NAM AIR QUALITY DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1030 AM EDT MON AUG 29 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). ***


...TENNESSEE VALLEY/INTERIOR SOUTHEAST...

SURFACE TEMPERATURES WERE OBSERVED TO BE 5 TO 7 DEG F COOLER THAN
WHAT THE NAM INITIALIZED OVER PORTIONS OF SOUTHERN
KENTUCKY...EAST-CENTRAL TENNESSEE AND INTO NORTHEASTERN ALABAMA.


...CENTRAL/EASTERN TEXAS INTO LOUISIANA...

RADAR IMAGERY SHOWS EXTENSIVE SHOWER AND THUNDERSTORM ACTIVITY
SETTLING SOUTHWARD ACROSS EASTERN OKLAHOMA AND ARKANSAS WHICH IS
ADVANCING INTO NORTHEAST TEXAS AND NORTHERN LOUISIANA. THE 12Z NAM
DID NOT INITIALIZE THIS ACTIVITY WELL AS IT IS CONSIDERABLY
UNDERDONE WITH THE COVERAGE AND INTENSITY OF THE RAIN.
CONSEQUENTLY...THE NAM IS NOT WELL INITIALIZED WITH THE RESULTING
CLOUD COVER SHIELD. SURFACE WINDS ACROSS NORTHEAST TEXAS ARE
OBSERVED TO BE NORTHEAST AT 10 TO 20 KTS IN ASSOCIATION WITH SOME
OF THE STRONGER THUNDERSTORMS VERSUS INITIALIZED SOUTHEAST WINDS
OF 5 KTS. SURFACE TEMPERATURES ARE OBSERVED TO BE 5 TO 10 DEG F
COOLER THAN INITIALIZED ACROSS PORTIONS OF SOUTHERN AND EASTERN
OKLAHOMA...WESTERN ARKANSAS AND NORTHERN LOUISIANA.


...INTERIOR VALLEYS OF CALIFORNIA/LOS ANGELES BASIN/DESERT
SOUTHWEST...

SURFACE TEMPERATURES WERE OBSERVED TO BE 5 TO 10 DEG F WARMER THAN
WHAT THE NAM INITIALIZED OVER MANY OF THE INTERIOR DESERTS OF
SOUTHERN CALIFORNIA...SOUTHERN NEVADA AND SOUTHWEST ARIZONA.
HOWEVER...ALONG THE COAST OF SOUTHERN CALIFORNIA FROM SANTA
BARBARA DOWN TO SAN DIEGO...SURFACE TEMPERATURES WERE OBSERVED TO
BE 5 TO 10 DEG F COOLER THAN WHAT WAS INITIALIZED. SURFACE
TEMPERATURES ACROSS THE SAN JOAQUIN VALLEY WERE ALSO OBSERVED TO
BE 5 TO 10 DEG F COOLER THAN WHAT WAS INITIALIZED.


ORRISON