Monday, February 10, 2014

February 12-14 Potentially Historic Winter Storm

Things appear to be coming together for a potentially historic winter storm, though model biases mean intense model forecasts are likely overdone.

This image shows the ECMWF model's snowfall forecast for the next 144 hours, and it is not that hard to see the big storm system this model believes will strike a large portion of the Eastern US. We see that the ECMWF model begins by dropping heavy snow in excess of 12" on the areas of northern Georgia and the Carolinas into western Tennessee and Kentucky, before amounts max out near 2 feet in the Virginias. Heavy snow continues into the Northeast, with widespread 12-18" totals across the map for that region.

The ECMWF model has remained consistent on this idea of a major winter storm for the East Coast, including the Southeast. These big amounts are relatively unchanged from previous forecasts, except for the 24" jackpot zone in the Virginias. The environment looks highly favorable for an East Coast storm synoptically, with a west-northwest flow solution prevailing over the contiguous United States. This is shown well by storminess in Alaska leading to strong yet suppressed ridging over the Southwest US. Considering northwest flow scenarios typically can lead to Northeast snow events, it is of little surprise that a strong storm system in the Southeast is able to shift northward and ride the coastline to produce heavy snowfall across the far Eastern US.

The CMC model (Canadian model) above shows heavy snow extending from far northern Georgia to eastern Canada, in a similar fashion as the ECMWF (though not identical). The heaviest snow hits Maine, where amounts flirt with the 16" benchmark, and the remainder of the East Coast stays within the realm of 6-12" or a little higher, as the model shows some higher totals in New Jersey and a few other coastal places.

Surprisingly, the CMC model may have shed its too-snowy bias in this forecast and is actually showing a more reasonable solution compared to the ECMWF. It does look like the crucial point will come when we determine how far south the storm system goes. In the ECMWF's forecast, the storm is a bit to the south of the CMC, hence the heavier snow totals located deeper into Georgia. In future forecasts, I wouldn't be surprised to see totals bumped up a bit along the coast, but other than that, this forecast isn't that far fetched in my eyes.

Lastly, we see the NAM model's snowfall forecast above. The NAM drops heavy snow amounts of over 12" in a large swath of Georgia in what would be a truly paralyzing snowstorm for those who went through the agonizing snow event in Atlanta just a couple of weeks ago. If we look at the NAM forecast further north, we see the heavy amounts extend into the Carolinas, and a strip of 24" to 31" snow amounts in eastern Virginia and the coastal portion of the Mid-Atlantic. The heavy snow then continues into the coastal New England area, but the full storm is not in the NAM model's forecast timeframe yet, so we cannot get total snow amounts in the Northeast yet. Regardless, it's clear that this event would be historic for those down south.

The NAM model is notorious for making forecasts laden with a noticeable too-snowy bias. I expect that this forecast is well within that bias, and it would be wise to cut totals in half or so to be safe until we get closer to the event. Amounts in the Southeast also are unlikely to end up as high as they are shown- I would expect totals maxing out at 6" at this time.



Anonymous said...

I hope vineland nj gets a snowstorm if not I will be pissed

Anonymous said...

Andrew when are you posting the latest updates? I'm here in northern Connecticut.

Anonymous said...


It think you are getting a little so excited with winter referring to the second post on your page.. You haven't even put out a spring forecast, or a summer forecast, or a fall forecast but you are already making forcasts that are a year in advance. In my opinion you are out of your mind. Post about something that is close to a month away rather than posting something 1 year away. You need this nap out of the winter mood cause some people here don't want to hear you talking about cold and snow all the time..

Andrew said...

This is a blog that focuses more on winter than not, and the reception to such a style of blogging has been good. I'll put out those other seasonal forecasts at a later date.

Andrew said...

Additionally, this is not a forecast- I'm outlining different model guidance outlooks and describing what they say. Far too early for myself to make such a forecast.