Fog Threat Calculator

(last updated 8/3/2005)

Update: Todd Lericos sent a new version of the program (available from the link below) on 9/24/03. He says that the new version now has an archive function and better instructions. Also, if the forecaster enters the data, they can save it for post-analysis or case studies. He has also updated the interface.

Todd Lericos from NWS Spokane has developed a fog threat calculator based on the the methods described by the UPS Fog Technique. The user inputs variables such as cross-over temperature, forecasted low temperature, average wind and temperature in the boundary layer, and soil temperature. The program then calculates the threat of fog or stratus via the UPS technique. Output is color coded for quick analysis of data.

Download the Zipped Calculator File

The following is taken from an e-mail in which Todd Lericos gives an explanation of the program, why it's useful, and possible future developments for the next version:

The program itself is nothing fancy. It just does some calculations on input data and spits out parameters used in the UPS fog technique. There are other similar programs out there as well. However, many of them just ingest model numbers and calculate. I believe the strength of my program is that you can quickly adjust the input numbers and recalculate very quickly. In other words, you are not simply inputting model guidance numbers. The forecaster can make an assessment of the boundary layer based on other sources of data(e.g. ACARS,soundings,VWP, etc). These data sources, combined with forecaster brain power, can beat the model numbers (at times).

We have had great success with this out here in Spokane. It will even work in advection fog cases provided you can assess the boundary layer upstream. This winter (our fog/stratus season) we will begin an in- depth study on this method with verification numbers. Also, we are teaming up with Tallahassee WFO to compare and contrast how this method works in different weather regimes.