218
FXUS10 KWNH 151836
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
235 PM EDT SUN MAR 15 2020
VALID MAR 15/1200 UTC THRU MAR 19/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP UPPER TROUGH/CLOSED LOW IMPACTING THE WEST COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF, SOME INCLUSION OF THE 00Z UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
ADJUSTMENTS IN TIMING FROM THE 12Z ECMWF/UKMET/CMC COMPARED TO
THEIR PREVIOUS 00Z CYCLES INCLUDE A SLOWING IN THE CMC, MORE
SIGNIFICANT SLOWING IN THE UKMET AND ALMOST NEGLIGIBLE SLOWING IN
THE ECMWF. THE FINAL RESULT IS THAT THE 12Z NAM AND 12Z CMC
CONTINUE TO APPEAR TOO QUICK AND THAT PERHAPS THE 12Z UKMET IS TOO
SLOW, ESPECIALLY TUESDAY NIGHT COMPARED TO THE LATEST ENSEMBLE
DISTRIBUTION. THE FINAL PREFERENCE WILL WEIGHT THE 12Z GFS/ECMWF
WITH SOME INCLUSION OF THE 00Z UKMET.
..PREVIOUS DISCUSSION FOLLOWS
AS A DEEP UPPER TROUGH AND EMBEDDED CLOSED LOW ALONG THE WEST
COAST SETTLES SOUTH OVER THE NEXT FEW DAYS, GOOD MODEL AGREEMENT
EXISTS UNTIL ABOUT TUESDAY EVENING. A TREND IN THE ENSEMBLES HAS
BEEN NOTED TO SHIFT THE UPPER TROUGH/CLOSED LOW FASTER TO THE EAST
INTO THE SOUTHWESTERN U.S. OVER THE PAST 3 12/00Z CYCLES VALID ON
TUESDAY. HOWEVER, THE 12Z NAM IS THE FASTEST TO PROGRESS THE LOW
EASTWARD, AND DESPITE THE TREND, APPEARS TO BE AN OUTLIER AT THE
MOMENT. THE 00Z CMC IS ALSO FASTER TO TAKE THE LOW INLAND AND DOES
NOT EXHIBIT THE DOUBLE BARREL APPEARANCE SEEN IN THE REMAINING
DETERMINISTIC GUIDANCE WEDNESDAY MORNING. THE RESULT IN THE 00Z
CMC IS A FASTER PROGRESSION WITH THE BASE OF THE MID-LEVEL TROUGH
INTO ARIZONA/NEW MEXICO BY WEDNESDAY EVENING.
THE ENSEMBLE MEANS SUPPORT A MIDDLE GROUND BETWEEN THE SOMEWHAT
FASTER 12Z GFS/00Z UKMET AND SLOWER 00Z ECMWF. THE PREFERENCE WILL
LEAN TOWARD THIS MIDDLE GROUND BUT WILL BE SUBJECT TO CHANGE
PENDING THE 12Z ECMWF/UKMET/CMC.
..TROUGH CROSSING THE UPPER MIDWEST/GREAT LAKES BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
THE 12Z UKMET AND 12Z ECMWF SPED UP THEIR TIMING OF THE MID-LEVEL
TROUGH ACROSS ONTARIO ON TUESDAY WHILE THE 12Z CMC SLOWED DOWN,
RELATIVE TO THEIR PREVIOUS 00Z CYCLES. THESE ADJUSTMENTS SHRINK
THE MODEL SPREAD MORE BUT MAKE THE 12Z NAM STAND OUT AS THE
SLOWEST AND 12Z GFS AS THE FASTEST. THE PREFERENCE WILL REMAIN A
GENERAL MODEL BLEND AS THE DIFFERENCES REGARDING IMPACTS TO THE
LOWER 48 ARE RELATIVELY MINOR AND THE BLEND RESOLVING TIMING
DIFFERENCES FARTHER NORTH INTO ONTARIO.
..PREVIOUS DISCUSSION FOLLOWS
THE 00Z UKMET AND 12Z GFS WERE NOTED TO BE SLIGHTLY FASTER WITH
THE UPPER TROUGH PROGRESSION AS IT CROSSES THE GREAT LAKES INTO
SOUTHERN ONTARIO. THE 12Z NAM WAS SLIGHTLY SLOWER WITH THE
ENSEMBLE MEANS IN THE MIDDLE OF THE SPREAD. OVERALL, TIMING
DIFFERENCES ARE MINOR WITH POTENTIAL FOR FUTURE CYCLES TO ADJUST A
LITTLE FASTER OR SLOWER. THE PREFERENCE IS TO BE IN THE MIDDLE
WHICH IS BEST REPRESENTED BY A GENERAL MODEL BLEND AT THIS TIME.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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