New forecast data is available for Winter 2022/2023. It shows the growing influence of the third phase of La Nina. A high pressure barrier system is forecast to develop over the North Pacific, altering the jet stream over North America. The latest forecast also shows more snow across the United States.
Many factors come together to affect the Winter season each year. But this year, one of the main factors is the cold La Nina in the ENSO regions of the equatorial Pacific.
But how can the ocean affect winter weather? We will first examine how La Nina works and how we predict its effects will change as we approach the winter of 2022/2023.
WINTER FROM THE OCEAN AND ATMOSPHERE
La Nina occurs in the ENSO region, abbreviated as “El Niño Southern Oscillation.” This region of the equator of the Pacific Ocean is between a warm and a cold front. On the same subject : President Biden Announces Three New Nominees to serve as U.S. Attorneys, One to serve as U.S. Marshal. There is usually a phase change every 1-3 years.
The cold phase is called La Nina, the warm phase is called El Nino. We are currently in a La Nina phase, entering its 3rd year, which is a rare event.
The image below from NOAA Weather shows the normal cycle during the cold phase of ENSO. The air settles in the eastern Pacific, promoting calm and dry weather. At the same time, air rises in the western Pacific, with low pressure and more rain.
In this way, ENSO greatly affects tropical rainfall and pressure patterns and thus affects the oceanic atmospheric feedback system. Through this oceanic atmospheric system, the effect of ENSO spreads across the globe.
When you look at the latest global ocean conditions, you can see a cold La Nina over the tropical Pacific Ocean. The rest of the world shows strong warm coordination in the North Pacific and North Atlantic, playing their role in the development of the regional system.
Below we have a closer look at the tropical Pacific analysis. We can see cold anomalies in marked ENSO regions. An active La Nina is now entering its third year, increasing cold ocean anomalies over much of the tropical Pacific.
La Nina forms a period of strong easterly trade winds, which can tell us a lot about the general state of the global circulation. In this way, we can use these anomalies as “indicators” to determine the current state of the global climate system.
Below, you can see the progression of some La Nina events over many years of history, with only two events already having a 3rd-year occurrence. Three events were moderate in the third year, and three phases turned into El Nino in the third season.
To understand ENSO’s development, we have produced a visualization of ocean temperature anomalies from June to October 2022.
LA NINA ENSEMBLE FORECAST
ENSO cooling resumed in August as cold waves moved across the equatorial Pacific. To see also : China warns of ‘counter-measures’ as US approves $1.1bn arms sale to Taiwan. But it picked up in September when the easterly trade winds intensified.
Below we have the ECMWF analysis/forecast graph, which shows the ENSO central region forecast. La Nina conditions (below -0.5) will prevail in late fall and winter. But a weakening La Nina is expected early next year, with a warm phase possible in late 2023.
WINTER AND THE MODIFIED JET STREAM
Looking at the IRI probability forecast, we can see a high agreement for the cold phase that lasts during the Winter. This may interest you : Joint statement on the extended deterrence strategy and consultation group meeting. We expect the cold front to break down as we enter next spring, with a warm front becoming more likely later in the year.
The integrated ocean forecast model shows cold anomalies in the Pacific regions during the winter average. A stable La Nina is predicted in all long-range systems, giving high confidence also in its climate impact.
Usually, the first effect of these sea faults can be seen in the change of the jet stream. A jet stream is a large, powerful stream of air (wind) that is around 8-11km (5-7mi). It interacts with stress processes and affects their course and development.
The jet stream is an important part of the forecast. It is one of the main ways that La Nina can directly change weather patterns, especially in North America.
Historically, a strong blocking high pressure system in the North Pacific is the dominant influence of the cold ENSO phase. That usually redirects the polar jet stream over the northern United States.
The image below shows the average pattern during several La Nina winters. We can see a high pressure system in the North Pacific and a low pressure area in Canada and southwest Europe.
A strong high pressure system circulation promotes the development of a low pressure region in Canada. That diverts the jet stream down between the two pressure systems, bringing cold air to the northern United States.
