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Severe weather preparedness: Tornadoes

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Do you recall learning about tornadoes in elementary school? I do. In Mississippi, we were taught the basics: tornadic storms form when warm, moist air from the Gulf of Mexico clashes with cold, dry air crossing the Rockies. That information was pretty accurate when my whole world consisted of the town in which I lived. Knowing what I know now, it wasn’t wrong, but it wasn’t totally right either.

Tornadoes can occur anywhere, which means the Gulf of Mexico and the Rocky Mountains are not required for their formation. What is required is a battle zone between two conflicting air masses. Warm, moist air and cooler, drier air are definitely needed. The bigger the difference between them, the stronger the frontal system.

Rotation in the atmosphere is also needed to spin up a twister. Not every strong cold front will spawn tornadic storms. All the right pieces have to be in place.

We’re still in the process of learning exactly why some storms with all the right ingredients will produce tornadoes and some will not. For the longest time, we thought they all reached down from the base of a supercell cloud. Last year, a study discerned that at least some tornadoes may form from the ground up. Each year brings new data and hopefully a better understanding of why twisters happen.

The good news is with each little increase in knowledge, we are getting better at forecasting potential severe weather days. It used to be that we couldn’t be very accurate more than three days in advance. Now, we can see the potential for severe weather up to eight days out. As with any forecast, the closer we get to the day of the storm, the more precise we can be about when and where the battle zone will be.

SPC 5-Day outlook

The Storm Prediction Center’s 5-day Outlook shows a 15% risk for severe weather in the highlighted region from Sunday morning through Monday morning (3/10-3/11/19)

Yesterday, while looking at the Storm Prediction Center website, I noted there was already a region highlighted with a 15% risk for severe weather five days out – Saturday morning through Sunday morning. The map wasn’t a surprise to me after having made the forecast for the weekend. I could see the setup for a strong frontal system to cross the Midwest and the south during that period. Seeing that risk highlighted was actually a small point of pride in our science. We’re getting better at this!

Today, the five-day outlook is for Sunday morning through Monday morning and shows a risk across the southeast. It makes sense given the forecasted movement of the same frontal system.

So, what does a 15% risk of severe weather across an area mean? It means that there is a 15% chance that a severe thunderstorm will occur within 25 miles of any point. So, at any one point, the risk is slight, but across a region that covers several states, it means someone is probably going to experience severe weather – possibly many someones.

Anyone within that highlighted area needs to be situationally aware with respect to changing weather conditions during that time period. Situational awareness means knowing where the storms are in relation to where you are. It also means thinking ahead about where you would take shelter if a severe storm, or worse – a tornado – hits your location.

Think ahead because in the middle of a crisis, there isn’t always time to think.

Whether we have five days of advanced notice or just 15 minutes to get to safety, being weather aware and situationally aware can make a world of difference when it comes to surviving the worst.

tornado safety

Graphic courtesy of North Carolina Emergency Management and the National Weather Service

Weather Blog

In like a snow leopard?

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The old adage about March weather is “In like a lion, out like a lamb.” Whether you use the climatological calendar on which spring begins on March 1 or the astronomical calendar on which spring begins on the equinox, March 20, it’s a month of transition. Wild swings in weather are expected in the mid-latitudes, where we live.

In central North Carolina, we are almost as likely to experience snow and ice storms through mid-March as warmth and thunderstorms. Our geographic location between the mountains and the Atlantic Ocean positions us perfectly for cold air damming events – when cold air from the north is trapped against the mountains and warm air from the ocean overruns it. Rain falling into the cold air near the surface freezes and creates icy situations.

We’re also in a good spot to experience coastal low-pressure systems running up our eastern shore and becoming nor’easters. Those tend to bring mixed precipitation events, too, if cold air is already in place or moves in quickly behind the storm.

It’s also possible in early March for the polar vortex to weaken enough to allow a blast of arctic air to shoot down this way. At this writing, it looks like that will be the case next week.

A cold front will cross the state Sunday, and the temperature will drop behind it. Any rain falling late Sunday night into early Monday morning may change over to or mix with snow. Accumulation shouldn’t be too much of a problem with milder temperatures in place this week and a rebound back into the 40s expected on Monday.

Cold air from the Arctic will pour into the eastern half of the nation behind the front and bring much cooler-than-normal temperatures to the region through most of next week. For reference, the 30-year average high temperature at RDU International Airport for today is 59 degrees. In contrast, the GFS forecast model is predicting our high temperatures will not surpass the 40s after the cold front passes on Sunday until the cold air finally retreats next Saturday.

