604
FXUS10 KWNH 230645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 AM EST SUN FEB 23 2020
VALID FEB 23/0000 UTC THRU FEB 26/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID LEVEL SHORTWAVE AND ATTENDANT FRONT CLIPPING THE GREAT
LAKES/NORTHERN ME SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
DIFFERENCES WITH THIS SYSTEM ARE RELATIVELY MINOR AND CAN BE
RESOLVED WITH A GENERAL MODEL BLEND. NO SIGNIFICANT CHANGES WERE
NOTED IN THE 00Z ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 12Z
CYCLES.
...CLOSED MID LEVEL LOW REACHING THE CENTRAL/SOUTHERN ROCKIES SUN,
WEAKENING OVER THE UPPER MS/OH VALLEY MON INTO TUES...
...SURFACE LOW TRACKING FROM NORTHEAST NM INTO OHIO VALLEY BY
TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..07Z UPDATE
THE 00Z UKMET SLOWED DOWN WHILE THE 00Z CMC REMAINED ABOUT THE
SAME COMPARED TO THEIR PREVIOUS 12Z CYCLES. THE 00Z ECMWF EDGED
SLIGHTLY FASTER THAN ITS PREVIOUS 12Z CYCLE, BUT IS RELATIVELY
SIMILAR. GIVEN THESE CHANGES, HAVE ADDED THE 00Z UKMET INTO THE
PREFERENCE, LEAVING OUT THE 00Z CMC GIVEN IT LIKELY REMAINS TOO
SLOW.
..PREVIOUS DISCUSSION FOLLOWS
AS THE CLOSED LOW NEAR THE FOUR CORNERS SUNDAY MORNING TRANSLATES
EASTWARD INTO THE SOUTHERN/CENTRAL PLAINS SUNDAY NIGHT, IT IS
EXPECTED TO OPEN UP AND WEAKEN TOWARD THE OHIO VALLEY THROUGH
MONDAY NIGHT. MINOR STRENGTH DIFFERENCES REMAIN BUT TIMING
DIFFERENCES ARE MORE SIGNIFICANT. THE 12Z UKMET ENDS UP THE
FASTEST, WHILE THE 12Z CMC IS THE SLOWEST OF THE DETERMINISTIC
GUIDANCE. THE 00Z GFS IS THE SECOND FASTEST MODEL, BEHIND THE 12Z
UKMET WITH THE 00Z NAM/12Z ECMWF SIMILAR TO ONE ANOTHER AND IN THE
MIDDLE.
GIVEN THE DIFFERENCES AMONG THE 00Z NAM, 00Z GFS AND 12Z ECMWF ARE
RELATIVELY MINOR, A 3-WAY BLEND OF THESE MODELS WILL BE PREFERRED,
FALLING WITHIN THE MIDDLE OF THE SPREAD AND SLIGHTLY AHEAD OF THE
12Z ECMWF MEAN. THE 12Z ECMWF MEAN HAS BEEN VERY CONSISTENT OVER
ITS PAST 3 12/00Z CYCLES, BUT A NUDGE AHEAD IN THE DIRECTION OF
THE 00Z GFS/00Z NAM IS WARRANTED GIVEN OFTEN TIMES THE ECMWF WILL
TREND IN THE DIRECTION OF THE LATEST NAM/GFS WHEN THE VERIFYING
TIME IS WITHIN THE FIRST 24-48 HOURS.
...MID-LEVEL SHORTWAVE CROSSING THE PACIFIC NORTHWEST SUNDAY,
DIGGING INTO NORTHERN/CENTRAL PLAINS MON...
