Hello and welcome to the 2020-21 Southern Connecticut Weather Winter Forecast!
Introduction
It’s that time of the year again! Fall is winding down and meteorological winter, which begins on December 1 and lasts until the end of February, is just about here. That means it is time for the SCW Winter Forecast. Our forecast is based on the major factors that influence the synoptic (large-scale) pattern and the weather in our backyard. As we’ve found among our readers, there is a sharp divide between those that like a cold and snowy winter and those that prefer the opposite!
This forecast will examine the key elements that will determine the progression, length, and severity of winter 2020-21. We weigh these elements differently to develop our final forecast. Below you will see our analysis for each.
Now, before we begin, we must add a caveat. It’s hard to forecast ten days out let alone three months. There are a number of winter outlooks and each, including ours, should be taken with a grain of salt. There are always parts that will be wrong. This is our somewhat educated guess as to what will unfold this winter. Let’s hope our final grade is an A!
Methodology
When all is said and done, our final grade will rise and fall on these factors below. Each figure differently in our overall thoughts.
Introduction
It’s that time of the year again! Fall is winding down and meteorological winter, which begins on December 1 and lasts until the end of February, is just about here. That means it is time for the SCW Winter Forecast. Our forecast is based on the major factors that influence the synoptic (large-scale) pattern and the weather in our backyard. As we’ve found among our readers, there is a sharp divide between those that like a cold and snowy winter and those that prefer the opposite!
This forecast will examine the key elements that will determine the progression, length, and severity of winter 2020-21. We weigh these elements differently to develop our final forecast. Below you will see our analysis for each.
Now, before we begin, we must add a caveat. It’s hard to forecast ten days out let alone three months. There are a number of winter outlooks and each, including ours, should be taken with a grain of salt. There are always parts that will be wrong. This is our somewhat educated guess as to what will unfold this winter. Let’s hope our final grade is an A!
Methodology
When all is said and done, our final grade will rise and fall on these factors below. Each figure differently in our overall thoughts.
- Seasonal models (10%): These models are longer range versions of some of the global models we use for short-range forecasting. Here, we look at their composite averages. They have a little skill, but have several distinct biases. We’re not looking at them that much.
- Analogs (10%): We look at past years that have similarities to this year, whether it be conditions observed during the fall, ENSO state, teleconnections, or previous winters.
- ENSO (35%): ENSO stands for the El Nino Southern Oscillation, and it represents water temperatures in the central and eastern equatorial pacific. El Nino represents warmer than normal temperatures, and La Nina represents cooler than normal water temperatures. These phases have distinct and outsized impacts upon the larger-scale pattern, and as a result on our sensible weather.
- Teleconnections (30%): There are many indices measuring current conditions in different parts of the world, from upper level features to regional ocean temperatures. We will discuss the major drivers in the Atlantic and Pacific, and explain what their current and forecast states mean for our weather.
- Current conditions (10%): This time of year, some parts of the upper level pattern have a strong correlation to what the default weather pattern is during the winter months. We take a look at that here.
Seasonal Models
Let’s take a look at the seasonal models. There are four of them; the Euro seasonal, the JAMSTEC, the CanSIPS, and the CFS.
A note on how the seasonal models work. Essentially, they attempt to model the upcoming months in much the same way that the midrange global models attempt to model the upcoming forecast period, that is, start with a set of initial observations and apply some physics package to those observations to make future forecasts for the next period on some interval. Then, that forecast is fed back into the model as the initial observations for the next period to be created off of, and so on.
As you can imagine, small inaccuracies in initial data or calculations grow exponentially as the recursive cycle continues, and as a result, global models, especially the seasonal ones, are notoriously inaccurate, hence our relatively low weight of them compared to other factors. They are still worth considering and looking at, as what they show (and don’t show) can be valuable when taken in the right context.
First, let’s take a look at the CFS. Here are temperature and precipitation departures from normal on the CFS for December, January, and February, courtesy of weathermodels.com.
December
Let’s take a look at the seasonal models. There are four of them; the Euro seasonal, the JAMSTEC, the CanSIPS, and the CFS.
A note on how the seasonal models work. Essentially, they attempt to model the upcoming months in much the same way that the midrange global models attempt to model the upcoming forecast period, that is, start with a set of initial observations and apply some physics package to those observations to make future forecasts for the next period on some interval. Then, that forecast is fed back into the model as the initial observations for the next period to be created off of, and so on.
As you can imagine, small inaccuracies in initial data or calculations grow exponentially as the recursive cycle continues, and as a result, global models, especially the seasonal ones, are notoriously inaccurate, hence our relatively low weight of them compared to other factors. They are still worth considering and looking at, as what they show (and don’t show) can be valuable when taken in the right context.
First, let’s take a look at the CFS. Here are temperature and precipitation departures from normal on the CFS for December, January, and February, courtesy of weathermodels.com.
