Prognostic Meteorological Discussion
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000
FXUS10 KWNH 030649
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 AM EST TUE MAR 03 2015

VALID MAR 03/0000 UTC THRU MAR 06/1200 UTC

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

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


SHORTWAVE CROSSING THE ROCKIES THIS MORNING AND ASSOCIATED SFC LOW
  + COLD FRONT MOVING OUT INTO THE CNTRL PLAINS THROUGH TODAY
UPPER TROUGH AXIS DROPPING OUT OF CANADA INTO THE N-CNTRL U.S. TUE
EVENTUAL STRONG COLD FRONT REACHING THE SOUTHEAST THU MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS / 00Z ECMWF BLEND
CONFIDENCE: A LITTLE BELOW AVERAGE

BY TUE EVENING...TIMING DIFFERENCES BEGIN TO APPEAR WITH A LEAD
COLD FRONT EXTENDING FROM THE OHIO VALLEY BACK INTO THE SRN
PLAINS. THE 00Z UKMET REMAINS SLOWEST WITH THIS BOUNDARY AND THE
00Z GFS BEGINS TO PULL AHEAD OF THE REMAINING DETERMINISTIC
GUIDANCE. THROUGH 12Z/04...ENSEMBLE SPAGHETTI HEIGHTS AT 500 MB
HAVE SHIFTED NORTH COMPARED TO SUN EVENING FOR LOCATIONS FROM THE
CNTRL PLAINS TO LAKES ERIE AND ONTARIO...IN THE DIRECTION OF THE
SLOWER UKMET...BUT THE UKMET REMAINS ON THE EDGE OF THE ENSEMBLE
SPREAD.

BEYOND 12Z/04...THE 00Z NAM SHOWS UP AS A LOW PROBABILITY OUTLIER
WITH RESPECT TO ENSEMBLE SPAGHETTI HEIGHTS...AND THE LATEST
DETERMINISTIC MODEL CONSENSUS. THE 00Z GFS IS TOWARD THE FASTER
SIDE OF THE GUIDANCE...AND GIVEN TRENDS IN THE DIRECTION OF THE
SLOWER GUIDANCE...PREFER TO STAY A BIT SLOWER THAN THE FASTER GFS.
THE SLOWER 12Z UKMET ADJUSTED FASTER WITH ITS 00Z RUN AND THE
FASTER 12Z ECMWF ADJUSTED SLOWER. CONVERGENCE! THEREFORE...SINCE
THE 00Z NAM IS NOT BEING CONSIDERED AND GIVEN THE TRENDING OF
MODEL SOLUTIONS...AND CONSIDERATION OF THE LATEST ENSEMBLE
MEANS...A 00Z GFS/ECMWF BLEND IS PREFERRED...WHICH IS A BIT FASTER
THAN THE LATEST 00Z UKMET.


CLOSED LOW CURRENTLY OFF SRN CALIFORNIA CROSSING BACK INTO THE
  SOUTHWEST LATE TUESDAY
REMNANT LOWER MID-LEVEL HEIGHTS OVER THE SWRN U.S. BORDER THROUGH
  THE END OF THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS / 00Z ECMWF BLEND
CONFIDENCE: A LITTLE BELOW AVERAGE

THE MODELS SHOW REASONABLY CLOSE AGREEMENT HERE AFTER TRENDING
TOWARD A COMMON MIDDLE GROUND...BUT WITH THE REMAINING
SPREAD...PREFER TO STAY TOWARD THE MIDDLE. THIS IS BEST
REPRESENTED BY THE 00Z GFS AND 00Z ECMWF...BOTH MODELS SHOWING
ONLY MINOR RUN TO RUN CHANGES SINCE THEIR 00Z RUNS YESTERDAY.


POTENTIAL SHORTWAVE OVER SWRN CANADA FRI MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/CMC BLEND
CONFIDENCE: AVERAGE

THE MODELS ARE FORECASTING SHORTWAVE ENERGY FROM THE GULF OF
ALASKA TO TRACK INTO WRN CANADA ON THU...ATOP A STRONG MID-LEVEL
RIDGE CENTERED NEAR THE COAST OF CNTRL CALIFORNIA. THE 12Z ECMWF
ENSEMBLE MEAN IS LESS AMPLIFIED THAN THE 12Z ECMWF WITH ENSEMBLE
SPAGHETTI HEIGHTS SHOWING A FAIR AMOUNT OF SPREAD BY 12Z/06...BUT
THE 00Z ECMWF HAS ADJUSTED FLATTER. GIVEN THE STRONG RIDGE IN
PLACE ACROSS THE WEST COAST OF NORTH AMERICA...PREFER TO STAY LESS
AMPLIFIED...AND THE 00Z ECWFM/UKMET/CMC SUPPORT THIS IDEA WITH A
TIMING SLOWER THAN THE NAM. THEREFORE THE PEFERENCE IS BEING
ADJUSTED SLIGHTLY TO REPLACE THE NAM WITH THE ECMWF AND CMC WHICH
SHOW SIMILAR AMPLITUDE BUT A SLOWER TIMING THAN THE 00Z GFS/NAM.


...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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