767
FXUS10 KWNH 211648
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1145 AM EST FRI FEB 21 2020
VALID FEB 21/1200 UTC THRU FEB 25/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED MID LEVEL LOW REACHING THE ROCKIES SUN
WEAKENING OVER
THE UPPER MS VALLEY MON...
...SURFACE LOW TRACKING FROM NORTHEAST NM INTO MID MS VALLEY BY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/00Z ECMWF ENSEMBLE MEAN/00Z UKMET BLEND
CONFIDENCE: AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH THE CLOSED MID
LEVEL LOW OFF THE SOUTHWEST CA COAST EARLY SAT, BUT BY 23/00Z,
BOTH MODELS BECOME FASTER THAN THE 00Z NON-NCEP MODEL
SOLUTIONS,AND THE DIFFERENCE MAXIMIZES NEAR 23/12Z. AFTER THAT
TIME, THE TIMING DIFFERENCES LESSEN, THOUGH THE 00Z ECMWF/ECWMF
ENSEMBLE MEAN LAGS A GENERAL CONSENSUS WITH THE MID LEVEL SYSTEM
AS IT OPEN UP OVER THE MID AND UPPER MS VALLEYS BEFORE 25/00Z. THE
NCEP CAMP HAS SLOWED WITH THIS FEATURE OVER THE PAST THREE RUNS,
AND THE NON-NCEP GUIDANCE HAS INCREASED ITS FORWARD SPEED WITH THE
MID LEVEL FEATURE, BRIDGING THE GAP. AT THIS POINT, A BLEND OF THE
TWO CAMPS WOULD ELIMINATE THE DIFFERENCES WITH THE MID LEVEL
SYSTEM.
HOWEVER, DIFFERENCES BETWEEN THE NCEP AND NON-NCEP CAMPS REGARDING
THE SURFACE LOW FORMING OVER NORTHEAST NM BECOME LARGER WITH TIME,
MAXIMIZING JUST BEFORE THE END OF THE PERIOD (25/00Z). BY THIS
TIME, THE 00Z ECMWF/00Z ECMWF ENSEMBLE MEAN AND THE 00Z UKMET SEEM
TO FORM THE BEST CLUSTER WITH THE SURFACE LOW POSITION OVER
SOUTHEAST MO (WHICH IS SUPPORTED BY THE PREPONDERANCE OF THE MULTI
MODEL ENSEMBLE SURFACE LOW POSITIONS). GIVEN THE ABOVE, A BLEND OF
THE 00Z ECMWF/00Z ECMWF ENSEMBLE MEAN AND THE 00Z UKMET ARE
PREFERRED, THOUGH THE DIFFERENCES BETWEEN THE NCEP AND NON-NCEP
SOLUTIONS APPEARS TO THE NARROWING.
...WEAK MID LEVEL SHORTWAVE AND ATTENDANT COLD FRONT REACHING THE
GREAT LAKES SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS AS THE SHORT WAVE
ENERGY COMES ASHORE ACROSS WEST CENTRAL BRITISH COLUMBIA AROUND
22/12Z. AFTER THAT TIME, THE 12Z GFS BECOMES FASTER WITH THE MID
LEVEL SHORT WAVE (AND ITS SURFACE COLD FRONT), A TREND SEEN IN THE
LAST THREE RUNS OF THE OPERATIONAL GFS.THE 12Z NAM REMAINS CLOSER
TO THE RELATIVELY TIGHTLY CLUSTERED MODEL CONSENSUS WITH THE SHORT
WAVE AND COLD FRONT. FROM THIS VANTAGE POINT, THE 12Z GFS IS NOT
SIGNIFICANTLY FASTER WITH THE MID LEVEL AND SURFACE SYSTEMS, SO A
GENERAL MODEL BLEND IS PREFERRED HERE. DUE TO THE SPEED OF THE MID
LEVEL FLOW, IT IS POSSIBLE MODEL SOLUTIONS MAY NOT YET HAVE A GOOD
HANDLE ON HOW FAST THE MID LEVEL SHORT WAVE CROSSES SASKATCHEWAN
INTO ONTARIO, SO FORECAST CONFIDENCE IS ONLY AVERAGE.
...MID LEVEL SHORTWAVE CROSSING THE PACIFIC NORTHWEST
SUN...CLOSING OFF OVER THE
NORTHERN/CENTRAL PLAINS MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z GFS BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
BOTH THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS BRINGING SHORT
WAVE ENERGY FROM 48N 150W AT 22/12Z TO THE PACIFIC NORTHWEST
BEFORE 24/00Z. AFTER THAT TIME, THE 12Z GFS BECOMES FASTER THAN
THE CONSENSUS (AND THE 06Z GEFS MEAN) WITH THE SHORT WAVE AS IT
CLOSES OFF OVER THE NORTHERN AND CENTRAL PLAINS BY 25/00Z. MUCH OF
THE REST OF THE GUIDANCE ALSO CLOSES OFF THE MID LEVEL SYSTEM IN
THE WAKE OF THE MID LEVEL TROUGH OVER THE UPPER GREAT LAKES, BUT
DOES SO FURTHER NORTHWEST OVER THE NORTHERN PLAINS.
BASED ON THE TIMING OF THE UPSTREAM MID LEVEL SYSTEM, A SLOWER
SOLUTION SEEMS TO FITS THE PATTERN BETTER. FOR THAT REASON, THE
12Z GFS WAS NOT INCLUDED IN THE PREFERENCE. HOWEVER, GIVEN THE
SPREAD IN THE GUIDANCE TOWARD THE END OF THE PERIOD, FORECAST
CONFIDENCE IS SLIGHTLY BELOW NORMAL.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAYES
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