Thursday, January 24, 2013

Stormy, Cold February Could Vindicate Winter

It appears that the potential for a stormy and cold February could vindicate at least part of what has been lost this winter, with some snow and intense cold hitting the nation throughout the incoming month of February.

The Madden Julian Oscillation, or MJO, involves placement of enhanced convection over certain areas of the Indian Ocean, Pacific Ocean and even the far western Caribbean. These different areas are divided into 8 different regions, called phases, which each affect the national weather differently. Their effects change with each season as well. Above is the ECMWF Ensemble Prediction System's MJO forecast from January 24th to February 7th. It is predicting a decrease in intensity in coming days as we remain in Phase 7, and the weakening is exhibited by the forecast line moving closer to the circle in the middle of the image, called the 'Circle of Death', because the MJO is too weak at that point to impact the weather significantly. We see that the ECMWF predicts the MJO to move into Phases 8 and 1 as we enter February. These two phases are widely acknowledged as the best phases for cold and snow during the winter, with the cold hitting the hardest across the Central and East US, and snow hitting the same areas. It is for this reason that I support a cold and potentially stormy open to February.

Something else we must keep in mind is that we have recently had a historic sudden stratospheric warming. In the sudden stratospheric warming (SSW), warm air is suddenly forced up from lower levels of the atmosphere in an act that greatly weakens the polar vortex. The polar vortex is the machine that essentially maintains control of the cold air in the Arctic. If you recall, much of the nation experienced very cold temperatures just a couple days ago. This happened as the polar vortex skirted by Southern Canada. Imagine what it could do if it was inside the US. As we enter February, the 2-4 week lag time between SSW and cold air from the stratosphere reaching the surface (because the warm air has displaced it down to the troposphere) becomes valid, meaning we could see another cold shock, and this one could be stronger, depending on where the polar vortex goes this time around.

Finally, I have been a big advocate of the proven theory that snow cover observed in Siberia during the month of October can have a big effect on the Arctic Oscillation come the following winter. We have seen this theory verify, with warmer than normal temperatures in December and early January correlating with below normal snow cover in the first half of October. However, as we enter February, we find that there was a spike in snow cover in late October, which does count as February in this sense. If we use this snow cover theory, I do see a legitimate possibility for strong, sustained cold to last in the US, but only if the rest of the atmospheric pattern cooperates.

It's certainly looking good for cold and even snow in much of the nation to kick off February, and some indications even suggest this could persist to end the final month of winter.