GMOS Case Study Land/Water Mask Change

GMOS Development: December 2007 Gridded MOS Changes

On December 18, 2007, we will be making modifications to the GFS-based gridded MOS guidance for the CONUS. Based on feedback we have received from users of the gridded MOS, we will:

1) modify the mask that designates whether a gridpoint is land or water (land/water mask)
used in the analysis process
2) modify the QPF analysis scheme, and
3) remove stations from the analysis

More details are provided below.

 

Change 1: Modifications to Land/Water Mask

Presentation - "Creation of Gridded MOS Land Water Mask" (PDF)
Summary of Land/Water Mask creation (PDF)

Images for Comparison (PDF images)


Current
Land/Water Mask

Proposed
Land/Water Mask

Difference between
Land/Water Masks

Max Temperature
w/Operational Mask

Max Temperature
w/Proposed Mask

Min Temperature
w/Operational Mask

Min Temperature
w/Proposed Mask

2-m Temperature
w/Operational Mask

2-m Temperature
w/Proposed Mask

 

Change 2: Change to Precipitation Amount analysis scheme

The analysis was modified slightly because it was felt our expected value approach was too conservative. This new method results in higher precipitation amounts.
 

Current Precipitation Amount

"current" precipitation amount map

Precipitation Amount with new scheme

"new" precipitation amount map

 

Change 3: Removal of stations from analysis

The following list of stations will be removed from the analysis for the given elements based on user feedback indicating these stations were causing errors in the analysis.
 

Element Stations Removed
Max/Min Temperature KHZY -- Ashtabula, OH
171381/CHAM1 -- Chamberlain Bridge, ME -- cooperative observer site
Dew point Temperature KTZR -- Columbus/Bolton Field, OH
KIDI -- Stewart Field, PA
All elements QOSA3 -- Piney Hill, AZ - mesonet site
NS006 -- O W Saddle, AZ - mesonet site

MOS