Chances of snow appear minimal during the first week of February
RICHMOND, Va. (WWBT) – Predicting seasonal trends can be a fool’s errand, but here we are. The strong El Niño that began in the fall has remained strong, resulting in a warm and (mostly) wet winter so far.
Last week’s brush with wintry weather was a temporary respite from a winter that was warmer than usual. Strong El Niño years tend to be wet in Virginia with no clear sign of temperatures. This means it could be colder or warmer than usual.
*Note: Climatic winter begins on December 1st*
Watching 50 degrees today at 11 a.m. breaks a 10-day stretch of below-average temperatures. Wednesday begins a noticeable warm-up into the weekend. Although the weather will be warm, we won’t be anywhere near the record highs of around 80 degrees for this time of year.
Check out the collections from both of our major computer models. I’ve posted about ensemble forecasting in the past – it can be very useful in identifying trends, without trying to be too precise.
There is no sign of snow falling on the US GFS teams
It is similar to the European model, which lasts for 15 days until the first week of February.
There’s still plenty of time for snow lovers in Virginia, but the next two weeks don’t look good if you want some snow. However, the long-term forecast indicators we often look to to see signs of change in the overall weather pattern start to look better and better for winter weather fans after February 5 and most likely from February 10 onwards.
So what are some of these indicators that we’re looking at more closely? The Arctic Oscillation (AO), the East Pacific Oscillation (EPO), the North American Oscillation (NAO) index, and the Pacific North American Oscillation (PNA) index.
The Arctic Oscillation (AO) index indicates the pattern of atmospheric circulation over the middle to high latitudes of the Northern Hemisphere. It can be in a positive (+) or negative (-) phase and represents the north-south location of the storm’s direction, at mid-latitudes.
If you want the cold of winter and the possibility of snow, it is best to see the negative (-) phase of the Arctic Oscillation. When the Arctic Oscillation is negative, higher than normal pressures are present over the Arctic region, allowing a buildup of very cold air available to sweep southward into the midlatitudes of North America, Asia, Europe, and so on. Below you can see the Arctic Oscillation (AO) forecast from the extended GEFS model for February.
The model average clearly shows a trend towards negativity after February 5:
The East Pacific Oscillation (EPO) index is the variation in total atmospheric flow across the eastern half of the Pacific Ocean as well as over Alaska. When the EPO is in a positive phase, moderate Pacific air flows directly to the west coast of North America and typically bathes the United States with below-normal temperatures. In the negative phase of the EPO, we tend to see atmospheric flow coming from the Arctic region and Canada into the US and coupled with the negative Arctic Oscillation (AO), this can mean that some very cold outbreaks are likely.
Below you will see the EPO forecast as we move deeper into February, and the model average from the extended GEFS clearly shows a trend towards the negative phase of EPO after February 5:
The North American Oscillation (NAO) index is another important factor we look at regarding winter weather potential in our region. This indicator looks at high and low pressure patterns in the North Atlantic region.
Lower than normal pressures often lead to milder conditions here in the eastern United States as well as a storm track that is often unsuitable for snow in the lower mid-Atlantic region where we live. This is considered the positive (+) phase of NAO.
Higher-than-normal pressures in the North Atlantic or the negative (-) phase of the NAO often help suppress the path of organizing low-pressure systems as they move across the eastern U.S., along with a negative AO and EPO that can help increase the potential for a snow event, especially during the El Niño season. When the subtropical branch of the jet stream is more active than usual.
As you can see below, the average NAO forecast from the extended GFS model guidance shows a tendency towards the negative phase as we move deeper into February, especially after February 5th. This is probably another positive sign for snow lovers:
Finally, we would also like to take a look at the Pacific North American (PNA) Volatility Index. The PNA strongly influences our weather by influencing the strength and location of the jet stream in East Asia, and thus the weather it transmits to North America. A positive phase of the PNA usually places a trough or dip in the jet stream centered over the central and eastern United States allowing cold air masses from the Arctic region and Canada to be directed into this part of the country.
On the other hand, the negative phase of the PNA does the opposite, and we are likely to see the decline in the jet stream centered in the western United States. The trough in the west is often associated with a ridge of high pressure in the east with warmer than normal temperatures in the east and much cooler than normal temperatures occurring in the west.
Here’s a closer look at what these two distinctly different stages look like:
So when we look at the Pacific North American Oscillator (PNA) forecast going forward into February, the trend is a more positive outlook which is another good sign for those of you who want a little more cold and at least the chance of some snow in the second half of winter season:
Bottom line, the indicators are telling us that we still have a very good chance of ending the winter reasonably strong with more cold snaps coming and perhaps some chances of some snow. As you all well know, all it takes is one good storm here in February to push us into an above-average snowfall winter. We will continue to monitor the trends closely and keep you updated!
In the meantime, enjoy lowering your heating bills with this short-term warm air.
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(Tags for translation) Snow