Regular readers of this blog know that I have trust issues with forecasts that go beyond four or five days because the errors in the models compound quite a bit that far out. However, this cold snap has been pretty well forecast by some of the more trusted long-range prognosticators for the last couple of weeks. Now that the time period is getting closer, the models seem to be coming into agreement. I think this one will verify as truth.

So, this year, March will come in like a snow leopard, or an Arctic wolf. Pick your favorite cold climate predator. Only time will tell if it will go out like a lamb.

cpc map

The Climate Prediction Center’s 6-10 day temperature outlook map shows very good chances of below normal temperatures for most of the country next week.

Weather Blog

Rain, runoff, and our part in the water cycle

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As of 6:30 this morning, I’ve had more than two inches of rain over the last nine days in my CoCoRaHS gauge. My front yard has become a pond – a normal occurrence during wet periods as I’ve learned over the exceedingly rainy past year. Part of my little triangular plot of land backs up to a farm field, which sits a couple feet higher than mine. Excess water from the field creates miniature waterfalls across the property line and floods my yard. Because of a slight hill in advance of the drainage ditch in the front yard, the water has no place to go. So, it sits. Sometimes for days. I joke with my friends that I’m going to teach my black cat to snorkel out there.

rain report

The author’s rain gauge report for the Community Collaborative Rain, Hail & Snow Network (CoCoRaHS) showing her daily rain totals for the last 9 days.

When I watch the little rivers of runoff coming down from the field, I wonder what nutrients or pollutants are coming with it. To be sure, there must at least be fertilizer and possibly pesticides. In a way I’m glad the water stops there and doesn’t run down the ditch and into the closest stream which flows into the closest river, which isn’t far from my house. My front yard is serving as a filter. Sure, it’s a mucky mess to look at after days of rain, but it’s actually serving a higher purpose.

Rain is typically clean when it falls.

We poetically say it washes away the dirt, pollen, and grime of the world, and it does. What most people rarely consider, though, is to where it washes the dirt, pollen, grime and pollutants.

We learned in elementary school that part of the water cycle includes the rainwater draining into streams which run into rivers which lead to the oceans. In a perfect world, by the time the rainwater reaches the ocean, it should be clean again. Unfortunately, our world is rarely perfect.

From cigarette butts discarded from a car window to drink containers dropped by a carefree child, trash ends up on the ground. In urban areas, when the rain comes, the refuse is carried to storm drains. From the storm drains, it makes its way into streams – possibly even streams nobody remembers exist – and from the streams into the rivers, and so on.

Rocks, soil, and plants along the water’s route help to filter out small pollutants including fertilizer and pesticides caught in the runoff. Some of the larger trash may end up on the shoreline. Still, plenty continues to float downstream.

Beyond aesthetics, one huge reason to not litter – and even to pick up litter that isn’t yours – is to protect our water.

It’s too easy to wave off someone else’s trash as disgusting without doing anything about it. After all, it’s not ours. Why should we clean up after someone else? I agree that we shouldn’t have to. Unfortunately, that’s not how the world works. Pollution happens, and we can’t just ignore it because we didn’t have a hand in causing it.

So, what can we do?

On my property, I pick up the trash people lazily throw out of their car windows. (Who said living in the country guaranteed a clean environment?) When I visit the beach, I take two plastic bags on my morning walks: one for special seashells and one for trash. Sadly, the seashell bag usually ends up full of trash, too. It’s not my trash and it’s not my beach, but it is my planet. I take ownership.

As we head toward spring, local community volunteer and government organizations will start posting stream clean-up dates. If you want to make a difference in just a few hours, pick a date (or multiple dates) and join the effort. It’s easy. I’ve done it. You meet new people and get some exercise in the process of helping to divert garbage from our water supply.

You could even take it a step further and form a group to adopt a stream within the city of Raleigh. If you’re not in the Raleigh area, check with your local government. It may have a similar program. The state of North Carolina also has a program called NC Stream Watch. Its website explains ways to get involved including trash pickup, water source tracking, and submitting photos of the waterway.

Grab some friends or make new ones, set a good example for the children in your life, and get involved.

It’s your world. Take ownership!

