Friday, October 19, 2012

Special Long Range Lookout: Strong Greenland Block Setting Up

This is a Special Long Range Lookout, made and published on October 19, 2012.

I am monitoring the potential for a very strong Greenland Block to emerge in the next several weeks, as the pattern continues to slip further into a more winterized pattern. But before we get into this potentially significant development, let's review what the Greenland Block is.

The Greenland Block refers to a semi-permanent high pressure system over Greenland. That means that there is a tendency for a high pressure system to form over Greenland repeatedly. This 'Block' in the term Greenland Block is for what happens to the atmosphere when this phenomena hits. The high pressure system develops over Greenland and blocks the atmosphere's traffic of disturbances and ridges from progressing around the world, 'blocking' these systems. The Greenland Block is associated with the North Atlantic Oscillation's negative phase. In the NAO negative phase, this block encourages a stormy and cold pattern to emerge over the eastern US.

The chart above is depicting 500mb height anomalies in the 10-11 day forecast range. While many more 'informed' weather folk may know that such long range forecasts have a high chance to fail, this particular image is composed of the 12z GFS Ensemble members averaged out. This significantly strengthen's its argument. The forecast is calling for a very strong Greenland Block to develop over Greenland. At the moment, this would most likely be borderline East Based, which typically benefits the Midwest and Great Lakes for snow and cold.

The GFS Ensembles are shown here individually, with blue areas defining disturbances and red areas showing high pressure. The deeper the color, the stronger its respective atmospheric apparatus is. These ensembles are also valid for the 10-11 day forecast, and are all in unusually good agreement with a strong Greenland Block and stormy pattern over the US. The unusual high confidence in these ensembles leads me to believe one thing...

Winter is being revealed.

Think about it. This whole month, the eastern US has been hit by strong systems, with many areas being above normal in precipitation. If this stormy pattern continues through the month of October, trends show that fall patterns correlate with winter patterns. Thus, such a stormy pattern now may very well induce a stormy winter for the East US. And yes, the LRC does factor in here.



Cam Smith said...

When do you think this strong cold front will hit NJ and what will it bring? Thanks!

JC said...

Will western PA receive our first snow from this Greenland block? Fingers crossed!!