Looking at the temperature analysis for the same winter, we can see a cold anomaly below the jet stream over western Canada and the northern United States. Warmer-than-normal winters are common in the southwestern and southeastern United States and eastern Canada.
Rainfall-wise, La Nina winters are usually dry in the southern United States. Drier conditions also develop in the southeastern United States as La Nina produces a weak subtropical jet stream and less moisture in the east. More rain falls in the northwestern United States, the Great Lakes, and parts of the northeast.
You can see that the jet stream is delayed in the image below. The figure shows the average position of the jet stream during a La Nina winter and weather patterns in the United States and Canada.
The jet stream brings cold temperatures and storms from the polar regions to the north and northwest of the United States and hot and dry weather to the southern parts.
WINTER SEASON 2022/2023 – OCTOBER FORECAST UPDATE
In the northern part of the country, cold and wet events are more frequent, as the jet stream directs storm systems. But that could shut down the southern United States a bit, creating a warm and stable climate with less frequent storms and colder areas.
As cold air is more easily accessible in the northern United States, it also increases the potential for snow. Especially places like Alaska, Canada, and the north/northwest of the United States benefit from more snow during the cold phase of ENSO. Image below provided by NOAA-Climate.
Now you know what the origin of the La Nina effect will be next Winter and how it affects the jet stream and the weather. We will also take a look at the actual model forecasts, which were recently updated this month, and their indications for Winter 2022/2023.
ECMWF WINTER SEASON FORECAST UPDATE
In this update, we focused on three seasonal models. ECMWF in Europe, CFSv2 in the US, and the CanSIPS version in Canada. Images from the Copernicus Climate Project, CPC/NCEP, and tropical tidbits.
All these forecasts are an average of a three-month meteorological picture (December-January-February) and show the prevailing weather patterns.
Even if the models were 100% accurate, it does not mean that the weather conditions will last for three months straight. It just suggests what the weather might look like most of the time.
The ECMWF model is often considered one of the most reliable forecasting systems. But since we only look at trends and weather patterns on a large scale over a long period of time, it is difficult to estimate the true reliability.
The updated winter pressure model in the ECMWF forecast below further strengthens the La Nina high pressure system in the North Pacific, extending over the western United States. Low pressure is forecast over western Canada as expected, bringing the jet stream to the northern United States.
We also see a weak North Atlantic Oscillation (NAO) in the North Atlantic. Also, a low pressure area above the southwest of Europe and the Azores, opening several different types during the winter.
The ECMWF monthly NAO forecast below indicates negative trends in early Winter. That increases the chances of a cold front in the eastern United States and parts of Europe. A negative NAO means high pressure over Greenland and Iceland, disrupting the normal westerly jet stream pattern.
Global surface temperature forecasts show an expected pattern. Western Canada and parts of the northern United States saw cool to moderate temperatures. A heat wave is forecast for the western and southern United States.
Europe shows a weak warm anomaly in the west, with the influence of a nearby low pressure area. A hot anomaly is forecast for parts of central Europe, moving north-east.
Looking at the probability forecast for Europe’s surface temperature, we see an interesting pattern. Most of the central and western continents are in average temperatures. However, the probability of higher than normal temperatures is higher in the southern and northern regions.
ECMWF WINTER 2022/2023 SNOWFALL FORECAST UPDATE
Over the Americas, the updated ECMWF forecast shows higher average temperatures over most of western Canada, extending into parts of the northern United States. Warmer than normal temperatures are forecast for the southern United States, with a weak system moving northeast.
A negative NAO typically means more northerly flow over the Midwest and eastern United States. We have seen this development before in La Nina winters.
In this forecast, we see a weak probability of warm anomalies in the northern United States. But it is still unclear how much of a negative NAO signal it is. That will become more clear in future news.
Looking at the precipitation forecast, we can see Europe with a sign of mostly moderate rainfall, with dry areas in the western and central parts. More rain is forecast for the Mediterranean and far northern Europe.
Anomalous North American precipitation forecasts show a typical La Nina pattern in Canada and the United States. More rain is forecast for Canada and the northwestern and northeastern United States. Dry conditions remain in the south-central United States, as is often seen in La Nina patterns.