December
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January
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February
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The CFS advertises an active winter in Connecticut, with above normal temps to start off winter in December and cooling to near normal by February. It also has above-average precipitation all three months, which we’ll see is a recurring theme across some of the other seasonal models.
Next, here’s the Canadian CANSIPS.
Next, here’s the Canadian CANSIPS.
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The CANSIPS advertises a classic La Nina gradient pattern, with warmer and drier conditions to the south and cooler and wetter conditions in the north. However, the dividing line for both is far to our north, and we are firmly in the warm/dry band on the model. On a monthly basis, December and January are near to slightly above normal precipitation whereas February is very dry, which is also very common in a La Nina where we often see an early start and an early end to winter. Temps are above normal in all three months, with January forecast as the warmest month.
Next, let’s go across the Pacific and look at the Japanese JAMSTEC model.
Next, let’s go across the Pacific and look at the Japanese JAMSTEC model.
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A very similar story to the CFS, and once again showing the classic gradient pattern of a La Nina, at least with the temperature distribution. The gradient is further south here so we are a little bit cooler than on the CFS and much cooler than on the CANSIPS, but still would probably see above normal temperatures. We’d see above normal precipitation as well.
Finally, let’s look at the Euro seasonal.
Finally, let’s look at the Euro seasonal.
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Once again, above normal for temperatures, and near normal for precipitation. We see some semblance of a gradient pattern when it comes to temps, but the Euro is the warmest of the seasonal models to our north.
Blending these together, it’s clear that the consensus is for above normal temperatures across the state. All four seasonal models show colder air remaining up in Canada for the duration of the winter and most of the US being flooded with milder Pacific air. While it’s not uncommon to see this gradient pattern set up in a La Nina, typically, one would see the gradient further south, where the northern tier of the US is in the cooler than average temps as well. If you believe the seasonal models, that doesn’t seem to be the case this year. Normally we wouldn’t put a ton of stock in them, but we have been seeing a similar pattern throughout the fall so far – primarily warmer days mixed in with a few shots of below normal temperatures. It’s not unreasonable to expect that will persist as we move into the winter.
That’s not to say that we won’t have cold shots – in fact, we suspect that we’ll see a fair amount of volatility this winter as the gradient shifts back and forth and brings quick shots of colder air with it, but on the whole, it’s clear that the forecast from the seasonal models is for above normal temps.
Precipitation is more uncertain, with two models having above normal precipitation (JAMSTEC and CFS), one normal (Euro) and one below normal (CANSIPS). Traditionally, the wettest anomalies will be along the temperature gradient from above normal to below normal as storms track along the boundary, and with the temp boundary to our north, one might think the storm track would be less active. However, the models that are suggesting above normal precipitation are implying a pattern with many “cutter” storms, where lows pass to our west and put us into the warm sector, bringing warm temps and heavy rain.
We’ve seen this pattern develop at times this fall where we see warm and wet systems, and it’s likely that the models are seeing this continue into the winter. All in all, the seasonal models point to near normal to slightly above normal precipitation, but with a lot of volatility and low confidence.
Overall summary of the seasonal models: Above average temperatures and slightly above average precipitation.
Blending these together, it’s clear that the consensus is for above normal temperatures across the state. All four seasonal models show colder air remaining up in Canada for the duration of the winter and most of the US being flooded with milder Pacific air. While it’s not uncommon to see this gradient pattern set up in a La Nina, typically, one would see the gradient further south, where the northern tier of the US is in the cooler than average temps as well. If you believe the seasonal models, that doesn’t seem to be the case this year. Normally we wouldn’t put a ton of stock in them, but we have been seeing a similar pattern throughout the fall so far – primarily warmer days mixed in with a few shots of below normal temperatures. It’s not unreasonable to expect that will persist as we move into the winter.
That’s not to say that we won’t have cold shots – in fact, we suspect that we’ll see a fair amount of volatility this winter as the gradient shifts back and forth and brings quick shots of colder air with it, but on the whole, it’s clear that the forecast from the seasonal models is for above normal temps.
Precipitation is more uncertain, with two models having above normal precipitation (JAMSTEC and CFS), one normal (Euro) and one below normal (CANSIPS). Traditionally, the wettest anomalies will be along the temperature gradient from above normal to below normal as storms track along the boundary, and with the temp boundary to our north, one might think the storm track would be less active. However, the models that are suggesting above normal precipitation are implying a pattern with many “cutter” storms, where lows pass to our west and put us into the warm sector, bringing warm temps and heavy rain.
We’ve seen this pattern develop at times this fall where we see warm and wet systems, and it’s likely that the models are seeing this continue into the winter. All in all, the seasonal models point to near normal to slightly above normal precipitation, but with a lot of volatility and low confidence.
Overall summary of the seasonal models: Above average temperatures and slightly above average precipitation.
