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

...INTERIOR CA VALLEYS/DESERT SOUTHWEST...

THE 12Z NAM INITIALIZATION DEPICTED TEMPERATURES APPROXIMATELY 10
TO 15 DEGREES TOO COOL ACROSS SECTIONS OF THE SOUTHERN CA VALLEYS
WITH SUCH ERRORS EXTENDING INTO THE DESERT SOUTHWEST. ISSUES ALSO
PERSIST WITH THE 10-METER WINDS OBSERVED UP TO 15 KT OUT OF THE
WEST WHILE THE MODEL INDICATED WINDS WOULD BE LESS THAN 5 KT.
DIRECTIONAL ERRORS WERE ALSO EVIDENT OVER THE SAN DIEGO DESERTS
WITH WEST TO NORTHWESTERLY FLOW INITIALIZED WHILE SOUTHERLY WINDS
WERE OBSERVED.


...CENTRAL/SOUTHERN ROCKIES...

A VARIABLE WIND PATTERN WAS INDICATED IN THE SURFACE OBSERVATIONS
ACROSS THE FRONT RANGE OF THE ROCKIES WHILE THE 12Z NAM
INITIALIZED BROAD WESTERLY FLOW.


...SOUTHERN PLAINS TO THE SOUTHEASTERN U.S...

CONVECTION SEEN STREAMING INTO COASTAL TX OFF THE GULF OF MEXICO
WAS OCCURRING FURTHER ALONG THE COAST THAN THE 12Z NAM INITIALIZED
AND NOT AS FAR INLAND AS RADAR TRENDS SHOWED.



...MIDDLE MISSISSIPPI VALLEY INTO THE NORTHEASTERN CONUS...

SOME OF THE OBSERVED TEMPERATURES AT 12Z WERE NEARLY 10 DEGREES
ABOVE WHAT THE NAM INDICATED ACROSS THE FOOTHILLS OF WV AS A
TEMPERATURE INVERSION WAS NOT RESOLVED. AN ISSUE WAS ALSO NOTED
ACROSS WESTERN IOWA WHERE ACTIVE CONVECTION WAS PRESENT. NOT ONLY
WAS THE HIGHEST 100O-470 MB RELATIVE HUMIDITY DISPLACED TO THE
EAST ACROSS NORTHERN IL...BUT THE NAM DID NOT PRODUCE ANY
MEASURABLE RAINFALL ACROSS EASTERN NE/WESTERN IA WHERE ONGOING
STORMS WERE EVIDENT ON RADAR. FURTHER TO THE NORTH AND EAST...A
THUNDERSTORM COMPLEX EXITING NJ WHICH HAD THE MOST ENHANCED
BRIGHTNESS TEMPERATURES ON WATER VAPOR IMAGERY DID NOT COINCIDE
WITH THE HIGHEST RELATIVE HUMIDITY VALUES INDICATED BY THE 12Z NAM
WHICH PLACED IT ACROSS NEW ENGLAND.


RUBIN-OSTER