763
FXUS10 KWNH 151835
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
134 PM EST SAT FEB 15 2020
VALID FEB 15/1200 UTC THRU FEB 19/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES & CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..LARGE SCALE PATTERN OVER THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/GFS BLEND
EXCEPTION: REMOVE GFS FOR NAM/UKMET ALONG GULF COAST SUN/MON)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z ECMWF TRENDED A BIT WEAKER/FASTER AND
THEREFORE A BIT SOUTH THROUGH THE GREAT LAKES, VERY NEAR THE 12Z
GFS, COMBINE THIS WITH THE 12Z CMC TRENDING BACK TOWARD THE
GFS...THERE IS SOME GROWING CONFIDENCE THROUGH DAY 3 ACROSS THE
CENTRAL PLAINS INTO THE GREAT LAKES. THESE SLIGHT SHIFTS,
HIGHLIGHTED THE SLOWNESS OF THE UKMET, WHICH REMAINED SIMILAR TO
THE 00Z RUN, MAKING IT A BIT LESS FAVORABLE IN A BLEND. THE CMC
STILL HAS AN ISSUE BEING TOO FAR NORTH WITH THE QPF AXIS (WELL
NORTH OF THE EXPECTED COASTAL BOUNDARY) ACROSS THE SOUTH ON
TUESDAY, STILL FAVORING THE ECMWF/GFS AXIS/ORIENTATION OVERALL.
AS SUCH TO BEST ENCOMPASS BOTH THE MASS FIELDS AS WELL AS QPF,
WILL SUPPORT A STRONGER 12Z ECMWF/GFS BLEND WITH SOME MINOR
INCORPORATION OF THE CMC (GREAT LAKES) AND UKMET CENTRAL/SOUTHERN
PLAINS AND GULF COAST REGION (LESS GFS ALONG GULF ON SUN/MON).
---PRIOR DISCUSSION---
A FAIRLY ZONAL PATTERN CURRENTLY EXISTS ACROSS THE CONUS WITH SOME
BROAD CYCLONIC CURVATURE CENTERED AROUND THE CENTRAL PLAINS AS
PACIFIC AIR REPLACES THE ARCTIC SOURCED AIR THAT DOMINATES THE
EASTERN THIRD OF THE US (WITH DUE EXCEPTION TO THE SUBTROPICAL
RIDGE OVER THE EASTERN GULF OF MEXICO/FLORIDA). A STRONGER
SHORTWAVE EXISTS WELL INTO CANADA WITH SOME MODERATE INFLUENCE FOR
QPF/SNOWS ACROSS THE GREAT LAKES TODAY THROUGH SUNDAY. GUIDANCE
IS QUITE AGREEABLE WITH THIS SYSTEM EVEN AS IT CLIPS THE INTERIOR
NORTHEAST LATE SUNDAY INTO MONDAY. ADDITIONALLY, RETURN MOISTURE
AROUND THE SUBTROPICAL RIDGE ALONG THE COASTAL FRONT APPEARS TO BE
SET BEST WITH A NAM/UKMET/ECMWF BLEND AS THE GFS APPEARS TO BE
WELL SOUTH OF THE COASTAL FRONT/WELL OFFSHORE.
THE ZONAL PATTERN WILL USHER IN ANOTHER PACIFIC SHORTWAVE INTO THE
PACIFIC NORTHWEST LATER TODAY INTO SUNDAY AND WILL SPREAD ACROSS
THE NORTHERN ROCKIES INTO THE CENTRAL PLAINS BY MONDAY MORNING.
THE ELONGATED SHORTWAVE WILL START TO SPLIT WITH THE TRAILING EDGE
AMPLIFYING ACROSS THE CENTRAL ROCKIES, WHILE THE LEADING EDGE WILL
START TO SHIFT EAST INTO THE GREAT LAKES UNDER INFLUENCE/DIRECTION
FROM SHARPENING ARCTIC SHORTWAVE DROPPING OUT OF CENTRAL CANADA
INTO TUESDAY. AS TYPICAL SMALL VARIATION IN WAVE LENGTH/SPACING
BETWEEN THE FEATURES LEADS TO THE DIFFERENCE IN TIMING/ORIENTATION
OF THE SURFACE MASS FIELDS, MOISTURE FLUX AND THEREFORE QPF AXES.
THE GUIDANCE IS FAIRLY AGREED UPON WITH THE TIMING OF THE PACIFIC
FEATURE, WITH EXCEPTION OF THE CMC WHICH IS A BIT FURTHER SOUTH
AND UNCHARACTERISTICALLY FASTER, OTHERWISE; THE MAIN SPREAD IS IN
THE TIMING OF THE ARCTIC WAVE. THE GFS IS VERY FAST BUT WEAKER
NARROWING THE SPREAD WITH THE PACIFIC WAVE, WHICH LEADS TO
SLIGHTLY FASTER ADVECTION AND TRACK OF THE SURFACE WAVE ALONG THE
FRONTAL ZONE INTO THE GREAT LAKES. THIS IS OPPOSED BY THE SLIGHTLY
SLOWER ECMWF/UKMET AND ECENS ENSEMBLE SOLUTIONS THAT FAVOR A BIT
GREATER SPACING AND THEREFORE STRONGER/SLOWER AMPLIFICATION OF THE
SURFACE WAVE. THE 12Z NAM IS MORE IN THIS SLOWER CAMP, BUT IS
MUCH FURTHER WEST AND COMPACT WITH THE ARCTIC WAVE THAT DOESN'T
BARE MUCH SUPPORT IN THE OVERALL LARGER SCALE FLOW. AS SUCH WILL
FAVOR A NON-NAM, NON-CMC SOLUTION WITH THIS WAVE, SURFACE CYCLONE
AND QPF PATTERN. WEIGHTING TOWARD THE ECMWF/UKMET QPF/SURFACE
PATTERN IS HIGHER IN THE BLEND BUT WHILE A BIT FAST, THE EVOLUTION
OF THE GFS/GEFS SEEMS PLAUSIBLE GIVEN THE FAST OVERALL FLOW
INITIALLY. CONFIDENCE IS SLIGHTLY ABOVE AVERAGE IN THIS BLEND
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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