Prognostic Meteorological Discussion
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000
FXUS10 KWNH 231707
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
106 PM EDT SAT MAY 23 2015

VALID MAY 23/1200 UTC THRU MAY 27/0000 UTC

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

12Z MODEL EVALUATION AND PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


...WAVE EJECTING THROUGH THE PLAINS TOWARD SE CANADA...
...INCLUDING A SHORTWAVE COMING THROUGH SOUTH TX TONIGHT AND THEN
LIFTING...

PREFERENCE: BLEND OF 12Z NAM/GFS WITH 00Z ECMWF

THE CORE OF THE WESTERN U.S. TROUGH WILL MOVE OUT INTO THE PLAINS
WHILE A SHORTWAVE LIFTING THROUGH EAST TEXAS SUNDAY MORNING ACTS
TO DRAW HEIGHT FALLS EASTWARD INTO THE UPPER MIDWEST / NORTHERN
GREAT LAKES MONDAY. THE GREATEST MODEL DIFFERENCES THROUGH MONDAY
IN THE PLAINS / MIDWEST CENTER ON THE TRACK AND STRENGTH OF A
SURFACE LOW PUSHING FROM THE DAKOTAS TOWARD ONTARIO. THERE IS
STILL RUN TO RUN VARIABILITY WITHIN EACH INDIVIDUAL MODEL...AND NO
APPARENT CONVERGENCE TOWARD A TIGHT CONSENSUS. THE NAM/GFS/ECMWF
ARE REASONABLY WELL CLUSTERED...THOUGH...AND ARE PREFERRED. THE
00Z UKMET AND CANADIAN WERE SLOW...AND DID NOT APPEAR TO CAPTURE
THE INFLUENCE OF THE SHORTWAVE LIFTING OUT OF TEXAS TOWARD THE
MIDWEST.


...SHORTWAVE OVER CA/NV EJECTING INTO THE SOUTHERN PLAINS MONDAY...

PREFERENCE: BLEND OF 12Z UKMET WITH *06Z* GFS AND 00Z ECMWF

THE 00Z CANADIAN WAS SLOW AND WEAK WITH THIS FEATURE...BUT THE
REST OF THE 00Z AND 06Z GUIDANCE SHOWED A STRONG CONSENSUS. AT
12Z...HOWEVER...THE NAM TRENDED DEEPER/COLDER AT MID LEVELS AND
THE GFS TRENDED WEAKER AND MORE PROGRESSIVE. SINCE THE TRENDS DO
NOT MATCH...CONFIDENCE IN THEIR SOLUTIONS IS LESSENED. THE 12Z
UKMET WAS AVAILABLE...AND MAINTAINED CONTINUITY WITH THE PREFERRED
00Z MODEL CONSENSUS. THIS LEADS US TOWARD A MIXTURE OF RECENT RUNS
IN OUR PREFERENCE...THE 06Z GFS BEING THE MOST TRUSTED OF THE
RECENT NCEP RUNS.


...UPPER LOW DRIFTING ACROSS THE PACIFIC NORTHWEST...

PREFERENCE: BLEND OF THE 12Z NAM/GFS WITH 00Z ECMWF/CANADIAN

THERE IS GOOD LARGE SCALE AGREEMENT HERE...ALTHOUGH THE UKMET HAS
SHOWN POOR RUN TO RUN CONTINUITY. THE NAM IS ALSO SOMEWHAT BROAD
WITH ITS MID LEVEL HEIGHT CONTOURS...BUT AGREES WITH THE
GFS/ECMWF/CANADIAN AS TO THE CHARACTER OF THE SYSTEM AND ITS
PLACEMENT THROUGH TIME.


...PACIFIC CLOSED LOW OPENING UP AND APPROACHING CALIFORNIA
TUESDAY...

PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF

THE 00Z CANADIAN WAS SLOW HERE. THE 12Z NAM TRENDED
STRONGER...WITH A MUCH MORE PRONOUNCED VORTICITY CENTER OVER THE
SOUTHERN CA COAST AND GENERALLY COLDER HEIGHTS BY 27/00Z. THIS
TREND DID NOT HAVE MUCH SUPPORT...AND WOULD NOT BE EXPECTED FOR A
LOW WHICH HAD BEEN CLOSED AND WILL BE OPENING AS IT APPROACHES.
THE GFS/ECMWF/UKMET KEEP MORE ENERGY IN THE BASE OF THE TROUGH
FARTHER SOUTH OFF THE COAST. THE GFS/ECMWF ARE SLIGHTLY
PREFERRED...WHEREAS THE 12Z UKMET WAS SLIGHTLY FAST...ESPECIALLY
WITH THE 700 MB TROUGH AXIS.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE
$$





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