Analogs
Each day, the CPC produces a list of analogs that match the upper air patterns over the US. We look for frequent matches and seasons that correlate to what we’ve seen so far as we approach winter, and also use our own observations of the pattern to determine strong analogs. We’ve identified four seasons that share characteristics to this fall: 1995-1996, 2005-2006, 2008-2009, and 2016-2017. The latter two are the closest, so we weigh them doubly compared to the first two.
Seasonal Composites
When you combine all of those analogs, you get seasonal composites that look like this.
Each day, the CPC produces a list of analogs that match the upper air patterns over the US. We look for frequent matches and seasons that correlate to what we’ve seen so far as we approach winter, and also use our own observations of the pattern to determine strong analogs. We’ve identified four seasons that share characteristics to this fall: 1995-1996, 2005-2006, 2008-2009, and 2016-2017. The latter two are the closest, so we weigh them doubly compared to the first two.
Seasonal Composites
When you combine all of those analogs, you get seasonal composites that look like this.
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Looking at the analogs, we see a fairly classic La Nina gradient pattern for temperatures, with the coolest anomalies in the northwest and warmer air in the south. Connecticut avoids the warmest anomalies but is still about a degree above normal on average throughout the winter.
For precipitation, normal to slightly above normal is shown, with a concentration of wetter anomalies to our west and drier anomalies to our south. This suggests a potential lack of large coastal storms, with the pattern instead favoring “cutters” that pass to our west up into the great lakes before finally moving northeast past our latitude.
These tend to be warm and wet storms for Connecticut. However, there’s also a suggestion for “clipper” type storms given that there is a string of wetter anomalies at around the same latitude from us west to the lakes and even up into Minnesota – the classic storm track for a clipper. These smaller systems can occasionally re-develop into coastal storms (known as “Miller B’s” vs the traditional “Miller A” that comes slowly up the coastline from the Gulf of Mexico) once they hit the Atlantic. This re-development often occurs just south of our area, and, when timed right, can take advantage of a blocking pattern to produce snow. Our suspicion is that if we see a large snowstorm this winter, it will be from this sort of setup.
When looking at the monthly breakdowns, things start to differ a bit. Here they are for temperature and precipitation.
Monthly Breakdowns
December
For precipitation, normal to slightly above normal is shown, with a concentration of wetter anomalies to our west and drier anomalies to our south. This suggests a potential lack of large coastal storms, with the pattern instead favoring “cutters” that pass to our west up into the great lakes before finally moving northeast past our latitude.
These tend to be warm and wet storms for Connecticut. However, there’s also a suggestion for “clipper” type storms given that there is a string of wetter anomalies at around the same latitude from us west to the lakes and even up into Minnesota – the classic storm track for a clipper. These smaller systems can occasionally re-develop into coastal storms (known as “Miller B’s” vs the traditional “Miller A” that comes slowly up the coastline from the Gulf of Mexico) once they hit the Atlantic. This re-development often occurs just south of our area, and, when timed right, can take advantage of a blocking pattern to produce snow. Our suspicion is that if we see a large snowstorm this winter, it will be from this sort of setup.
When looking at the monthly breakdowns, things start to differ a bit. Here they are for temperature and precipitation.
Monthly Breakdowns
December
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January
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February
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The analogs suggest a quick start and a quick end to winter, with below normal temps and above normal precipitation for December giving way to a warmer and wet January and warmer and drier February. That said, given that January is our coldest month on average, it can still snow in an overall above average pattern.
Overall, the analogs support the idea of a slightly warmer than average winter with about average precipitation. They suggest an active start to the season before moderating in the back half of the winter, but there will likely still be chances for wintery weather through at least January.
Overall Summary of the Analogs: Above normal temperatures and normal precipitation.
ENSO
ENSO is the big driver of global weather patterns. The significant shift to La Nina conditions helped drive one of the most active Atlantic hurricane seasons on record. As of the mid-November ENSO update by the Climate Prediction Center, La Nina conditions are present and have an approximately 95% chance of continuing through winter. In fact, La Nina conditions may persist into the spring, as there is currently a 65% forecast of that happening.
Overall, the analogs support the idea of a slightly warmer than average winter with about average precipitation. They suggest an active start to the season before moderating in the back half of the winter, but there will likely still be chances for wintery weather through at least January.
Overall Summary of the Analogs: Above normal temperatures and normal precipitation.
ENSO
ENSO is the big driver of global weather patterns. The significant shift to La Nina conditions helped drive one of the most active Atlantic hurricane seasons on record. As of the mid-November ENSO update by the Climate Prediction Center, La Nina conditions are present and have an approximately 95% chance of continuing through winter. In fact, La Nina conditions may persist into the spring, as there is currently a 65% forecast of that happening.
Above, you can see the scale of the La Nina so far. As mentioned earlier, a Nina shifts storm tracks further to the north and west, meaning that we are flooded with warm air as a storm approaches, and flooded with warmer air in general as the jet stream stays to the north more often. One thing to keep in mind here is that the strength of an El Nino or La Nina matters quite a bit too. A strong Nina makes it less likely that we stay on track with normal snowfall or temperatures. We will need to monitor the ENSO strength into the winter, but this is looking like a moderate (most likely) to strong Nina event looking at the guidance predictions of ENSO.
