NCEP is the National Center for Environmental Prediction in USA. It belongs under the NOAA agency. They have developed many modelling systems, including the very famous GFS model, which is the most widely used global medium-range forecast model. They also have a long range modelling system, called CFS (Climate Forecasting System).
The current designation of the long range modelling system at NCEP is CFSv2. It is the second generation of climate/long range forecasting at NCEP.
All these forecasts are an average picture over 3 months (Dec-Jan-Feb), and show the general prevailing weather pattern. Even if the models would be completely accurate, it does not mean that such weather conditions would last for 3 months straight. There can still be cold fronts and snowfall in between such milder patterns in the mid-latitudes. The difference is that instead of the usual 10-20 snow days for example, you only get 3-6 snow days (as an example). So the models don’t suggest what the weather will be like for 3 months straight, but just how it might look 40-60% of the time.
Upper level forecasts.
We always want to know how the pressure forecasts look like. That tells us a lot about the overall global circulation and weather patterns. You can learn more about the importance of long range pressure forecasts in our previous post, that contains basic information that you need to know about long range forecasts, and graphics from the September model runs to compare:
Unlike the UKMO or ECMWF, the CFS model uses 700mb pressure level for the pattern forecasts. Nonetheless, the geopotential height forecasts is similar to the ECMWF forecast. We see a deep low in the North Atlantic, surrounded by the “highs” from east USA across the Atlantic into Europe. This is yet another model with the most classical positive NAO pattern that you can see on the long range forecasts. This is a typical pattern for windy and wet weather across the UK and Scandinavia, and mild conditions across central/southern Europe. In the USA, we have warmer and drier conditions in the east, and mild and more wet in central/southern parts. We see a hint at trough development over western USA, and a blocking high in North Pacific, similar to the ECMWF and UKMO. Unlike UKMO and ECMWF, the CFS has the trough hints further west, which limits the amount of possible cold shots into western USA compared to UKMO and ECMWF.
Staying at altitude, we have the 850mb temperature forecast, which is on average around 1.500 m altitude in the mid-latitudes. Here, we can see what we expected from the 700mb height forecast. Warm conditions across Europe and east USA. CFS also has most of the USA warmer, due to the trough positioning a bit further west.
One of the most used long range parameters is of course the 2-meter temperature anomaly forecast, also simply referred to as the surface temperature forecast. It is the main forecast to tell us what to expect in terms of temperatures (warmer/colder). As we have interpreted already from the charts above, there are warmer than average conditions across Europe and most of USA. The temperature forecast across the USA is perhaps not entirely realistic, since with the much warmer eastern half, it is more likely to see at least some colder weather across the western half, like the UKMO and ECMWF have suggested.
Looking at precipitation forecast, we also see a typical positive NAO signature. Wetter than normal over UK and northern Europe, and drier than normal across southwest and southern Europe. Over USA we see wetter conditions over southeast/east parts.
To summarize, the October CFSv2 forecast shows a typical positive NAO pattern, with milder winter in Europe and entire USA, which might not be as realistic, given the pressure pattern it forecasts, and the usual atmospheric wave dynamics over the continent.
We still have the stratosphere as a major factor. Long range forecasts are generally not as good at forecasting stratospheric dynamics in detail, which means they tend to underestimate any potential sudden stratospheric warming events (SSW’s), since the final forecast is made out of many individual calculations, which have different ideas about the stratospheric development. An SSW event can have a major impact on the circulation and can cause major pattern changes in the Northern Hemisphere. So a potential SSW event is an important factor that can change the course of winter in either way across the North Hemisphere.
There are more long range models waiting to be explored, so click below to go back to the model selection page: