STARTS WITH RECORD WARMTH
The first three days of February have been exceptionally warm. There should be several record high temperatures today. Then, the four days after that will be kind of warm, at least for the middle of winter. Then, next week it’s back to winter. And, yes, that includes snow.
THE OVERALL PATTERN CHANGE
Don’t put away the heavy coats and boots yet, no matter what the Groundhog supposedly said. (How could it NOT see its’ shadow-it was nothing but sunshine in Punxsutawney Tuesday morning)?
Here is the map of temperatures compared to “normal” at around 5000 feet up today:
That shows unseasonable-even record-warmth in the Eastern U.S., with cold weather, even for winter, in the western half of the country.
That’s almost the exact opposite! The label on the map says “EPS” which means that it is a product of the European model-the best in the world overall. And it’s also an “ensemble”, meaning the AVERAGE of what happens when the world’s best is run 51 times. In short, it’s “the best of the best.”
WHAT HAPPENS AFTER NEXT WEDNESDAY?
It looks like a colder pattern setting up for at least the middle of the month. For signs, we look toward Canada, the Arctic, and Greenland, among other areas. Here is the upper-air map for next Wednesday. Assume the upper winds follow the lines on the map. So, trace the line back from Philadelphia and it will take you into Canada and even to the top of the map-near the North Pole!
The blue colors indicate lower than normal pressures, and the reddish colors indicate the opposite. The deep blue in the Eastern U.S. extends up into Eastern Canada until you see a small circle. That’s the POLAR VORTEX. As we’ve seen in recent winters, its’ position is very important. It’s not far enough south to put us in the ice box, but it is an overall cold pattern.
The red colors near the top of the map indicate high pressure building into the Arctic. This is the now infamous –AO, or negative Arctic Oscillation. This helps force the polar vortex southward, and can be a major factor in our snowstorms. Here is the history-and forecast-of the AO:
The lower the line drops, the “more negative” the AO gets. Notice how low it got around January 16th. A very low –AO followed by a quick rise has historically led to snowstorms in the East. And, one week after the –AO, we had our blizzard of 2016.
Now look at the forecast, which are the red lines. The closer the lines are together, the higher the confidence in the forecast. So the AO bottoms out around Feb. 13th, and then rises quickly. If this actually happens, we would be in a more favorable position for a snowstorm around Feb. 20th.
BUT WHAT ABOUT SNOW NEXT WEEK?
Neither the AO or NAO (North Atlantic Oscillation) are favorable for major winter storms, but there are signs of some sort of storm along the East Coast early next week. Here is the map from the European model, run today. The ensembles of the European are fairly similar for so far in advance. This would bring the area snow Monday into Tuesday.
Some other computer models are “not on board” with this forecast yet, but agreement is unusual a week out (Except for our January blizzard, of course).
More updates coming this week….
Glenn “Hurricane” Schwartz
Chief Meteorologist, NBC10 Philadelphia