NAM AIR QUALITY DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1034 AM EDT MON JUN 06 2011
 
*** The following information pertains to initialization errors
noted on the 12Z NAM that may negatively impact the performance of
the 12Z CMAQ output as used for air quality forecasting.
Specifically, errors that apply to temperature, winds, relative
humidity and precipitation are included. This discussion only
applies to geographical regions of the CONUS where air quality is
currently forecast to be degraded (i.e. CODES:
YELLOW/ORANGE/RED/PURPLE/MAROON). ***

...MIDWEST/OHIO VALLEY/MID AND UPPER MISSISSIPPI VALLEY...

THE MOST SIGNIFICANT ERROR WAS WITH REGARD TO THE LOCATION OF THE
CONVECTIVE SYSTEM CURRENTLY MOVING THROUGH WISCONSIN. THE 12Z NAM
ANALYZED THIS FEATURE MOSTLY OVER ILLINOIS...WHERE LITTLE TO NO
PRECIPITATION HAS BEEN OBSERVED. ERRORS WITH THE 12Z NAM WIND
INITIALIZATION WERE LIMITED TO SOUTHWESTERN WISCONSIN...WHERE
SURFACE WINDS WERE EASTERLY WHILE THE NAM ANALYZED WINDS OUT OF
THE SOUTH-SOUTHEAST. 

...TENNESSEE VALLEY/MID-ATLANTIC...

NO SIGNIFICANT INITIALIZATION ERRORS WERE NOTED.

...SOUTHEAST/GULF COAST...

THE 12Z NAM APPEARS TO BE TOO FAR SOUTH WITH A BAND OF MOISTURE
MOVING THROUGH THE DEEP SOUTH. AS A RESULT...PRECIPITABLE WATER
OBSERVATIONS ALONG THE GULF COAST ARE HIGHER THAN THE NAM
ANALYSIS.

...EASTERN TEXAS/CENTRAL OKLAHOMA/ARKANSAS/NORTHERN LOUISIANA...

SURFACE OBSERVATIONS OVER NORTH CENTRAL TEXAS ARE NEARLY EASTERLY
WHILE THE NAM ANALYZED THEM AS SOUTHERLY IN PLACES. OTHERWISE NO
SIGNIFICANT INITIALIZATION ERRORS WERE NOTED.

 ...DESERT SOUTHWEST...

THE 12Z NAM INITIALIZED TEMPERATURES ARE ABOUT 5-9 DEGREES TOO LOW
ACROSS CENTRAL AZ AND THE CA IMPERIAL VALLEY. INITIALIZED WINDS
ARE ALSO 20 KTS TOO WEAK ACROSS THE SOUTHERN IMPERIAL VALLEY...AND
ARE NEARLY SOUTHERLY ACROSS THE PHOENIX METRO AREA DESPITE
OBSERVED WINDS OUT OF THE EAST. IN ADDITION...THE NAM APPEARS TO
PLACE THE SURFACE BOUNDARY NEAR THE CO RIVER A LITTLE FARTHER WEST
THAN THE SURFACE OBSERVATIONS WOULD SUGGEST.

...NORTHERN FRONT RANGE IN COLORADO...

THE 12Z NAM WAS ABOUT 5 DEGREES TOO WARM ACROSS LOCATIONS SLIGHTLY
DISPLACED FROM THE FRONT RANGE...SUCH AS LIMON...WHILE ABOUT 5-9
DEGREES TOO COOL ACROSS THE DENVER METRO AREA. MESOSCALE WIND
FEATURES IN THE LEE OF THE FRONT RANGE WERE NOT PICKED UP BY THE
NAM...AS IT DID NOT ANALYZE THE CONVERGENCE ZONE BETWEEN DENVER
AND GREELEY...NOR THE CONVERGENCE ZONE SOUTH OF LIMON.
INSTEAD...THE NAM DEPICTED A NEARLY UNIFORM EASTERLY TO
SOUTHEASTERLY WIND FIELD ACROSS THE REGION.


SOLTOW
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