MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1230 AM EST WED FEB 10 2010
 
VALID FEB 10/0000 UTC THRU FEB 13/1200 UTC
 

...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z NAM/GFS EVALUATION INCLUDING THE NEW UKMET/CANADIAN AND
PREFERENCES

ANY INITIALIZATION ERRORS ARE DESCRIBED UNDER THE RELEVANT SYSTEM
HEADINGS.

...UPPER LOW TRACKING EASTWARD FROM THE OHIO VALLEY...
...SURFACE LOW DEEPENING EAST OF DELMARVA/NEW JERSEY...

PREFERENCE: THROUGH 00Z TUE...NAM OR GFS
              AFTER 00Z TUE...1/3 EACH NAM/GFS/12Z ECMWF

RADAR AND SATELLITE TRENDS SHOW A SMALL BUT SIGNIFICANT LOW/MID
LEVEL CYCLONIC VORTICITY CENTER MOVING EAST OF THE WASHINGTON DC
AREA...WHICH IS NOT ADEQUATELY RESOLVED BY THE NAM BUT IS SLIGHTLY
BETTER RESOLVED BY THE GFS...AND HAS MAGNIFIED THE NORTHWESTERN
PERIPHERY OF THE DEVELOPING PRECIPITATION SHIELD. 

DESPITE SOME CONCERNS WITH MESOSCALE ASPECTS OF THE LOW PRESSURE
AREA FORMING EAST OF DELMARVA...MODELS AS A WHOLE SHOW STRONG
AGREEMENT ALOFT AND AT THE SURFACE WITH RELATIVELY SMALL SPATIAL
AND STRENGTH DIFFERENCES. THROUGH THE 1ST 24 HRS OF THE
FORECAST...THE NAM AND GFS HAVE TRENDED SLIGHTLY NORTHEASTWARD
WITH THE DEVELOPING LOW PRESSURE OFFSHORE AND AGREE ON COMPRISING
THE MOST EASTWARD POSITIONS OF THE SOLUTION ENVELOPE THROUGH THIS
TIME...WHILE THE 12Z ECMWF AND OTHER NON-NCEP GUIDANCE AVERAGE
ABOUT 30-40 NM WEST. GIVEN TRENDS...THEIR
AGREEMENT...AND MORE RECENT INITIALIZATION...A BLEND OF THE
NAM/GFS IS MORE PREFERRED THROUGH THE 1ST 24 HRS. AFTER 24
HRS...DIFFERENCES IN POSITION AND STRENGTH BECOME MORE DIFFICULT
TO DISCERN AS THE LOW MOVES INTO THE OPEN ATLANTIC...WITH A BLEND
OF THE NAM/GFS/12Z ECMWF PREFERRED THEREAFTER TO ADDRESS THE
GROWING UNCERTAINTY.

...UPPER LOW MOVING FROM CALIFORNIA TO THE GULF OF MEXICO THROUGH
THE PERIOD...

PREFERENCE: BEFORE 00Z THU...1/2 EACH GFS/ECMWF
             AFTER 00Z THU...1/2 EACH ECMWF/UKMET

WHILE THE NAM AND GFS HAVE TRENDED FASTER WITH THIS SYSTEM...THEY
CONTINUE TO LAG NON-NCEP GUIDANCE BY AT LEAST A FEW HOURS THROUGH
THE PERIOD...WITH THE NAM THE SLOWEST. THE NEW UKMET IS CLOSEST TO
THE GFS CROSSING THE GULF WHILE THE OLD UKMET IS CLOSER TO THE 12Z
ECMWF BUT MUCH STRONGER EAST OF FLORIDA. GIVEN RECENT TRENDS...A
SOLUTION TOWARD THE NON-NCEP OR FASTER SIDE OF THE GUIDANCE IS
PREFERRED WITH THE GFS A REASONABLE ALTERNATIVE TO THE ECMWF
CROSSING ARIZONA BEFORE TIMING DIFFERENCES BECOME MORE
APPRECIABLE. ONCE THE LOW REACHES NEW MEXICO AND AREAS
EAST...PREFER TO LEAN MORE HEAVILY TOWARD A BLEND OF THE 12Z
ECMWF/NEW UKMET WHICH ARE FASTER AND A BIT NORTH OF THE GFS WITH
ITS LOW PRESSURE CENTER OVER THE EASTERN GULF OF MEXICO...WITH THE
AVERAGING ALSO ADDRESSING SOME OF THE UNCERTAINTY WITH THE LOW'S
DEPTH. FINALLY...THE NEW CANADIAN WHICH WAS THE CLOSEST TO THE
SOUTHEAST COAST AND DEEPEST ON ITS 12Z CYCLE...HAS TRENDED EAST
AND WEAKER...WHICH IS TOWARD THE PREFERRED BLEND.  