Weather Blog

Confidence levels in forecasting

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This weekend’s weather will be unsettled – meaning we’re in an active pattern that will bring clouds, showers and swings in temperature. That much I’m sure of. Sunday’s forecast carries a little less certainty, though, which is why I have low confidence in the forecast.

I’ve written before about what the word “confidence” means when it comes to forecasting, but the idea is worth revisiting since we have such a great example this weekend.

When the computer models meteorologists use to forecast the weather are in total agreement, it’s easy to have high confidence in a forecast. Generally, that scenario happens in a quiet, relatively simple weather pattern. The more complicated the pattern and the more dynamic the atmosphere, the less the models tend to agree, especially when looking more than 48 to 72 hours out.

Sometimes, the difference between the models is only in how high or low the temperature will go. Other times, it’s how much or little precipitation will fall. One model may call for sunny skies and the other shows 90% cloud coverage most of the day. When these differences occur, the forecaster has some decisions to make. Which model seems to be the most believable based on how it has handled recent similar situations? Which one seems to be seeing everything that is currently happening at the moment the forecaster is viewing them?

A skilled, experienced forecaster has a better chance of getting the forecast right in these situations because experience is often the key differentiator. For example, someone who has lived in the Triangle area for a long time will be more likely to spot the kind of forecast-busting, cold air damming-like situation that could happen on Sunday.

As of this writing on Wednesday morning, the Global Forecasting System (GFS) model is showing a cold, cloudy, rainy Sunday, at least through the afternoon. With light breezes from the east and overcast skies, showers are possible. The high temperature may not even make it to the low 40s by afternoon. It’s also showing that the temperature may jump quickly from around 40 degrees into the lower 50s between 7:00 PM and 10:00 PM as a warm front passes and the winds turn from easterly to southerly. If that scenario plays out, our high temperature for the day will happen during the late evening hours.

On the other hand, the European model is showing slower progression of the warm front moving up from South Carolina through the day. By midnight, Wake County may still only be in the mid 40s, and the area from Fayetteville south could be in the low 50s.

The difference between these two models may not seem that great, but when forecasting a high temperature for the 24-hour period of midnight Sunday morning to midnight Monday morning, the timing of that front can make a huge difference. With the GFS solution, the high temperature for Sunday could be about 55 degrees and occur close to midnight Sunday night. With the European model’s solution, the high may only be about 46 degrees.

After so many of us experienced forecasters were burned on Tuesday with that day’s warm front stalling out in the southern part of the state, it’s hard to buy into the warmer solution. Because I know from more distant past experience that when moist wind from the east butts up against our mountains to the west, it’s hard to break down the cold air that gets trapped at the surface, I went with the cooler solution in my weekend forecast this morning.

How confident am I? If I had to give it a number on a scale of one to ten with ten being absolution sure, I’d say I’m at a six. For me, that’s low confidence. I prefer to be at an eight or higher when putting a forecast in print.

As Sunday gets closer, the models should start to agree more. This morning’s model runs were already getting closer than yesterday morning’s. It will be interesting to see how Sunday plays out. One thing I can say with certainty is that if the day turns out warmer than I predicted, that’s one forecast I don’t mind busting.

GFS map

Map credit: College of Dupage Next Generation Weather Lab. This map shows the GFS model’s temperature forecast for late Sunday night. Notice the temperature at Raleigh-Durham International Airport is expected to be 55 degrees at that time.

 

Euro map

Map credit: weather.us. This map shows the European model’s temperature forecast for midnight Sunday night. Notice the temperature range in Wake County will be in the mid to upper 40s.

Weather Blog

Winter isn’t over

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Disagreeing with a groundhog is not a popular thing to do, especially when the little rodent predicts an early spring just a few days after a brutal Arctic blast the way Punxsutawney Phil did on Saturday. However, I’ve never really been concerned about popularity, and I prefer my weather forecasts grounded in science as opposed to random rodent lore.

While you can definitely count this week’s weather as spring-like, it’s just part of the natural roller coaster ride that is central North Carolina winter. Our geographic location allows us to experience wild swings between unseasonable warmups and bitter Arctic cold, which is a blessing and a curse depending on whom you ask. Personally, I count the warmups as a blessing, but I recognize that snow lovers aren’t fans.

The temperatures will trend back toward normal this weekend with morning lows in the 30s and afternoon highs in the lower 50s. By mid-February, it looks like we could see the polar vortex weaken again and allow another Arctic air mass to head our way.

