Precipitable Water Vapor Forecasting

ForO (Forecasting the Observatories)

WRF 3.8

System monitoring


The ForO concept embeds a numerical weather forecasting model (WRF), a framework (WEMFO) and a number of tools and scripts to perform the pre and post processing tasks to generate final forecast products which will be available through this website on a 24x7x365 basis.

ForO performs WRF forecasts separately for each observatory: Observatorio del Roque de los Muchachos (ORM) and Observatorio del Teide (OT). The WRF model run consists of 3 main phases: pre-processing, simulation (model run) and post-processing. Those 3 main phases (or blocks of a WRF model execution) are shown in the System Monitoring section of ForO as in the next figure, when the model is not being executed (i.e: it is in an idle state):

Pre-processing phase:

When a new simulation starts, the system indicates the observatory over which the prediction is been performed. The pre-processing phase consists of 4 steps, mostly done by the WPS module in WRF:
  • Get the external meteorological data from GFS model
  • Run the geogrid.exe program: this creates terrestrial (static) data for the simulation domains
  • Run the ungrib.exe program: this unpacks GFS external files and pack it into a intermediate format
  • Run the metgrid.exe program: this interpolates meteorological (GFS) data horizontally into the simulation domains
This subphases are indicated in the "System monitoring" section as they progress. When the system is performing tasks in this phase, the "Pre-processing box" changes to yellow, as shown in the figure below, when the external meteorological data from GFS model is being executed:

Simulation (WRF model run) phase:

Now we move onto the WRF module, which in turn consist of 2 executables:
  • The real.exe program: vertically interpolates the data onto the model coordinates. It generates initial and boundary conditions files for each model domain (For example, in the case of ForO for a simulation with 3 nested domains d01, d02 and d03).
  • The wrf.exe program: executes the WRF model.
In the next two figures, the REAL program is being executed first, and upon its completion, the WRF is started for a simulation:

Post-processing phase

Once the WRF model has been executed for the whole forecast window (currently, 72 hours), the post-processing phase starts to generate the final forecast products separately for each observatory: PWV forecasted Time Series and 2D plots for the three simulation domains:

After all final products have been generated, the system returns to its idle state, reflected again in the three phases pictured in grey:

Note, as shown in this figure, that while in the idle state, the system informs the scheduled time for the next forecast job.

This procedure is executed four times a day at 00, 06, 12 and 18 UTC. In the event of a failed simulation, a warning text would appear in the top of the web page, before the PWV time series plot, indicating also the date and time corresponding to the current forecast available in this website.

For more information regarding the WRF model arquitecture, configuration and usage, please refer to the publications listed in section references.


G Pérez-Jordán, J A Castro-Almazán, C Muñoz-Tuñón; Precipitable water vapour forecasting: a tool for optimizing IR observations at Roque de los Muchachos Observatory, Monthly Notices of the Royal Astronomical Society, Volume 477, Issue 4, 11 July 2018, Pages 5477-5485,

Skamarock, W. C., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, M. G Duda, X.-Y. Huang, W. Wang, and J. G. Powers, 2008: A Description of the Advanced Research WRF Version 3. NCAR Tech. Note NCAR/TN-475+STR, 113 pp.doi:10.5065/D68S4MVH

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