...SHORTWAVE TROUGH GRAZING THE PACIFIC NORTHWEST TDY/TNGT...

PREFERENCE: NAM OR ECMWF

THE NAM AND 12Z ECMWF ARE COMPARABLE...WHILE THE GFS IS SLIGHTLY
FASTER AND LESS AMPLIFIED. THUS...DUE TO CONSENSUS RECOMMEND
EITHER THE NAM OR ECMWF.

...2ND SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST THU NGT...

PREFERENCE: NAM OR ECMWF

GUIDANCE IS NEARLY EVENLY SPLIT REGARDING TIMING...WITH THE
NAM/12Z ECMWF SLOWER AND GFS/NEW UKMET FASTER. SREF/GEFS MEANS ARE
IN BETWEEN...BUT WITH EARLIER PREFERENCES FOR AN EARLIER SHORTWAVE
TROUGH (MENTIONED ABOVE) FAVORING SLOWER TIMING...AND THE
POSSIBILITY THAT THE GFS IS BEGINNING TO SHOW SOME OF FAST BIAS AT
THIS TIME FRAME...PREFER A SOLUTION TOWARD THE SLOWER SIDE OF THE
GUIDANCE. 

...3RD SHORTWAVE TROUGH NEARING THE PACIFIC NORTHWEST FRI...

PREFERENCE: GFS OR ECMWF

THE NAM IS CONSIDERED A SLOW OUTLIER WITH ARRIVAL OF THIS SYSTEM
ALONG THE COAST WITH THE GFS/12Z ECMWF OTHERWISE IN GOOD
AGREEMENT.

...SHORTWAVE TROUGH MOVING FROM THE UPPER MIDWEST TO THE OHIO
VALLEY THU NGT/FRI...

PREFERENCE: NAM OR ECMWF

THE GFS GRADUALLY MOVES TOWARD THE FAST EDGE OF THE GUIDANCE WHICH
MAY BE ATTRIBUTED TO ITS FASTER SOLUTIONS FOR UPSTREAM SHORTWAVE
TROUGHS ENTERING THE PACIFIC NORTHWEST PREVIOUSLY. MEANWHILE...THE
NAM HAS TRENDED SLOWER AND TOWARD THE 12Z ECMWF. THUS...CONSENSUS
AND CONCERNS THAT THE GFS MAY BE TOO FAST UPSTREAM...PREFER A
SLOWER SOLUTION.

...SMALL UPPER LOW NEARING THE DAKOTAS FRI...

PREFERENCE: HALFWAY BETWEEN THE GFS/ECMWF

THE ECMWF IS ABOUT 12 HRS EARLIER IN REACHING NORTH DAKOTA
COMPARED TO THE NAM/GFS BUT IS SUPPORTED BY THE NEW UKMET/OLD
CANADIAN...WHILE THE NEW CANADIAN HAS TRENDED SLOWER AND IS NOW
NEAR THE SLOWER CAMP OF SOLUTIONS. GEFS/ECMWF ENSEMBLE MEANS AND
SPAGHETTI DIAGRAMS ARE ALSO EVENLY SPLIT BETWEEN SUPPORTING THE
SLOW AND FAST CAMPS. THUS...GIVEN THE SOLUTION SPREAD AND
UNCERTAINTY IN THIS COMPLEX SYSTEM AT THIS TIME FRAME...RECOMMEND
AN INTERMEDIATE SOLUTION WHICH AVERAGES THE DIFFERENT TIMING OF
THE GFS AND ECMWF.

...MODEL TREND GRAPHICS AT
WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML...

...500 MB FORECAST AT WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML...

JAMES