CANSIPS WINTER SEASON FORECAST UPDATE
As always, we have derived the individual snow precipitation forecast from the ECMWF data provided by the Copernicus-EU project. In Europe, we see low average snow, which is surprising given the lack of strong warm anomalies and normal precipitation. A possible increase in the ice age is predicted for a few parts of central Europe.
The next image below shows the change in snow depth predictions between the latest model data and the previous model. We can see that the latest ECMWF forecast shows more snow in central and western Europe than last month’s forecast.
In North America, most of the country has below-average snowfall, except for the Northwest and upper Midwest. Keep in mind that less snow than average does not equal snow. So snow could still fall even though the forecast shows less snow than usual.
But, when comparing the latest forecast to the previous one, we can see that more snow is predicted for much of the western and northern United States than the previous forecast. Again, this is an indication of the pressure change in the latest model predictions.
We will release a separate forecast article for ice age predictions. There, we’ll take an in-depth look at the possibilities of an ice age, including multiple models and a month-by-month breakdown.
Our second model in this update is CanSIPS from the Canadian conference office. The name stands for Canadian Seasonal and Interannual Forecast System (CanSIPS). It consists of two types of climate-ocean-land-ocean climate.
This pattern shows the typical La Nina pattern, which we have already seen in historical analysis. A high pressure area exists in the North Pacific with a small response over North America. Another high pressure area can be found in Europe.
CFSv2 WINTER SEASON FORECAST UPDATE
This is the pattern of the “jet stream bend” over North America, which sends the jet stream into the upper atmosphere of the northern United States.
The air temperature forecast also looks like a typical La Nina winter. In North America, we have the cold pool in western Canada, which reaches down into the northern United States. The southern half of the United States is predicted to be warmer than normal.
Europe has mostly warmer than normal continental conditions, with stronger warm anomalies in the northwest.
When we look closer to Europe’s high temperatures, we see warm anomalies focused across the central and western parts of the continent.
In North America, we are seeing cold north west of Canada. A colder than normal winter is in the forecast for the northwestern United States. An extension of the intrusion of persistent cold air has extended into the upper Midwest. But much of the southern and eastern United States is forecast to be warmer than normal compared to the Canadian model.
Moving on to precipitation, the Canadian pattern shows generally less precipitation than western and southern Europe. More winter rain is forecast only in the southwest.
WINTER 2022/2023 UPDATE FORECAST SUMMARY
More winter rain is also forecast for the northwestern United States and the Great Lakes region. In anticipation of a La Nina winter, the southern and southeastern United States are expected to be drier than normal.
CFSv2 is the US NOAA/CPC long-term/seasonal forecast system. We use it differently than ECMWF, as it is the seasonal forecast system most commonly used in the United States.
Looking at the latest data, CFS is close to ECMWF with a La Nina high pressure area in the North Pacific and a low pressure response in Canada. However, the Atlantic/Greenland pattern is different, as the CFS extends the low pressure area over the North Atlantic and Greenland.
The air temperature is the most interesting in North America, with a strong cold pool growing over Canada and warm air in the southern and western United States. A jet stream is usually found between two air masses. Europe is seen as generally warmer than normal.
Surface temperature projections show a very strong dipole pattern over North America. Colder than normal temperatures are forecast for much of western and central Canada, extending into the northern and northeastern United States. The CFS predicts a warmer than normal winter for the southern half of the United States.
Anomalous precipitation forecasts for North America show the greatest weather activity (with more precipitation) over the northwestern and eastern parts of the United States. Drier than normal conditions are forecast for the south-central United States, with updated forecasts showing much less precipitation in the far southeast.
We must remember that the strongest weather movements usually occur between cold and warm anomalies, including snowfall. CFS does not have a snow forecast, but this temperature and precipitation pattern suggests more snow in the northwestern United States, the upper Midwest, and parts of the northeastern United States.