Because this could be a moderate event, we think that unlike past years ENSO will factor in quite a bit more. This should have an impact on teleconnections, as we will describe in the next section, and result in a warmer storm track, more East Coast and southeast ridging, and a much smaller period where traditionally wintry conditions are likely to happen. In keeping with La Nina events, we are likely to see more wintry conditions in the first half of the season, followed by what effectively becomes a quick end to winter. One caveat here is if the Nina is weakening by the end of February and into March, we could see a secondary (albeit small) window for wintry conditions in March. That’s up in the air though. Given how our last few winters have seen wintry conditions...and some of the “bigger” snowfall events in March, we’re going to leave that door slightly ajar in making this forecast.
Overall Summary of ENSO: Above normal temperatures, normal precipitation, and below normal snowfall.
Teleconnections
The thing you will hear most about during the winter season will be teleconnections. If you’re looking for a short to medium range signal to what the winter potential is, this is it, as teleconnections are essentially the elements of the upper level pattern that determine the orientation of the Jet Stream, location of coldest temperatures, and the activity level (storminess) in the flow.
These indices measure current conditions at certain placements in the atmosphere, most commonly, the presence of a ridge or a trough. In New England, we place heavy attention to four major teleconnectors--the AO and NAO in the Atlantic, and the PNA and EPO in the Pacific.
Arctic Oscillation (AO)
First, the Arctic Oscillation, or AO. This is an index measuring pressure anomalies in the Arctic, and is strongly correlated with temperatures in our area for the winter months. A positive phase of the AO consists of below average geopotential heights. A negative phase consists of the opposite. In a negative phase of the AO, the polar vortex over the Arctic is weaker, resulting in weaker upper level winds that make it easier for Arctic air to penetrate further south. Another result is a further south storm track. With a positive AO, the opposite is true. Stronger upper level winds keep the polar vortex in check, making it less likely for deep cold air intrusions and ideal storm tracks. This year, the polar vortex (PV) looks very strong, though there are a few signals that it could weaken in the coming weeks. This likely means that it will be more difficult, on balance, to get big and long lasting intrusions of colder than normal air, if the PV stays strong. Even then, that doesn’t mean it won’t be cold at all, it just means that overall things are looking milder unless there is a significant event that weakens the polar vortex.
Below is an image showing what a strong AO looks like. The image is merely illustrative, but note how the heights are well below average in the polar region. That’s a warm period.
Overall Summary of ENSO: Above normal temperatures, normal precipitation, and below normal snowfall.
Teleconnections
The thing you will hear most about during the winter season will be teleconnections. If you’re looking for a short to medium range signal to what the winter potential is, this is it, as teleconnections are essentially the elements of the upper level pattern that determine the orientation of the Jet Stream, location of coldest temperatures, and the activity level (storminess) in the flow.
These indices measure current conditions at certain placements in the atmosphere, most commonly, the presence of a ridge or a trough. In New England, we place heavy attention to four major teleconnectors--the AO and NAO in the Atlantic, and the PNA and EPO in the Pacific.
Arctic Oscillation (AO)
First, the Arctic Oscillation, or AO. This is an index measuring pressure anomalies in the Arctic, and is strongly correlated with temperatures in our area for the winter months. A positive phase of the AO consists of below average geopotential heights. A negative phase consists of the opposite. In a negative phase of the AO, the polar vortex over the Arctic is weaker, resulting in weaker upper level winds that make it easier for Arctic air to penetrate further south. Another result is a further south storm track. With a positive AO, the opposite is true. Stronger upper level winds keep the polar vortex in check, making it less likely for deep cold air intrusions and ideal storm tracks. This year, the polar vortex (PV) looks very strong, though there are a few signals that it could weaken in the coming weeks. This likely means that it will be more difficult, on balance, to get big and long lasting intrusions of colder than normal air, if the PV stays strong. Even then, that doesn’t mean it won’t be cold at all, it just means that overall things are looking milder unless there is a significant event that weakens the polar vortex.
Below is an image showing what a strong AO looks like. The image is merely illustrative, but note how the heights are well below average in the polar region. That’s a warm period.
North Atlantic Oscillation (NAO)
The NAO is the North Atlantic Oscillation, and is a close relative of the AO. Here, forecasters look at two pressure centers in the Atlantic--an area of low pressure near Iceland, and a high pressure system near the Azores. Generally, during the winter we’re paying close attention to heights around Iceland. The strength and exact placement of these features tend to have a significant impact on the placement of the jet stream--absolutely critical for cold air placement and storm track in tandem. During a negative phase, we see higher heights over the Iceland area, and below average heights over the western Atlantic and (usually) the eastern US. The opposite generally occurs with a +NAO, which means more progressive tracks and more warmer storm tracks.
