146
FXUS10 KWNH 270655
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT FRI MAR 27 2020
VALID MAR 27/0000 UTC THRU MAR 30/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-LEVEL TROUGH TRACKING FROM THE WEST COAST TO THE UPPER
MIDWEST AND INTO QUEBEC BY MONDAY MORNING...
...SURFACE LOW MOVING FROM EASTERN CO INTO THE MID/UPPER MS VALLEY
AND ONTARIO/QUEBEC...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/CMC (WITH SLIGHTLY LESS WEIGHT BY SUNDAY)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MODELS ARE COMING INTO BETTER AGREEMENT WITH RESPECT TO A
MID-LEVEL TROUGH TRACKING ACROSS THE SOUTHWEST INTO THE MIDSECTION
OF THE COUNTRY THURSDAY INTO EARLY FRIDAY. HOWEVER, THE GUIDANCE
STARTS TO DIVERGE ONCE THE MID-LEVEL WAVE BECOMES A CLOSED LOW IN
THE CENTRAL PLAINS. THE 00Z NAM IS TOO PROGRESSIVE AND FARTHER
NORTH WITH BOTH THE MID LEVEL LOW AND SURFACE LOW. CONVERSELY, THE
12Z UKMET IS TOO SLOW AND THUS THE SURFACE LOW LAGS BEHIND.
MEANWHILE, THE 00Z GFS/EC/CMC ARE IN LOCKSTEP THROUGH MUCH OF THIS
STORM SYSTEMS EVOLUTION. WHILE THE 12Z CMC WAS WEAKER AND OUTPACED
THE REST OF THE GUIDANCE LATER SATURDAY INTO SUNDAY, THE 00Z CMC
IS NOW IN BETTER AGREEMENT WITH THE GFS/EC. THUS, THE MIDDLE OF
THE ROAD WOULD SUPPORT THE DETERMINISTIC 00Z GFS/12Z EC FALLING IN
LINE WITH BOTH OF THEIR CORRESPONDING ENSEMBLE MEANS. IT SHOULD
BE NOTED THAT WHILE THE TRACK OF THIS SYSTEM IS IN FAIRLY GOOD
AGREEMENT WITH THE BLEND OF CHOICE, THE 12Z/00Z EC MAY BE A BIT
TOO STRONG WITHIN THE 500MB/850MB LEVELS WHICH COULD IMPACT
THERMAL PROFILES.
...SHORTWAVE TROUGH AND SURFACE COLD FRONT APPROACHING PACIFIC
NORTHWEST SATURDAY WITH THE TROUGH AXIS DIVING INTO THE SOUTHWEST
BY SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF
CONFIDENCE: AVERAGE
THERE REMAINS SOME MODEL DIFFERENCES WITH RESPECT TO A TROUGH AXIS
APPROACHING THE PACIFIC NORTHWEST. BOTH THE 00Z NAM AND 12Z UKMET
CONTINUE TO BE MORE PROGRESSIVE WITH THE TROUGH AXIS AND SHORTWAVE
ENERGY MOVING INTO THE SOUTHWEST BY LATE SUNDAY; THOUGH A SLIGHT
IMPROVEMENT WAS NOTED WITH THE 00Z UKMET. THE 00Z GFS/EC ARE
REASONABLE OUTER BOUNDS IN TERMS OF TIMING AND AMPLITUDE (GFS A
BIT SLOWER/ EC A BIT MORE PROGRESSIVE AND AMPLIFIED) AND ARE IN
DECENT AGREEMENT WITH THEIR ENSEMBLE MEANS. THE 12Z CMC WAS A NICE
MIDDLE GROUND BETWEEN THE GFS/EC, THOUGH THE 00Z CMC SEEMS LESS
AMPLIFIED WITH THE TROUGH AS COMPARED TO CONSENSUS. THEREFORE,
THE PREFERRED MODEL BLEND FOR THIS SYSTEM IS THE 00Z GFS/EC.
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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