653
FXUS10 KWNH 141954
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 PM EST SAT DEC 14 2019
VALID DEC 14/1200 UTC THRU DEC 18/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP SURFACE LOW OVER THE NORTHEAST TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THERE REMAINS VERY GOOD AGREEMENT AND CONSISTENCY WITH THE
DEEPENING SURFACE LOW OVER THE NORTHEAST U.S. TODAY AND AS THE LOW
TRACKS NORTH/NORTHEAST, THE MOST RECENT GUIDANCE SHOWS LITTLE
VARIABILITY WITH THE DEPTH/TRACK/POSITION THROUGH 48 HOURS. A
GENERAL MODEL BLEND IS PREFERRED.
...MID-LEVEL TROUGH AMPLIFYING INTO THE WESTERN U.S. THIS WEEKEND
AND REACHING THE CENTRAL PLAINS MONDAY...
...SURFACE LOW ORGANIZING EAST OF THE MISSISSIPPI RIVER MONDAY
INTO TUESDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
20Z UPDATE: NO REAL SIGNIFICANT CHANGES NOTED WITH THE REST OF THE
12Z GUIDANCE. THE 12Z NAM STILL REMAINS THE OUTLIER SOLUTION AND
IS NOT INCLUDED IN THE OVERALL BLEND PREFERENCE. THERE ARE SOME
TIMING DIFFERENCES WITH THE LOW LIFTING THROUGH THE OH VALLEY BY
MONDAY EVENING BUT A BLEND OF THE OTHER DETERMINISTIC GUIDANCE
SUFFICES FOR NOW.
WITH THE NEXT SHORTWAVE TROUGH DIGGING THROUGH THE SOUTHWEST U.S.
AND THEN REACHING THE CENTRAL PLAINS EARLY NEXT WEEK, THE
DETERMINISTIC GUIDANCE IS BEGINNING TO SHOW LESS SPREAD THIS
CYCLE. THERE IS SOME LATITUDINAL DIFFERENCES IN THE LOW TRACK
ACROSS THE MID-SOUTH AS WELL AS SOME TIMING DIFFERENCES (A RUN TO
RUN ANALYSIS SHOWS A SLOWING TREND) BUT OVERALL THERE IS GOOD
AGREEMENT. THE EXCEPTION IS THE 12Z NAM, WHICH IS CONSIDERABLY
STRONGER WITH THE VORTICITY MAXIMA SWINGING THROUGH THE SOUTHWEST
U.S. ON DAY 1/2. THIS LEADS TO A MUCH MORE AMPLIFIED WAVE ACROSS
THE CENTRAL PLAINS AND CONTRIBUTES TO HIGHER QPF. WITH LITTLE
SUPPORT FROM THE REST OF THE GUIDANCE AND ITS SOLUTION OUTSIDE OF
THE ENSEMBLE SPREAD, IT WAS DISCARDED FOR THIS CYCLE. OTHERWISE,
THE REST OF THE DETERMINISTIC PROVIDE A GOOD BLEND FOR THE LARGE
SCALE MASS FIELDS.
...MID-LEVEL SHORTWAVE NEARING THE UPPER MISSISSIPPI VALLEY
TUESDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
IN THE WAKE OF THE SOUTHERN STREAM SHORTWAVE THAT TRACKS ACROSS
THE CENTRAL PLAINS, A SECONDARY SHORTWAVE TROUGH WILL DROP THROUGH
THE NORTHERN TIER AND GREAT LAKES REGION TUESDAY. MODEL
DIFFERENCES ARE MINIMAL, BUT THE ONE NOTABLE DIFFERENCE IS THE 00Z
UKMET WHICH IS A BIT MORE AMPLIFIED/DEEP COMPARED TO THE REST OF
THE GUIDANCE. THE 00Z CMC IS ALSO STRONGER COMPARED TO THE REST OF
THE GUIDANCE. THESE DIFFERENCES DO NOT APPEAR TO MAKE MUCH
DIFFERENCE IN THE QPF, SO OVERALL A GENERAL MODEL BLEND IS
SUFFICIENT FOR THIS SYSTEM.
..TROUGH APPROACHING WESTERN U.S. TUESDAY EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE
TOWARD THE END OF THE FORECAST PERIOD (TUESDAY EVENING), A TROUGH
WILL APPROACH THE WESTERN U.S. COAST. OVERALL SETUP IS WELL AGREED
UPON FOR THE DAY 3 FORECAST WITH THE ONLY NOTABLE DIFFERENCE IS
THE 12Z CMC WHICH IS FASTER THAN THE REST OF THE GUIDANCE. LOOKING
AT THE ENSEMBLES, THERE IS RELATIVELY SIMILAR CLUSTERING OF LOW
POSITIONS AT 18.00Z, SO A NON-CMC BLEND IS PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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