Model output statistics
Encyclopedia
Model Output Statistics is an omnipresent statistical
technique that forms the backbone of modern weather forecasting
. The technique pioneered in the 1960s and early 1970s is used to post-process output from numerical weather forecast models. Generally speaking, numerical weather forecast models do an excellent job of forecasting upper air patterns but are too crude to account for local variations in surface weather. Pure statistical model
s, on the other hand, are excellent at forecasting idiosyncrasies in local weather but are usually worthless beyond about six hours. The MOS technique combines the two, using complex numerical forecasts based on the physics of the atmosphere to forecast the large-scale weather patterns and then using regression equations in statistical post-processing to clarify surface weather details. The accuracy is generally far better than either a pure statistical model or a pure numerical model (NWP).
for their suite of weather forecasting models by 1976. The United States Air Force developed their own set of MOS based upon their dynamical weather model, the NOGAPS, by 1983. This differs from the perfect prog technique, which assumes that the output of numerical weather prediction
guidance is perfect.
, GFS
(short and long range) and 22-member GFS ensemble are used to create MOS products; the NGM
-derived MOS products were discontinued in March 2009. (List of MOS products from the MDL)
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
technique that forms the backbone of modern weather forecasting
Weather forecasting
Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Human beings have attempted to predict the weather informally for millennia, and formally since the nineteenth century...
. The technique pioneered in the 1960s and early 1970s is used to post-process output from numerical weather forecast models. Generally speaking, numerical weather forecast models do an excellent job of forecasting upper air patterns but are too crude to account for local variations in surface weather. Pure statistical model
Statistical model
A statistical model is a formalization of relationships between variables in the form of mathematical equations. A statistical model describes how one or more random variables are related to one or more random variables. The model is statistical as the variables are not deterministically but...
s, on the other hand, are excellent at forecasting idiosyncrasies in local weather but are usually worthless beyond about six hours. The MOS technique combines the two, using complex numerical forecasts based on the physics of the atmosphere to forecast the large-scale weather patterns and then using regression equations in statistical post-processing to clarify surface weather details. The accuracy is generally far better than either a pure statistical model or a pure numerical model (NWP).
Definition
Because forecast models on their own do not reliably determine weather conditions near ground level, statistical models based upon the three dimensional fields output from numerical weather models, surface observations, as well as the climatology for specific locations were developed. These statistical models are called Model Output Statistics (MOS).History
MOS was developed by the National Weather ServiceNational Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
for their suite of weather forecasting models by 1976. The United States Air Force developed their own set of MOS based upon their dynamical weather model, the NOGAPS, by 1983. This differs from the perfect prog technique, which assumes that the output of numerical weather prediction
Numerical weather prediction
Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic...
guidance is perfect.
Leading MOS scientists
MOS has a very small field of practitioners. The most often cited pioneers are Glahn, Lowry, and Klein. Currently, most work in the field is done from the Meteorological Development Lab (MDL) http://www.nws.noaa.gov/mdl/synop/index.htm. Significant work has been contributed to the field by Murphy, Dallavalle, Mass, Vislocky, Fritsch, Allen, Hughes, and Antolik. http://www.nws.noaa.gov/mdl/synop/smbpublications.phpCurrent operational forecasts
MOS is run operationally using millions of equations from the MDL. As of 2010, the NAMNorth American Mesoscale Model
The North American Mesoscale Model , refers to a numerical weather prediction model run by National Centers for Environmental Prediction for short-term weather forecasting. Currently, the Weather Research and Forecasting Non-hydrostatic Mesoscale Model model is run as the NAM, thus, three names ...
, GFS
Global Forecast System
The Global Forecast System is a global numerical weather prediction computer model run by NOAA. This mathematical model is run four times a day and produces forecasts up to 16 days in advance, but with decreasing spatial and temporal resolution over time...
(short and long range) and 22-member GFS ensemble are used to create MOS products; the NGM
Nested Grid Model
The Nested Grid Model was a numerical weather prediction model run by the National Centers for Environmental Prediction, a division of the National Weather Service, in the United States...
-derived MOS products were discontinued in March 2009. (List of MOS products from the MDL)