Prognostic Meteorological Discussion
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000
FXUS10 KWNH 280424
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1124 PM EST FRI FEB 27 2015

VALID FEB 28/0000 UTC THRU MAR 03/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


UPPER LOW/TROUGH DRIFTING THROUGH CA SAT-MON
SHORTWAVE APPROACHING THE NRN CONTINENTAL DIVIDE MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS...12Z ECMWF...12Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 00Z NAM/12Z CANADIAN ARE QUICKER TO MOVE THE UPPER TROUGH
EASTWARD THAN THE OTHER GUIDANCE.  BELIEVE THE CANADIAN AND NAM
ARE TOO FAST HERE SINCE ENERGY KEEPS TRYING TO DIG INTO THE
BACKSIDE OF THE TROUGH, KEEPING IT SLOW-MOVING.  A COMPROMISE OF
00Z GFS/12Z UKMET/12Z ECMWF IS PREFERRED.S


FRONTAL BOUNDARY DEVELOPING TODAY FROM THE SRN PLAINS TO THE NRN
  APPALACHIANS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM...12Z ECWMF...12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS SHOW FAIR AGREEMENT WITH THIS FEATURE BUT THE 00Z GFS
STANDS OUT AS BEING A BIT MORE AGGRESSIVE THAN THE OTHER GUIDANCE
WITH LOW LEVEL WARM AIR RETURNING THROUGH THE SRN HIGH PLAINS
THROUGH SAT NIGHT. THE 12Z CMC BECOMES QUICKER WITH THE NRN
PORTION OF THE BOUNDARY AS IT MOVES TO THE EAST SUN NIGHT. AT THIS
TIME...THE NAM/ECMWF/UKMET REPRESENT A GOOD MIDDLE GROUND.


NORTHERN STREAM SHORTWAVE TRACKING FROM THE N-CNTRL U.S. ON SUN TO
  NEW ENGLAND ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS...12Z ECMWF...12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GFS AND ECMWF SHOW THE BEST RUN TO RUN
CONTINUITY...CONSIDERING 12/00Z CYCLES ONLY...WITH THE AMPLITUDE
AND TIMING OF THE UPPER TROUGH AND CORRESPONDING SURFACE LOW NEAR
MAINE MON MORNING. HOWEVER...THE GFS/ECMWF FALL TOWARD THE WRN
SIDE OF THE LATEST DETERMINISTIC SPREAD AND ENSEMBLE LOW PLOTS
SUGGEST THE LOW COULD BE FARTHER EAST...BUT NOT AS FAR EAST AS THE
OUTLIER 12Z CMC POSITION. THE 12Z UKMET HAS A SIMILAR AMPLITUDE
WITH THE UPPER TROUGH BY MON MORNING...BUT IS SLIGHTLY AHEAD OF
THE ENSEMBLE MEANS. THEREFORE...A BLEND OF THE 00Z GFS...12Z
ECMWF...12Z UKMET IS PREFERRED.


COLD FRONT LIKELY REACHING MONTANA ON MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

AN UPPER TROUGH REACHING THE NRN ROCKIES ON MON IS DOWNSTREAM OF A
HIGHLY AMPLIFIED RIDGE IN THE EAST PACIFIC...AND CURRENTLY...THE
00Z NAM/GFS ARE ON THE FLATTER SIDE OF THE GUIDANCE. BETTER
ENSEMBLE SUPPORT EXISTS FOR A 12Z ECMWF/UKMET BLEND WHICH ALSO
FITS CONCEPTUAL THINKING.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

$$





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