NAM AIR QUALITY DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1035 AM EDT TUE JUL 31 2012


*** 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). ***


...CALIFORNIA/SOUTHERN NEVADA/SOUTHERN ARIZONA...
THE NAM INITIALIZES TEMPERATURES 5F LOWER THAN OBSERVED NUMBERS
ACROSS VALLEY AREAS OF SOUTHERN NEVADA AND SOUTHERN CALIFORNIA. 
THE NAM WAS 15F-18F TOO WARM NEAR LAKE TAHOE. 


...NEW MEXICO/COLORADO...
THE NAM WAS 3-5F TOO COOL ACROSS NORTH CENTRAL NEW MEXICO.


...SOUTHERN PLAINS/MIDWEST/CENTRAL APPALACHIANS/MID ATLANTIC
STATES/WESTERN GULF COAST...
THE NAM WAS 5F TOO COOL NEAR HARRISON ARKANSAS...AND NEAR
INDIANAPOLIS IN AND COVINGTON KY (CINCINNATI INTL AIRPORT).
THE NAM INITIALIZED WINDS NEAR THE CO/KS/PANHANDLE OF OK/NORTHEAST
NM WERE ON THE ORDER OF 5 KT AND THE OBSERVED WINDS WERE 10-15 KT
IN THE AREA.

THE NAM INITIALIZED A PRECIPITABLE WATER MINIMUM BELOW 1.25 INCHES
IN CENTRAL MO.  SURROUNDING SOUNDINGS SHOW HIGHER VALUES OF 1.5
INCHES TO 2 INCHES.  ALSO...THE NAM INITIALIZED THE 12Z TOPEKA
PRECIPITABLE WATER AS 1.5 INCHES VS 1.95 INCHES OBSERVED AT TOPEKA.

THERE IS POTENTIAL FOR THE PRECIPITABLE WATER ANALYSIS NEAR 1.5
INCHES IN CENTRAL IN TO BE LOW...BUT THE CENTRAL IN SOUNDING WAS
MISSING AT 12Z. CIRA BLENDED PRECIPITABLE WATER MAPS ESTIMATE
1.75-2 INCHES. 


PETERSEN