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Last winter had a strong and stable polar vortex like a robust doughnut, holding cold air in the Arctic regions.
Well... Stick a fork in winter for Eastern U.S this winter too.
The Vortex is on Steroids.
Can it still get Cold? Yes.
Can we have clippers and Snow at times? Yes.
Can we get persistent cold and snow? No.
The Vortex would have to start splitting up and weakening BEFORE mid January to save winter. If it does it in February than early Spring wont be Spring
One way it would split up is if the Stratosphere had a sudden warming event
A strong polar vortex usually means strong polar circulation even in the lower levels. This can usually lock the cold air into the Polar regions, creating milder winters for most of the United States and Europe.
On the other hand, a Polar Vortex collapse is just as dynamic as it sounds, sending higher pressure crashing from the stratosphere to the surface, releasing the colder air out of the polar regions, into the United States and/or Europe.
Typically, a polar vortex circulation collapses due to a rise in temperature and pressure in the stratosphere. That is called a Sudden Stratospheric Warming (SSW) event.
The strength of the polar vortex is most often measured by the power of the winds inside it. Usually, this is done is by measuring the zonal (west to east) wind speeds around the polar circle (60°N latitude). Below we have an ensemble forecast for the 10mb winds
Hmmm. So there could still be frigid temps with a strong Polar Vortex? I always thought it has to weaken and split.
Quote:
We find that the strength of the vortex significantly affects the behavior of the regimes. While a regime associated with Greenland blocking is strongly favored following weak vortex events, it is not the primary regime associated with a widespread, elevated risk of extreme cold in North America. Instead, we find that the regime most strongly associated with widespread extremely cold weather does not show a strong dependency on the strength of the lower stratospheric zonal mean zonal winds. We also suggest that stratospheric vortex morphology may be particularly important for cold air outbreaks during this regime
A 4th Stretched Vortex coming?! Lets come back to this post end of month and see if it verified with the results.
"Lather, rinse, repeat" or in terms of the Polar Vortex "strong, stretched, repeat." Are we in an uninterrupted feedback loop through the end of the winter and what are the implications for the weather? New blog is now public"
The big soap opera of the winter of if and when will the stratosphere-troposphere couple, has finally been answered affirmatively. The cold/negative polar cap geopotential height anomalies (PCHs) that have been omnipresent in the stratosphere have finally landed, descending all the way to the surface. The strong polar vortex and positive stratospheric AO have translated to the surface beginning the end of last week; as we observe a consistently positive AO and a predicted mild week across much of the US and Europe. The one exception this week is Central and East Asia. And as I have said earlier this winter, look towards Asia for hints of future atmospheric circulation and weather changes.
As I have been discussing in recent blogs the GFS was suggesting the fourth stretched PV of the winter and first for February during the second week of February and based on today’s GFS analysis and forecasts, it looks to be underway (you can see the stretched configuration to the PV in Figure 13a). As I have been doing of late in the blog, I also include the polar vortex animation (see Figure i) which shows what I believe is a stretched PV this week with cross polar flow from Siberia towards the Great Lakes and the Northeastern US. So though this will be a mild week in the Eastern US, in part related to the coupling of the cold/negative PCHs in the stratosphere to the surface, I do expect that the stretched PV this week will start to influence the temperatures in the Eastern US. And as is typical of stretched PV events, cold temperatures begin in Central and East Asia but finish in eastern North America. Therefore, the cold temperatures of East Asia this week are likely foreshadowing cold temperatures in Eastern Canada and the Eastern US next week.
Winter Weather patterns over the Northern Hemisphere are a combination of different drivers. New data and studies show that a larger October snow cover is also one of these drivers. It impacts the Polar Vortex more directly, thus potentially having a long-term effect on winter weather over the United States and Europe.
Fall weather can influence the Polar Vortex by building an extensive snow cover over Siberia. Multiple studies have proved that the snow cover extent in October over Siberia affects the weakening of the stratospheric polar vortex at a later period.
Looking at the graph above, we can take the top 5 snow cover years and compare the following winters to the lowest 5 snow cover years. Top 5 years with the highest October snow extent are 1976,2014,2016,2002, and1968. The years with the lowest October snow extent were 1988, 1987, 1980, 1991, and 1994.
In contrast, we have the winter pressure composite for the 5 winters following the highest Fall snow extent. You can see an almost opposite pattern: high pressure over the polar regions and disrupted circulation. Low-pressure areas span from the United States to Europe
From this, you can see that having a larger Fall snow extent can actually mean a colder Winter and more snowfall over the United States and Europe. So, having a large October snow extent should be on your bucket list if you are a colder winter weather fan
Literally the only one of those winters that was a 'good' winter for my tracking was 2016-17. I guess at this point, all I can hope for is that the snow cover brings something similar.
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