1. NAEFS-Experimental Precipitation Forecasts
NAEFS is an acronym for the North American Ensemble Forecast System, a combination of medium-range ensemble forecasts produced by the US National Weather Service and the Meteorological Service of Canada. Ensembles are great for weather forecasting, but the NAEFS lacks sufficient resolution to capture the detailed effects of the mountains of western North America.
The NAEFS-experimental precipitation forecasts takes forecasts from the NAEFS and downscales them to higher resolution. The downscaling method is quite simple and based on monthly high-resolution precipitation climatologies for the western U.S. The good news here is that the resulting forecasts are much better than those produced directly by the NAEFS. The bad news is that this method does not account for other unresolved effects (e.g., lake effect) and when you downscale using climatological precipitation-altitude relationships, you don't account for situations that depart dramatically from those relationships. For example, frontal passages feature weaker enhancement over the mountains compared to climatology, whereas some pre- and post-frontal periods can produce much larger enhancement.
Despite these warts, the NAEFS products we produce are quite useful. We generate plots of 7-day downscaled quantitative precipitation forecasts (water equivalent) and snowfall for several regions. Below is an example for northern Utah.
We also do plumes for many locations including Alta-Collins, Canyons (mid mountain), Park City Base, Brighton, Sundance, Snowbasin, etc. Below is the latest for the base of Park City.
2. HRRR forecasts
The HRRR is the High-Resolution Rapid Refresh, a 3-km model run hourly at the National Centers for Environmental Prediction that is used for short-range (< 18 hour) forecasting. It can be quite useful for anticipating the timing of frontal passages, whether or not snow will develop in a few hours, etc. We provide plots of (1) surface wind and simulated radar reflectivity and (2) surface wind and 1-h accumulated precipitation. Below is a forecast of the former for later this afternoon showing just a few showers along the UT-ID border.
Because I like to look at long loops of past data for context, the loops on the Utah Weather Center include a large number of analysis frames showing the past weather. I suppose that chews up a lot of data on your mobile phone plan, but hey, you get what you pay for!
For those of you who think resolution is everything, we provide forecasts from the high-resolution NAM nest, which has 4-km grid spacing compared to the regular 12-km NAM. We also provide high resolution forecasts from the GFS at 13-km grid spacing, which is as close to native resolution as you can get.
I don't use these much for precipitation because they have an overforecast problem over the mountains. They always forecast large precipitation amounts and about 1 in 10 times they get it right. Unfortunately, they give you a false alarm the other 9 out of 10 times and false alarms are extremely damaging for ones meteorological reputation!
4. NCAR 3-km Ensemble (Coming Soon)
The National Center for Atmospheric Research (NCAR) runs a 10 member high-resolution (3-km grid spacing) ensemble once a day. It produces forecasts out to 48 hours. We're working with it offline right now and hope to put it up on the Utah Weather Center sometime this winter. I don't know how skillful the forecasts are, but the horizontal plots sure look awesome. Here's an example from a couple of days ago.
We've been working on plume and box-and-whisker plots to indicate accumulated precipitation and periods when heavier precipitation rates are likely.
Special thanks to Trevor Alcott, Tom Gowan, NCEP, and NCAR for their coding expertise or models!
I'll try and cover some more tools in a future post as I couldn't get to them all today.