029
FXUS10 KWNH 190653
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 AM EDT THU MAR 19 2020
VALID MAR 19/0000 UTC THRU MAR 22/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP TROUGH/CLOSED LOW IMPACTING THE WEST
...LOW PRESSURE CROSSING THE CENTRAL PLAINS INTO THE UPPER GREAT
LAKES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
A POTENT SHORTWAVE IN THE SOUTHERN STREAM PIVOTING AROUND THE MAIN
UPPER LOW OVER THE INTERMOUNTAIN WEST IS FORECAST TO EVOLVE INTO A
CLOSED LOW ALOFT OVER EASTERN COLORADO BY THURSDAY AFTERNOON, AND
THEN BECOME AN OPEN WAVE AS IT EVENTUALLY PHASES WITH A NORTHERN
STREAM SHORTWAVE REACHING THE NORTHERN GREAT LAKES BY FRIDAY
AFTERNOON. THE RESULT AT THE SURFACE WILL BE LEE CYCLOGENESIS
OVER THE WESTERN HIGH PLAINS AND THEN THE SURFACE LOW TRACKS
NORTHEASTWARD TO THE GREAT LAKES REGION BY FRIDAY MORNING, WITH
FURTHER DEEPENING OF THE LOW THEREAFTER AS IT LIFTS NORTHWARD
ACROSS QUEBEC.
THE 12Z UKMET IS SLOWER WITH THE PROGRESSION OF THE SHORTWAVE AND
NORTHWEST OF THE MODEL CONSENSUS WITH THE SURFACE LOW OVER THE
CENTRAL PLAINS AND THUS SLOWER WITH THE COLD FRONT PASSAGE. THE
GFS BECOMES FASTER AND MORE AMPLIFIED WITH THE NORTHERN STREAM
TROUGH APPROACHING THE GREAT LAKES BY THURSDAY NIGHT, BUT DOES NOT
APPEAR TO HAVE A MAJOR EFFECT ON THE SURFACE PRESSURES. A BLEND
OF THE 00Z NAM AND 12Z ECMWF APPEARS TO BEST REPRESENT THE
EVOLUTION OF THIS STORM SYSTEM.
7Z UPDATE: THE 00Z UKMET TRENDED CLOSER TO THE OTHER MODELS WITH
REGARD TO TIMING COMPARED TO ITS PREVIOUS RUN. THE 00Z GEFS MEAN
TRENDED CLOSER TO THE AMPLIFIED 00Z GFS SOLUTION WITH THE NORTHERN
TROUGH.
..SECOND UPPER LEVEL TROUGH TO REACH THE NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z CMC/ECMWF/EC MEAN BLEND
CONFIDENCE: AVERAGE
THE NEXT SHORT WAVE IN THE PROGRESSIVE NORTHERN STREAM FLOW
CROSSES THE NORTHERN PLAINS FRIDAY NIGHT INTO SATURDAY MORNING,
ORIGINATING FROM THE NORTHWEST TERRITORIES OF CANADA. MODEL
DIFFERENCES BECOME MORE NOTABLE WITH THIS FEATURE, AS BOTH THE 18Z
AND 00Z NAM ARE SLOWER AND MORE AMPLIFIED THAN THE OTHER GUIDANCE,
AND THE 00Z GFS IS SLIGHTLY FASTER. THE 18Z GEFS MEAN IS ALSO
MORE PRONOUNCED WITH THE AMPLITUDE COMPARED TO THE EC MEAN. TO
RESOLVE SOME OF THESE DIFFERENCES, A BLEND OF THE EC MEAN, CMC,
AND ECMWF SHOULD SUFFICE AS A GOOD STARTING POINT.
7Z UPDATE: THE UKMET IS SLIGHTLY WEAKER WITH THIS SHORTWAVE, AND
THE NAM REMAINS NOTABLY STRONGER.
..MID LEVEL TROUGH CROSSING SOUTHWEST ON SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z CMC/12Z ECMWF/00Z NAM BLEND
CONFIDENCE: AVERAGE
THE NEXT SOUTHERN STREAM SHORTWAVE TO AFFECT THE DESERT SOUTHWEST
IS PROGGED TO ARRIVE BY SATURDAY MORNING. SIMILAR TO THE PREVIOUS
MODEL EVALUATION, THE UKMET REMAINS THE SLOWEST MODEL WHILST THE
GFS IS MOST PROGRESSIVE. A BLEND OF THE REMAINING GUIDANCE WOULD
REPRESENT THE MODEL CONSENSUS AND THUS A BLEND OF THE NAM, CMC,
AND ECMWF WORKS WELL AS A STARTING POINT.
7Z UPDATE: NO SIGNIFICANT CHANGES TO PREVIOUS DISCUSSION
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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