662
FXUS10 KWNH 220647
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 AM EST SAT FEB 22 2020
VALID FEB 22/0000 UTC THRU FEB 25/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z 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 GFS/ECMWF BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
THE 00Z ECMWF/UKMET/CMC REMAIN SIMILAR TO THEIR PREVIOUS CYCLES
BUT ARE A LITTLE SLOWER AS THE WEAKENING MID-LEVEL VORTICITY MAX
NEARS THE OHIO VALLEY LATE MONDAY. THIS APPEARS TO BE IN RESPONSE
TO STRONGER RIDGING DOWNSTREAM GIVEN SOME STRONGER TROUGH
AMPLIFICATION UPSTREAM NEARING THE GREAT PLAINS. THE PREFERENCE
WILL REMAIN THE SAME AS EARLIER, EXCEPT TO REPLACE THE 12Z ECMWF
WITH THE 00Z ECMWF.
..PREVIOUS DISCUSSION FOLLOWS
TRENDS IN THE ENSEMBLE GUIDANCE HAVE GENERALLY SHOWN CONVERGENCE
VALID ON SUNDAY WITH THE CLOSED LOW WITH A SUBTLE SHIFT TO BE
SLOWER. THE 00Z GFS SLOWED DOWN FROM EARLIER CYCLES BUT REMAINS
SLIGHTLY QUICKER THAN THE 12Z ECMWF, WITH THE 12Z ECMWF MEAN
BETWEEN THE 00Z GFS AND 12Z ECMWF. REGARDING STRENGTH, THE 00Z GFS
MAY BE A BIT TOO STRONG, WHILE THE 12Z ECMWF MAY BE A BIT TOO WEAK
GIVEN ENSEMBLE MEAN AVERAGES APPEAR TO BE IN THE MIDDLE OF THE TWO
MODELS. MEANWHILE THE 00Z NAM IS STRONGEST WITH THE LOW-MID LEVEL
LOW AND FASTEST THROUGH SUNDAY, WITH THE 12Z UKMET SLOWEST
FOLLOWED BY THE 12Z CMC. DOWNSTREAM ACROSS THE MIDWEST, THE 12Z
CMC BECOMES THE SLOWEST DETERMINISTIC MODEL WITH THE CLOSED LOW.
THE PREFERENCE IS TO BE NEAR THE MIDDLE OF THE TIGHTENING MODEL
SPREAD, WHICH IS NEAR A BLEND OF THE 00Z GFS AND 12Z ECMWF. WHILE
SOME OF THE DIFFERENCES OBSERVED FOR SUNDAY REDUCE LATER IN THE
SHORT RANGE PERIOD, A 00Z GFS/12Z ECMWF BLEND REMAINS CONSISTENT
AND PREFERRED AT ALL FORECAST HOURS.
...WEAK MID LEVEL SHORTWAVE AND ATTENDANT COLD FRONT REACHING THE
GREAT LAKES SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/GFS/ECMWF BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
DESPITE SOME MINOR ADJUSTMENTS IN TIMING AND AMPLITUDE FROM THE
00Z UKMET AND 00Z CMC, THE 00Z NAM/GFS/ECMWF STILL MATCH CLOSEST
TO THE ENSEMBLE MEANS REGARDING THE SYSTEM ALOFT AND AT THE
SURFACE. HOWEVER, THROUGH MONDAY MORNING, A GENERAL MODEL BLEND
APPEARS FINE AS MODEL AGREEMENT IS GOOD. BEYOND MONDAY MORNING,
THE 00Z UKMET WINDS UP A LITTLE SLOWER WHILE THE 00Z CMC IS A BIG
DEEPER WITH THE MID-LEVEL TROUGH.
..PREVIOUS DISCUSSION FOLLOWS
THE 00Z NAM, 00Z GFS AND 12Z ECMWF ARE REASONABLY SIMILAR TO ONE
ANOTHER AND MATCH BEST TO THE AGREEABLE ENSEMBLE MEANS WITH THE
SURFACE AND UPPER LEVEL REFLECTION OF THIS SYSTEM. THE 12Z
UKMET/CMC ARE FLATTER AND FASTER WITH THE MID-LEVEL SHORTWAVE.