We can expect the moderate peaks and dramatic valleys so common with the roller coaster through at least early March, and that wavy nature of our winter temperatures really is normal. Anyone who has lived here for more than a few years will recall 70-plus degree days in January and February and ice storms in early March.

I’ll allow Phil fans to claim victory this week if they really feel the need because it won’t be long before Mother Nature brings them back to reality.

February 2018 temp graph

Graph credit: weather.gov. This graph shows the range of daily temperatures recorded in February 2018 at RDU International Airport. Notice the ups and downs from day to day with some afternoon highs in the 40s and others in the 70s.

Weather Blog

Lessons learned from Puerto Rico

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I’ve written before about how humans are good at adapting and figuring out ways to mitigate risk with respect to climate change and weather extremes. That theme echoed throughout my days at the National Meeting of the American Meteorological Society in Phoenix earlier this month.

While some of the talks focused just on the latest research studies of what is changing and where with respect to climate, there were many about the lessons learned so far from specific case studies and extreme storms. I attended many of those presentations.

One in particular explained how Puerto Rico is still dealing with the aftermath of Hurricane Maria. Ada Monzon is one of my new heroes. Until I attended the conference, I had never heard of this passionate and brilliant broadcast meteorologist. She lives and works in Puerto Rico, and she told us what the island has learned from Maria’s devastating landfall.

A few of her key points:

  • Nearly everyone on the island has post-traumatic stress disorder from the storm.
  • Homes and roads still need a lot of work. Many homes are not safe, especially with respect to weathering another hurricane.
  • Energy and communications have been restored, but the energy grid is still fragile and the energy infrastructure needs to be completely rethought.
  • Of the almost 3,000 deaths blamed on the storm, less than 10% were directly caused by Maria; the rest were due to the loss of electricity – especially in hospitals – and access to care.
  • Puerto Rico can’t handle another hurricane right now. Landslides and coastal erosion are still to this day ongoing problems.

Since the storm hit in 2017, Monzon has changed the way she presents the forecast during the news broadcasts because she has to be careful about the tone and terms she uses because the people respond emotionally now. So, she focuses on hope and education, and she makes sure that she gives information that is as specific and useful as possible.

Her personal goal is to teach the people of the island to be self-sufficient. Monzon talks to them about sustainability, health, and well-being. To that end, she founded a pop-up science museum that she says will soon have a permanent location. She has developed the Resilient School Program that uses STEM activities to build resilience and empower kids. She has introduced Community Emergency Response Team (CERT) training for teens, and her group has built a network of weather stations with 4K cameras.

Many of the inspired ideas Monzon has implemented are things we on the mainland could – and probably should – copy. She stated emphatically, “Kids are resilient!” and she’s right. Teach them what they need to know to help themselves, their families and their neighbors survive a natural disaster. Educate them about the basics of risk mitigation on a level they can understand, so they start thinking about it early in life. Show them technology that can aid in communication after a disaster disrupts the cell towers and landlines – short wave radio – so that if and when a disaster damages their world, they understand they are not totally helpless. That sense of empowerment brings hope, not just to them, but to their communities.

Satellite of Maria

Credit: NOAA. The GOES-16 satellite image shows Hurricane Maria as it crossed Puerto Rico and destroyed much of the island’s infrastructure, electric grid, homes, and businesses.

Weather Blog

Weather geeks unite!

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What happens when you put almost 4,000 meteorologists, climatologists, social scientists, and data miners in one convention center? People talk about the weather, of course!

Last week was the 99th Annual Meeting of the American Meteorological Society, and for the first time in over a decade, I attended. The size of the meeting was overwhelming to say the least. With dozens of conferences and symposia embedded within the larger meeting, there was no shortage of options to choose from. Some were technical, getting into the minutia of radar, satellites, programming and coding. Others were discussions about how to effectively communicate confidence or lack thereof in a forecast, risk to different subsections of the public, and what we know and don’t know about climate change.

With the partial government shutdown in place, there were fewer attendees this year. Many who work for the EPA, NOAA and NASA were unable to travel. That situation led to several talks being canceled because the speakers and moderators worked for those federal agencies. For example, I was disappointed to learn that one keynote speech was canceled because Administrator of NASA Jim Bridenstine, who was the speaker, could not attend.

