Prognostic Meteorological Discussion
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000
FXUS10 KWNH 020446
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 AM EDT THU APR 02 2015

VALID APR 02/0000 UTC THRU APR 05/1200 UTC

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

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


CLOSED LOW NEAR THE PACIFIC NORTHWEST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM / 12Z ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE ENSEMBLE SPREAD IN THE 500 MB HEIGHTS IS STILL QUITE LARGE OUT
HERE BY 12Z/05...BUT IT APPEARS THE 00Z GFS COULD BE TOO FAST WITH
THE BASE OF THE UPPER TROUGH MOVING ACROSS THE WEST COAST AT THE
END OF THE SHORT RANGE PERIOD. WE WILL LEAN TOWARD THE PREVIOUS
PREFERENCE WITH A SLIGHT ADJUSTMENT TOWARD THE 00Z NAM GIVEN ITS
SOLUTION FITS IN CLOSELY TOWARD THE MIDDLE OF THE LATEST MODEL
SPREAD.


SHORTWAVE OVER THE SOUTHWEST REACHING THE PLAINS BY FRI MORNING
ASSOCIATED COLD FRONT REACHING THE EAST COAST FRI NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS...12Z UKMET...12Z ECMWF COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THERE ARE SOME RELATIVELY MINOR SPEED/TRACK ISSUES WITH THIS
SYSTEM...WITH THE 00Z NAM/CMC SHOWING A SLOWER PROGRESSION WITH
THE UPPER TROUGH AND RELATED COLD FRONT. THE 00Z GFS...12Z ECMWF
AND 12Z UKMET SHOW A SIMILAR TIMING WHICH MORE CLOSELY RESEMBLES
THE ENSEMBLE MEANS COMPARED TO THE NAM/CMC.


SHORTWAVE TROUGH AXIS MOVING ENEWD FROM THE N-CNTRL U.S. TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE SYSTEMS.


COLD FRONT MOVING ACROSS THE N-CNTRL U.S. SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM COMPROMISE
CONFIDENCE: AVERAGE

BY THE END OF THE SHORT RANGE PERIOD...12Z/05...THE NAM ENDS UP ON
THE NRN SIDE OF THE LATEST DETERMINISTIC SPREAD WITH THE FRONTAL
BOUNDARY ACROSS THE NRN PLAINS. OUTSIDE OF THE NAM...THE REMAINING
MODELS WHEN BLENDED TOGETHER REPRESENT AN ACCEPTABLE COMPROMISE.


MID-UPPER LEVEL SHORTWAVE REACHING THE SOUTHWEST SAT NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS / 12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE TIMING DIFFERENCES WITH A MID-UPPER LEVEL SHORTWAVE REACHING
THE SOUTHWEST DO NOT REALLY SHOW UP UNTIL SUN MORNING. THE MODEL
SPREAD IS NOT TOO LARGE...AND AT THIS TIME...GOING TOWARD THE
MIDDLE SEEMS BEST GIVEN THE LARGE SCALE FLOW DOES NOT REALLY
SUPPORT A SLOWER/AMPLIFIED NOR FASTER/ZONAL PATTERN.
THEREFORE...THE 00Z GFS/12Z ECMWF COMPROMISED POSITION SHOULD
REPRESENT THE BEST MIDDLE GROUND AT THIS TIME.


...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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