634
FXUS10 KWNH 051845
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 PM EST THU MAR 05 2020
VALID MAR 05/1200 UTC THRU MAR 09/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEPENING NORTHERN STREAM LOW MOVING OUT OF THE GREAT LAKES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/UKMET/ECMWF (SLIGHTLY LESS WEIGHT ON ECMWF)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
THE 12Z NON NCEP GUIDANCE ALL TRENDED SLIGHTLY IN DIRECTION FRIDAY
NIGHT AND SATURDAY (12Z ECMWF, WESTWARD...12Z UKMET, SLIGHTLY
WESTWARD...12Z CMC, SLIGHTLY NORTHWARD), BUT THE BIGGEST
ADJUSTMENT WAS IN THE 12Z ECMWF. THE 12Z ECMWF JUMPED WEST NEAR
THE ALREADY WESTERN 12Z CMC SURFACE LOW TRACK LATE FRIDAY NIGHT
INTO SATURDAY MORNING. THE CMC REMAINS FARTHEST WEST THROUGHOUT
THE SHORT RANGE PERIOD, BUT THE PREFERENCE AND THINKING REMAINS
THE SAME. THIS THINKING IS NEAR THE 12Z GFS/UKMET WITH SOME SLIGHT
INCORPORATION OF THE 12Z ECMWF GIVEN RECENT TRENDS IN THE
DETERMINISTIC GUIDANCE. WITH THE ENSEMBLE MEANS EAST OF THE
DETERMINISTIC CONSENSUS, THERE IS A CHANCE THE DETERMINISTIC RUNS
WILL JOG A BIT FARTHER EAST AGAIN WITH THE 00Z/FRIDAY CYCLE.
..PREVIOUS DISCUSSION FOLLOWS
THE ENSEMBLES CONTINUE TO EXHIBIT RUN TO RUN CHANGES WITH THE
UPPER TROUGH CROSSING THE GREAT LAKES AND EAST COAST FOR
FRIDAY/FRIDAY NIGHT AS WELL AS THE SURFACE LOW OFFSHORE. THERE HAS
BEEN A WESTWARD SHIFT FROM THE ECMWF/CMC/GEFS ENSEMBLES VALID
FRIDAY MORNING AND FRIDAY EVENING WITH THE UPPER TROUGH AND
SURFACE LOW OVER THEIR PAST 3 12/00Z CYCLES. HOWEVER, THE TRENDS
HAVE NOT BEEN SO LARGE AS TO REACH THAT OF THE CMC...EVEN
WEDNESDAY'S CYCLES OF THE CMC WHICH WERE CONSIDERED TOO FAR WEST.
CURRENTLY, THE NON 00Z CMC GUIDANCE SHOWS REASONABLY SIMILAR, BUT
THE SURFACE TO 850 MB LOW IS MUCH WEAKER IN THE 12Z NAM COMPARED
TO THE REMAINING CONSENSUS THROUGH FRIDAY EVENING. THE 00Z ECMWF
IS ALSO A LITTLE WEAKER WITH ITS LOW, WHILE THE 12Z GFS AND 00Z
UKMET ARE MORE DEVELOPED AND A LITTLE WEST OF THE 00Z ECMWF LOW
TRACK. GIVEN PROXIMITY TO THE GULF STREAM AND RECENT TRENDS IN THE
DETERMINISTIC GUIDANCE TOWARD THE WEST AND TO BE SOMEWHAT
STRONGER, MORE WEIGHT TOWARD THE 12Z GFS AND 00Z UKMET IS
PREFERRED, BUT WITH SOME INCLUSION OF THE WEAKER/MORE-EAST 00Z
ECMWF INCLUDED TO ACCOUNT FOR POTENTIAL SHIFTS IN THE GUIDANCE
BACK IN THE OTHER DIRECTION. THIS 3-WAY BLEND OF THE 12Z GFS, 00Z
UKMET AND 00Z ECMWF IS PREFERRED AT THIS TIME.
..LONGWAVE TROUGH MOVING INTO THE WEST COAST SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
THE 12Z CMC SPED UP ITS TIMING OF THE SHORTWAVE TROUGH AXIS MOVING
ACROSS THE WEST COAST ON SATURDAY. LITTLE CHANGE WAS NOTED WITH
THE 12Z ECMWF/UKMET COMPARED TO THEIR PREVIOUS CYCLES, SO THE
PREFERENCE HAS BEEN UPDATED TO INCLUDE THE 12Z CMC AS A GENERAL
MODEL BLEND.
..PREVIOUS DISCUSSION FOLLOWS
A DEEPENING LONGWAVE TROUGH DROPPING FROM THE GULF OF ALASKA WILL
APPROACH THE PACIFIC NORTHWEST TODAY AND THEN EXTEND DOWN TOWARDS
THE CA COAST FRIDAY BEFORE LIFTING INLAND BY THE WEEKEND. THERE IS
REASONABLE AGREEMENT AMONG ALL OF THE DETERMINISTIC GUIDANCE, BUT
THE 12Z GFS IS SLIGHTLY FASTER WITH THE MID-LEVEL TROUGH AXIS
CROSSING CA/OR ON SATURDAY COMPARED TO THE REMAINING CONSENSUS.
THE 00Z CMC WAS NOTED TO BE SLOWER WITH THIS TROUGH AXIS. WHILE
THE 12Z GFS IS A LITTLE FASTER, IT IS NOT UNREASONABLE GIVEN THE
ENSEMBLE DISTRIBUTION, BUT THE 00Z CMC DOES STAND OUT MORE. A
GENERAL MODEL BLEND MAY BE FINE ACROSS THE WESTERN U.S., BUT AT
THIS TIME, WE PREFER TO LEAVE OUT THE SLOWER 00Z CMC GIVEN GREATER
SUPPORT FOR A FASTER TIMING.
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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