While our cohorts and the education and information they would have imparted were certainly missed, there was still an abundance of insight and wisdom to be gained. I spent most of my time in the sessions focused on education, communication, and risk mitigation. I rubbed elbows with broadcast meteorologists, federal employees (who were willing to foot their own travel bills), and employees of private industries – all of whom were trying to improve their understanding of current scientific knowledge and share their professional experiences in the field.

In future posts, I’ll share some of what I gleaned from my trip. For now, suffice it to say that there are thousands of people from around the world who traveled to Phoenix, Arizona, to spend nearly a week talking about the weather, how it affects everyone, and what we can do to keep lives and property safe.

Weather Blog

Oh, the pressure!

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(Originally written for Allen Publishing’s print products published on January 3, 2019)

 

Meteorologists talk about barometric pressure or atmospheric pressure when explaining the forecast. We use the terms “low pressure” and “high pressure” to describe the causes for different types of weather. We throw around terms like millibars as if everyone understands what we’re talking about, but do they? Not necessarily.

So, what is pressure in weather terms?

If pressure in general is the force exerted on a unit area, then atmospheric pressure is the force exerted by the atmosphere on a specific area. We use the term barometric pressure almost interchangeably with atmospheric pressure because we use barometers to measure atmospheric pressure.

There are different types of barometers and units used to quantify pressure. The two most common units are inches of mercury and millibars (mb). In a mercury barometer, a column of mercury is used to physically show the amount of pressure on the column. The column will expand or shrink dependent upon the pressure exerted on it by the air surrounding it. The measurement is taken in inches of mercury. Measured this way, the global average air pressure at the surface of the earth is 29.92 inches of mercury.

Millibars are used more often by meteorologists. They are the lines typically seen on weather maps of sea level pressure. It’s not really a metric system unit, although it would be easy to assume that’s the case since in most other situations, the two most common units are based on the British and metric systems. In fact, mercury barometers can give their readings in millimeters of mercury, so they are the metric system version as well as the British system version of pressure reading.

Instead, a millibar is a pressure unit of 1,000 dynes per square centimeter, which is an old way of measuring pressure. Millibars are convenient for reporting atmospheric pressure despite the fact that you don’t see it used for much else. Measured this way, the global average air pressure at the surface of the earth is 1013.25 mb.

When the atmosphere exerts more force per area, we call the pressure “high.” When it exerts less, we call the pressure “low.” Often during the winter, high pressure systems in the mid-latitudes will exert pressure in the 1030 mb to 1040+ mb range. Low pressure systems crossing the continent can bring pressure in the range around 990 mb. By contrast, at her peak intensity, Hurricane Florence’s pressure was measured at 939 mb.

Atmospheric pressure plays a huge role in our weather. High pressure brings clear skies because the air is sinking to ground level. Low pressure brings unsettled weather – possibly even stormy – because the air is rising, which creates clouds and rain. The area directly under the center of a high-pressure system often has calm or very light winds. The area between a system of high pressure and one of low pressure can be quite breezy because the air wants to move from high pressure to low pressure. The closer the two systems are to one another, the windier it is.

In the Northern Hemisphere, the winds around a high-pressure system flow in a clockwise direction away from the center, and the winds around a low-pressure system go counter-clockwise toward the center. Remember, the air wants to go toward where the pressure is lower.

The movement of these systems determines the hour-to-hour and day-to-day forecasts for any given location. They bring our weather.

One thing to note: for this discussion, I’m writing about the weather and the pressure at the earth’s surface. Meteorologists also consider the air pressure at different levels above the ground, which is why you sometimes hear us mentioning an upper level or mid-level low bringing a change in the forecast.

map example of pressure

Credit: National Weather Service. The blue H on the map represents the center of high pressure. The red L represents the center of low pressure. Winds rotate clockwise and outward from the high pressure center and counter-clockwise and inward toward the center of low pressure.

Weather Blog

2018’s notable weather

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(Originally written for Allen Publishing’s print products on January 10, 2019)

The weather word for 2018 across much of North Carolina was “wet.” In fact, records for the wettest year on record fell one after the other in the last few weeks of the year.

According to my count on the Southeast Regional Climate Center’s CLIMPER tool, which maps data recorded at official and coop weather stations, 24 locations – excluding duplicate reporting stations such as Greensboro area versus the Greensboro airport – broke records for the wettest year on record.

2018 reord rainfal map

Credit: Southeast Regional Climate Center. Map showing cities and towns in the region with record-breaking or near record-breaking precipitation in 2018.

