711
FXUS10 KWNH 211836
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM 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 MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED MID LEVEL LOW REACHING THE ROCKIES SUN
THEN 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/12Z GFS BLEND
CONFIDENCE: SLIGHTLY BELOW 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 12Z ECMWF
CONTINUES TO LAG A GENERAL CONSENSUS WITH THE MID LEVEL SYSTEM AS
IT OPENS 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 (MINUS THE 12Z ECMWF) 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). THERE ARE
SOME DIFFERENCES WITHIN THE 12Z NON-NCEP CAMP, WITH THE 12Z UKMET
SPEEDING UP, AND THE 12Z ECMWF/CMC SLOWING DOWN (WITH THE 12Z CMC
BECOMING THE WESTERN EDGE OF THE CONSENSUS ENVELOPE). AT THIS
POINT, WITH THE INCREASE IN THE SPREAD OF THE GUIDANCE CONCERNING
THE TRACK OF THE SURFACE LOW, THE 12Z GFS HAS BEEN INCLUDED IN THE
PREFERRED BLEND. DUE TO THE DIVERGENCE IN THE 12Z
NON-NCEP CAMP, FORECAST CONFIDENCE HAS DROPPED TO SLIGHTLY BELOW
NORMAL.
...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
SUNDAY...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 (INCLUDING THE 12Z ECMWF/UKMET/CMC) 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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