Data Sources & Additional Information

• Weather maps on this page depict output from the operational NOAA Global Forecast System (GFS) model. GFS utilizes a 13 km Finite-Volume Cubed-Sphere dynamical core (FV3) to produce 16-day forecasts 4x daily. The maps here are generated using NCAR Command Language (NCL). Daily means are calculated from eight 3-hourly timeslices beginning 0000 UTC. Source GFS files are downloaded from NOMADS.


• 2m Temperature refers to air temperature at 2 meters above the surface. 2m Temperature Anomaly refers to the departure of the current day's forecasted temperature from a long-term mean for the same day of the year. The anomalies here are based on a 1979-2000 reference climatology derived from the NCEP Climate Forecast System Reanalysis (CFSR). This 22-year baseline is used instead of the more common 1981-2010 climate normal because 1979-2000 represents conditions prior to rapid Arctic warming and sea-ice loss. A comparison of different climate baselines against the historical temperature record is shown here.


• Temperature anomalies calculated between GFS (forecast) and CFSR (reanalysis) will differ somewhat from those calculated entirely within the Climate Forecast System framework (see this NCEP/NWS discussion on model bias). For the most reliable temperature anomaly estimates, refer to the Daily Reanalysis Maps page. The image archive is updated once or twice per month.


• Sea Surface Temperature (SST) and SST anomaly maps are generated from NOAA Optimum Interpolation SST version 2 (OISST V2). OISST is a 0.25° gridded dataset derived by blending satellite, ship, and buoy measurements. The SST anomalies is based on a 1971-2000 climatology calculated by NOAA.