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Acquire GEFS data

About the data

WGS84 - EPSG:4326

  • Bounding box 94,-12,142,7

  • GeoJSON 

    {"type":"FeatureCollection","features":[{"type":"Feature","properties":{},"geometry":{"type":"Polygon","crs":"EPSG:4326","coordinates":[[[94,-12],[94,7],[142,7],[142,-12],[94,-12]]]}}]}

BBox

GEFS Forecast

GEFS forecast data only available for the latest 3-days and updated every 6-hours period. Accessible via this GRIB filter: https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?

If today is 4 Nov 2020, then GEFS only available from 1 - 4 Nov 2020.

Download and subset for Indonesia via GRIB filter

Example parameters

Forecast available every 6-hours, we will focus from f006 (start of data) until f120 (day-5)

  • Release hour (00, 06, 12, 18): geavg.t00z
  • Forecast hour (f006, f012, f018, f024, f030, f036, f042, f048, f054, f060, f066, f072, f078, f084, f090, f096, f102, f108, f114, f120): f006
  • Level: surface
  • Variable: APCP
  • Subset: Indonesia (94,142,7,-12)
  • Date (YYYYMMDD): 20201103
  • Release hour (00, 06, 12, 18): 00

Script: 

https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?file=geavg.t00z.pgrb2s.0p25.f006&lev_surface=on&var_APCP=on&subregion=&leftlon=94&rightlon=142&toplat=7&bottomlat=-12&dir=%2Fgefs.20201103%2F00%2Fatmos%2Fpgrb2sp25

Download process

Each time we run the download process procedure (Example: Date 3 Nov 2020, release hour 00), it means we need to download all the forecast hour from f006 to f120

https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?file=geavg.t00z.pgrb2s.0p25.f006&lev_surface=on&var_APCP=on&subregion=&leftlon=94&rightlon=142&toplat=7&bottomlat=-12&dir=%2Fgefs.20201103%2F00%2Fatmos%2Fpgrb2sp25

https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?file=geavg.t00z.pgrb2s.0p25.f012&lev_surface=on&var_APCP=on&subregion=&leftlon=94&rightlon=142&toplat=7&bottomlat=-12&dir=%2Fgefs.20201103%2F00%2Fatmos%2Fpgrb2sp25

https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?file=geavg.t00z.pgrb2s.0p25.f018&lev_surface=on&var_APCP=on&subregion=&leftlon=94&rightlon=142&toplat=7&bottomlat=-12&dir=%2Fgefs.20201103%2F00%2Fatmos%2Fpgrb2sp25

...

...

https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?file=geavg.t00z.pgrb2s.0p25.f114&lev_surface=on&var_APCP=on&subregion=&leftlon=94&rightlon=142&toplat=7&bottomlat=-12&dir=%2Fgefs.20201103%2F00%2Fatmos%2Fpgrb2sp25

https://nomads.ncep.noaa.gov/cgi-bin/filter_gefs_atmos_0p25s.pl?file=geavg.t00z.pgrb2s.0p25.f120&lev_surface=on&var_APCP=on&subregion=&leftlon=94&rightlon=142&toplat=7&bottomlat=-12&dir=%2Fgefs.20201103%2F00%2Fatmos%2Fpgrb2sp25

When new forecast released (for example release hour: 06, 12 and 18), we need to repeat all download procedure above and adjust the script with current release hour.

Naming convention for GEFS product

All downloaded GEFS files must be renamed using following standard.

apcp.gefs.0p25.YYYYMMDDID.fxxx.grib2

where

  • apcp: GEFS apcp.gefs.0p25 precipitation code
  • gefs: name of product
  • 0p25: code for 0.25deg product
  • YYYY: year
  • MM: month
  • DD: date
  • ID: release hour
  • f: forecast data
  • xxx: forecast hour

Example

apcp.gefs.0p25.2020102100.f024.grib2

Prepare input data (rainfall forecast) for model

Conversion from GRIB2 to GeoTIFF

All downloaded subset GEFS are in GRIB2 format. We need to convert it to GeoTIFF, the easiest way is using GDAL: 

gdal_translate -of GTiff input.grib2 output.tif

Resample

GEFS data available at 0.25deg ~ 27.75km/pixel spatial resolution

While GPM IMERG available at 0.1deg ~ 11.1km/pixel. So we need to resample (250%) GEFS to match with IMERG using GDAL. 

gdal_translate -r bilinear -outsize 250% 250% input.tif output_resample.tif

Clip the raster with Indonesia boundary

Then we need to crop the GeoTIFF using Indonesia boundary. GDAL can handle this task: 

gdalwarp --config GDALWARP_IGNORE_BAD_CUTLINE YES -srcnodata -999 -dstnodata NoData -cutline idn_bnd_subset_clip_imerg_grid_a.shp -crop_to_cutline input.tif clip_output.tif

Calculate accumulation 1 to 5 days rainfall forecast.

Example: pre-downloaded and renamed GEFS data: https://on.istan.to/32v1tVY

Date: 3 Nov 2020, release hour 00

  • 1-day

    apcp.gefs.0p25.2020110300.f006 + f012 + f018 + f024

  • 2-days

    apcp.gefs.0p25.2020110300.f006 + f012 + f018 + f024 + f030 + f036 + f042 + f048

  • 3-days

    apcp.gefs.0p25.2020110300.f006 + f012 + f018 + f024 + f030 + f036 + f042 + f048 + f054 + f060 + f066 + f072

  • 4-days

    apcp.gefs.0p25.2020110300.f006 + f012 + f018 + f024 + f030 + f036 + f042 + f048 + f054 + f060 + f066 + f072 + f078 + f084 + f090 + f096

  • 5-days

    apcp.gefs.0p25.2020110300.f006 + f012 + f018 + f024 + f030 + f036 + f042 + f048 + f054 + f060 + f066 + f072 + f078 + f084 + f090 + f096 + f102 + f108 + f114 + f120