A quick update to the blog from last night. Data continues to support the idea of a prolonged cold wave as we head into January. Today's runs of both the GFS and Euro support a full scale Arctic Invasion into the Central US by midweek next week.
The EURO EPS or European Ensemble Prediction System temperature anomaly map shows an ENORMOUS area of below normal temps that almost covers the entire US grid by next Thursday. Locally this would represent temps running about 15°F below normal with highs perhaps not escaping the 20's and lows much colder than that!
With the cold will come snow chances too late next week. Full discussion below...
As discussed with the release of the 2016-2017 Winter Outlook, I believe the months of January and February remain primed for harsh winter conditions over much of the Central and Eastern United States. For the purpose of this article, I will focus on only next month.
While we have seen a nice reprieve from the cold over the last few days, Arctic air remains firmly in place over Siberia, Greenland, Northern Canada and Alaska where temps remain well below zero. In fact, a jaw dropping low temperature of -79.6°F was recorded last week over Central Siberia breaking all-time records for the region!
Eventually, this cold will spill over into our side of the hemisphere opening the door for major arctic outbreaks during the month of January.
The real question becomes when?
While data from both the Euro and GFS agree that January starts off on a mild note with temps running in the 50's and perhaps even 60's early next week. After that, it appears that we will go into a progressively colder pattern that could last for much of the next month to come.
Taking a look at a forecast snapshot of jet stream winds from the GFS valid on January 9th reveal several telltale signs of what may be coming our way.
The first thing to notice are the lobes of high pressure over both Alaska (think EPO here) and also the North Atlantic (NAO). The locations of these highs, as described in the Winter Outlook, help promote a "cross-polar flow" while trapping the exit of cold air intrusions out of Eastern North America. Also of note is the presence of that giant low over Southern Canada, you guessed it, that's the Polar Vortex!
Explaining a couple "teleconnections"...
A "teleconnection" is a connection or correlation between meteorological phenomena that occur a long distance apart and can help to signal changes in climate and weather patterns from region to region.
NAO - North Atlantic Oscillation
One of the most commonly looked at teleconnection patterns for weather forecasting. The value of the NAO is determined by the differences in pressures over the high latitudes and central latitudes of the North Atlantic. The positive phase of the NAO is characterized by a low difference in pressure between the two regions, a below average pressure over the high latitudes, and an above average pressure over the central latitudes. The opposite occurs during the negative phase. The NAO is significant in forecasting because its state affects the intensity and location of the jet stream and storm track in the North Atlantic. As a result, significant changes in temperature and precipitation occur in Europe and North America based on the NAO.
EPO- Eastern Pacific Oscillation
A dipole pattern similar to the NAO in the Atlantic, but located in the eastern Pacific. There is a tendency for heights/pressures/temperatures to be higher to the north and lower to the south in the negative phase and lower to the north and higher to the south in the positive phase. The negative phase corresponds to widespread cooling over central and eastern North America and the positive phase to warming.
The Euro and the GFS agree that both the NAO and the EPO look to go into their negative phase over the next week to ten days leading to a likely outbreak of arctic air into portions of the United States.
Looking into the Crystal Ball...
While the medium range forecast models such as the GFS and Euro show arctic air arriving into the Northern US in about one week, you have to turn to the long range or "climate" models to get a handle on what to expect over the course of several weeks.
Here's a look at three snapshots of temperature anomalies via the "Euro Weeklies" climate model during the month of January 2017...
EPS: Valid January 5 - 9
The Euro EPS clearly shows the arrival of a massive amount of Arctic air into much of North America with the heart of it building into the Northern Rockies and Northern Plains. Locally, temps fall a few degrees below normal for this time of the year, which by the way is pretty cold.
The Climate Prediction Center
The folks at CPC wholeheartedly agree with this forecast with the vast majority of the Continental US expected to be below normal temperature wise in the 8 to 14 day range.
EPS: Valid January 17 - 21
While the Euro EPS shows some modification of the arctic air mass over the Northern Rockies, the cold spreads throughout the Eastern US and remains firmly in place here locally during the middle of the month, which is also our climatological coldest part of the year.
EPS: Valid January 26 - 30
Finally, during the final week of the month the EPS shows temps gradually recovering to near normal in our area and a little above normal for much of the Eastern US.
So what do I think?
As mentioned in the 2016-2017 Winter Outlook, I remain confident that we are looking at a rough January with brutal cold for much of the month. Keep in mind, that the above mentioned Euro EPS temp anomalies are with respect to "normals" for this time of the year and normal is cold with average highs running in the lower 40's and average lows into the 20's during the month of January. So a prolonged stretch of below normal temps could mean highs routinely not escaping the 30's and even 20's especially if we get decent snow cover.
What about snow?
While I remain confident that this will turn out to be a cold January, the prediction of snow is much more complex. Typically you can't predict snow with much accuracy at all outside of a few days out. However, with the expectation of plenty of cold this month, it certainly helps our chances. Now all we need is the moisture.
According to the Climate Prediction Center (CPC), in addition to the cold, we are looking at above normal precipitation during in the 8 to 14 day range with near normal precip during the remainder of the month.
With that being said, and all else being equal, I remain bullish on the idea of catching some decent snow this month.
The devil will be in the details however, so stay tuned!
WDRB Meteorologist Jeremy Kappell
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