NAM AIR QUALITY DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1024 AM EDT FRI AUG 19 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). ***


...DESERT SOUTHWEST...
...INTERIOR CENTRAL VALLEY IN CALIFORNIA...
...WEST-CENTRAL OREGON...

SURFACE TEMPERATURES WERE UNDERESTIMATED BY THE 12Z NAM ACROSS THE
SOUTHERN CALIFORNIA VALLEYS/DESERTS LOCALES. FURTHER...THE WIND
FIELD INITIALIZED BY THE MODEL WAS TOO WEAK...ESPECIALLY NEARBY
THE LOS ANGELES BASIN. IN ADDITION...THE ONSHORE FLOW THE 12Z NAM
SHOWED DID NOT VERIFY WELL AS WINDS WERE MORE VARIABLE IN
DIRECTION.


...EASTERN HALF OF SOUTHERN PLAINS...
...LOWER MISSISSIPPI VALLEY...

ACROSS NORTH-CENTRAL OKLAHOMA...SOUTHERLY WINDS INITIALIZED BY THE
12Z NAM DID NOT VERIFY AS LOCAL LOW-LEVEL FLOW INDICATED SOME
NORTHERLY/EASTERLY WINDS. THIS MIGHT HAVE BEEN DUE TO CONVECTIVE
DEVELOPMENT IN THE VICINITY OF THE OKLAHOMA/KANSAS BORDER.


...SOUTHERN PORTION OF GREAT LAKES...
...OHIO AND TENNESSEE VALLEYS...
...NORTHERN SECTION OF THE SOUTHEASTERN U.S...
...MID-ATLANTIC AND INTO COASTAL NEW ENGLAND...

ACCORDING TO THE MOST RECENT WATER VAPOR IMAGERY...THE MODEL DOES
NOT SEEM TO HAVE AN ACCURATE PLACEMENT OF THE MID/UPPER LEVEL
MOISTURE. CURRENT SATELLITE TRENDS SHOWED THE BEST MOISTURE ACROSS
SOUTHERN ILLINOIS/INDIANA AND WESTERN KENTUCKY WHILE THE NAM
PLACES THIS AXIS FARTHER TO THE NORTH AND EAST. ANOTHER ISSUE WITH
THIS SECTOR OF THE U.S. IS THE LACK OF PRECIPITATION FORECAST BY
THE 12Z NAM AS THERE WAS AN ORGANIZED AREA OF CONVECTION DEPICTED
ON THE RADAR. THE SAME CAN BE SAID FOR A BATCH OF
SHOWERS/THUNDERSTORMS ENTERING WEST-CENTRAL VIRGINIA WITH THE NAM
NOT INDICATING ANY MEASURABLE PRECIPITATION.


RUBIN-OSTER