(Premium) Long Range: Is the End of Winter in Sight?

In the world of meteorology, Spring begins on March 1st. While the calendar doesn’t turn until the end of the month, meteorologists end winter statistics on the last day of February. Some winters, however, have featured major cold or snowstorms well into March and even April. Remember last year? Still, a year makes a big difference, as they say, and there are growing signs that after this week, cold and snow will become increasingly unlikely.

Looking back at February, temperatures will likely average above normal throughout the area. While we saw the first below zero temperatures in New York City in over two decades on Valentines Day, much of this month featured near or above average temperatures. Artic cold airmasses didn’t hang around for more than a few days. A couple of winter storms we saw earlier in the month tracked too far east to give the entire region of significant snowfall. And in the past two weeks, we have seen a storm track farther west with warmer air and heavy rainfall, as cold air moves in behind the storms.

The NAO did not trend towards a negative modality that we had anticipated, during forecasts from several months ago, during February. Therefore, without more high latitude blocking on the Atlantic side, the pattern was more progressive. The lack of -NAO is likely due to stratospheric vortex remaining resilient this month, and the Kara Sea Ridge anomaly not having as much impact on tanking the Artic Oscillation, as it did in January.  The latest models indicate the stratosphere may finally completely break down after a final warming event during the next week. This could allow for the AO or NAO fall again sometime next month, depending how much tropospheric wave forcing occurs, with the continued active subtropical jet.

The ECMWF stratosphere forecast. Warming taking over the north pole at 10 hPA and zonal winds reversing.

The ECMWF stratosphere forecast. Warming taking over the north pole at 10 hPA and zonal winds reversing.

Model and ensemble guidance also shows the North Pacific trough or jet extending further east into West Coast of North America. That will allow for higher heights in the mid and upper levels — and flood the much of the Central and Eastern United States with mild Pacific air.  Also the CFSv2 model forecast the tropical forcing with convection to gradually weaken near dateline, as we go through middle to late March and early April.

CFSv2 forecast 200mb Velocity Potential amomalies (on the right) and 850mb OLR or convection (on the left). Both indicating tropical forcing gradually diminishing near the dateline in over next several weeks.

CFSv2 forecast 200mb Velocity Potential anomalies (on the right) and 850mb OLR or convection (on the left). Both indicating tropical forcing gradually diminishing near the dateline in over next several weeks.

The CFSv2 forecast would no longer support a North Pacific trough to persist closer to the Aleutian Islands. Instead, the slowly weakening El Nino will likely have more influence on the North Pacific trough or jet. At this time, there is little reason for us to doubt long-range guidance transition to a warmer pattern. It looks it like prolonged warm up of 60 degree temperatures or higher for the second week of March.

The 12z Euro ensemble showing very anomalous warm 850mb temperatures during 8-10 period.

The 12z Euro ensemble showing very anomalous warm 850mb temperatures with strong ridge over Eastern United Stateds during 8-10 period.

Beyond that it’s little certain if will this major warmth continue. If we see -AO or -NAO return next month, this could support more troughs or confluence over Southeast Canada. The result could be some backdoor cold fronts or slow-moving warm fronts, that would mitigate more warmth here. However, as we move closer and past March 20th,  it becomes much harder to see more snowstorms with our climatology. A highly anomalous atmospheric cold pattern, for late in the season would have to setup again to support more major cold or snowstorms.

So it might be time soon put those big coats and shovels away in the closet until next winter. Then start looking forward to some warmer temperatures and baseball. We will will keep you updated.