are three of the most intense deratios in recent memory.
18:27June 29, 2012, beginning in Illinois, a powerful deratio raced southeast all the way into Virginia.
18:33Oh, my God!
18:34Wind gusts top 90 miles an hour, toppling trees, tearing off roofs, and leaving millions without power for days.
18:39Tragically, 22 lives were lost with many deaths linked to falling trees and heat-related illnesses in the wake of widespread outages.
18:49Eight years later, another menacing deratio impacted the Midwest on August 10, 2020.
18:54While Iowa was hit the hardest, it swept through parts of Illinois, Wisconsin, Indiana, and Ohio, with damaging winds and embedded tornadoes causing a path of destruction across more than 700 miles.
19:06Augustan, Iowa was measured at a staggering 140 miles per hour, flattening homes and leveling more than 10 million acres of crops.
19:13The storm caused billions in damages and left four people dead, making it one of the most destructive deratios ever recorded in the United States.
19:21Most recently, on May 16, 2024, a violent deratio ripped through downtown Houston, Texas.
19:28Windows were blown out of skyscrapers and wind gusts reached 100 miles per hour, comparable to a strong hurricane.
19:34The storm knocked out power to over a million customers, downed thousands of trees, and tragically claimed seven lives.
19:41Thank you for joining us here on AccuWeather's Ask the Experts.
19:43I'm Jeff Cornish.
19:44Remember, when you have a question about weather, space, or science, you can email us at asktheexperts at accuweather.com.
19:51.