Today's Weather Maps

Forecast Image Forecast Image

Data Source

The weather maps shown here are generated from the NCEP Global Forecast System (GFS) model. GFS is the primary operational model framework underlying U.S. NOAA/NWS weather forecasting. The model is run four times daily on a global T1534 gaussian grid (~13 km) to produce 16-day forecasts. Here, we use 0.25°x0.25° (~30 km) output grids available from NOMADS, and calculate daily averages from eight 3-hourly timeslices starting at 0000 UTC.

Additional Details

  • Sea surface temperature (SST) and SST anomaly maps are generated from NOAA Optimum Interpolation SST version 2 (OISST V2). OISST is a 0.25°x0.25° blendend dataset derived from satellite, ship, and buoy measurements. The SST anomaly is based on a 1971-2000 NOAA climatology.

  • Temperature refers to air temperature at 2 meters above the surface. The temperature anomaly is made in reference to a 1979-2000 climatology derived from the reanalysis of the NCEP Climate Forecast System (CFSR/CFSV2) model. This climate baseline is used instead of the 1981-2010 climate normal because it spans a period prior to significant warming of the Arctic beyond historically-observed values. For context, see this timeseries plot showing how various climate baselines compare against the NASA GISS 1880-2014 global land-ocean temperature index.

  • GFS Model Bias Correction — GFS has a systematic model bias compared to CFSR/CFSV2 in which the diurnal cycle has greater amplitude over areas of snow/ice and hot desert. A correction term, calculated from the difference between GFS and CFSR/CFSV2 on average per month from June 2015 - May 2016, is therefore applied such that regional temperature anomaly values are consistent with CFSR/CFSV2. A timeseries plot showing the bias corrections for each region is shown here. Temperature anomaly maps showing uncorrected and corrected GFS vs. CFSR/CFSV2 can also be found here.

    Note that bias-corrected GFS-CFSR temperature anomalies will still differ slightly from those calculated from CFSV2-CFSR. The most reliable temperature anomaly estimates can be found in the Daily Reanalysis Maps image archive. The archive is updated once or twice per month.

    See this NCEP/NWS discussion for additional information on model bias.