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MOS Data Details

Forecast models postprocessors generate MOS (Model Output Statistics) which are statistically derived surface conditions for particular cities. Two types of plots include forecast surface conditions from the NAM model as well as maximum temperature predictions from the GFS out to 7 days. There are MOS based meteograms which give a graphical representation of the weather conditions for the next 60 hours for individual cities. The NAM plots are updated once every 12 hours at around 12:15 EST. The GFS plots are updated once a day at around 8 AM EST.

NAM MOS Forecast

Sample NAM MOS plot
Sample NAM MOS plot

This plot shows forecasted surface conditions at a particular forecast time for several major cities. The plot contains a contour analysis of 12 hour quantitative precipitation (colors) and plotted conditions for the forecast time.

Quantitative precpitation field

The quantitative precpitation field shows estimated 12 hour precipitation (liquid equivalent) for the 12 hour period prior to the valid time. For example a 12 hour precipitation field valid 12Z THU 11 NOV 93 would show 12 hour accumulated precipitation from 00Z THU to 12Z THU. The contours follow this scale:

Black no measurable precip.
Dark Magenta .01 to .05 inches
Medium Magenta .05 to .10 inches
Light Magenta .10 to .25 inches
Blue-Magenta .25 to .50 inches
Blue .50 to 1.0 inches
Green 1.0 to 2.0 inches
Yellow 2.0 to 4.0 inches
Orange greater than 4.0 inches

In addition, the precipitation forecast can be used to estimate snow fall. A general 10 to 1 ratio can be used for snowfall based on the liquid equivalent shown in this chart.

Forecasted surface data

The plotted information is a station model plot of surface conditions for the forecast time. The MOS station model plot contains the following information:

Data Description
temperature (F) upper left
forecasted weather symbol center left
dewpoint (F) lower left
prob. of prec. (%) upper right
cloud cover center circle (white fill indicates % cloud coverage)
winds wind barb

Weather Symbols

Cloud_Lgnd Winds_Lgnd

GFSX MOS Forecast

Sample MRF MOS plot
Sample MRF MOS plot

This plot shows forecasted information from the Glocal Forecast System (GFS) model extended MOS surface data. This data include the predicted maximum temperature (colors) and probability of precipitation (POP) for 1 through 7 days.

Maximum temperature contour plot

The maximum temperatures are color contoured with a 5 degree contour interval.

Probability of precipitation plot

The POP data are contoured as well with the 10% line dashed, the areas from 30% to 50% filled with diagonal black lines, and the areas greater than 50% hatched. Therefore, the likely areas of precipitation would show up hatched.