NAM AIR QUALITY DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1032 AM EDT THU JUN 09 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). ***

...NORTHEAST...

OBSERVED TEMPERATURES ARE 5 TO 10 DEGREES F COOLER THAN ANALYZED
BY THE NAM AT SOME LOCATIONS WITHIN AN AREA FROM NORTH-CENTRAL TO
SOUTHWESTERN MAINE.  OVER SOUTHERN NEW ENGLAND THE NAM DOES NOT
APPEAR TO ACCOUNT WELL FOR RAINFALL OBSERVED NEAR THE START OF THE
FORECAST.  ALSO BOSTON AS WELL AS SOME LOCATIONS OVER NORTHERN AND
SOUTHEASTERN CONNECTICUT REPORT WINDS FROM THE NORTH AT 5 TO 15 KT
VERSUS THE NAM ANALYSIS THAT SHOWS WINDS FROM THE WEST AT 5 TO 10
KT.


...MID ATLANTIC...

NO SIGNIFICANT INITIALIZATION ERRORS ARE NOTED.


...TENNESSEE/LOWER MISSISSIPPI VALLEYS AND SOUTHEAST...

THE NAM DOES NOT DEPICT A SMALL AREA OF CONVECTION OBSERVED OVER
EXTREME NORTHEASTERN SOUTH CAROLINA INTO SOUTHERN NORTH CAROLINA. 
OTHERWISE THE NAM ANALYSIS COMPARES WELL TO OBSERVED DATA.


...OHIO VALLEY/MIDWEST......

NEAR THE BEGINNING OF THE NAM FORECAST THE MODEL DOES NOT DEPICT
THE RAINFALL SEEN OVER MUCH OF SOUTHERN IOWA INTO WESTERN
ILLINOIS.  OBSERVED WIND DIRECTIONS OVER SOME AREAS FROM SOUTHERN
IOWA INTO WESTERN ILLINOIS DIFFER FROM THE NAM ANALYSIS BY 50
DEGREES OR MORE... WITH THE DIFFERENCE IN DIRECTION VARYING BY
PARTICULAR LOCATION.  MEANWHILE WINDS FROM NORTH-CENTRAL TO
SOUTHWESTERN OHIO ARE OBSERVED FROM THE NORTH AT 5 TO 15 KT VERSUS
THE NAM ANALYSIS WHICH SHOWS WINDS FROM THE WEST OR SOUTHWEST AT 5
KT.


...DESERT SOUTHWEST/CENTRAL VALLEY OF CALIFORNIA...

OBSERVED TEMPERATURES AT SOME LOCATIONS OVER INTERIOR SOUTHERN
CALIFORNIA ARE 10 TO 15 DEGREES F WARMER THAN ANALYZED BY THE NAM.

RAUSCH