Reading the pictures and descriptions can be a bit confusing. So to keep things simple, here’s what the October update forecast shows for the Winter 2022/2023 season:
Europe is expected to have near-neutral temperatures in much of the western and central parts of the continent. Above normal temperatures are shown in the north and south.
This suggests that there may be colder periods ahead and more cold days in parts of western and central Europe. The moderate and negative NAO forecast by ECMWF in early winter supports this idea.
Such a pattern could allow for an easy breakdown of the pattern and the northerly flow in central Europe late this year and early next year.
The models are not in 100% agreement on the North Atlantic model. The key is the location and strength of the Iceland/Greenland pressure systems relative to the North American model.
Rainfall-wise, mostly average-to-dry conditions are forecast for central and western Europe. More rain is shown in the southern parts of the continent. The snow forecast shows little snow in Europe, with some central parts forecast to have more snow than average.
The North American winter forecast looks like a classic La Nina type winter. As a result, western and central Canada can expect cold and snowy conditions, along with Alaska.
The US can expect to see strong north-south development. The northern United States is expected to be normal or cold this winter with lots of rain. A cold front is forecast to move out of the northwestern United States and into the Midwest. Frequently, cold anomalies can spread across the far northeastern United States.
The southern United States has a high chance of warm and often drier than normal winter weather. This, however, does not mean that cold weather cannot reach the southern regions. Instead, it shows that in a La Nina pattern, there are less frequent cold spots in the deep south due to different jet stream positioning.
STRATOSPHERIC POLAR VORTEX IN WINTER
Below is NOAA’s official winter 2022/2023 temperature forecast. It shows the possibility of temperatures, with an increased chance of cold in the northern United States. As seen in the models above, the southwest part of the country and the east coast have a high probability of warmer than normal winter weather.
But watch for a possible “flat” temperature plume extending down into the southern plains. That could be interpreted as a possible path for cold winter air to descend from the Midwest.
Official NOAA Temperature Index:
The official rainfall forecast is the same as the latest model forecast. We see an equal-to-high chance of more rain (and snow) over the northern half of the US. The southern United States is expected to have a drier winter than usual.
NOAA’s official precipitation forecast score:
During La Nina winters, there is often a problem of sustaining drought conditions in the south and southwest. Below is the latest drought image from NOAA, which shows current drought conditions in the United States through mid-October.
Severe drought conditions exist in the south-central and western United States. We can see the difference in the southwest, especially in Arizona. This is thanks to the summer winds that bring a good amount of rain.
But drought conditions in the south are expected to continue and could worsen the La Nina winter. The same goes for parts of the western United States, especially California.
There is no certainty in the winter forecast with this long lead time. But there is also one very important factor that can change the winter season at any time. That is the Stratospheric Polar Vortex.
Winter weather is also highly dependent on the Polar Vortex. The Polar Vortex re-emerges each Fall and plays an important daily to weekly role in weather development during late fall, winter, and spring.
The Polar Vortex is a large area of cyclonic circulation that circulates throughout the Northern Hemisphere, from the ground to the top of the Stratosphere, reaching more than 50km/31 miles high.
Below is our 3-dimensional model of the Polar Vortex, from the lower levels up to the Stratosphere. The vertical axis is optimized for better visual purposes. You can see in the picture below what the actual shape of the Polar Vortex looks like in the middle of winter.
In the example above, the Polar Vortex has undergone a temporary warming event. These events can disrupt the Polar Vortex, weakening the circulation and changing the underlying weather patterns.
This is very important for winter weather patterns, as it can change the movement and circulation over the next few weeks. But even a strong Polar Vortex plays a role in developing weather patterns.
A strong Polar Vortex usually means a strong wind circulation. This often traps cold air in the Polar regions, leading to mild seasonal conditions in much of the United States and Europe.
In contrast, a weak Polar Vortex can create a disrupted jet stream pattern. This means that it is difficult to stay in the cold air of the Arctic, which now has an easy way to escape from the polar regions of the United States or Europe.
A sudden stratospheric warming (SSW) event can significantly affect the circulation and cause large pressure changes in the Northern Hemisphere. So we are closely monitoring those processes.
