431
FXUS10 KWNH 130658
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST FRI DEC 13 2019
VALID DEC 13/0000 UTC THRU DEC 16/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OUTSIDE OF THE TWO AREAS OF THE CONUS MENTIONED BELOW, MODEL
AGREEMENT IS GOOD ENOUGH TO SUPPORT A GENERAL MODEL BLEND.
..EASTERN 1/3 OF THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..07Z UPDATE
THE 00Z ECMWF/UKMET/CMC STAYED SIMILAR TO OR ADJUSTED SLIGHTLY
SLOWER THAN THAN THEIR 12Z CYCLES WITH THE 500 MB TROUGH AXIS
PROGRESSING INTO THE EAST THROUGH SATURDAY MORNING MAKING THE 00Z
GFS STAND OUT AS A FASTER OUTLIER OF THE DETERMINISTIC CAMP. WHILE
THE 00Z GFS'S SURFACE LOW IS LIKELY A BIT TOO FAR EAST SATURDAY
MORNING GIVEN STRONGER CLUSTERING BACK TO THE WEST, THE 00Z ECMWF
POSITION APPEARS A BIT TOO FAR WEST. BY SUNDAY MORNING, MODEL
DIFFERENCES ARE RELATIVELY MINOR. A GENERAL BLEND EXCLUDING THE
00Z NAM APPEARS BEST OVERALL GIVEN THE NAM'S DEPICTION OF LOW
LEVEL FLOW AND ITS 925-850 MB CIRCULATION STANDS OUT FROM THE
REMAINING CONSENSUS. THE 00Z GFS DISPLACEMENT SHOULD BE RESOLVED
WHEN BLENDED WITH THE NON-NCEP GUIDANCE.
..PREVIOUS DISCUSSION FOLLOWS
TIMING DIFFERENCES REMAIN WITH A MID-LEVEL TROUGH AXIS THAT IS
FORECAST TO EXTEND FROM THE OHIO VALLEY TO THE SOUTHEAST SATURDAY
MORNING. WHILE THE ENSEMBLE SPAGHETTI HEIGHT TRENDS HAVE BEEN
FASTER OVER THEIR PAST 4 12/00Z CYCLES, THE 00Z GFS STILL LOOKS A
TAD TOO FAST THROUGH SATURDAY MORNING. ON THE OTHER SIDE, THE 12Z
UKMET/CMC APPEAR TOO SLOW GIVEN THE LATEST ENSEMBLE DISTRIBUTION
AND THE FASTER TRENDS. THE 00Z NAM IS IN THE MIDDLE REGARDING
TIMING BUT IS NOT SUPPORTED WITH ITS STRONGER 925-850 MB FLOW INTO
THE MID-ATLANTIC REGION AND ITS 925-850 MB LOW THAT DEVELOPS
FRIDAY NIGHT. A STRONG SURFACE LOW DEVELOPS OVER THE INTERIOR
NORTHEAST ON SATURDAY, TRACKING INTO SOUTHERN QUEBEC SUNDAY
MORNING.
MODEL AGREEMENT OVER THE EAST GETS BETTER BY SATURDAY EVENING, BUT
A 00Z GFS/12Z ECMWF BLEND IS PREFERRED TO KEEP CONSISTENT FROM
START TO END WITH THE EVOLUTION OF THE EAST COAST STORM SYSTEM.
..WESTERN 2/3 OF THE CONUS.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/00Z UKMET BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
THE 00Z ECMWF ADJUSTED SLIGHTLY SLOWER AND MORE AMPLIFIED WITH THE
UPPER TROUGH REACHING THE GREAT PLAINS MONDAY MORNING. THIS
ADJUSTMENT IS IN A GOOD DIRECTION BUT PERHAPS TOO FAR WITH GREATER
RIDGING DOWNSTREAM. THE 12Z ECMWF APPEARS LIKE A BETTER FIT WHEN
BLENDED WITH THE 00Z UKMET. THE 00Z CMC IS FLATTER AND ITS LACK OF
SURFACE WAVE ACROSS TEXAS IS NOT SUPPORTED IN THE REMAINING
GUIDANCE.
..PREVIOUS DISCUSSION FOLLOWS
ZONAL FLOW AT THE ONSET OF THE SHORT RANGE TRANSITIONS TO MORE
AMPLIFIED BY MONDAY MORNING WITH A RIDGE JUST OFF OF THE WEST
COAST AND TROUGHING ALONG AND JUST EAST OF THE CENTRAL ROCKIES.
SOME RELATIVELY MINOR DIFFERENCES DEVELOP WITH AN AMPLIFYING
SHORTWAVE OFF OF THE WEST COAST SATURDAY MORNING AND WITH A
RELATED SURFACE LOW OFF OF THE OREGON COASTLINE LATER IN THE DAY.
ENSEMBLE SCATTER LOW PLOTS HAVE BEEN CONSISTENT AND SUGGEST THE
00Z NAM/GFS ARE TOO FAR SOUTH WITH THE SURFACE LOW VALID 00Z/15.
BETTER SUPPORT EXISTS FOR A 12Z ECMWF/UKMET BLEND HERE.
THE 12Z ECMWF/UKMET BLEND IS ALSO SUPPORTED DOWNSTREAM AS THE
TROUGH AXIS TRANSLATES EAST AND A SURFACE RESPONSE DEVELOPS OVER
THE SOUTHERN PLAINS. THE FASTER 00Z NAM/GFS AT 500 MB GOES AGAINST
THE SLOWING TRENDS OBSERVED IN THE ENSEMBLES AND AGAINST
CONCEPTUAL THINKING WITH AN AMPLIFYING FLOW PATTERN OVER THE
EASTERN PACIFIC. ENSEMBLE MEANS SUPPORT A BLEND OF THE 00Z
ECMWF/UKMET WITH THE FRONTAL BOUNDARY EXTENDING FROM
KENTUCKY/TENNESSEE BACK INTO TEXAS WITH THE SURFACE WAVE IN THE
VICINITY OF THE ARKLATEX.
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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