While a persistently negative NAO is not necessary for a cold and snowy winter, having a -NAO, even if transient, can be a major factor in producing some of our biggest winter weather events, as a -NAO usually implies more blocking is available, while a +NAO represents a faster pattern with less room for storms to amplify. Further complicating matters is the position of the heights. A west based -NAO is more likely to produce a cold and stormy period than an east based -NAO. A persistent -NAO is far less likely this year given the general ENSO state and strength of the polar vortex region. However, there is an increasing chance we see a negative NAO in December and perhaps a more neutral regime into January. That would certainly not hurt for those on the cold and snowy train.
Again, here's a historical look at a negative NAO from 1966.
The NAO is the North Atlantic Oscillation, and is a close relative of the AO. Here, forecasters look at two pressure centers in the Atlantic--an area of low pressure near Iceland, and a high pressure system near the Azores. Generally, during the winter we’re paying close attention to heights around Iceland. The strength and exact placement of these features tend to have a significant impact on the placement of the jet stream--absolutely critical for cold air placement and storm track in tandem. During a negative phase, we see higher heights over the Iceland area, and below average heights over the western Atlantic and (usually) the eastern US. The opposite generally occurs with a +NAO, which means more progressive tracks and more warmer storm tracks.
While a persistently negative NAO is not necessary for a cold and snowy winter, having a -NAO, even if transient, can be a major factor in producing some of our biggest winter weather events, as a -NAO usually implies more blocking is available, while a +NAO represents a faster pattern with less room for storms to amplify. Further complicating matters is the position of the heights. A west based -NAO is more likely to produce a cold and stormy period than an east based -NAO. A persistent -NAO is far less likely this year given the general ENSO state and strength of the polar vortex region. However, there is an increasing chance we see a negative NAO in December and perhaps a more neutral regime into January. That would certainly not hurt for those on the cold and snowy train.
Again, here's a historical look at a negative NAO from 1966.
Pacific/North American Pattern (PNA)
Although a lot of attention is often given to the Atlantic and NAO, the pattern in the Pacific is vital to determining the course of a Connecticut winter. The PNA is one of the most important teleconnectors, with a significant influence over North America. A positive PNA phase occurs when there are higher heights over the Pacific and western US. This correlates to ridging over the western US and a trough (transporting colder air) over the eastern US. In a negative phase, the opposite occurs.
The position of the western ridge matters quite a bit. Too far west and storms can cut to our west, bringing rainy systems or nothing at all. Too far east and storm tracks could develop too far offshore to bring significant precipitation events. While there is less likely to be a favorable Atlantic pattern, there are some mixed signals on what happens in the Pacific, especially early. We think that there will be a window for a more favorable winter pattern that is driven by the Pacific, most likely in the early to mid winter period consistent with ENSO. Then, we think the door will all but close, pleasing winter haters across Connecticut.
Although a lot of attention is often given to the Atlantic and NAO, the pattern in the Pacific is vital to determining the course of a Connecticut winter. The PNA is one of the most important teleconnectors, with a significant influence over North America. A positive PNA phase occurs when there are higher heights over the Pacific and western US. This correlates to ridging over the western US and a trough (transporting colder air) over the eastern US. In a negative phase, the opposite occurs.
The position of the western ridge matters quite a bit. Too far west and storms can cut to our west, bringing rainy systems or nothing at all. Too far east and storm tracks could develop too far offshore to bring significant precipitation events. While there is less likely to be a favorable Atlantic pattern, there are some mixed signals on what happens in the Pacific, especially early. We think that there will be a window for a more favorable winter pattern that is driven by the Pacific, most likely in the early to mid winter period consistent with ENSO. Then, we think the door will all but close, pleasing winter haters across Connecticut.
East Pacific Oscillation (EPO)
Finally, we have the East Pacific Oscillation, or EPO. The EPO is a major driver in allowing Canada to develop cold air that feeds into the US, or shutting off any mechanism to deliver cold to much of Canada or the US. Here, we’re looking at heights over the northeast Pacific and Alaska. Higher heights over this region brings warmer than normal weather over that region, but it serves up an almost ideal mechanism for cold air delivery in the continental US, as a resulting Arctic high in northwest Canada and trough over the US work in tandem to funnel cold into the region. At times, we can see as sprawling enough -EPO to develop what is called “cross-polar flow”. This is the extreme cold that comes straight from the polar region without much moderation.
On the other hand, with a positive EPO phase, we (potentially) see the worst of what winter can offer if you like cold and snow. In a +EPO, we get a persistent low (vortex) in the northeast Pacific and Alaska, which creates favorable conditions for the dreaded PAC jet to inundate Canada and much of the continental US with warm Pacific air. If you have this kind of pattern persist, you can almost guarantee little cold and snow.
Here's a look at the positive and negative phases of the EPO and their effects on our sensible weather.
