398
FXUS10 KWNH 041900
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST SAT JAN 04 2020
VALID JAN 04/1200 UTC THRU JAN 08/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..UPPER TROUGH CROSSING FROM THE MIDWEST TO THE EAST COAST
..SURFACE LOW NEAR NEW ENGLAND TODAY/TONIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. NO SIGNIFICANT CHANGES
WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC COMPARED WITH THEIR
PREVIOUS 00Z CYCLES.
...SHORTWAVE EJECTING OUT ACROSS THE PLAINS, REACHING THE GREAT
LAKES BY SUN NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z CMC BLEND
CONFIDENCE: ABOVE AVERAGE
THERE REMAIN SOME MINOR PLACEMENT DIFFERENCES WITH THE MID-LEVEL
SHORTWAVE AS IT NEARS THE GREAT LAKES. THE 12Z CMC REMAINS FARTHER
SOUTH WITH THE 500 MB TROUGH AXIS BUT THE 12Z UKMET ADJUSTED
NORTHWARD ENOUGH TO BE INCLUDED IN THE REMAINING DETERMINISTIC
CONSENSUS. THE ENSEMBLE MEANS SUPPORT A NON 12Z CMC BLEND.
..SPLIT-FLOW TROUGH NEAR THE PACIFIC NORTHWEST BY SUN
..CLIPPER TYPE LOW APPROACHING THE GREAT LAKES BY TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
TIMING AND LATITUDINAL DIFFERENCES SHOW UP WITH THE NORTHERN
PORTION OF A MID-LEVEL TROUGH AMPLIFYING THROUGH THE CENTRAL TO
EASTERN U.S. MONDAY NIGHT. THE 12Z NAM AND 12Z CMC ARE SLOWER
WHILE THE 12Z UKMET IS DISPLACED SLIGHTLY NORTHWARD WITH THE
VORTICITY MAXIMA COMPARED TO THE ENSEMBLE MEANS AND REMAINING
DETERMINISTIC GUIDANCE. THE 12Z GFS AND 12Z ECMWF ARE THOUGHT TO
BE CLOSER TO THE MIDDLE OF THE MODEL SPREAD AND ARE PREFERRED AT
THIS TIME, WITH THE 12Z ECMWF SHIFTING A LITTLE NORTH OF ITS
PREVIOUS 00Z CYCLE.
..SOUTHERN STREAM TROUGH/LOW NEAR THE TN VALLEY BY TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM AND 12Z ECMWF
CONFIDENCE: AVERAGE
THE SOUTHERN PORTION OF A BROADENING MID-LEVEL TROUGH OVER THE
EASTERN TWO THIRDS OF THE NATION MONDAY NIGHT INTO TUESDAY IS
EXPECTED TO COINCIDE WITH A WEAK SURFACE LOW TO CROSS THE
TENNESSEE VALLEY. THE 12Z GFS BECOMES SIGNIFICANTLY FASTER BY
TUESDAY MORNING WHILE THE 12Z CMC SHOWS SLOWEST OF THE
DETERMINISTIC GUIDANCE. THE 12Z NAM AND 12Z ECMWF SHOW CLOSEST TO
THE ENSEMBLE MEANS BUT THE 12Z UKMET ADJUSTED A BIT FASTER WITH
ITS 500 MB TROUGH TAKING ITS SURFACE LOW AWAY FROM THE FAVORED
CONSENSUS.
..SHORTWAVE/FRONTS APPROACHING THE PACIFIC NORTHWEST TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: AVERAGE
MODERATE SPREAD CONTINUES TO EXIST WITH A SHORTWAVE TROUGH TO
APPROACH THE PACIFIC NORTHWEST LATE MONDAY INTO TUESDAY. A WARM
FRONT IS FORECAST TO REACH WESTERN BRITISH COLUMBIA AND COASTAL
WASHINGTON MONDAY MORNING AS A LOW NEARS JUST NORTH OF VANCOUVER
ISLAND. THERE ARE SOME MINOR PLACEMENT DIFFERENCES WITH THE
SURFACE LOW, THE 12Z UKMET IS TOWARD THE SOUTHERN SIDE OF THE
DETERMINISTIC SPREAD WHILE THE 12Z NAM IS FARTHER NORTH. A BLEND
TOWARD THE MIDDLE (LESS 12Z UKMET INFLUENCE) WILL ALIGN BEST WITH
THE LATEST ENSEMBLE SCATTER LOW PLOTS.
HOWEVER, LARGER DIFFERENCES SHOW UP DUE TO THE APPROACHING
SHORTWAVE TO THE WEST. WITH THIS FEATURE, THE 00Z ECMWF WAS FASTER
BUT THE 12Z ECMWF SLOWED DOWN. THE 12Z NAM WAS WEAKEST WITH THE
TROUGH AND CONSIDERED THE LEAST LIKELY TO VERIFY. TIMING
ADJUSTMENTS FROM THE 12Z ECMWF/UKMET/CMC COMPARED WITH THEIR
PREVIOUS 00Z CYCLES ALLOW FOR THEIR INCLUSION AS PART OF THE
PREFERENCE, EXCLUDING THE 12Z NAM. OF THE NON 12Z NAM GUIDANCE,
THE 12Z CMC WAS SLOWEST, BUT JUST WITHIN TOLERANCE GIVEN THE
LATEST ENSEMBLE SPREAD. THEREFORE, A NON 12Z NAM BLEND WILL BE
PREFERRED WITH THIS SYSTEM GIVEN DIFFERENCES FROM THE 12Z UKMET'S
SURFACE LOW INFLUENCE IS FELT FARTHER NORTH AWAY FROM WASHINGTON.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page