690
FXUS10 KWNH 061850
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 PM EST FRI MAR 6 2020
VALID MAR 6/1200 UTC THRU MAR 10/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z FINAL MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OVERALL PATTERN ACROSS THE CONTINENTAL UNITED STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z SUNDAY, THEN A
ECMWF/CMC/GEFS MEAN BLEND AFTER THAT
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z ECMWF HAS TRENDED STRONGER AND SLOWER WITH
THE TROUGH REACHING THE WESTERN HIGH PLAINS BY 12Z MONDAY, AND A
SLIGHTLY SLOWER PROGRESSION OF THE COLD FRONT ACROSS THE PLAINS
THROUGH MONDAY NIGHT. THE 12Z UKMET IS NOW CONSIDERABLY FASTER
WITH A COMPACT UPPER LEVEL LOW OVER SOUTHERN CANADA, WHICH RESULTS
IN A SURFACE OVER THE NORTHERN GREAT LAKES BEING DISPLACED TO THE
NORTHEAST OF THE MODEL CONSENSUS.
A SYNOPTIC SCALE TROUGH INITIALLY OVER THE NORTHEASTERN U.S. IS
FORECAST TO EVOLVE INTO A CLOSED UPPER LOW SOUTH OF NOVA SCOTIA BY
SATURDAY MORNING AND SUPPORT A RAPIDLY DEVELOPING OCEANIC SURFACE
LOW THROUGH SATURDAY NIGHT, WITH THE VAST MAJORITY OF THE IMPACTS
CONFINED TO THE OFFSHORE WATERS. THERE IS NOW ENOUGH MODEL
AGREEMENT WITH RESPECT TO SPEED AND PLACEMENT TO MERIT A
MULTI-MODEL DETERMINISTIC BLEND FOR THIS EVENT.
IN THE WAKE OF THAT SYSTEM, UPPER LEVEL RIDGING AND SURFACE HIGH
PRESSURE DOMINATES MUCH OF THE CENTRAL AND EASTERN U.S. FOR THE
UPCOMING WEEKEND. BY SATURDAY NIGHT, A SHORTWAVE TROUGH REACHES
CALIFORNIA AND TRACKS ACROSS THE INTERMOUNTAIN WEST AND THEN
REACHES THE WESTERN HIGH PLAINS BY MONDAY, AT WHICH POINT THE GFS
IS MORE PROGRESSIVE WITH THE TROUGH AND THE NAM/CMC ARE A LITTLE
LESS AMPLIFIED. AT THE SURFACE, THE 00Z UKMET APPEARS DISPLACED
FARTHER NORTH THAN THE MODEL CONSENSUS. A SECOND SYSTEM IS
PROGGED TO REACH THE PACIFIC NORTHWEST SUNDAY MORNING AND TRACK
EASTWARD NEAR THE CANADIAN BORDER THROUGH MONDAY NIGHT, WITH THE
NAM A BIT MORE AMPLIFIED AND FASTER, AND THE GFS IS SLOWER THAN
THE MODEL CONSENSUS. A CLOSED UPPER LEVEL LOW THEN MEANDERS OFF
THE CALIFORNIA COAST AT 84 HOURS, BUT ITS INFLUENCE ON SENSIBLE
WEATHER HOLDS UNTIL AFTER THE PERIOD.
OVERALL A GENERAL MODEL BLEND IS FAVORED THROUGH 48 HOURS, THEN A
ECMWF/CMC/GEFS MEAN BLEND SHOULD SERVE WELL AS A STARTING POINT IN
THE FORECAST PROCESS.
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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