958
FXUS10 KWNH 151834
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT THU AUG 15 2019
VALID AUG 15/1200 UTC THRU AUG 19/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION...INCLUDING PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
EXCEPTION: NON-CMC ACROSS NORTHERN TIER/S CANADA
CONFIDENCE: AVERAGE
19Z UPDATE: SMALL ADJUSTMENTS WERE NOTED WITH THE TIMING OF THE
LEAD SHORTWAVE HEIGHT FALLS PROGRESSING THROUGH THE NORTHERN
PLAINS INTO THE GREAT LAKES BY 00Z MON WITH THE UKMET/ECMWF, WITH
LITTLE NEGATIVE AFFECT TO THE INCREASING AGREEMENT, THOUGH TOWARD
THE END OF DAY 3; THE SPREAD INCREASES IN A TYPICAL MANNER. AS
SUCH NO ADJUSTMENT IS SUGGESTED FOR THIS AREA WITH RESPECT TO
THESE MODELS. THE CMC HOWEVER, DID SLOW FURTHER AND THEREFORE
POSITIONS THE CLOSED LOW AND SURFACE REFLECTION WELL WEST OF THE
OTHER GUIDANCE ENOUGH TO SUGGEST ITS REMOVAL FROM THE BLEND
OUTRIGHT. CONFIDENCE REMAINS AVERAGE FOR THIS AREA.
---PRIOR DISCUSSION---
THE UPPER-LEVEL PATTERN CONTINUES WITH STRONG SOUTHWEST RIDGE AND
BROAD CYCLONIC FLOW ALONG THE MUCH OF THE NORTHERN PORTION OF THE
UNITED STATES. THIS TROF PRODUCES BROADLY NORTHWESTERLY FLOW
ACROSS THE NORTHERN PLAINS INTO THE GREAT LAKES WITH EMBEDDED
SMALL SCALE SHORTWAVES MOVING THROUGH IT. THE BASE OF THE TROF IS
CENTERED OVER THE OHIO AND TN VALLEY, WHERE IT INTERSECTS WITH
RETURN EASTERLY FLOW UNDER THE SUBTROPICAL HIGH NEAR BERMUDA (SW).
THE FRONTAL/CONFLUENCE ZONE AT THIS INTERSECTION CONTINUES TO
REMAIN FAIRLY ACTIVE BUT ALSO VERY STATIONARY, WITH WEAK WAVES
ALONG IT. MODELS DO NOT HAVE A STRONG AGREEMENT ON TIMING, BUT
THERE IS GOOD AGREEMENT ON THE EXISTENCE OF A DOMINANT WAVE
EMERGING OUT OF THE SOUTHEAST SAT INTO SUNDAY INTO THE NORTHWEST
ATLANTIC NORTH OF BERMUDA ALONG 40N INTO SUNDAY. THE 12Z NAM/00Z
UKMET ARE STRONG WHILE THE 12Z GFS/00Z ECMWF SUGGEST MORE
FLAT/STRUNG OUT FEATURES, BUT OVERALL THE
PATTERN/ORIENTATION/PLACEMENT SUPPORTS A GENERAL MODEL BLEND FOR
THIS AREA.
BACK INTO THE NORTHERN STREAM, CONVECTIVELY INDUCED SHORTWAVES
EMERGE FROM THE NORTHERN ROCKIES THROUGH THE CENTRAL PLAINS INTO
THE OHIO VALLEY FOR THE NEXT FEW NIGHTS, BEFORE A STRONGER
NORTHERN STREAM CANADIAN WAVE DROPS EAST OF THE CANADIAN ROCKIES
INTO THE PRAIRIES, DANGLING A FRONTAL ZONE ACROSS THE NORTHERN
HIGH PLAINS INTO DAKOTAS DUE TO THE LEAD HEIGHT-FALLS BY EARLY
SATURDAY. THE 00Z UKMET IS A BIT NORTH/SLOWER WITH THE FRONTAL
PUSH BUT THE 12Z NAM/GFS HAVE TRENDED TOWARD BETTER AGREEMENT WITH
THE ECMWF; YET REMAIN SLIGHTLY FASTER TYPICAL OF BIAS. THE 00Z
CMC ALSO APPEARS A BIT SLOWER THAN CONSENSUS TO SUGGEST LOWER
WEIGHTING ESPECIALLY BY DAY 3 IN THE NORTHERN TIER/SOUTHERN
CANADA, BUT OTHERWISE A GENERAL MODEL BLEND APPEARS SOLID. AS
SUCH A GENERAL MODEL BLEND TRENDING TOWARD A NON-CMC BLEND OR A
GFS/ECMWF HEAVY WEIGHTED BLEND WILL SUFFICE. WHILE THIS IS
SHAPING UP A BIT BETTER IN TIMING/PLACEMENT...CONFIDENCE REMAINS
AVERAGE GIVEN THE IMPORTANCE OF CONVECTION (UPSCALE GROWTH).
THE FAR WESTERN PORTION OF THE LARGE SCALE TROF WILL ALSO START TO
BECOME A BIT MORE AMPLIFIED AT THE END OF THE WEEKEND, THOUGH THE
NAM/GFS AND CMC ARE MOST AGGRESSIVE, THE ECMWF, UKMET ARE A BIT
WEAKER, ALLOWING FOR A SLIGHTLY FASTER SOUTHWARD PROGRESSION.
LONGER TERM TRENDS SUGGEST THE FORMER HAS A SLIGHTLY PREFERRED
TREND IN THE ENSEMBLE SUITE BUT NOT SIGNIFICANT ENOUGH TO SUPPORT
ANYTHING GREATER THAN A GENERAL MODEL BLEND WITH MAYBE A SLIGHT
INCREASE/WEIGHT TOWARD GFS/GEFS/ECENS AND CMC SOLUTIONS.
CONFIDENCE IS AVERAGE.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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