Understanding Model Resolution
Before I jump into the latest model runs I want to talk about model resolution. The 3 main long to medium-term models I reference are the US GFS model, the Canadian GEM (sometimes referred to as the CMC), and the European model. For short-term forecasting, I often use the US NAM high-resolution model.
Weather models have varying levels of resolution. When I think of the term resolution the first thing I think of is a TV screen. A TV screen’s resolution has to do with the number of pixels that create the picture. The more pixels the greater the resolution on the TV. Weather models do not have pixels, they use grids. The smaller the grid the more grids you can fit on a weather model map. This is similar to a TV, when you add pixels they have to be smaller to fit the screen. The more grids (or pixels) you have, the higher the resolution gets.
A TV screen measures the number of pixels per inch. A weather model’s grid is measured in kilometers. The smaller the grid the higher the resolution.
Here are the grid sizes for the most common models I frequently use. Again, the larger the grid the lower the resolution.
Canadian (CMC) 15 km (9.3 miles)
German (ICON) 13 km (8 miles)
US (GFS) 13 km (8 miles)
Euro (ECMWF) 9km (5.6 miles)
US (NAM 3km) 3 km (1.9 miles)
So what does this mean? Some people are better than others at figuring out where they are on the weather maps. Yesterday a follower noticed that on that particular model run, the Euro was showing about 20 inches of snow for Edgemont. This person’s interpretation of where Edgemont was on the map was 100% correct. This is where it gets difficult. Edgemont was in the grid space that was showing 20 inches, however even with a 9km grid space, which is the most detailed of any long or mid -term-model, it leaves a huge margin of error for where that snow may fall within that grid space (assuming the model is correct at all).
I mentioned this yesterday or Tuesday when I said the Canadian model spreads the higher precipitation amounts over a larger area.
I mentioned the NAM 3 km model earlier. Within 12 hours or so of the storm arriving I use that model with its high resolution to try to hone in on precipitation amounts.
There have been a few minuscule changes over the last 24 hours. What is most encouraging is that all three of these models we have been following show a closed area of low pressure moving across California, into Arizona, and across New Mexico. The timing and track of the low’s progression are very important. This is a two-pronged storm. The only way we get precipitation is if there is a favorable position of the southern track of the low. If it is too far south, or too late, most of the precipitation will elude the forecast area.
That being said, the Euro and the Canadian still show it tracking favorably across the area. The GFS seems to go back and forth with every run.
I have multiple services I use for weather models. Occasionally, I like to sneak in a different service that employs different algorithms to highlight different locations. This version shows both Durango in town and DRO airport, as well as Wolf Creek, Pass instead of Pagosa. One of the good things is that Wolf Creek pass is pretty much two Euro grids so the accuracy is closer.
Euro liquid, “version one”
Compare that to Euro “version two”
Euro snow “version one”
Euro snow “version two”
Any and all precipitation at this point will be great. And I have reached cautious optimism that we will see some precipitation. We will see how everything pans out.
If you are going to be driving anywhere things will likely start to go downhill by Sunday afternoon. Sunday night, Monday, and perhaps Tuesday will all be affected by the storm. This may include northern New Mexico FYI. I will continue to dial this in as we get closer. Overnight lows in the lower elevations may approach 20 degrees or lower by midweek. Highs on Monday and Tuesday in the lower elevations may struggle to get out of the 40s on Monday and Tuesday.
I have not seen a major slowdown in the cold front yet. The models have slowed down the closed low coming from the southwest. I would love to see the cold front slow down and the closed low stay with its Euro timing. Those are ingredients for a perfect storm. I hope the line at the car wash on Saturday urges the storm on. A week ago a deer hit my car on North Main and I can’t get my car into the body shop until November 4th, so I will not be washing my car. It is up to you all.
Next Update Friday afternoon, thanks for following and supporting the page!