Tuesday, February 5, 2013

Valentine's Day Potential Coastal Snowstorm

There is potential for a coastal snowstorm near Valentine's Day on the 14th.

Above, the mean sea level pressure forecast is shown for February 12th. The synoptic overview is very stagnant, with strong high pressure in place across the nation. A large swath of modest low pressure is present north of the Yucatan Peninsula in the western Gulf of Mexico. This is the storm system we are watching for this event. To be perfectly honest, the prized Nor'easter track is quite nearly the only option this storm has. You have two strong high pressure masses that are essentially rolling out the red carpet between them. With strong high pressure over land and equally strong high pressure out to sea, any storm systems are easily persuaded into going up the East Coast.

Moving ahead to February 13th, the storm system has taken that red carpet path up the coast and is in the Mid-Atlantic. Although it shows two low pressure systems, I have a pretty good feeling that they would have a fair shot at merging, if this forecast were to verify. Regardless, both high pressure areas previously mentioned have now moved out of their domains, with the US high pressure pushing south and the Atlantic high pressure system also pushing south. This then raises the question, can the storm still continue on a path that would favor a lot of snow for the Northeast? Well, if we look again at the storm system, we see a tendency for lower pressure to apparently be trying to spread east towards the Atlantic. That tells me that it wants to go out to sea rather than going up the coast. In the Nor'easter track's defense, the storm is well enough inland that, even if it were to try and go out to sea, it would be moving northeast and would still make a clean hit on the Northeast for accumulating snow.

I want to dabble in that February 13th timeframe some more, but now we are looking at 500 millibar height anomalies, with warm colors indicating high pressure and cold colors showing low pressure. I'm taking a look at the atmospheric set-up for this storm, and i'm not really getting good vibes about it. In order for the storm to go up the coast, high latitude blocking in Greenland is almost a necessity. And while we do have some high pressure anomalies over Greenland, the majority is too far south for my liking. Also, high pressure in the Pacific Northwest and low pressure trying to rebuild in the Southwest makes me think a Rex Block is trying to form. The Rex Block consists of high pressure stacked on top of low pressure. Downstream of this blocking pattern is more zonally-oriented (west-to-east jet stream, little cold) wind flow, something that would try to force this storm to go more out to sea rather than up the East Coast.

Finally, we arrive on Valentine's Day. The storm has 'bombed out' to a central minimum pressure of 980 millibars in typical Nor'easter fashion. It is certainly giving quite a bit of love to the New England area, as very heavy snow is accumulating in much of the region as this event happens. As the projected snowfall graphic shows below, the accumulations would be extreme if this event happened:

I need to see multiple runs of the ECMWF in coming days to see if this event is still a go in the model's eyes, because right now, there is little support in other models and ensembles for an event of this magnitude to happen. I'm very on-edge about the lack of blocking high pressure over Greenland; I really want to see more enthusiastic high pressure over that land mass before I can look more positively at this storm's prospects. I would also like to see less of that Rex Block set-up; that puts me at an uneasiness I need to settle before I go ahead with more confidence on this event's potential.


1 comment:

Logan said...

Happy National Weatherperson's Day!