The CFSv2 climate model

At a glance

What CFSv2 is

Weather models forecast a few days to two weeks, mostly by tracking the atmosphere. Beyond that, the slow parts of the climate system matter more: the ocean, sea ice and soil. CFSv2 couples all of these to the atmosphere, so it can carry an ocean influence such as El Niño into a forecast for the coming months.

It runs as a large ensemble, four times a day, and CPC groups the runs by their starting dates. The anomalies CPC shows are measured against a hindcast reference of past forecasts for 1991 to 2020, so a forecast shows departure from that reference and not an absolute value. 4070 renders the full ensemble itself and offers daily, weekly and monthly views.

Seasonal and subseasonal products are about tendencies. A map that is warmer than normal for a month does not say what any one day will do, and it says nothing about a particular storm.

Where it does well

• It reaches far past a weather model, to weeks and months ahead.
• It is coupled, so it carries the influence of the ocean and sea ice, including El Niño and La Niña patterns.
• It is an ensemble, so the average of many runs smooths the daily noise out of a long-range lean.
• It updates frequently, so you can watch the lean shift as new runs arrive.

Where it falls short

• Skill is modest, especially in weeks 3 and 4 and beyond. Read a CFSv2 map as a lean and not a forecast.
• It cannot tell you about a particular storm or the weather on a particular day.
• A single model is a single opinion. Compare it with other seasonal systems and with what CPC publishes.
• Anomalies depend on the reference period used, so check what a map is compared with.

What it is typically used for

• Seeing how the pattern may lean over the next few weeks and months.
• Looking at 500 mb height and its anomaly to see the large-scale pattern the model favors.
• Planning conversations: which regions lean warm or cold, wet or dry.
• Following seasonal snowfall water-equivalent totals and departures.

How to see CFSv2 in 4070

CFSv2 has three views in Model Explorer under Long-Range Models, plus a seasonal snowfall tool. They are part of 4070 Pro, which starts with a seven-day free trial.

• CFSv2 Daily steps day by day through 44 days, with anomalies for 2 meter temperature, precipitation rate and snowpack, and actual values for highs, lows and wind.
• CFSv2 Weekly shows weeks 1 to 6 and two-week means for 2 meter temperature and precipitation rate anomalies.
• CFSv2 Monthly covers monthly leads, with anomalies of temperature, precipitation, 850 mb temperature, soil moisture, sea surface temperature and upper-air heights, and a 500 mb height monthly mean and anomaly. Choose the full ensemble or one group of starting dates.
• CFSv2 seasonal snowfall shows monthly and three-month snowfall water-equivalent totals and departures. That is liquid content, not forecast snow depth.

The nine-month and regional outlooks in 4070 Pro are separate products from the model maps. A regional lean is not an address forecast.

How it fits with the other models

CFSv2 sits at the long end. For the next two weeks, use the GFS, ECMWF IFS and their ensembles GEFS and ECMWF EPS. The 500 mb guide explains the height anomalies, and the model accuracy guide explains why long-range maps are read as leans. 4070 also offers other seasonal systems for comparison.

Specifications change when agencies upgrade their models. The Sources below link to the producing agency. Official National Weather Service forecasts, watches and warnings remain the authority for what is expected where you live.