801
FXUS10 KWNH 020646
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 AM EDT TUE JUN 2 2020
VALID JUN 2/0000 UTC THRU JUN 5/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z INITIAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7Z UPDATE: THE MAIN CHANGE NOTED WITH THE ARRIVAL OF THE 00Z
NON-NCEP GUIDANCE IS A SLOWER TREND IN THE 00Z ECMWF WITH THE
CLOSED LOW TRACKING ACROSS SOUTH-CENTRAL CANADA BY THURSDAY AND
EXTENDING INTO FRIDAY AS IT EVOLVES INTO AN OPEN WAVE. THIS
BRINGS THE ECMWF MUCH CLOSER TO THE CONSENSUS COMPARED TO ITS 12Z
RUN. THE GFS REMAINS THE MOST PROGRESSIVE IN BRINGING THE CLOSED
LOW TOWARDS CALIFORNIA ON FRIDAY AND IS ALSO LOWER WITH MID-LEVEL
HEIGHTS ACROSS THE NORTHERN TIER STATES. OTHERWISE, NO
SIGNIFICANT CHANGES TO THE PREVIOUS PREFERENCES.
UPPER LEVEL TROUGH EXITING THE NORTHEAST U.S. ON TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
A PRONOUNCED UPPER LEVEL TROUGH BY EARLY JUNE STANDARDS WILL BE IN
PLACE ACROSS THE NORTHEASTERN U.S. ON TUESDAY BEFORE LIFTING OUT
ACROSS EASTERN CANADA AS THE UPPER LEVEL FLOW PATTERN BECOMES MORE
ZONAL AND THE AIRMASS WARMS UP SUBSTANTIALLY. ALTHOUGH THERE ARE
SOME MINOR DIFFERENCES ONCE THE TROUGH REACHES EASTERN CANADA,
THERE IS EXCELLENT AGREEMENT FOR THE NORTHEAST U.S. THROUGH
TUESDAY BEFORE THE TROUGH LIFTS OUT, SO A GENERAL MODEL BLEND CAN
BE RECOMMENDED.
UPPER LEVEL LOW SLOWLY LIFTING ACROSS WEST TEXAS AND INTO OKLAHOMA
THROUGH TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
A BROAD UPPER LOW CURRENTLY CENTERED OVER WESTERN TEXAS WILL
CONTINUE TO SLOWLY LIFT NORTHEASTWARD ACROSS OKLAHOMA THROUGH
TUESDAY NIGHT, AND THEN GRADUALLY WEAKEN OVER ARKANSAS AS IT
BECOMES EMBEDDED IN THE BROAD UPPER LEVEL RIDGE. ALL GLOBAL
GUIDANCE ARE IN CLOSE ENOUGH AGREEMENT ON THE MAIN FEATURES TO
MERIT THE USE OF A MULTI-DETERMINISTIC MODEL BLEND.
DEVELOPING CUT-OFF LOW LINGERING SOUTHWEST OF CALIFORNIA THROUGH
MIDWEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/00Z ECMWF/00Z UKMET
CONFIDENCE: MODERATE-HIGH
A BROAD UPPER LOW HAS BECOME PINCHED OFF FROM THE WESTERLIES
FARTHER NORTH, AND BECAUSE OF THE RIDGE AXIS OVER THE SOUTHERN
ROCKIES, IT SHOULD REMAIN NEARLY ANCHORED IN PLACE THROUGH
THURSDAY BEFORE BEGINNING TO EJECT SLOWLY EAST TOWARD SOUTHERN
CALIFORNIA BY FRIDAY MORNING. SIMILAR TO LAST NIGHT, THE ECMWF
ENSEMBLE MEMBERS ARE GENERALLY A LITTLE TO THE WEST THAN MOST OF
THE GEFS ENSEMBLE MEMBERS. BY FRIDAY MORNING, THE GFS AND THE
GEFS MEAN ARE THE QUICKEST TO PROGRESS THE LOW EASTWARD. THE 12Z
UKMET LIES NEAR THE MIDDLE OF THE ENSEMBLE SPREAD AND REPRESENTS A
GOOD CHOICE IN TERMS OF MODEL CHOICES, ALONG WITH SOME OF THE
ECMWF AND NAM.
ACTIVE FLOW PATTERN ACROSS NORTHERN TIER OF U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/00Z UKMET/00Z ECMWF
CONFIDENCE: MODERATE
THE WESTERLIES ON THE NORTHERN PERIPHERY OF THE CENTRAL U.S. RIDGE
ARE EXPECTED TO BE RATHER ACTIVE WITH THREE WELL DEFINED SHORTWAVE
DISTURBANCES TRACKING EASTWARD NEAR THE U.S./CANADA BORDER THROUGH
MID-WEEK. THE FIRST SYSTEM IS AN OCCLUDED LOW MOVING ACROSS
ONTARIO AND QUEBEC THAT WILL GRADUALLY WEAKEN, AND BRING A STRONG
WARM FRONT SURGING EASTWARD TOWARDS THE EAST COAST BY TUESDAY
NIGHT AND EARLY WEDNESDAY. THE SECOND DISTURBANCE IS A SHORTWAVE
OVER MONTANA AND ALBERTA WHICH WILL TRACK ACROSS SOUTH-CENTRAL
CANADA TO THE HUDSON BAY BY WEDNESDAY MORNING, WHICH WILL LEAVE A
FRONT NEAR THE CANADIAN BORDER THAT WILL DIRECT THE NEXT AND THIRD
SYSTEM REACHING THE BRITISH COLUMBIA COAST LATE TUESDAY WHICH WILL
TRACK JUST NORTH OF THE BORDER AND EVOLVE INTO AN UPPER LOW OVER
MANITOBA BY THURSDAY. THIS WILL SUPPORT A COLD FRONT ACROSS THE
NORTHERN GREAT PLAINS WEDNESDAY NIGHT.
GIVEN THE QUASI-ZONAL AND PROGRESSIVE FLOW PATTERN IN PLACE ACROSS
THE REGION, THIS IS WHERE THE GREATEST MODEL DIFFERENCES CURRENTLY
EXIST, MAINLY WITH THE SECOND AND THIRD SYSTEMS. BOTH THE 18Z AND
00Z GFS HAVE BEEN MORE SUPPRESSED WITH THE UPPER LEVEL HEIGHT
PATTERN ACROSS THE NORTHERN TIER STATES COMPARED TO THE OTHER
GUIDANCE, AND NEAR THE SOUTHERN EXTENT OF THE ENSEMBLE MEMBER
SPREAD. BY THURSDAY MORNING, THE ECMWF AND THE CMC BECOME FASTER
WITH THE UPPER LOW REACHING MANITOBA, AND THE ECMWF IS ALSO AHEAD
OF ITS ENSEMBLE MEAN.
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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