UPS Forecast Program

(last updated 8/3/2005)

Meteorologists at United Parcel Service (UPS) Airlines have developed a fog forecasting process for situations where radiative heat loss is an important component of cooling in the boundary layer. The abstract of a paper describing the process is given below, and the complete paper is available here (requires Adobe® Acrobat® Reader®; click here to download a free copy). The technique, along with examples, is also described in DLAC 1, Lesson 2d, Applying Diagnostic and Forecast Tools.

Todd Lericos in the Spokane office has developed a Fog Threat Calculator based on this technique. The Tallahassee WFO staff have been evaluating the UPS technique for their office and believe it may be of limited utility there. They are looking at combining it with another study (see "Tallahassee Decision Trees") in hopes that the two used together might yield some positive results.

Radiation Fog: UPS Airlines Conceptual Models and Forecast Methods
by
Randy Baker, UPS Airlines, Louisville, KY, Jim Cramer, and Jeff Peters

United Parcel Service (UPS) Airlines has developed conceptual models and forecast methods for the prediction of radiation fog. A potential fog layer is viewed as being several hundred feet in vertical extent, and the importance of the vertical distribution of moisture (hydrolapse) in this layer is discussed. A technique for roughly inferring the hydrolapse in the absence of direct observations above shelter height is presented.

Mechanical turbulence and its effect on fog formation is discussed, and a technique for quantitatively forecasting turbulence using common forecast data and Richardson number concepts is presented. The importance of soil temperature and the consequent heat exchange between the lower atmosphere and the ground is discussed, as well as the potential for some pre-existing stratus cloud decks to "build down" to the surface as fog. The synoptic situation involving weak fronts with cloud cover clearing during the hours around sunset is highlighted as particularly prone to fog formation. Several case studies are presented to demonstrate the application of the UPS concepts and techniques.