Raleigh-Durham International Airport recorded 60.29 inches of precipitation, which made 2018 its wettest year in the 74 years reports have been made at that station. Other record-breakers included Wilmington with 102.4 inches, New Bern with 79.18 inches, Greensboro with 64.11 inches, and Asheville with 79.49 inches.

Hurricanes Florence and Michael certainly assisted in reaching those milestones. However, anyone who tried to get yardwork done on the weekends can tell you more often than not, those plans were rained out, or at the very least soggy. In fact, the majority of the weekends in 2018 produced reported rainfall across the state.

Another record that fell at RDU International back in January was the most consecutive hours at or below 32 degrees when we hit 158, surpassing the record of 157 set in 1982. We spent the first 7 days of the year at or below freezing. The snow and ice that fell during a winter storm lingered in some areas for a week as the temperature struggled to get warm enough to make a difference.

RDU temp plot for January 2018

Credit: National Weather Service. RDU temperature plot for January 2018 showing a stretch of extremely cold weather that month.

Across the country, there was another trend in 2018 worth noting. Only this time, it was due to a lack of something happening. For the first time since 1950, there were no tornadoes rated EF-4 or EF-5 reported anywhere in the United States. Ironically, the same day I read that headline was the day I saw an abstract for a research letter entitled “Increasingly powerful tornadoes in the United States.” To be fair, the article reported on a study of the period 1994-2016.

Much of the country experienced a late winter/early spring with unusually cold weather, which limited tornado activity during what is usually the peak season for Tornado Alley. Of course, tornadoes don’t have to be highly rated on the Enhanced Fujita scale to be deadly. Ten people died as a result of tornadoes in 2018. While much lower than average, the number still represents tragic loss.

With last year behind us, we can now look ahead to 2019 and speculate on what the weather will bring. Perhaps an abnormally cold late January due to the weakening of the polar vortex? Possibly a few more inches of wintry precipitation? Or maybe a more active tornado season? Only time will tell for sure.

Weather Blog

What weather will the new year bring?

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(Note: This was written on December 20th for the December 27th Wake Weekly and Butner-Creedmoor News due to early deadlines.)

 

December started with a bang as far as the weather was concerned. Colder-than-normal temperatures and frozen precipitation hinted at a long cold winter to come. Thankfully, this week is milder, and a short stretch of dry days is giving our soggy yards a chance to recover. So, what’s next? What will the rest of the winter be like?

As of this writing, all signs point to the rest of December being in the normal range, which means high in the lower 50s and lows in the lower 30s. Of course, there may be a colder or warmer day embedded in the next week, but on average, the forecast looks… well… average.

January doesn’t look as promising for those of us who prefer the milder weather. I’ve been following several long-range forecasters over the past few weeks. Based on the global patterns that affect the weather across the United States, it looks like most of the country, including the east coast, will be plunged into below-normal temperatures.

One of the things forecasters watch is called the Madden-Julian Oscillation, and it’s a complicated thing to explain. The gist of it is by watching where thunderstorms are firing over the Indian Ocean and western equatorial Pacific Ocean, meteorologists can make an educated guess at what the U.S. will experience about 14 to 15 days later.

The most famous pattern long-range forecasters consider is the El Nino/Southern Oscillation (ENSO) in the eastern equatorial Pacific. Warmer-than-normal sea surface temperatures in this area signal an El Nino year. Cooler-than-normal sea surface temperatures signal a La Nina year. When the temperature falls somewhere in between, it’s called ENSO neutral. As of this month, it looks like we should be experiencing an El Nino winter, but the air circulation patterns that normal accompany the warmer-than-normal sea surface temperatures have been slow to show up.

There is also an Arctic Oscillation, which affects the weather and climate on an annual to decadal scale. It’s not very well understood yet, so researchers are studying it in earnest. So far, it appears that a warmer Arctic region during the winter causes a weakening of the polar vortex, which leads to changes in the jet stream and causes winter storms to dip farther into the southern U.S.

These are just three of the factors that seasonal forecasters consider when predicting the weather for weeks to months out. Right now, they seem to be adding up to a cold and potentially stormy January.

I’ll add my usual disclaimer about long-range forecasts here: There are still so many factors that go into creating the weather we don’t fully understand or know how to reliably account for in computer models that it’s quite possible even the most trusted seasonal prognosticators could be wrong. Only time will tell.