This post will be updated as the computer model information arrives Tuesday evening into Wednesday morning.
So, have you heard it may snow on Friday?
A few things:
12Z run = 7 am EST initialization time
00Z run = 7 pm EST initialization time
QPF = Quantitative Precipitation Forecast (how much liquid precipitation falls – must convert for snow totals)
GFS, ECMWF, Canadian Ensemble Mean
The mean (average) of all the different ensemble members of the GFS, ECMWF and Canadian models all bring a significant storm to Southern New England. The GFS and the ECMWF take the intense storm over “The Benchmark” 70W/40N – a textbook track for big Nor’easters. The Canadian is a bit farther south.
Short Range Ensemble Forecast (SREF)
This forecast is based on about 25 different computer model simulations using slightly different parameters to try and come to a consensus as to what will happen in the future. Ensemble forecasting is much more widespread and useful than it was just a decade ago. One way to interpret the ensemble forecast is to come up with a probability of certain criteria, such as snow totals, being reached. The 03Z SREF shows a relatively high probability of at least a foot of snow in Southeastern New England. Notice how it is away from the immediate coast.
European (ECMWF)
Whoa, nellie! If the GFS went beast mode at 00Z, I’ll have to find a new way to describe what the 00Z European looks like. The best way to put it is historic, and that’s kind of bothersome considering that it is less than 72 hours from the storm. It takes a 984mb storm to southeast of Nantucket and then slows it down for a bit, so the snow doesn’t end until Saturday afternoon. I need a calculator for the total QPF, which comes out to an astounding 2.94″ in the Providence area – and it’s mainly or all snow!
This isn’t the kind of computer model run that you hope happens, it’s the kind that you frame, put on the wall and hope doesn’t happen. It would be a widespread 18-30″ snowstorm, probably in the top 10 on record, for all of Southeastern New England except the Cape/Islands. I can’t overstate it enough, this is a straight analysis of a computer model, and not an official Right Weather forecast.
The wind would be strong and damaging on Cape Cod, the islands, and probably in RI, too. The height of the storm is from Friday evening through Saturday morning in this computer model run.
The European Ensemble run is also locked in on a major event.
Canadian, GFS, NAM on following pages…
Canadian (GEM)
The 00Z run of the Canadian model is stronger and closer to the coast than the 12Z run. It’s a knock ’em out of the park Major League Nor’easter for Southern New England. Total QPF is around 2″, and it does not look like much rain would be involved for all except the immediate coast, Cape Cod, and the islands. Even there it’s a close call. It also lasts a few hours longer, with accumulating snow until mid-morning. There is not as much extra data to dissect from the Canadian model compared to the US models. Here are a few images showing the track.
Global Forecast System (GFS)
It took a while for the GFS to come around, but the 00Z run picked up right where the 12Z left off with a raging storm south of Long Island by midday Friday. The storm is even more intense than the 12Z run, and it’s also a bit farther north – bringing some precipitation-type issues to Southern New England. The model has a beast just southeast of Nantucket at 72 hours (7 pm Friday). It ends the snow just after dawn on Saturday.
Total QPF is 1-2″ (1.5″ on the nose for Providence area), but the chance for mixing from the coast to I-95 is right at the height of the storm. Snow totals (see graphic below) are generally 8-16″ in Southern New England. You can ignore the Cape/Islands on that map because of grid point issues with the model. Note: When using the BUFKIT tool there is a six hour period of rain or mixed precipitation in the Providence area. That keeps the totals down considerably, with a final amount near 8″.
The 00Z run shows the potential for 65 mph sustained winds on Nantucket. Gusts would be over hurricane force for the Cape and Islands.
It should be noted that the models bring single-digit Arctic air into Southern New England following the storm, with it arriving by Sunday morning.
North American Model (NAM)
The last remaining holdout on the significant storm front was the NAM model. It still was not phasing the northern and southern systems as they hit the East Coast. The Tuesday evening (00z) run changed significantly, but not to the degree that the Tuesday morning (12z) GFS, European, and Canadian were showing. There is a storm that intensifies near Cape Hatteras and moves northeast, but it is not as close to the coast as it is in the other model projections.
The storm gets underway by mid-morning, and the peak of it is in the mid to late evening. It is over by dawn Saturday. The NAM has a precipitation type issue from the coast to Providence around midday Friday. A little surge of milder air arrives just before the storm intensifies. This would lead to a brief period of rain and knock a few inches off the snow accumulation potential. The wind is gusty in Eastern MA, but nowhere near as strong as the other models with closer, more intense storms are projecting. Peak winds in SE MA would be 35-50 mph. Continues on next page with graphics…
Interestingly, it still uses the energy from the northern system to keep the snow piling up in Southern New England. The end result is about the same as far as snowfall totals, but there is considerably less wind. Check out the maps below, and, remember, this is all inside baseball, and should not be construed as the official Right Weather forecast.
