330
FXUS10 KWNH 021646
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1245 PM EDT SAT MAY 2 2020
VALID MAY 2/1200 UTC THRU MAY 6/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SHORTWAVE AND SURFACE LOW TRACKING FROM GREAT LAKES TO THE
NORTHEAST THROUGH MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/EC MEAN/NAM BLEND
CONFIDENCE: MODERATE
A POSITIVELY TILTED SHORTWAVE TROUGH IN AN ACTIVE NORTHERN STREAM
MID-LEVEL FLOW WILL CROSS ONTARIO AND QUEBEC THROUGH THE WEEKEND
AND SUSTAIN A SURFACE LOW AND COLD FRONT CROSSING THE GREAT LAKES,
OHIO VALLEY, AND THEN REACHING THE EAST COAST BY SUNDAY NIGHT.
THE MODELS ARE IN EXCELLENT AGREEMENT THROUGH SUNDAY MORNING,
AFTER WHICH THE 00Z UKMET BECOMES FASTER WITH THE UPPER LEVEL
FEATURE. THE GFS AND ITS ENSEMBLE MEAN ARE FASTER BRINGING THE
COLD FRONT ACROSS THE EAST COAST AND THE ARRIVAL OF HEIGHT FALLS
ACROSS THE NORTHEAST, AND THE CMC IS NOT QUITE AS AMPLIFIED AS THE
OTHER DETERMINISTIC GUIDANCE ALOFT. A BLEND OF THE ECMWF/NAM AND
SOME OF THE EC MEAN WOULD WORK WELL AS A STARTING POINT AND
MAINTAINS PREVIOUS OVERNIGHT MODEL PREFERENCE.
TROUGH TRACKING FROM PACIFIC NORTHWEST TO THE GREAT LAKES THROUGH
TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/CMC/EC MEAN BLEND
CONFIDENCE: LOW-MODERATE
SHORTWAVE ENERGY PIVOTING AROUND THE GULF OF ALASKA UPPER LEVEL
GYRE BREAKS OFF TO THE EAST AND TRACKS NEAR THE U.S./CANADA
BORDER, BRIEFLY BECOMING A CLOSED UPPER LOW OVER ALBERTA AND
SASKATCHEWAN ON MONDAY BEFORE EVOLVING INTO AN OPEN WAVE AGAIN.
THIS WILL SUSTAIN A COLD FRONT CROSSING THE INTERMOUNTAIN WEST,
ROCKIES, AND THEN THE WESTERN HIGH PLAINS BY MONDAY.
SIMILAR TO PREVIOUS RUNS, THE GFS AND TO A LESSER EXTENT THE GEFS
MEAN ARE STILL MORE AMPLIFIED WITH THE TROUGH CROSSING THE
NORTHERN ROCKIES AND NORTHERN PLAINS, AND THE UKMET LIKELY TOO
WEAK WITH THE UPPER TROUGH AS IT REACHES THE GREAT LAKES BASED ON
ENSEMBLE SPREAD. BY THE END OF THE FORECAST PERIOD, THE NAM
BECOMES MORE AMPLIFIED AND IS A LITTLE FASTER THAN THE OTHER
MODELS, AND ALSO LOSES ENSEMBLE SUPPORT.
NEXT STORM SYSTEM APPROACHING PACIFIC NORTHWEST EARLY IN THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/12Z NAM/00Z EC MEAN BLEND
CONFIDENCE: MODERATE
THE THIRD AREA OF INTEREST WILL BE ACROSS THE NORTHEAST PACIFIC
AND THE PACIFIC NORTHWEST BY LATE MONDAY AND INTO TUESDAY AS A
PAIR OF SHORTWAVES PIVOT AROUND THE BROADER UPPER LEVEL LOW OVER
THE GULF OF ALASKA, WITH A COUPLE OF RELATIVELY WEAK COLD FRONTS
APPROACHING THE REGION.
THE 00Z UKMET IS A BIT STRONGER WITH THE FIRST SHORTWAVE/FRONT
APPROACHING THE REGION, HOWEVER IT IS STILL WITHIN THE ENSEMBLE
SPREAD AND THE OTHER MODELS ARE RELATIVELY CLOSE IN AGREEMENT.
WITH THE SECOND SHORTWAVE, THE NAM AND GFS ARE A LITTLE FASTER,
THE UKMET STRONGER, AND THE GEFS MEAN SLOWER AND WELL BEHIND THE
OPERATIONAL GFS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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