Prognostic Meteorological Discussion
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000
FXUS10 KWNH 281643
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 PM EDT SAT MAR 28 2015

VALID MAR 28/1200 UTC THRU APR 01/0000 UTC

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

12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


LONGWAVE TROUGH DEPARTING THE EAST COAST ON SUN
DEEPENING SURFACE LOW TRACKING UP EAST OF NOVA SCOTIA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ANY REMAINING MODEL SPREAD IS SMALL ENOUGH TO HAVE MINIMAL IMPACTS
OVER THE U.S....THEREFORE A GENERAL MODEL COMPROMISE IS
RECOMMENDED.


SHORTWAVE TRACKING FROM THE NORTHWEST U.S....REACHING NEW ENGLAND
  ON MON
COLD FRONT REACHING THE EAST COAST ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

CONVERGENCE IN MODELS FROM YESTERDAY AND ENSEMBLE SPAGHETTI
HEIGHTS SUPPORT A 12Z GFS / 00Z ECMWF BLEND. THE MODEL SPREAD IS
RELATIVELY MINOR WITH THIS SYSTEM...BUT THE 00Z CMC APPEARS SLOW
BY MON MORNING...AND WHILE THE GFS IS A LITTLE AHEAD OF THE
ECMWF...THE GFS/ECMWF COMBO IS A GOOD MIDDLE GROUND.


SHORTWAVE CROSSING THE UPPER MS VALLEY/GREAT LAKES LATE MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 70% 00Z ECMWF / 30% 12Z NAM
CONFIDENCE: AVERAGE

THE 12Z GFS GETS AHEAD OF THE MODEL CONSENSUS BY THE END OF THE
WEEKEND REGARDING THE MID-LEVEL SHORTWAVE AND IS JUST OUTSIDE OF
THE LATEST ENSEMBLE SCATTER LOW PLOT CLUSTERING WHICH HAS TRENDED
A BIT SLOWER SINCE YESTERDAY ACROSS THE OHIO VALLEY. THE 00Z ECMWF
IS CLOSE TO THE MIDDLE OF THIS CLUSTERING...BUT THE 12Z NAM IS NOT
TOO FAR OFF BUT PERHAPS A BIT NORTH OF THE DESIRED TRACK. THE 00Z
UKMET APPEARS FLATTEST WHILE THE 00Z CMC IS ON THE SLOW SIDE. THE
ECMWF/NAM BLEND...WITH A BIT MORE WEIGHT TOWARD THE 00Z ECMWF...IS
CLOSEST TO THE BETTER ENSEMBLE CLUSTERING.


WEAK MID LEVEL TROUGH NEAR BAJA CA ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z GFS/00Z ECMWF REMAIN IN THE MIDDLE OF THE MOST RECENT
DETERMINISTIC SPREAD...AND CLOSER TO THE CONSENSUS OF THE LATEST
ENSEMBLE MEAN SOLUTIONS. THE 12Z NAM IS SLOWER THAN THE ENSEMBLES
BY MON NIGHT AND THE 00Z CMC IS INITIALLY FASTER WITH THE
PROGRESSION OF THE UPPER TROUGH ACROSS NRN MEXICO. MODEL SPREAD
HAS SHRUNK ENOUGH TO RAISE CONFIDENCE TO AVERAGE.


SOUTHWEST FLOW INTO THE PACIFIC NORTHWEST
SHORTWAVE/COLD FRONT REACHING THE PACIFIC NORTHWEST MON NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF/00Z CMC
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THERE IS REASONABLY GOOD MODEL AGREEMENT THROUGH MON EVENING
CONCERNING THE TIMING AND PLACEMENT OF THE LONG WAVE TROUGH
APPROACHING THE PACIFIC NORTHWEST/BRITISH COLUMBIA. THE MODEL
SPREAD DEVELOPS DURING BY MID-DAY MONDAY...AS MODELS HANDLE THE
SHORT WAVE AT THE BOTTOM OF THE LONG WAVE TROUGH DIFFERENTLY. THE
12Z NAM ENDS UP SLOWER...00Z UKMET FASTER...WITH THE 12Z GFS/00Z
ECMWF/00Z CMC FORMING AN AGREEABLE MIDDLE GROUND IN LINE WITH THE
LATEST ENSEMBLE MEANS.


...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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