ON JUNE 13 2006...BEGINNING WITH THE 1200 COORDINATED UNIVERSAL
TIME /UTC/ RUN...THE NATIONAL CENTERS FOR ENVIRONMENTAL
PREDICTION /NCEP/ WILL REPLACE THE FORECAST MODEL CURRENTLY RUN
IN THE NORTH AMERICAN MESOSCALE SYSTEM. THE 12 KM HORIZONTAL
RESOLUTION ETA MODEL IS CURRENTLY USED IN THIS SYSTEM. THE MODEL
WILL BE REPLACED WITH A 12 KM HORIZONTAL RESOLUTION WEATHER
RESEARCH AND FORECASTING /WRF/ VERSION OF THE NON-HYDROSTATIC
MESOSCALE MODEL /NMM/.
THE DIFFERENCES BETWEEN THE NCEP ETA AND WRF NMM SYSTEMS ARE AS
FOLLOWS:
1. MODEL CHANGES
- REPLACE ETA PREDICTION MODEL WITH WRF VERSION OF THE NON-
HYDROSTATIC MESO MODEL (WRF-NMM)
- EXTENDED MODEL TOP PRESSURE FROM 25 MB TO 2 MB
- REPLACE ETA STEP-MOUNTAIN VERTICAL COORDINATE WITH NMM HYBRID
SIGMA-PRESSURE VERTICAL COORDINATE
- REFINED/RETUNED NUMEROUS ASPECTS OF THE ETA MODEL PHYSICS FOR
USE IN THE NMM
2. ANALYSIS CHANGES
- REPLACE ETA 3DVAR ANALYSIS SYSTEM WITH THE NEW UNIFIED GSI
ANALYSIS SYSTEM THAT HAS BEEN ADAPTED FOR APPLICATION TO THE WRF-
NMM
- REPLACE NEXRAD LEVEL II.5 DATA IN ETA 3DVAR WITH NEXRAD LEVEL
II RADIAL WIND DATA IN GSI
- GSI USES BACKGROUND ERRORS BASED ON WRF-NMM FORECASTS...ETA
3DVAR USED BACKGROUND ERRORS BASED ON GFS FORECASTS
- USE OF DYNAMICALLY RETUNED OBSERVATIONAL ERRORS
3. DATA ASSIMILATION CHANGES
- IMPLEMENT DIRECT USE OF OBSERVED PRECIPITATION ANALYSIS VALUES
IN THE LAND-SURFACE PHYSICS MODULES. THIS REPLACES PRIOR USE OF
NUDGING /TO PRECIPITATION AND GOES CLOUD TOP PRESSURES/ [/b]
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