NOUS41 KWBC 131639



Public Information Statement, Comment Request

National Weather Service Headquarters Washington, DC

1238 AM EDT Thu Oct 13 2011


To:      Subscribers:

         -Family of Services

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network


         Other NWS Partners and NWS Employees


From:    Kathryn Gilbert

         Chief, Statistical Modeling Branch

         Meteorological Development Laboratory


Subject: Soliciting Comments on Proposed Enhancements to the

         Global Forecast System (GFS)-Based Gridded MOS Product

         Through November 30, 2011


The NWS is soliciting public comments by November 30, 2011, on the proposed increase in horizontal resolution over the CONUS from 5 km to 2.5 km and the future addition of several weather elements to the GFS-Based Gridded Model Output Statistics (MOS) Guidance.  We will continue to provide the GFS-based gridded MOS guidance at a horizontal resolution of 5 km to allow sufficient time for necessary software or hardware upgrades.


1. Proposed increase in horizontal resolution


The current GFS-based gridded MOS guidance over the CONUS is available on a Lambert Conformal grid at a horizontal resolution of 5 km. The resolution of the gridded MOS guidance over the CONUS will be increased from 5 km to 2.5 km to support the planned 2.5 km National Digital Forecast Database (NDFD) and provide greater spatial detail in areas of complex terrain.


Customers can expect the characteristics of the temperature, dewpoint temperature, daytime maximum/nighttime minimum temperature, relative humidity, sky cover, probability of thunderstorms, wind speed, wind direction, wind gusts, and 24-hr snowfall amount to remain very similar to the current operational 5 km products with more detail noticeable in and around complex terrain. The enhanced resolution grids will be made available in grib2 format in the experimental area of the National Digital Guidance Database (NDGD) on a date to be advertised in an upcoming Technical Implementation Notice.  Currently the grids are available at the link provided below.


Table 1 below lists representations of the WMO headers for each 2.5 km gridded MOS element.


Table 1: Communication Identifiers for the Experimental 2.5-km GFS-based Gridded MOS Grib2 Products for the CONUS




    YAUXXX KWBQ   Total Sky Cover

    YBUXXX KWBQ   Wind Direction

    YCUXXX KWBQ   Wind Speed

    YDUXXX KWBQ   12-Hour Probability of Precipitation

    YEUXXX KWBQ   2-Meter Temperature

    YFUXXX KWBQ   2-Meter Dew Point Temperature

    YGUXXX KWBQ   Daytime Maximum Temperature

    YHUXXX KWBQ   Nighttime Minimum Temperature

    YIUXXX KWBQ   6-h Quantitative Precipitation Amount

    YJUXXX KWBQ   6-h Probability of a Thunderstorm

    YRUXXX KWBQ   Relative Humidity

    YSUXXX KWBQ   24-h Snowfall Amount

    YUUXXX KWBQ   6-Hour Probability of Precipitation

    YVUXXX KWBQ   12-h Quantitative Precipitation Amount

    YWUXXX KWBQ   Wind Gusts

    YXUXXX KWBQ   12-h Probability of a Thunderstorm

    YYUXXX KWBQ   3-h Probability of a Thunderstorm


2. Proposed removal of some stations from gridded MOS analysis


An additional proposed change is the removal of some Cooperative Observer Program (Coop) stations from the analysis of MOS daytime maximum and nighttime minimum temperature guidance.  Forecasts for Coop sites within 10 km of a METAR station will no longer influence the temperature analysis.  This is in response to complaints from users concerning discrepancies between the max/min MOS grids and the MOS point values at nearby locations.  Coop sites contribute a large amount of detail to gridded MOS max/min forecasts, especially in data-sparse regions; however, the local 24-hour reporting period valid for Coop observations can be difficult to match with the appropriate daytime maximum and nighttime minimum forecast periods.  A list of Coop sites  proposed for removal and images from several case studies can be found at the following site:


3. Proposed enhancement of PoP and QPF forecasts


The experimental 2.5 km gridded MOS suite will include enhanced-resolution, GFS-based MOS probability of precipitation (PoP) and quantitative precipitation forecasts (HRMOS QPF).  The improved QPF forecasts are developed from archived stage IV national mosaic precipitation data that defines the precipitation predict.  In addition, high resolution topographic and climatological interactive predictors are incorporated into the equations to enhance resolution of the PoPs and QPFs.  See the following link for more details:


4. Proposed future additions to gridded MOS


Future additions to the 2.5 km gridded MOS suite will include GFS-based precipitation type and MOS predominant weather.  The precipitation type guidance will include best category and probabilities of freezing, frozen and liquid precipitation types out to 192 hours in advance. Gridded precipitation type is produced differently from other gridded MOS elements.  Generalized operator equations are used to generate forecasts directly at each 2.5 km gridpoint while incorporating gridded climatologies and logit 50 percent values as predictors, which help to capture localized effects and produce enhanced terrain detail.  


The experimental 2.5 km MOS weather grid is the predominant weather valid at the indicated hour, generated from a collection of other gridded MOS elements.  The gridded MOS weather element provides type, probability, and intensity information valid every 3 hours out to 192 hours in advance.


At this time, all of the above proposed enhancements are an addition to the gridded MOS suite, not a replacement for the current 5 km gridded MOS guidance.  Customers who use the 5 km guidance over the CONUS can continue to use these products without disruption until all customers and systems are able to use the higher resolution guidance.


Graphics, links to GRIB2 data for download, and more details on these experimental products can be found at:


General information on the gridded MOS file structure and additional references is available at:


Submit comments and questions regarding the proposed enhancements to the GFS-Based Gridded MOS products to:


  Kathryn Gilbert

  NWS Meteorological Development Laboratory

  301 713-0023 x130


National Public Information Statements are online at: