916
FXUS10 KWNH 021839
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 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 FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
19Z UPDATE: THE 12Z CMC HAS TRENDED TO A MORE AMPLIFIED SOLUTION
WITH THE SHORTWAVE ACROSS THE UPPER MIDWEST AND OHIO VALLEY IN
RESPONSE TO A STRONGER UPSTREAM RIDGE ACROSS THE ROCKIES COMPARED
TO ITS 00Z RUN, AND SLIGHTLY STRONGER (ALONG WITH THE 12Z UKMET)
WITH THE TROUGH OVER THE NORTHEAST ON MONDAY AND SLOWER WITH THE
SECOND DISTURBANCE APPROACHING THE PACIFIC NORTHWEST. THERE IS
ALSO A SLIGHTLY SLOWER TREND WITH THE 12Z UKMET OVER THE NORTHEAST
PACIFIC AND THE RIDGE AXIS OVER THE INTERMOUNTAIN WEST, AND THE
ECMWF TRENDED MORE AMPLIFIED. TAKING ALL OF THE MODELS INTO
ACCOUNT, THE NAM REMAINS FASTER AND STRONGER WITH THE SHORTWAVE
CROSSING THE NORTHERN PLAINS, AND THE CMC SLIGHTLY STRONGER WITH
THE SURFACE LOW CROSSING THE MID-SOUTH WITH THE MORE AMPLIFIED
TROUGH CROSSING THE OHIO VALLEY. THE GFS REMAINS SLIGHTLY FASTER
WITH THE FRONT REACHING THE EAST COAST, AND THE UKMET IS STRONGER
AND FARTHER SOUTH WITH THE SURFACE LOW APPROACHING THE PACIFIC
NORTHWEST BY TUESDAY EVENING, AND MORE IN LINE ACROSS THE GREAT
LAKES REGION COMPARED TO ITS FASTER 00Z RUN.
SHORTWAVE AND SURFACE LOW TRACKING FROM GREAT LAKES TO THE
NORTHEAST THROUGH MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET/NAM BLEND
CONFIDENCE: MODERATE-HIGH
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: 12Z ECMWF/UKMET/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. THIS SYSTEM CONTINUES TO
HAVE THE MOST VARIABILITY AMONG THE GUIDANCE, THUS REDUCING
OVERALL CONFIDENCE IN DETAILS.
NEXT STORM SYSTEM APPROACHING PACIFIC NORTHWEST EARLY IN THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/CMC/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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