FogPlot
(last updated 9/2006)
The following is from an e-mail from George Phillips (Topeka ) to the AllSOOs digest. It discusses a method his office developed that produces a graphical output for help in using the UPS method. FogPlot is available from the Local Applications Database. This e-mail was originally written in January of 2003. Changes as of September 2006 have been made in RED.
The UPS radiation fog forecast method has been promoted a great deal in the last year in our region. I read the paper with some interest this last summer, and made it mandatory reading for the mets in September. However, it was obvious we needed some type of graphical/tabular output to view in order for the forecasters to use it effectively. I asked our ITO, Brian Walawender, to create an application that would:
1. Produce a graphical trace of the time history of temperature and dewpoint (for help in estimating the crossover temp).
2. Output the low temperature forecast from the RDF to determine whether/how much temps will fall below the crossover temp. (The low temp is now retrieved directly from the GFE grids.)
3. Produce tabular output of the FRH/FRHT output used in the MRi calculation and using RDF temperatures for the zones containing TAF sites for the "shelter temp". (Approximated FRH type output can now be retrieved from the Eta Model netCDF file (see below). The shelter temps are now retrieved directly from the GFE grids instead of the RDF.)
4. Output the soil temperatures from our agricultural observation sites.
We started utilizing the FogPlot program in October and the forecasters have been relatively enthused about using it. It hasn't been a silver bullet, but it's really helped in getting them thinking more about fog possibilities. Has it helped our forecasts for LIFR conditions associated with radiation fog? A little. There is still a reluctance to "go low". But I expect that as we gain experience using the program/method, we will get better.
Interacting with the forecasters, it became apparent that I needed to re-emphasize the situations where this method would be useful, and the limitations of the method and program output. *Anyone using the program should have read the UPS paper and fully understood it.*
Obviously this method works better in some locations than others. Additionally, the MRi was developed from FRHT/FRH and there are only so many FRH sites. To minimize the 2nd concern, Brian has added the ability to extract the FRH type output directly from the NAM40 netCDF file. However, the T1 and T3 temperatures in the FRH output do not directly correspond with any level/layer available in the NAM or NAM40 netCDF files (see item #1 at http://www.srh.noaa.gov/topics/attach/html/ssd97-36.htm for more explanation). The NAM model output is post-processed to get the FRH, to attempt to get it to correspond the the same layers available in the NGM FRHT (sigma). In the FogPlot's NAM grids output, the T1 and Boundary Layer winds are taken directly from the AWIPS NAM BL level. To get T3, interpolation is performed to obtain a temperature at 0.897 x Psfc (should be similar to FRH interpolated T3). But the BL temp values available on AWIPS from the NAM are not infrequently off by 2 or 3 degrees from the FRH T1 values at a given FRH site. Just a cautionary note for those who want to compare the FRH values to those derived from the NAM model netCDF file.
Very low visibilities associated with radiation fog are relatively infrequent here. But so far this fall and early winter, we've had more hours of dense fog than the entire 2001/2002 cool season, so it's been a good experience.
You may want to give the program a try if you think the UPS Method could have merit for your TAF sites, and you don't already have some other type of program output for this method.
If you decide to try it out, be sure you read the installation/readme file that comes with it as it explains how the estimated cross-over temperature and other output is derived, as well as other cautions and limitations. It could be a two person installation as your GFE Focal Point may be required to create new edit areas for the TAF sites.
