Computer Model Trends: Midweek storm

Fred Campagna

11 years ago

Half of the (ahem) fun of a four to five-day storm forecast is following the run to run computer model trends. That’s what we’re doing here. Seeing how the models are swinging back and forth and hopefully not flip-flopping on their solution for the middle of next week. I will list the different model names and include some pertinent graphics. Let’s take a look at what’s going on…

GFS Model

The GFS was out to sea with the storm a couple of days ago. Last night it trended very close to the Canadian and European. As of the 12Z (7AM EST) model run, it has shifted a bit farther east, but still brings a wintry mix to Southern New England. As we stated in the Long Range Forecast, this is not an ideal setup for a winter storm in Southern New England with no high pressure to the north to lock in the cold air. If this GFS track occurs, however, there should be enough cold air around to allow for snow accumulation – especially in the hilly part of western RI.

12Z GFS – storm track is well offshore, and that allows for snow on the northern fringe of the precipitation over SNE

12Z GFS – Snow in E CT, RI, and interior E MA on Wednesday

12Z GFS snow forecast – Offshore track pushes the snow farther south and east into the I-95 corridor, but the totals are not nearly as heavy as Thursday night’s run

00Z GFS Snow totals – Thursday night’s run had a big snowstorm from Albany to the Berkshires and Northern New England. The track near the coast kept the heavy snow out of the I-95 corridor. The big Northeast cities received heavy rain.

Canadian Model

The 12Z Friday run of the Canadian model is farther inland than earlier runs. Rather than tracking the storm over Southeastern New England like the 00Z run, the 12Z run takes it over New York City. The upshot is a wind-driven rain with temperatures approaching 60° for Southeastern New England if the storm takes the latest projected track. I think it’s a little overdone with the inland track, but I expect a track closer than what the 12Z GFS is showing.

12Z Canadian – Latest run has an “inside runner” that moves over NYC and Albany putting SNE on the wind, wet, and mild side of the storm. I’m not really buying a solution this far west.

00Z Canadian – This solution is similar to the ECMWF and GFS. It seems a lot more plausible than the 12Z run.

ECMWF Model

The European model has been most consistent with delivering a storm that brings rain and snow to the Northeast. The track has wavered back and forth a bit, and that has major implications for the big cities on precipitation type. The 00Z Friday run of the Euro brought heavy snow to interior SNE and most of NH and ME. It also had accumulating snow in the rest of SNE as a second storm moved by Wednesday night. While the first snow in interior SNE makes perfect sense, we’re always a little leery of computer model forecasts that bring a lot of accumulating snow on the back side of these fast-moving storms or, in this case, a second wave of low pressure immediately in the wake of the first storm. Usually, when a storm gets north of Cape Cod, there is not a lot of wrap around moisture left.

00Z Fri ECMWF – Final snow totals after wrap around are plowable in all SNE. While possible, I think the odds still favor a mainly rain evening for Southeastern New England

00Z Fri ECMWF – This is the snow forecast *before* the wrap around snow Wednesday night.

12Z ECMWF Snow totals – round one is all rain for most of SNE. This is a warmer forecast than the 00Z run

12Z ECMWF Snow totals – this is the total as of 7 am on Thanksgiving. Notice how there is a small bullseye over Southeastern New England. Not a big storm at 1-3″, but enough to make the high school football games interesting

12Z ECMWF – First storm brings rain to most of SNE, second storm off NC coast could bring snow

GFS Ensemble

The Bottom-Line

We favor the track of the first storm that is much closer to the coast than the GFS is projecting. The start of the storm will most likely be rain for the I-95 corridor. The ECMWF has an interesting solution with a second storm right on the heels of the first. It’s a bit unusual, but could happen. The Japanese model hints at it, too. With a wet ground and a damp airmass starting in the upper 30s to low 40s, a change to accumulating snow could be difficult. It’s possible that it would change to snow Wednesday night, but not accumulate to the extent that the ECMWF is showing.