Winter is coming! But probably not in the way that you want it to. I guess this year it decided to come three weeks early and it looks like it's here to stay.
As many of you have probably heard by now, the "polar vortex" is coming and we're all going to freeze to death!
No, just kidding.
But this is how many media outlets are presenting the latest outlook for the period of mid-late November.
And it's a myth. It's a sensationalist fabrication of the journalist attempting to make a "newsworthy" story.
First, the "polar vortex" is not coming down from the Arctic. It didn't even technically come down "last winter" either. In reality, intense warming in the lower stratosphere, aided by a meridional polar jet stream caused the polar vortex to split, forcing the cold air southward on both sides of the hemisphere. It was a "piece" of the polar vortex, but it wasn't the "polar vortex" itself.
What's happening right now is the same thing.
Second, it isn't "comparable" to Hurricane Sandy or any other extreme event. The only thing "extreme" about it is that temperatures in the core of the Arctic air mass associated with it will be nearly three standard deviations below the mean temperature for this time of year. In other words, temperatures will be colder than approximately 99% of all recorded Novembers for many locations. It will definitely be cold and definitely close to historic in terms of longevity and intensity.
So, let me give a brief synopsis of what's happening, and what we expect to happen over the next few weeks.
Let's begin with looking at today's weather map. Right now, we have a sprawling low-pressure system centered in the Central Plains and quickly developing to the northeast. By late tonight, the surface low will become closed and quickly move eastward. By Tuesday night, the storm system will swing a polar front through the region, dropping temperatures into the upper 20's by early morning.
By Wednesday, a vast Canadian vortex will be centered to our north, pivoting multiple minor waves across the area at the same time. The vortex will keep the cold-air mass in place through the weekend. By Sunday, the general model consensus is that a slight moderation in temperatures will occur, as another wave of low pressure approaches from the west. While nothing major is anticipated, we could see a few snow showers and/or light snow during the day. Temperatures will likely be in the mid-upper 30's.
This is when major model discrepancies come into play. There are numerous variations between model solutions right now in terms of the strength, placement, and timing of another wave of Arctic air into the region. The only thing that is somewhat certain at this point is that temperatures will likely be colder than what they will be with the first wave of Arctic air. Models continue to contradict each other in terms of when this cold wave will make it to the area, how long it will last, and ultimately, how cold it will get. At this point, there's nothing much else I can say.
However, given current observations and trends in long-term indicators, it appears to me that a more prolonged period of Arctic air is likely. This is due to two significant factors:
1. Intense ridging across Alaska and far northwestern Canada will be nearly three standard deviations above normal, which indicates an incredibly strong ridge of high-pressure. This will likely cause an omega block to form, which will trap cold, Arctic air in most of the United States, especially east of the Continental Divide. Blocking across Greenland could become a major factor as well, depending upon the strength of the Scandinavian ridge that is expected to develop in response to the polar-vortex breakdown.
2. Snow-cover build up has accelerated once again across Canada and now across the Northern Plains and Upper Midwest [especially after the current snowstorm]. This will lessen any air mass modification that might occur over the next few weeks and help to lock the cold-air in. This will especially be the case if we see several more winter weather events in the next two weeks or so. Right now, I am monitoring the possibility for a possible snow-accumulation event occurring sometime next week, but the details are too uncertain to say much else.
As many of you have probably heard by now, the "polar vortex" is coming and we're all going to freeze to death!
No, just kidding.
But this is how many media outlets are presenting the latest outlook for the period of mid-late November.
And it's a myth. It's a sensationalist fabrication of the journalist attempting to make a "newsworthy" story.
First, the "polar vortex" is not coming down from the Arctic. It didn't even technically come down "last winter" either. In reality, intense warming in the lower stratosphere, aided by a meridional polar jet stream caused the polar vortex to split, forcing the cold air southward on both sides of the hemisphere. It was a "piece" of the polar vortex, but it wasn't the "polar vortex" itself.
What's happening right now is the same thing.
Second, it isn't "comparable" to Hurricane Sandy or any other extreme event. The only thing "extreme" about it is that temperatures in the core of the Arctic air mass associated with it will be nearly three standard deviations below the mean temperature for this time of year. In other words, temperatures will be colder than approximately 99% of all recorded Novembers for many locations. It will definitely be cold and definitely close to historic in terms of longevity and intensity.
So, let me give a brief synopsis of what's happening, and what we expect to happen over the next few weeks.
Let's begin with looking at today's weather map. Right now, we have a sprawling low-pressure system centered in the Central Plains and quickly developing to the northeast. By late tonight, the surface low will become closed and quickly move eastward. By Tuesday night, the storm system will swing a polar front through the region, dropping temperatures into the upper 20's by early morning.
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| WPC North American surface analysis |
By Wednesday, a vast Canadian vortex will be centered to our north, pivoting multiple minor waves across the area at the same time. The vortex will keep the cold-air mass in place through the weekend. By Sunday, the general model consensus is that a slight moderation in temperatures will occur, as another wave of low pressure approaches from the west. While nothing major is anticipated, we could see a few snow showers and/or light snow during the day. Temperatures will likely be in the mid-upper 30's.
This is when major model discrepancies come into play. There are numerous variations between model solutions right now in terms of the strength, placement, and timing of another wave of Arctic air into the region. The only thing that is somewhat certain at this point is that temperatures will likely be colder than what they will be with the first wave of Arctic air. Models continue to contradict each other in terms of when this cold wave will make it to the area, how long it will last, and ultimately, how cold it will get. At this point, there's nothing much else I can say.
However, given current observations and trends in long-term indicators, it appears to me that a more prolonged period of Arctic air is likely. This is due to two significant factors:
1. Intense ridging across Alaska and far northwestern Canada will be nearly three standard deviations above normal, which indicates an incredibly strong ridge of high-pressure. This will likely cause an omega block to form, which will trap cold, Arctic air in most of the United States, especially east of the Continental Divide. Blocking across Greenland could become a major factor as well, depending upon the strength of the Scandinavian ridge that is expected to develop in response to the polar-vortex breakdown.
2. Snow-cover build up has accelerated once again across Canada and now across the Northern Plains and Upper Midwest [especially after the current snowstorm]. This will lessen any air mass modification that might occur over the next few weeks and help to lock the cold-air in. This will especially be the case if we see several more winter weather events in the next two weeks or so. Right now, I am monitoring the possibility for a possible snow-accumulation event occurring sometime next week, but the details are too uncertain to say much else.
While I do not expect this wave of cold-air to last much longer than a week or two at the current time, it is possible that this colder-than-normal weather sticks around for Thanksgiving time. Given the fact that long-range meteorologists are even surprised at the magnitude of this event, it would not even surprise me if we see a significant winter weather event around the time of Thanksgiving.
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