Finally, we have the East Pacific Oscillation, or EPO. The EPO is a major driver in allowing Canada to develop cold air that feeds into the US, or shutting off any mechanism to deliver cold to much of Canada or the US. Here, we’re looking at heights over the northeast Pacific and Alaska. Higher heights over this region brings warmer than normal weather over that region, but it serves up an almost ideal mechanism for cold air delivery in the continental US, as a resulting Arctic high in northwest Canada and trough over the US work in tandem to funnel cold into the region. At times, we can see as sprawling enough -EPO to develop what is called “cross-polar flow”. This is the extreme cold that comes straight from the polar region without much moderation.
On the other hand, with a positive EPO phase, we (potentially) see the worst of what winter can offer if you like cold and snow. In a +EPO, we get a persistent low (vortex) in the northeast Pacific and Alaska, which creates favorable conditions for the dreaded PAC jet to inundate Canada and much of the continental US with warm Pacific air. If you have this kind of pattern persist, you can almost guarantee little cold and snow.
Here's a look at the positive and negative phases of the EPO and their effects on our sensible weather.
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Overall, we anticipate that the teleconnection pattern will provide a 4-6 week window for the bulk of our colder and snowier winter. This pattern is likely to begin flipping in early December, but really take hold between mid-December and mid January. However, after this period it looks like the Pacific may shut down, bringing a quick flip to warmer and less snowy conditions into February and potentially the first half of March.
Overall summary of the teleconnections: Above normal temperatures and normal precipitation.
Overall summary of the teleconnections: Above normal temperatures and normal precipitation.
Current Conditions
In the past we looked at snow cover across Siberia to help determine the longer term forecast. Not this year because we don’t think the data is there for a meaningful correlation.
Here, we’re looking at the current upper level pattern heading into December, as there seems to be a fairly strong correlation between the upper level pattern, especially in the Pacific, and the default pattern during the winter season. Of course, this doesn’t always work. Last year we saw a roaring start to winter, with a favorable pattern and above normal snowfall that flipped and never returned. So we’re looking at this, but with wary eyes.
The signal has been all over the place for much of November. Just a few days ago, it looked like we would see a Pacific pattern setup that would all but torch much of the US as the month of December begins. Since then, we’ve seen a slow but steady retreat from that idea on the guidance and reversal to a good pattern. That doesn’t mean that we’re going to cold and snowy conditions at the beginning of December, it will take time for cold to load in Canada, which is our source region for cold, but it does make it less likely that December is a torch, which is critical to the overall progression of the winter as the latter half looks unfavorable.
Given current conditions, and the projected conditions as we start December, we think despite above normal temperatures on balance, there will be enough of a window to bring snowfall closer to normal than last year. When looking at the EPS and GEFS below you can see why. The Pacific pattern looks good for cold loading heading into mid-December.
In the past we looked at snow cover across Siberia to help determine the longer term forecast. Not this year because we don’t think the data is there for a meaningful correlation.
Here, we’re looking at the current upper level pattern heading into December, as there seems to be a fairly strong correlation between the upper level pattern, especially in the Pacific, and the default pattern during the winter season. Of course, this doesn’t always work. Last year we saw a roaring start to winter, with a favorable pattern and above normal snowfall that flipped and never returned. So we’re looking at this, but with wary eyes.
The signal has been all over the place for much of November. Just a few days ago, it looked like we would see a Pacific pattern setup that would all but torch much of the US as the month of December begins. Since then, we’ve seen a slow but steady retreat from that idea on the guidance and reversal to a good pattern. That doesn’t mean that we’re going to cold and snowy conditions at the beginning of December, it will take time for cold to load in Canada, which is our source region for cold, but it does make it less likely that December is a torch, which is critical to the overall progression of the winter as the latter half looks unfavorable.
Given current conditions, and the projected conditions as we start December, we think despite above normal temperatures on balance, there will be enough of a window to bring snowfall closer to normal than last year. When looking at the EPS and GEFS below you can see why. The Pacific pattern looks good for cold loading heading into mid-December.
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Overall summary of current conditions: Near to slightly above normal temperatures, fading to normal to slightly below normal temperatures in mid-December. Above normal precipitation. Normal to slightly above normal snowfall (especially late December).
Gut Feeling
At the end of the day, when there are conflicting signals you have to make a call one way or the other. Although it looks highly likely that we end up with a warmer than normal winter on balance, snowfall and precipitation are less clear. When you are relying on a relatively small window to meet snowfall normals, that creates a lot of ways totals can end much lower than normal. On the other hand, with a period of blocking you can get one blockbuster storm that dominates one’s perception of the season and has an outsized impact on seasonal snowfall totals.
It’s hard to get less wintry than last season, so we do not believe we will see a repeat of that. However, Connecticut has been in a bit of a streak where winter has been backloaded to March, or hasn’t really produced a normal snowfall season.
