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GEFS REFORECAST·dataset

Practice forecasts replaying past weather (NOAA)

NOAA Global Ensemble Forecast System (GEFS) Re-forecast
atmosphere NOAA NOAA active
In plain English

What it measures. Retrospective weather forecasts that re-run the modern forecast system over past years (2000 to 2019), so today's model can be tested against what actually happened.

How it's made. Generated by NOAA alongside version 12 of its Global Ensemble Forecast System, with a handful of forecast members run daily and a larger set once a week extending to 35 days out.

How & where you'd use it. Lets forecasters calibrate and improve predictions and helps researchers gauge how reliable the forecast model is.

What's measured

aws-pdsagricultureclimatemeteorologicalweather

Coverage & cadence

  • Time span— → ongoing

What you can do with it

  • Map air pollutants — NO₂, aerosols, ozone
  • Track greenhouse gases and Earth's energy budget
  • Feed weather and air-quality analysis
Official description

NOAA has generated a multi-decadal reanalysis and reforecast data set to accompany the next-generation version of its ensemble prediction system, the Global Ensemble Forecast System, version 12 (GEFSv12). Accompanying the real-time forecasts are “reforecasts” of the weather, that is, retrospective forecasts spanning the period 2000-2019. These reforecasts are not as numerous as the real-time data; they were generated only once per day, from 00 UTC initial conditions, and only 5 members were provided, with the following exception. Once weekly, an 11-member reforecast was generated, and these extend in lead time to +35 days.

Get the data

noaa_access.py
# NOAA Open Data on AWS — public S3, no login
import s3fs

fs = s3fs.S3FileSystem(anon=True)
# find this dataset's bucket in the docs link in the sidebar, then:
# files = fs.ls("noaa-<bucket>/...")
# open NetCDF/GRIB with xarray, COGs with rioxarray
NOAA Open Data is on public AWS S3 — no login at all (anonymous access).