NAM AIR QUALITY DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1008 AM EDT WED JUL 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). ***

...MID-ATLANTIC STATES/OHIO VALLEY/SOUTHEAST...

THE 12Z NAM SURFACE TEMPERATURES AND WINDS COMPARED TO
OBSERVATIONS SUGGEST LITTLE DIFFERENCE... WHICH MAKES SENSE WITH
THE LARGE SUBTROPICAL RIDGE BASED OFF THE SOUTHEAST COAST AND
STEERING CURRENT WELL NORTH OF THE REGIONS. THE ONLY NOTICEABLE IS
WITH PRECIPITATION AND QPF FORECAST... THE NAM FOCUSES ALL THIS
ACTIVITY ACROSS NORTH AND SOUTH CAROLINA INTO SOUTHWESTERN
VIRGINIA. CURRENT NATIONAL RADAR DEPICTS NO ACTIVITY IN THESE
STATES... WHILE LIGHT SHOWERS ARE FARTHER NORTH AND EAST INTO
NORTHERN VIRGINIA/MARYLAND AND SOUTHEASTERN VIRGINIA.


...SOUTHERN PLAINS...

NOCTURNAL THUNDERSTORM COMPLEX OVER KANSAS THIS MORNING APPEARS TO
BE INCREASING THE MEAN LAYER RELATIVE HUMIDITY OVER EAST CENTRAL
OKLAHOMA... VIA WATER VAPOR IMAGERY. THIS INDICATES THE EASTERN
PORTION OF THE UPPER RIDGE NOT AS STRONG... WHICH THE 12Z NAM DOES
NOT SEEM TO CAPTURE. PLUS... THE 12Z NAM DOES NOT SEEM TO BE
HANDLING THIS HEAVY RAIN COMPLEX WELL BUT DOES HAVE CORRECTLY NOT
PRECIPITATION ACROSS OKLAHOMA INTO NORTH TEXAS.


...SOUTHWEST/CALIFORNIA...

NOCTURNAL THUNDERSTORM COMPLEX OVER WESTERN ARIZONA/SOUTHEASTERN
CALIFORNIA SEEMS TO BE FADING-OUT BUT THE 12Z NAM DID CAPTURE THIS
FEATURE WELL WITH SOLID MEAN LAYER RH VALUES AND SOME LIGHT QPF.
THE GUSTY WINDS WITH THIS SMALL SCALE FEATURES IS SHOWING SOME
LIGHT DISCREPANCY BETWEEN THE OBSERVATIONS AND 12Z NAM DATA BUT
NOTHING SIGNIFICANT.


KONG/MUSHER