Given the data we have, it looks like mid-December to mid January is most likely to be the wintry period. That doesn’t mean it won’t be cold or snowy at another time, but things look to flip to warmer (maybe outright torch) conditions for February and perhaps the first half of March before we go into another uncertain period where we could see a brief wintry period return. Our gut says we are warm overall, but in that 4-6 week period find a way to get close to normal seasonal snowfall. That likely means at least one significant snowfall event. We should also say that given the La Nina, this could be a gradient winter, where snowfall events and totals have sharp differences in just a few miles due to the warm air that is likely to be lurking for many storms.
Overall summary of gut feeling: Above normal temperatures, normal precipitation, and slightly below normal snowfall.
The Forecast
To recap, here are the summaries of our six variables that make up the forecast:
Overall summary of the seasonal models: Above average temperatures and slightly above average precipitation.
Overall Summary of the Analogs: Above normal temperatures and normal precipitation.
Overall Summary of ENSO: Above normal temperatures, normal precipitation, and below normal snowfall.
Overall summary of the teleconnections: Above normal temperatures and normal precipitation.
Overall summary of current conditions: Near to slightly above normal temperatures, fading to normal to slightly below normal temperatures in mid-December. Above normal precipitation. Normal to slightly above normal snowfall (especially late December).
Overall summary of gut feeling: Above normal temperatures, normal precipitation, and slightly below normal snowfall.
Temperatures
Temperatures are where the highest confidence is found. There are virtually no signals that suggest that we will see a colder than normal winter. In fact, we are inclined to say that each month of the winter period is warmer than normal. We’ll see if next April and May are colder than normal like they were this year, but that’s outside of our forecast period. December and January look to be our coolest months, even as they are above normal on balance. February looks much warmer than normal. March could go either way, but we lean warmer than normal. Again, this is outside of our forecast period.
Summarizing, temperatures look like this:
December: .5 to 1.5 degrees above normal
January: 1 to 2 degrees above normal
February: 2 to 4 degrees above normal
Winter Composite: 1.5 degrees above normal to 3 degrees above normal
Precipitation
With regard to precipitation, there isn’t a whole lot that suggests that we go back to the drought conditions we saw much of the year, especially during the summer. The signals are mixed as to whether we see above normal precipitation or normal precipitation but overall it’s probably not going to matter too much because if we are wetter than normal it’s not likely to be by much. This is consistent with La Nina, but also with having a period with favorable teleconnections for stormy conditions, whether they lead to wet or white. Our thought is that December and January determine whether we go above normal or not, while February is warm and dry.
Here’s the forecast for precipitation:
December: 100% to 120% of normal
January: 90% to 120% of normal
February: 50% to 75% of normal
Winter Composite: 90% to 110% of normal
Snowfall
Now for what you’ve been waiting for. Nobody really cares if we are off on the amount of precipitation or temperatures. It is snowfall that dominates our perception of winter. Last year we were off to a blazing fast start in the snowfall department before it ground to a halt and never really picked up until we had a March event that boosted very low totals. In addition, it was also a gradient year, where there was a massive difference between shoreline locations and central Connecticut, and central Connecticut and northern Connecticut. That makes a snowfall forecast difficult as well. Central and northern Connecticut are most likely to see a normal snowfall winter, but even here, things are tricky. We are really depending on a large enough window in December and January to offset what we anticipate will be an early start to spring.
With a less active southern stream we are likely to see storm tracks that are mostly to our west or close enough to introduce mixing problems. Clippers and Miller B systems are forecasted to be our most common storm track.
December: 120% to 140% of normal
January: 100% to 120% of normal
February: 25% to 50% of normal
March: 80% to 100% of normal
Winter Snowfall: 75%-100% of normal, with the highest chance of normal snow in the NW hills and northern CT.
We think this is one of those winters with something for everyone. For winter weather lovers, the earlier start to winter means that we could have chances at significant snow events during the holiday season and just after. For those that dislike wintry weather, we could see an early start to spring, and warmer temperatures in February/early March. The state as a whole will likely see a rollercoaster winter, starting out relatively strong in our 4-6 week period before falling back during a warm and dry February. That will leave March as the wildcard.
The Winter Ahead
SCW has grown to over 24,000 followers and we are humbled by the opportunity to forecast for you. As you are already seeing, we are working to update our website to make the page more accessible for you.
This is our busy season, and we’re ready to have another good season of no-hype forecasting and grading ourselves after significant events. Maybe we will have a few surprises too along the way.
You can also follow us on Twitter @southernctwx for information on advisories, models, and news and on Facebook for continued high quality analysis, including model interpretations and quick thoughts.
Thank you for reading and trusting SCW. Please continue to like, share, visit our website, and encourage others to do the same.
-SCW Team
Gut Feeling
At the end of the day, when there are conflicting signals you have to make a call one way or the other. Although it looks highly likely that we end up with a warmer than normal winter on balance, snowfall and precipitation are less clear. When you are relying on a relatively small window to meet snowfall normals, that creates a lot of ways totals can end much lower than normal. On the other hand, with a period of blocking you can get one blockbuster storm that dominates one’s perception of the season and has an outsized impact on seasonal snowfall totals.
