053
FXUS10 KWNH 011908
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 PM EST SUN DEC 01 2019
VALID DEC 01/1200 UTC THRU DEC 05/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP CLOSED LOW CROSSING THE MIDWEST/MID-ATLANTIC REGIONS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
ADJUSTMENTS SEEN WITH THE 12Z ECMWF/UKMET/CMC WERE GENERALLY
TOWARD THE WEST/CLOSER TO THE NORTHEAST COAST, MOST NOTABLY MONDAY
NIGHT/TUESDAY MORNING WITH THE TRIPLE POINT SURFACE LOW
DEVELOPMENT. THE 12Z GFS/ECMWF/UKMET ARE NO ON THE WESTERN SIDE OF
THE ENSEMBLE SCATTER LOW PLOTS. DESPITE THESE DETERMINISTIC
TRENDS, ENSEMBLE SCATTER LOW PLOTS HAVE NOT TRENDED MUCH OVER
THEIR PAST 4 12/00Z CYCLES VALID 12Z TUESDAY. ALSO OF NOTE, THE
ECMWF HAS BEEN FLIP FLOPPING BETWEEN A WESTWARD AND EASTWARD
SURFACE LOW POSITION BETWEEN ITS 12Z AND 00Z CYCLES. FOR THIS
REASON, AND GIVEN THE RELATIVE GOOD AGREEMENT AMONG THE LATEST
GUIDANCE A GENERAL MODEL BLEND IS PREFERRED, WITH THE 12Z NAM/CMC
HELPING TO PULL THE SURFACE LOW A LITTLE FARTHER AWAY FROM THE
COAST COMPARED TO WHAT THE 12Z GFS/ECMWF/UKMET WOULD SHOW BY
THEMSELVES.
..PREVIOUS DISCUSSION FOLLOWS
DIFFERENCES WITH THIS SYSTEM ARE RELATIVELY MINOR ALOFT, REGARDING
THE 500 MB CLOSED LOW POSITION AND STRENGTH. THERE ARE NO MAJOR
OUTLIERS BUT THERE ARE ARTIFACTS OF THE GUIDANCE WHICH FALL ON THE
EDGES OF THE ENSEMBLE ENVELOPE, MAINLY WITH THE SURFACE TO 850 MB
LOW. THE 00Z CMC DEPARTS THE GREATEST FROM THE REMAINING
DETERMINISTIC CONSENSUS REGARDING ITS SURFACE LOW(S) TRACK OFF OF
THE NEW ENGLAND COAST WITH A POSITION FARTHER OFFSHORE AND LIES ON
THE OUTER EDGES OF THE ENSEMBLE SCATTER LOW PLOTS.
THE REMAINING NON-00Z CMC GUIDANCE ALSO SHOWS SOME DIFFERENCES,
WITH EACH HAVING ONE OR TWO FORECAST FEATURES WHICH DEVIATE FROM
THE FAVORED MIDDLE GROUND. THE 12Z NAM IS PERHAPS THE CLOSEST TO
THE MIDDLE OF THE LATEST MODEL SPREAD CONCERNING THE SURFACE LOW
POSITION MONDAY MORNING WITH THE 12Z GFS FARTHER WEST AND 00Z
ECMWF A BIT FARTHER EAST. MONDAY NIGHT, A TRIPLE POINT LOW
DEVELOPS OFFSHORE OF CAPE COD WITH AGAIN THE 12Z GFS FARTHER WEST
AND THE 12Z NAM FARTHER EAST WITH THE REDEVELOPED LOW, WHILE THE
00Z ECMWF/UKMET LIE SOMEWHERE IN THE MIDDLE. BY TUESDAY MORNING,
THE 12Z NAM SURFACE LOW IS PERHAPS TOO STRONG, THE 12Z GFS IS ON
TOP OF CAPE COD WITH ITS SURFACE LOW (TOO FAR WEST?) WHILE THE 00Z
ECMWF/UKMET ARE SOMEWHERE BETWEEN THE 12Z NAM/GFS REGARDING
POSITION AND STRENGTH. FOR TUESDAY EVENING, THE 12Z NAM, 12Z GFS,
00Z ECMWF AND 00Z UKMET ARE IN REASONABLE AGREEMENT AS THE LOW IS
PULLING AWAY FROM NEW ENGLAND.
IN SUMMARY, A 4-WAY BLEND OF THE 12Z NAM, 12Z GFS, 00Z ECMWF AND
00Z UKMET SEEMS BEST TO SMOOTH OUT SMALLER SCALE ISSUES CONTAINED
WITHIN EACH MODEL AT VARIOUS TIMES AND NEAR THE GEFS/ECMWF
ENSEMBLE MEANS. THE PROBLEM WITH USING THE ENSEMBLE MEANS 100%
HOWEVER, AT CERTAIN TIMES, THEY WILL BLEND THE PRIMARY SURFACE LOW
WITH THE SECONDARY/TRIPLE-POINT LOW RESULTING IN A WASHED OUT
MIDDLE POSITION.
..UPPER LOW APPROACHING THE WEST COAST BY SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
EXCEPT FOR THE WESTWARD 12Z UKMET, ADJUSTMENTS FROM THE LATEST
NON-NCEP GUIDANCE ARE IN BETTER AGREEMENT WITH THE ENSEMBLE MEANS
AND PREVIOUS PREFERENCE. THEREFORE, A NON 12Z UKMET BLEND LOOKS
REASONABLE FOR THIS SYSTEM.
..PREVIOUS DISCUSSION FOLLOWS
THE ENSEMBLE SPAGHETTI HEIGHT PLOTS AT 500 MB CONTINUE TO SHOW
WEST/EAST SPREAD REGARDING A MID-LEVEL CLOSED LOW AS IT DROPS
SOUTHWARD OFF OF THE WEST COAST TUESDAY INTO WEDNESDAY. THERE
HAVEN'T BEEN ANY CLEAR TRENDS WITH THE PAST 4 12/00Z CYCLES OF THE
ENSEMBLE GUIDANCE AS TO WHICH WAY TO LEAN (WEST OR EAST). FOR NOW,
THE PREFERENCE IS TO GO IN THE MIDDLE, TOWARD THE RATHER AGREEABLE
ENSEMBLE MEANS AND STAYING AWAY FROM THE EDGES OF THE ENSEMBLE
SPREAD. THE 12Z GFS IS CLOSEST TO THE ENSEMBLE MEANS, WITH THE 00Z
CMC THE SECOND CLOSEST. THE 00Z ECMWF/UKMET ARE FARTHER OFFSHORE
WHILE THE 12Z NAM IS SOUTH OF THE GFS POSITION.
...SHORTWAVE APPROACHING THE NORTHERN PLAINS/UPPER MIDWEST
MONDAY/TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
..19Z UPDATE
NO SIGNIFICANT DIFFERENCES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES.
..PREVIOUS DISCUSSION FOLLOWS
THE MODELS BRING A NORTHERN STREAM SHORTWAVE SOUTHEAST ACROSS
PORTIONS OF THE NORTHERN PLAINS AND UPPER MIDWEST BY MONDAY AND
THEN DROP IT DOWN ACROSS THE OH VALLEY THROUGH TUESDAY. THE
GUIDANCE IS IN GOOD AGREEMENT THROUGH WEDNESDAY EVENING (THE END
OF THE SHORT RANGE PERIOD), WITH ONLY MINOR TIMING/STRENGTH
DIFFERENCES. A GENERAL MODEL BLEND IS THEREFORE PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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