Accessing Real-Time Rapid Update Cycle Data

NWS/NCEP Office Note 388 - GRIB / NCEP output grid information - available at http://www.nco.ncep.noaa.gov/pmb/docs/on388/download/

Updated November 2002

Main RUC homepage

RUC grids are available from two sources:

An NWS file server called the TG server (Telecommunications Gateway)
The National Weather Service's Family of Services

There are three sections to this document:

ftp access via the NWS TG Server
Access via the Family of Services
Fields available from the TG server

Information on GRIB available at these web sites:
ftp://ftp.ncep.noaa.gov/pub/nws/nmc/docs/gribed1/
http://www.unidata.ucar.edu

1. ftp Access via the TG server

The Rapid Update Cycle (RUC) output is available on the National Weather Service's TG file server. For more information on the TG server, see

Type in the following:

ftp

open tgftp.nws.noaa.gov

account: anonymous
password: your email address

Once you're in:

cd /SL.us008001/ST.opnl to get to a directory for all NCEP operational cycles for the last day.

Next, cd MT.ruc_CY.hh where hh is the hour of the initial time. There is a separate directory for each hourly cycle. From this point, for instance, cd MT.ruc_CY.12 for the 1200 UTC cycle. Sorry, you're not quite there yet; still two more subdirectory levels to go:

cd RD.yyyymmdd where yyyy is the year, and mmdd is the month/date of month.

cd PT.grid_DF.gr1

The entire path for grids is /SL.us008001/ST.opnl/MT.ruc_CY.hh/RD.yyyymmdd/PT.grid_DF.gr1

Different types of grids (20km/40km fields in each file listed here ) are then in different directories. All of these files are in GRIB format:

us40km - isobaric main (6 3-d fields on 25 mb levels, plus 79 2-d (special level plus sfc) - 40km resolution, us20km - same at 20km resolution
sgrib - sfc - (25 2-d fields) - 40km resolution, sgrib20 - same at 20km resolution
bgrib - native coordinate fields - 40km resolution, bgrib20 - same at 20km resolution
us80km - RUC grids interpolated to 80-km AWIPS 211 grid (matching similar output from previous RUC versions)

File name convention

   fh.hhhh_tl.press.gr.#### 
     where 
     #### is the file name extension as listed above, e.g., sgrib20
     hhhh is the forecast projection hour (or 'anal' for analysis)

The entire path for BUFR sounding data is /SL.us008001/ST.opnl/MT.ruc_CY.hh/RD.yyyymmdd/PT.sndn_DF.buf

Output times available and when available

Cycles divisible by 3 except 1200 and 0000 UTC (initial times at 03,06,09,15,18,21 UTC)
- Analyses available about 40 min after the analysis valid time - e.g., 1500 analysis available about 1540 UTC
- Forecasts (projections available for 1,2,3,6,9,12 h forecasts) are all available about 60 min after the analysis valid time - e.g., 1500 UTC forecasts are available about 1600 UTC)
0000 and 1200 UTC cycles
- Analyses are done twice for these times. The first analysis is an early look analysis and is available at about 40 min past the analysis time. This analysis contains only about half of the rawinsonde data, but contains most of the other data sets. The second analysis has a data cut-off at 55 min past the hour and is available by about 67 min after the analysis time.
- Forecasts for these cycles are run from the second analysis to catch the late rawinsonde data. A larger number of processors are applied to get the model run quickly and the 12-h forecast is complete and output files are available by about 90 min after the analysis time.
Cycles not divisible by 3 (initial times at 1,2,4,5,7,8,10,11,13,14,16,17,19,20,22,23 UTC)
- Analyses are available at about 40 min after the analysis time
- Forecasts are available at about 60 min after the analysis time (1,2,3 h forecasts only for these cycles)

2. RUC Grid Access via the Family of Services

The RUC is also available from the National Weather Service via the Family of Services. This is a service which must be subscribed to for a fee. Some current subscribers include WSI, Kavouras, and Accu-Weather. This service is maintained by the Office of Systems Operations (OSO). NCEP puts the proper headers on the GRIB files and sends it to the National Weather Service Telecommunications Gateway. There, a switching directory maintained by OSO directs it to the proper location.

3. List of contents of RUC files available from the Rapid Update Cycle

20-km/40-km grids

Click here for list of 20/40-km grid output variables in each file

80-km AWIPS 211 grid format

These files are created every three hours (8 times per day). Separate files are created for the analysis , and forecasts outputs at 1,2,3,6,9,12 hours. The grid is a 93 X 65 80 km Lambert-Conformal grid. Only points within the RUC grid domain are given values. Each file contains the following (exceptions are noted):

Isobaric levels: (37 levels) every 25 mb 1000 - 100 mb

height
temperature
relative humidity
u and v wind components

Mean sea level

pressure (MAPS reduction method, Benjamin and Miller 1990, Monthly Weather Review)

Tropopause level

pressure
potential temperature
u and v wind components

Maximum wind level

pressure
u and v wind components

Freezing level

pressure
height
relative humidity

Layers near ground (0-30 mb, 60-90 mb, 150-180 mb above ground)

relative humidity
u and v wind components
temperature

Surface

10 m u and v wind components
2 m relative humidity
2 m temperature
1 hr accumulation non-convective precipitation (fcst files only)
1 hr accumulation convective precipitation (fcst files only)
1 hr accumulation total precipitation (fcst files only)
3 hr accumulation non-convective precipitation (3,6,9,12 hr fcst files only)
3 hr accumulation convective precipitation
(3,6,9,12 hr fcst files only)
3 hr accumulation total precipitation (3,6,9,12 hr fcst files only)
instantaneous precipitation rate (fcst files only)