It’s hard to get less wintry than last season, so we do not believe we will see a repeat of that. However, Connecticut has been in a bit of a streak where winter has been backloaded to March, or hasn’t really produced a normal snowfall season.
Given the data we have, it looks like mid-December to mid January is most likely to be the wintry period. That doesn’t mean it won’t be cold or snowy at another time, but things look to flip to warmer (maybe outright torch) conditions for February and perhaps the first half of March before we go into another uncertain period where we could see a brief wintry period return. Our gut says we are warm overall, but in that 4-6 week period find a way to get close to normal seasonal snowfall. That likely means at least one significant snowfall event. We should also say that given the La Nina, this could be a gradient winter, where snowfall events and totals have sharp differences in just a few miles due to the warm air that is likely to be lurking for many storms.
Overall summary of gut feeling: Above normal temperatures, normal precipitation, and slightly below normal snowfall.
The Forecast
To recap, here are the summaries of our six variables that make up the forecast:
Overall summary of the seasonal models: Above average temperatures and slightly above average precipitation.
Overall Summary of the Analogs: Above normal temperatures and normal precipitation.
Overall Summary of ENSO: Above normal temperatures, normal precipitation, and below normal snowfall.
Overall summary of the teleconnections: Above normal temperatures and normal precipitation.
Overall summary of current conditions: Near to slightly above normal temperatures, fading to normal to slightly below normal temperatures in mid-December. Above normal precipitation. Normal to slightly above normal snowfall (especially late December).
Overall summary of gut feeling: Above normal temperatures, normal precipitation, and slightly below normal snowfall.
Temperatures
Temperatures are where the highest confidence is found. There are virtually no signals that suggest that we will see a colder than normal winter. In fact, we are inclined to say that each month of the winter period is warmer than normal. We’ll see if next April and May are colder than normal like they were this year, but that’s outside of our forecast period. December and January look to be our coolest months, even as they are above normal on balance. February looks much warmer than normal. March could go either way, but we lean warmer than normal. Again, this is outside of our forecast period.
Summarizing, temperatures look like this:
December: .5 to 1.5 degrees above normal
January: 1 to 2 degrees above normal
February: 2 to 4 degrees above normal
Winter Composite: 1.5 degrees above normal to 3 degrees above normal
Precipitation
With regard to precipitation, there isn’t a whole lot that suggests that we go back to the drought conditions we saw much of the year, especially during the summer. The signals are mixed as to whether we see above normal precipitation or normal precipitation but overall it’s probably not going to matter too much because if we are wetter than normal it’s not likely to be by much. This is consistent with La Nina, but also with having a period with favorable teleconnections for stormy conditions, whether they lead to wet or white. Our thought is that December and January determine whether we go above normal or not, while February is warm and dry.
Here’s the forecast for precipitation:
December: 100% to 120% of normal
January: 90% to 120% of normal
February: 50% to 75% of normal
Winter Composite: 90% to 110% of normal
Snowfall
Now for what you’ve been waiting for. Nobody really cares if we are off on the amount of precipitation or temperatures. It is snowfall that dominates our perception of winter. Last year we were off to a blazing fast start in the snowfall department before it ground to a halt and never really picked up until we had a March event that boosted very low totals. In addition, it was also a gradient year, where there was a massive difference between shoreline locations and central Connecticut, and central Connecticut and northern Connecticut. That makes a snowfall forecast difficult as well. Central and northern Connecticut are most likely to see a normal snowfall winter, but even here, things are tricky. We are really depending on a large enough window in December and January to offset what we anticipate will be an early start to spring.
With a less active southern stream we are likely to see storm tracks that are mostly to our west or close enough to introduce mixing problems. Clippers and Miller B systems are forecasted to be our most common storm track.
December: 120% to 140% of normal
January: 100% to 120% of normal
February: 25% to 50% of normal
March: 80% to 100% of normal
Winter Snowfall: 75%-100% of normal, with the highest chance of normal snow in the NW hills and northern CT.
We think this is one of those winters with something for everyone. For winter weather lovers, the earlier start to winter means that we could have chances at significant snow events during the holiday season and just after. For those that dislike wintry weather, we could see an early start to spring, and warmer temperatures in February/early March. The state as a whole will likely see a rollercoaster winter, starting out relatively strong in our 4-6 week period before falling back during a warm and dry February. That will leave March as the wildcard.
The Winter Ahead
SCW has grown to over 24,000 followers and we are humbled by the opportunity to forecast for you. As you are already seeing, we are working to update our website to make the page more accessible for you.
This is our busy season, and we’re ready to have another good season of no-hype forecasting and grading ourselves after significant events. Maybe we will have a few surprises too along the way.
You can also follow us on Twitter @southernctwx for information on advisories, models, and news and on Facebook for continued high quality analysis, including model interpretations and quick thoughts.
Thank you for reading and trusting SCW. Please continue to like, share, visit our website, and encourage others to do the same.
-SCW Team
