The human race must question everything!
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30 Jan 2017
Well, this storm potential has been talked about a few times in the winter thread and clipper thread, so I figured I'd get the discussion started. First of all, a warning of caution when looking at the models: the system does not come fully ashore until Saturday between 00z and 12z, so until then expect fairly major run-to-run variation and inconsistencies. However, we can look at ensembles to get an idea of whether there is any clustering going on as well as looking at forecast teleconnections.
Let's start with the latter:
From this image we can see that in the period leading up to storm system (which is important because three of the 4 indices shown are in the pacific so its downstream effects are not usually felt until several days after) we have a transitioning PNA from negative to positive, an increasingly negative WPO and EPO and an increasingly positive NAO. From this we can gather a few things:
1. Negative WPO and EPO generally signify more cold air available to central and eastern Canada.
2. Transition from negative to positive PNA signifies a transition to more ridging in the west and troughiness in the east
3. A positive NAO signifies a strengthening SE ridge.
Overall, these ingredients combined together certainly mean that a storm system, and potentially a potent one, is possible in the Great Lakes and/or eastern Canada/US. However, the devil's in the details of course, in terms of how these pieces come together in terms of storm formation and track.
This leads into the following images, some snapshots of ensemble forecasts:
Here is this morning's 00z ensemble forecast at hour 168:
What we should notice from each one of these individual ensemble members are either two area of lower pressure: one in northern Ontario and the other in the south-central or SE US, or one area of low pressure in and around the Great Lakes. This outlines well the issue that we seem to be dealing with: a phasing or lack thereof of a northern stream low pressure and a southern stream low pressure. Whether or not these phase and how amplified the trough can become will determine the strength and track of the storm(s).
For comparison sake, here's a look at the 00z Canadian ensembles at the same hour:
And the ECMWF Ensemble mean and spread, as well as the operational ECMWF on the right:
From these forecast charts, we can see that as of right now, there seem to be more individual ensemble members leaning towards an unphased solution, with the northern stream being the dominant one and essentially acting as another clipper-type system.
It's tough to say exactly what we'll happen but either way, precipitation is likely in this period in Eastern Canada; type and amounts to be determined (though I would say snow is the most likely given the amount of cold air).
26 Jan 2017
Well, we may have had one or two in December, but to be honest, this looks like the first true Alberta Clipper of the season! In fact, it looks like the original energy associated with this system will be impacting either or both southern Alaska/Yukon Saturday and Sunday.
From there, the system will make its way over the northern Rockies on Sunday into the Northwest Territories.
Then, the system will stall and spin for a little while up in the NWT, before it looks like some energy will come ashore further south into BC and eventually make its way over the Rockies, leading to the secondary development to the SE of the NWT low, as we see below with a new LP system over east-central Manitoba.
Eventually the system will make its way into Ontario and Quebec.
In general, this will probably be a fairly typical clipper in terms of track and moisture. Track through central Ontario and into south-central Quebec before eventually tracking and possibly strengthening in the Maritimes and NFLD.
The great things about clippers is that you don't have to be on the northern side to get the best snow. Usually there is light-moderate snow on both the northern and southern side, with in fact the southern side having more moisture sometimes. In general, this system will probably drop 3-10cm on average for the areas affected, but a few locales could get into the 10-15 cm range if it can pull enough moisture, but I wouldn't hold my breath for that.
Some of the models and ensembles have the system a bit further south or north which will change the areas affected and the moisture available for the system. For right now though, the operational GFS seems to be a good middle ground for both track and moisture.
Hopefully this will help whiten up some areas that have gone bare over the past couple of weeks
1 Dec 2014
This looks like it could be a decent event for Ottawa, Montreal and Quebec City potentially...
12z RGEM total snowfall out to hour 48:
12z NAM total snowfall:
12z GFS total snowfall:
Wouldn't be surprised to see 3-8cm, and if it sinks south some, perhaps 10cm.
Definite improvement from how it was looking earlier on this weekend, with +7 and rain more likely, as oppose to ranging from -3 to +3 with snow changing to wet snow and rain perhaps.
WE shall see!
17 Nov 2014
Looks like we'll see our first real clipper of the season!
Here's the 00z RGEM up to hour 48:
The further south this goes the better! With the lake enhancement some areas could pick up 5-10cm from this and if it digs far enough south, could pick up some extra moisture for southern Quebec. We shall see!
11 Nov 2014
Well, it's been awhile since I created a topic, so I'm excited to create this one! I've been watching this on the models the past few days, and have finally seen enough to think this is worthy of a topic, as I now believe this will impact someone in Eastern Canada, and possibly with a good amount of snow, wind and rain.
Here are the latest 12z models:
12z GFS Individual Members:
As you can see, some of the individual members show quite the impressive storm for the region, with the OP GFS on the top left.
12z OP ECMWF:
12z OP GGEM:
Let's have fun tracking this! I know I will, with midterms all done!!
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