Prognostic Meteorological Discussion
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000
FXUS10 KWNH 281841
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 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 MODEL EVALUATION INCLUDING FINAL 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/ECMWF/UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

CONVERGENCE IN MODELS FROM YESTERDAY AND ENSEMBLE SPAGHETTI
HEIGHTS SUPPORT A 12Z GFS/ECMWF/UKMET BLEND. THE MODEL SPREAD IS
RELATIVELY MINOR WITH THIS SYSTEM...BUT THE 12Z CMC STILL APPEARS
A LITTLE TOO SLOW BY MON MORNING...AND WHILE THE GFS IS A LITTLE
AHEAD OF THE ECMWF...THE GFS/ECMWF/UKMET 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 12Z
UKMET REMAINS FLATTER AND IS JOINED BY THE 12Z ECMWF...BOTH OF
WHICH ARE ON THE FASTER EDGE OF THE LATEST ENSEMBLE CLUSTERING
WITH THE SURFACE LOW. IT SEEMS THAT THE 12Z CMC IS IN A PRETTY
GOOD POSITION WITH RESPECT TO THE ENSEMBLES...BUT IS JUST TOO
STRONG. THEREFORE...THE PREVIOUS PRELIMINARY PREFERENCE REMAINS
HERE FOR THE FINAL.


WEAK MID LEVEL TROUGH NEAR BAJA CA ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z ECMWF/CMC ARE IN THE MIDDLE OF THE MOST RECENT
DETERMINISTIC SPREAD...AND CLOSER TO THE CONSENSUS OF THE LATEST
ENSEMBLE MEAN SOLUTIONS...FOLLOWED CLOSELY BY THE SOMEWHAT SLOWER
12Z NAM THE SLIGHTLY FASTER 12Z GFS TUE. THIS MAKES THE 12Z UKMET
STAND OUT AS A SLOW OUTLIER SO ITS SOLUTION WILL BE DISCOUNTED.


SOUTHWEST FLOW INTO THE PACIFIC NORTHWEST
SHORTWAVE/COLD FRONT REACHING THE PACIFIC NORTHWEST MON NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
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...BUT THE REMAINING MODELS SHOW SIMILAR
TIMING AHEAD OF THE NAM. DIFFERENCES WITH THE REMAINING MODELS ARE
WITH DEPTH..BUT A NON 12Z NAM BLEND WILL FORM A DECENT 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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