616
FXUS10 KWNH 021712
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1212 PM EST THU JAN 02 2020
VALID JAN 02/1200 UTC THRU JAN 06/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..UPPER LOW OVER MEXICO SHEARING TO THE NORTHEAST
..FRONTAL WAVE IMPACTING THE GULF COAST/TN VALLEY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
ONLY MINOR TIMING DIFFERENCES REMAIN WITH THE SHORTWAVE SHEARING
EASTWARD AND THE RELATED WEAK SURFACE LOW TO TRACK FROM MS TOWARD
THE EAST.
...AMPLIFYING LONGWAVE TROUGH ACROSS THE CENTRAL U.S.
..SURFACE LOW FROM THE LOWER MS VALLEY TO THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 06Z GEFS/00Z ECENS MEAN
(NEAREST TO 12Z GFS/00Z ECMWF)
CONFIDENCE: BELOW AVERAGE
THE INTERACTION BETWEEN A NORTHERN STREAM AND SOUTHERN STREAM
COMPONENT EMBEDDED WITHIN A LONGWAVE TROUGH PROGRESSING EASTWARD
FROM THE CENTRAL U.S. TRANSLATES INTO A DIFFICULT FORECAST
EVOLUTION. BY 12Z/04, THE 12Z GFS BEGINS TO PUSH AHEAD OF THE
REMAINING GUIDANCE WITH THE SOUTHERN STREAM AXIS OF VORTICITY
ALONG THE NORTHERN GULF COAST, DUE TO A MORE AMPLIFIED NORTHERN
STREAM COMPONENT ACROSS THE MIDWEST. HOWEVER, 12 HOURS LATER, AT
00Z/05, THE 12Z NAM IS FASTEST WITH ITS 500 MB TROUGH AXIS OVER
THE EASTERN U.S., FOLLOWED BY THE 12Z GFS/00Z UKMET. THE 00Z CMC
IS SLOWEST WITH THE 00Z ECMWF NEXT SLOWEST.
WITH A FAIR DEGREE OF CONFIDENCE, IT CAN BE SAID THAT THE 12Z NAM
AND 00Z CMC HAVE A LOW LIKELIHOOD OF VERIFYING. HOWEVER, AMONG THE
REMAINING 12Z GFS, 00Z ECMWF AND 00Z UKMET, THE RESULTING SURFACE
LOW SHOWS MODERATE SPREAD. WHILE THE ENSEMBLE SCATTER LOW PLOTS
ARE RATHER BROAD IN THEIR DEPICTION VALID 12Z/05, THE 12Z GFS'S
SURFACE LOW IS ON THE NORTHERN SIDE OF THE SURFACE LOWS, WHILE THE
00Z ECMWF IS TOWARD THE SOUTH SIDE. A SIGNIFICANT NUMBER OF
ENSEMBLE SURFACE LOW PLOTS ARE WEST OF THE 12Z GFS/00Z ECMWF/00Z
UKMET POSITION, HENCE THE RATHER AGREEABLE 06Z GEFS AND 00Z ECMWF
MEANS ARE WEST OF THEIR DETERMINISTIC COUNTERPARTS.
THE PREFERENCE IS TO BE BETWEEN THE 12Z GFS/00Z ECMWF AND 00Z
UKMET BUT WITH A SLIGHTLY WESTWARD TRACK OF THEIR SURFACE LOWS.
DUE TO POOR ENSEMBLE AGREEMENT AND POOR RUN TO RUN CONSISTENCY IN
THE GUIDANCE, CONFIDENCE IS BELOW AVERAGE.
..SHORTWAVE TROUGH/LOW IMPACTING THE PACIFIC NORTHWEST
..ENERGY EJECTING OUT ACROSS THE PLAINS/MIDWEST BY SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE
THE PREFERENCE IS TO GO TOWARD THE MIDDLE OF THE LATEST
ENSEMBLE/DETERMINISTIC MODEL SPREAD. THE 12Z NAM IS FASTEST
FOLLOWED BY THE 12Z GFS AS THE SHORTWAVE TROUGH TRACKS EAST INTO
THE NORTHERN PLAINS. THE RESULTING COLD FRONT SHOWS SIMILARLY, BUT
THE 00Z ECMWF APPEARS TO BE IN THE FAVORED MIDDLE GROUND POSITION.
...NEXT MID-LEVEL TROUGH AXIS TO REACH THE PACIFIC NORTHWEST BY
SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM, 12Z GFS, 00Z ECMWF BLEND
CONFIDENCE: AVERAGE
WHILE SOME AMPLITUDE DIFFERENCES EXIST WITH AN UPPER TROUGH AXIS
NEARING THE PACIFIC NORTHWEST BY SUNDAY, TIMING DIFFERENCES ARE
GREATER. THE RELATIVELY AGREEABLE ENSEMBLE MEANS SUPPORT A FASTER
TIMING WHEN COMPARED TO THE 00Z UKMET/CMC. WHILE MINOR DIFFERENCES
EXIST AMONG THE 12Z NAM, 12Z GFS AND 00Z ECMWF, A BLEND OF THESE 3
MODELS SEEMS BEST FOR NOW.
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