..CLOSED LOW LIKELY CROSSING THE MISSISSIPPI RIVER VALLEY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 00Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE
..07Z UPDATE
RELATIVE TO THEIR PREVIOUS 12Z CYCLES, THE 00Z UKMET/CMC SPED UP
TOWARD THE PREVIOUS PREFERENCE OF THE 12Z ECMWF. HOWEVER, THE
700-500 MB LOW FROM THE 00Z CMC REMAINS SLOWER AND FOR THE 00Z
UKMET, WEAKER. THE 00Z ECMWF REMAINS SIMILAR TO ITS PREVIOUS RUN
UNTIL TUESDAY NIGHT WHEN IT SPEEDS UP THE TIMING OF THE MID-LEVEL
TROUGH SLIGHTLY.
OVERALL THINKING REMAINS THE SAME, AS DOES THE PREFERENCE WHICH IS
NOW NEAR THE 00Z ECMWF, GIVEN THE TIMING ADJUSTMENTS MADE BY THE
ECMWF WERE CONSIDERED TO BE FAVORABLE...OR A NUDGE TOWARD THE 00Z
GFS.
..PREVIOUS DISCUSSION FOLLOWS
DIFFERENCES WITH THIS SYSTEM BECOME NOTABLE ON MONDAY AS MODELS
STRUGGLE TO HANDLE THE TIMING OF THE LEADING EDGE OF THE SHORTWAVE
ENERGY AS IT ENTERS THE GREAT PLAINS. THE 00Z NAM IS QUICKEST,
WHILE THE 12Z CMC IS SLOWEST. FROM TUESDAY INTO WEDNESDAY MORNING,
THE TIMING DIFFERENCES AMPLIFY WITH THE 12Z CMC AND 00Z NAM ON THE
EDGES OF THE ENSEMBLE SPREAD REGARDING A LIKELY CLOSED LOW
CROSSING THE MISSISSIPPI RIVER VALLEY.
TRENDS IN THE ENSEMBLES, LOOKING BACK AT THE PAST 4 12/00Z CYCLES,
HAVE JUMPED AROUND A BIT, WITH SLOWER FOLLOWED BY FASTER TRENDS
NOTED. THE MIDDLE OF THE AVERAGE OF THE RECENT ENSEMBLE CYCLES
SEEMS TO BE NEAR THE 12Z ECMWF MEAN AND THE 12Z ECMWF. HOWEVER,
RECENT VERIFICATION OF UPPER TROUGHS MOVING THROUGH THE CENTRAL
U.S. HAVE TENDED TO VERIFY BETWEEN THE FASTER GFS AND SLOWER
ECMWF. FOR THIS REASON, A SLIGHT NUDGE AHEAD TOWARD THE 00Z GFS IS
RECOMMENDED TO ACCOUNT FOR FUTURE ADJUSTMENTS IN THE GUIDANCE.
...MID-LEVEL SHORTWAVE TROUGH/SURFACE COLD FRONT CLIPPING THE
PACIFIC NORTHWEST ON TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
ONLY MINOR TRENDS WERE OBSERVED FROM THE 00Z NON-NCEP GUIDANCE,
AND THEY WERE CONVERGENT UPON A COMMON MIDDLE GROUND. LITTLE
DIFFERENCE NOW EXISTS WITH THIS SYSTEM, BUT GIVEN THE 3-DAY
OUTLOOK AND POTENTIAL FOR FUTURE ADJUSTMENTS, CONFIDENCE IS ONLY
AVERAGE.
..PREVIOUS DISCUSSION FOLLOWS
THERE IS REASONABLE AGREEMENT WITH A SHORTWAVE AS IT TRACKS INTO A
MID-LEVEL RIDGE SITUATED ALONG THE BRITISH COLUMBIA/PACIFIC
NORTHWEST COASTLINE TUESDAY MORNING. WHILE THE 12Z ECMWF IS
FLATTEST WITH THE TROUGH AS IT MOVES INLAND, THERE IS RELATIVELY
GOOD AGREEMENT AT LEAST THROUGH THE END OF THE SHORT RANGE PERIOD
(12Z/26). A GENERAL MODEL BLEND WILL BE RECOMMENDED AT THIS POINT
FOR THIS SYSTEM.
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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