855
FXUS10 KWNH 290655
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 AM EST WED JAN 29 2020
VALID JAN 29/0000 UTC THRU FEB 01/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SPLIT FLOW TROUGH CROSSING THE GREAT PLAINS TODAY AND REACHING
THE SOUTHEAST WEDNESDAY NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE LATEST NUMERICAL GUIDANCE REMAINS IN DECENT AGREEMENT WITH THE
EVOLUTION OF A SHORTWAVE WHICH WAS OVER THE SOUTHERN PLAINS AT
29/00Z. AS THE WAVE TRACKS EAST, THE 29/00Z NAM WAS SLIGHTLY
FASTER THAN THE 28/12Z RUNS AND WELL WITHIN THE CLUSTERING OF
OTHER 29/00Z MODEL GUIDANCE. A GENERAL MODEL BLEND SHOULD LOOK
VERY SIMILAR TO ANY OF THE INDIVIDUAL MODEL RUNS WHILE DAMPENING
THE MINOR DIFFERENCES IN AMPLITUDE AND SPEED OF PROPAGATION OF THE
WAVE.
...SPLIT FLOW TROUGH IN NORTHERN STREAM FROM THE UPPER MIDWEST TO
THE MID-ATLANTIC THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 29/00Z UKMET/CANADIAN BLEND
CONFIDENCE: AVERAGE
THE NUMERICAL GUIDANCE GOT INTO BETTER AGREEMENT WITH RESPECT TO
THE ENERGY IN THE NORTHERN STREAM DURING THE 28/12Z MODEL RUNS.
THERE WERE A COUPLE OF MINOR RUN TO RUN DIFFERENCES IN THE NAM AND
GFS...BUT THE OVERALL SOLUTION CHANGED LITTLE. THAT LEAVES THE
29/00Z UKMET OFFERED A SOLUTION THAT WAS A BIT SLOWER THAN MODEL
CONSENSUS THROUGH THURSDAY MORNING AND THE CANADIAN DEPICTED A
WEAKER WAVE THAN CONSENSUS WHICH MAKES ITS WAY ACROSS PARTS OF THE
GREAT LAKES/OHIO VALLEY AND TOWARDS THE MID-ATLANTIC REGION. NO
REASON TO CHANGE PREFERENCES BASED ON THE 29/00Z GUIDANCE.
...MID-LEVEL TROUGH OVER THE PACIFIC NORTHWEST TODAY AND
AMPLIFYING INTO THE DESERT SOUTHWEST WEDNESDAY, REACHING THE
SOUTHERN PLAINS THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 29/00Z GFS AND ECMWF BLEND
CONFIDENCE: AVERAGE
BOTH THE 29/00Z GFS AND 28/12Z OPERATIONAL ECMWF SHOWED SHORTWAVE
ENERGY DROPPING SOUTH AND FORMING A CLOSED LOW WHICH MAKES ITS WAY
INTO NORTHERN MEXICO...AN IDEA THAT WAS SUPPORTED BY THE ECMWF
ENSEMBLES...WHILE THE NAM AND UKMET WERE BOTH HEDGING TOWARDS A
FASTER SOLUTION WITHOUT THE DEPTH OF THE ECMWF/GFS. WILL NOT MAKE
ANY CHANGES TO THE EARLIER PREFERENCE FOR THE GFS/ECMWF BLEND.
...MID-LEVEL TROUGH ENTERING BRITISH COLUMBIA ON WEDNESDAY AND
AMPLIFYING SOUTHWARD INTO THE GREAT PLAINS BY FRIDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 28/00Z ECMWF/GFS BLEND
CONFIDENCE: BELOW AVERAGE
UNCERTAINTY REMAINED HIGH AS THE MODELS STRUGGLE WITH THE SOUTHERN
END OF A SHORTWAVE TROUGH AND HOW IT EVOLVES ONCE IT CROSSES
THROUGH A RIDGE CENTERED OVER SOUTHWESTERN CANADA AND THE
NORTHWESTERN U.S.. WHILE RUN TO RUN CONSISTENCY HAS BEEN
POOR...THERE WAS A MOVE BY BOTH THE ECMWF AND THE GFS IN THEIR
29/00Z RUNS TOWARDS A SOLUTION THAT SHOWED A MORE UNIFIED FLOW
PATTERN SETTING UP DOWNSTREAM OF THE WESTERN RIDGE, AND THE
DEVELOPMENT OF A CLOSED LOW WITHIN THAT LOW OVER PARTS OF THE
SOUTHERN PLAINS OR TENNESSEE VALLEY BY EARLY SATURDAY MORNING.
WHILE THE CANADIAN HAD BEEN SUGGESTING A LOW IN PREVIOUS MODEL
RUNS, IT BACKED AWAY TOWARDS THE 28/12Z ECMWF IDEA. AT THIS
POINT, THE IDEA OF A BROAD MID-LEVEL TROUGH WITH A LOW SEEMS MORE
REASONABLE GIVEN THE AMPLITUDE OF THE UPSTREAM RIDGE. SO WILL
FAVOR A BLEND OF THE 29/00Z GFS AND ECMWF...ALTHOUGH CONFIDENCE IN
ANY PARTICULAR DETAIL IS BELOW AVERAGE AND WILL NOT BE SURPRISED
AT ADDITIONAL RUN TO RUN CHANGES.
...LEADING EDGE OF LONGWAVE TROUGH, OFFSHORE OF THE WEST COAST OF
CANADA FRIDAY EVENING AND DOWNSTREAM ATMOSPHERIC RIVER INTO THE
PACIFIC NORTHWEST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 29/00Z NAM/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
AFTER THE PASSAGE OF A SHORTWAVE AND ACCOMPANYING COLD FRONT INTO
BRITISH COLUMBIA ON THE 30TH, INITIALLY ZONAL FLOW INTO WESTERN
CANADA WILL BEGIN TO AMPLIFY AS RIDGING INCREASES AHEAD OF AN
UPSTREAM SHORTWAVE NEAR 40N 145W BY 01/00Z. ENSEMBLE MEANS AND THE
REMAINING DETERMINISTIC CONSENSUS SUGGEST THAT THE 29/00Z GFS AND
29/12Z CMC MAY BE A BIT TOO QUICK WITH THE SHORTWAVE...SO A BLEND
OF THE 29/00Z NAM/ECMWF/UKMET REMAINS CLOSEST TO THE RELATIVELY
AGREEABLE ENSEMBLE MEAN'S POSITION AND THE DOWNSTREAM ATMOSPHERIC
RIVER MOVING INTO THE PACIFIC NORTHWEST.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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