DESPITE THE AGREEMENT FROM THE ENSEMBLE MEANS TO THE OFTEN
RELIABLE GFS AND ECMWF, COUPLED WITH THE NAM'S AGREEMENT,
CONFIDENCE IS ONLY ABOVE AVERAGE WITH THIS SYSTEM GIVEN SOME
LINGERING DIFFERENCES IN ENSEMBLE SPAGHETTI PLOTS AS THE TROUGH
MOVES ACROSS ONTARIO.
...MID LEVEL SHORTWAVE CROSSING THE PACIFIC NORTHWEST
SUNDAY...CLOSING OFF OVER THE
NORTHERN/CENTRAL PLAINS MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 00Z NAM
CONFIDENCE: SLIGHTLY BELOW AVERAGE
..07Z UPDATE
THE 00Z UKMET ADJUSTED TO MATCH THE REMAINING MODEL CONSENSUS AS
THE SHORTWAVE NEARS THE PACIFIC NORTHWEST. HOWEVER, DOWNSTREAM
INTO THE INTERIOR WESTERN U.S., TRENDS FROM THE 00Z
ECMWF/UKMET/CMC WERE A BIT SLOWER COMPARED TO THEIR PREVIOUS 12Z
CYCLES. THIS MAKES THE 00Z GFS LOOK TOO FAST WITH THE MID-LEVEL
SHORTWAVE BY TUESDAY MORNING AND PERHAPS A NEW MIDDLE GROUND NEAR
THE 00Z NAM IS BEST. THE 00Z NAM SPLITS THE DIFFERENCE BETWEEN THE
FASTER 00Z GFS, AND THE SLOWER 00Z ECMWF/UKMET/CMC.
..PREVIOUS DISCUSSION FOLLOWS
THERE IS BETTER AGREEMENT WITH THIS SYSTEM COMPARED TO YESTERDAY
BUT DIFFERENCES REMAIN AS THE SHORTWAVE NEARS THE COAST OF THE
PACIFIC NORTHWEST, AND DOWNSTREAM INTO THE GREAT BASIN AND GREAT
PLAINS. THE 12Z UKMET IS LIKELY TOO SLOW CONSIDERING THE REMAINING
GUIDANCE AS THE SHORTWAVE APPROACHES THE PACIFIC NORTHWEST EARLY
SUNDAY. THERE ARE MINOR TIMING DIFFERENCES OUTSIDE OF THE UKMET,
WITH THE 00Z NAM/GFS SLIGHTLY AHEAD OF THE 12Z ECMWF/CMC BUT A NON
12Z UKMET BLEND WILL WORK THROUGH EARLY SUNDAY ACROSS THE
NORTHWEST.
BY MONDAY MORNING, THE TROUGH WILL ADVANCE INLAND, CROSSING THE
NORTHERN ROCKIES AND EVENTUALLY REACHING THE GREAT PLAINS FOR
TUESDAY MORNING. THE INITIALLY SLOWER 12Z UKMET ENDS UP WITH A
CLOSED LOW NEAR THE TEXAS PANHANDLE TUESDAY MORNING, BUT THIS
SEEMS LIKE THE OUTLIER COMPARED TO THE REMAINING GUIDANCE. THE 00Z
GFS WINDS UP A BIT FASTER (TYPICAL BIAS) AND SLIGHTLY STRONGER
INTO THE NORTH-CENTRAL U.S. WITH A CLOSED LOW WHILE THE AGREEABLE
12Z ECMWF/00Z NAM ARE A BIT SLOWER. GIVEN THE RATHER LARGE SPREAD,
AND A TENDENCY FOR CONVERGENCE OF TIMING WITH SUBSEQUENT CYCLES, A
BLEND OF EQUAL WEIGHTING BETWEEN THE 00Z NAM, 00Z GFS AND 12Z
ECMWF BLEND IS PREFERRED. THIS PUTS A LITTLE MORE WEIGHT TO THE
SLOWER ECMWF/NAM. THE 12Z CMC WAS EXCLUDED FROM THE PREFERENCE
GIVEN IT DOES NOT SHOW AS MUCH OF A DEFINED CLOSED LOW TUESDAY
MORNING ACROSS THE GREAT PLAINS.
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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