The first official day of winter is still about a month away, but we’ve already started feeling a drop in temperatures and have seen a few snowflakes, too. So, what does that mean for this upcoming winter?
There are several things meteorologists look at when predicting a long range winter forecast. This includes global patterns like La Niña or El Niño, phases of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO), and also how past winters have played out. Each can help to determine what the upcoming winter will be like.
How does ENSO affect winter?
El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short. When the surface waters near the equatorial Pacific Ocean are unusually warm this is considered an El Niño. Cooler than normal waters indicate a La Niña.
El Niño causes the Pacific jet stream to move south and spread further east. During winter, this leads to milder and drier conditions across the Miami Valley.
La Niña causes the polar jet stream to move northward and to weaken over the eastern Pacific. During La Niña winters, the Miami Valley tends to be wetter and warmer.
How does the NAO affect winter?
The North Atlantic Oscillation (NAO) is the difference in pressure between two points located in the eastern Atlantic. When the oscillation is in its positive phase, a Subtropical High located near the Azores and a Subpolar Low located near Greenland is strong. That tends to allow for a warmer pattern in our region. In a negative phase, the pressure gradient between these two points is weaker and colder air can surge south from Canada.
How does the AO affect winter?
The Arctic Oscillation (AO) is a global weather pattern that is characterized by winds that circulate counterclockwise around the Arctic. When the AO is in its positive phase, the winds are stronger and acts to confine the colder air in the polar regions. When the AO becomes negative, the winds are weaker and the colder arctic air can slip southward and increase storminess in our region.
Now that you have a better understanding of these global patterns, I can talk to you about this upcoming winter.
According to NOAA, this winter will be a La Niña winter. Meaning there is a good chance for it to be warmer and wetter overall. That said, it doesn’t necessarily mean less snow. In fact, the past 5 La Niña winters were quite snowy with the exception of one.
The NAO and AO tend to be more of the deciding factor between snow and rain in the winter. When the NAO and AO patterns go into a negative phase, there is a better chance for cold air outbreaks and an active pattern of storms. That could mean bigger swings in temperatures and the potential for high snowfall. Unfortunately, these patterns can only be seen as far out as 10 days to two weeks at most, so it is harder to predict for high snowfall too far in advance.
So, my final thoughts on this winter is the following:
- It will be warmer than normal overall
- There will likely big swings in temperatures with cold air outbreaks at times
- High snowfall potential, especially late season
- Flooding threat, too
Stay safe this winter season and tune to WHIO-TV and the Storm Center 7 team for updates.
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Warmer and wetter winter expected for the Miami Valley – WHIO Radio