339
FXUS10 KWNH 301908
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
207 PM EST SAT NOV 30 2019
VALID NOV 30/1200 UTC THRU DEC 04/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEEP CLOSED LOW TRACKING EAST FROM THE PLAINS TO THE EAST
COAST...
..SECONDARY SURFACE LOW DEVELOPMENT SOUTH OF LONG ISLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 00Z ECMWF MEAN OR A 3-WAY BLEND OF THE 12Z
NAM/12Z GFS/ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
PREVIOUS THINKING CONTINUES TO HOLD TRUE FOR THIS STORM SYSTEM,
NEAR THE 00Z ECMWF MEAN, WITH THE UNDERSTANDING THAT FUTURE MODEL
CYCLES WILL CONTINUE TO MAKE MINOR ADJUSTMENTS. A BLENDED APPROACH
CONTINUES TO APPEAR BEST AT THIS TIME.
THE 12Z UKMET/CMC REMAIN DIFFERENT ENOUGH WITH THEIR HANDLING OF
THE SURFACE LOW AND REDEVELOPMENT OFF OF THE NORTHEAST COASTLINE
MONDAY INTO TUESDAY TO EXCLUDE THEM FROM THE WPC PREFERENCE. THE
12Z ECMWF TRENDED A BIT STRONGER AND WEST WITH ITS TRIPLE POINT
LOW REDEVELOPMENT (TERTIARY LOW) MONDAY NIGHT TOWARD THE NEW
ENGLAND COASTLINE. IT NOW LIES THE WEST-MOST OF THE NAM/GFS/ECMWF
COMBINATION AND SLIGHTLY WEST OF THE 00Z ECMWF MEAN. HOWEVER, WHEN
INCORPORATED INTO A BLEND WITH THE 12Z NAM/GFS, THE 12Z ECMWF IS
AN ACCEPTABLE BLENDED COMPONENT FOR THIS SYSTEM.
..PREVIOUS DISCUSSION FOLLOWS
MODEL AGREEMENT IS FAIR WITH A LARGE CLOSED LOW AS IT TRACKS EAST
THROUGH MONDAY/TUESDAY, BUT MINOR DIFFERENCES IN A RELATED SURFACE
LOW TRACK TRANSLATE INTO SIGNIFICANT DIFFERENCES AT THE SURFACE.
WHILE THE 12Z GFS/NAM AND 00Z ECMWF ARE IN GOOD AGREEMENT
INITIALLY WITH THE SECONDARY SURFACE LOW POSITION SOUTH OF LONG
ISLAND, THE 12Z GFS IS WARMER IN THE LOWER LEVELS ACROSS INLAND
LOCATIONS MONDAY MORNING/EVENING. THE 00Z UKMET/CMC DIFFER IN
POSITION FROM THE OTHERWISE GOOD MODEL AGREEMENT.
AS TUESDAY APPROACHES, THE MODEL DIFFERENCES GROW CONCERNING THE
SURFACE LOW WITH THE 00Z ECMWF EAST OF ITS ENSEMBLE MEAN, WITH THE
12Z NAM TOWARD THE WESTERN SIDE OF THE MODEL GUIDANCE. THE 12Z GFS
ENDS UP WITH A SIGNIFICANTLY STRONGER SURFACE LOW TOWARD THE SOUTH
SIDE OF THE MODEL SPREAD, WHILE THE 00Z UKMET/CMC ARE FASTER TO
EXIT THE LOW-MID LEVEL LOW AWAY FROM NEW ENGLAND BUT THE 00Z ECMWF
MEAN SHOWS A DECENT BLEND OF THE BETTER CLUSTERED GUIDANCE BETWEEN
THE 12Z NAM, 12Z GFS AND 00Z ECMWF.
..UPPER LOW OFF OF THE WEST COAST THROUGH TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z CMC BLEND
CONFIDENCE: AVERAGE
..19Z UPDATE
THE 12Z UKMET ADJUSTED TOWARD THE PREVIOUS PREFERENCE WHILE THE
12Z CMC REMAINED FARTHER EAST WITH CLOSED LOW AS IT DROPS
SOUTHWARD OFF OF THE WEST COAST SUNDAY INTO MONDAY. THE 12Z ECMWF
REMAINED RATHER SIMILAR TO ITS 00Z CYCLE, SO THE PREFERENCE IS FOR
A NON 12Z CMC BLEND WITH LESS WEIGHT ON THE 12Z GFS GIVEN DETAILS
MENTIONED BELOW.
..PREVIOUS DISCUSSION FOLLOWS
A PAIR OF MID-LEVEL CLOSED LOWS ALONG AND WEST OF THE WEST COAST
ARE EXPECTED TO CONSOLIDATE INTO A SINGLE LOW ON SUNDAY OFF OF THE
PACIFIC NORTHWEST. THIS CLOSED LOW IS THEN EXPECTED TO RETROGRADE
WEST AND SOUTH THROUGH TUESDAY. TRENDS IN THE ENSEMBLE SPAGHETTI
PLOTS INDICATE A BROAD RANGE OF LONGITUDES FOR THE CENTER OF THE
LOW, BUT THE 12Z GFS IS MUCH CLOSER TO THE EASTERN EDGE OF THE
ENSEMBLE GUIDANCE. WHILE THE 12Z GFS ENDS UP CLOSER TO THE MIDDLE
OF THE LATEST MODEL SPREAD BY A MIDDLE GROUND ON TUESDAY AND THE
VERIFYING POSITION MAY WIND UP BETWEEN THE EASTERN GFS AND WESTERN
ECMWF/NAM, MORE WEIGHT TOWARD THE WESTERN ECMWF/NAM IDEA IS
PREFERRED GIVEN THE LATEST ENSEMBLE DISTRIBUTION. TRENDS DO NOT
FAVOR ONE WAY VERSUS THE OTHER AT THIS TIME.
...SHORTWAVE APPROACHING THE NORTHERN PLAINS/UPPER MIDWEST
MONDAY/TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
..19Z UPDATE
THE 12Z UKMET TRENDED SLIGHTLY MORE AMPLIFIED AT 500 MB WHICH IS
TOWARD THE REMAINING GUIDANCE. OTHERWISE, ANY CHANGES WITH THE 12Z
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z CYCLES WERE MINOR
WITH THE LATEST 12Z MODEL CONSENSUS SHOWING WITHIN THE TIGHTLY
PACKED MODEL/ENSEMBLE GUIDANCE.
..PREVIOUS DISCUSSION FOLLOWS
DESPITE SOME MINOR TIMING/AMPLITUDE DIFFERENCES, THE MODELS ARE IN
DECENT AGREEMENT WITH A NORTHERN STREAM SHORTWAVE FORECAST TO
TRACK ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST.
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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