932
FXUS10 KWNH 170448
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 AM EDT FRI APR 17 2020
VALID APR 17/0000 UTC THRU APR 20/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORT WAVE ENERGY TRACKING FROM THE ROCKIES TO SOUTHERN NEW
ENGLAND...
...SURFACE LOW PRESSURE CROSSING THE OHIO VALLEY INTO NORTHERN MID
ATLANTIC...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 00Z NAM/GFS ARE CLOSE TO THE MODEL CONSENSUS WITH SHORT WAVE
ENERGY TRACKING OUT OF THE ROCKIES ACROSS THE OH VALLEY BEFORE
TAKING IT OFF THE SOUTHERN NEW ENGLAND COAST. THEY ARE ALSO
SIMILAR SPINNING UP SURFACE LOW PRESSURE ON A FRONT HERE, WHICH
TRACKS SOUTH OF SOUTHERN NEW ENGLAND AFTER 18/12Z. AFTER THAT
TIME, THE 12Z ECMWF REMAINS WEST OFF THE CONSENSUS SURFACE LOW
TRACK, AND BECOMES SLOWER WITH TIME. HOWEVER, MUCH OF THE SENSIBLE
WEATHER WITH THE SURFACE LOW AT THIS TIME IS OFFSHORE, SO A
GENERAL MODEL BLEND IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
..SHORT WAVE ENERGY IN THE SOUTHERN STREAM
...SURFACE LOW TRACKING FROM THE SOUTHERN PLAINS TO THE MID
ATLANTIC COAST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z GEFS BLEND
CONFIDENCE: AVERAGE
THE 00Z NAM/GFS ARE CLOSE TO THE CONSENSUS AS THEY TAKE A
WEAKENING MID LEVEL TROUGH ACROSS SOUTHERN CA AND THE SOUTHWEST
THROUGH SAT BEFORE WEAKENING IT. A SECOND SHORT WAVE FOLLOWING IN
THE WAKE OF THE FIRST MOVES ACROSS SOUTHWEST INTO THE SOUTHERN
PLAINS. INITIALLY, THE 12Z
ECMWF/UKMET ARE SLOWER WITH THE SECOND SHORT WAVE (AS THEY HAVE
BEEN FOR THE PAST THREE MODEL CYCLES), BUT GET CLOSER TO THE 00Z
NCEP GUIDANCE ACROSS THE DEEP SOUTH AFTER 19/12Z.
THE SHORT WAVE AIDS IN SPINNING UP SURFACE LOW PRESSURE OVER THE
SOUTHERN PLAINS AT 19/12Z. THOUGH THERE ARE SOME MODEL DIFFERENCES
(WHICH ARE MAINLY LATITUDINAL IN NATURE) WITH THE TRACK OF THE
SURFACE LOW, THERE IS BETTER MODEL CONSENSUS DEEPENING THE LOW
AFTER IT REACHES THE WESTERN EDGE OF THE GULF STREAM TOWARD
20/12Z. THE DIFFERENCES IN THE TRACK ARE WITHIN THE NOISE AT THIS
DISTANCE, BUT COULD HAVE SIGNIFICANT IMPACTS IN THE PLACEMENT OF
THE HIGHEST RAINFALL AXIS DURING SUN/SUN NIGHT.
BASED ON THE ABOVE, A MULTI MODEL BLEND IS PREFERRED, MINUS THE
12Z GEFS, WHICH CURIOUSLY TRAILS THE MULTI MODEL PLACEMENT OF THE
SURFACE LOW AFTER 20/00Z. GIVEN THAT THERE ARE SOME TRACK DETAILS
REMAINING (WHICH COULD HAVE IMPACTS ON THE QPF), FORECAST
CONFIDENCE IS AVERAGE.
...SHORT WAVE ENERGY IN THE NORTHERN STREAM FROM MANITOBA INTO THE
UPPER GREAT LAKES...
...ATTENDANT COLD FRONT CROSSING THE NORTHERN PLAINS INTO THE
UPPER GREAT LAKES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-00Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
BOTH THE 00Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH SHORT WAVE
ENERGY TRACKING FROM CENTRAL MANITOBA INTO THE UPPER GREAT LAKES
AFTER 19/00Z. DESPITE THE GENERAL AGREEMENT IN THE MID LEVEL
TIMING, THE 00Z NAM CONTINUES THAT MODEL'S TREND FOR A SLOWER COLD
FRONTAL PASSAGE ACROSS THE NORTHERN PLAINS INTO THE UPPER GREAT
LAKES THROUGH 20/12Z.
BASED ON THE GOOD MODEL CLUSTERING OTHERWISE, A NON-00Z NAM BLEND
IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE.
SHORT WAVE OVER THE PACIFIC NORTHWEST SAT INTO SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
SHORT WAVE ENERGY DROPPING SOUTH ACROSS WESTERN BRITISH COLUMBIA
AFTER 19/12Z BEGINS TO BREAK DOWN MID LEVEL RIDGING IN PLACE OVER
THE PACIFIC NORTHWEST SAT INTO SUN. THE 00Z NAM/GFS ARE CLOSE TO
THE CONSENSUS WITH THIS FEATURE, THOUGH THE 00Z NAM WEAKENS THE
FEATURE, AS IT IS WEAKER WITH THE MID LEVEL RIDGE BUILDING JUST
WEST OF IT.
AS THE SYSTEM BRIEFLY CLOSES OFF OVER WA/OR, THE NEXT SHORT WAVE
IN THE FLOW SENDS THE MID LEVEL SYSTEM SOUTHEAST ACROSS THE
NORTHERN ROCKIES. THERE IS A FAIR AMOUNT OF SPREAD HOW THIS
OCCURS, AS SHORT WAVE ENERGY UNDERCUTS THE MID LEVEL RIDGE OVER
THE PACIFIC. THE 00Z GFS/12Z ECMWF OFFER A LOOSE CONSENSUS WITH
THIS FEATURE, BUT GIVEN THE SPREAD CONCERNING HOW THE MID LEVEL
SYSTEM EVOLVES AFTER 19/12Z. FORECAST CONFIDENCE IS SLIGHTLY BELOW
AVERAGE,
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAYES
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