Prognostic Meteorological Discussion
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000
FXUS10 KWNH 291842
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
241 PM EDT SUN MAR 29 2015

VALID MAR 29/1200 UTC THRU APR 02/0000 UTC

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

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


SHORTWAVE TRACKING FROM THE UPPER MS VALLEY SUN TO NEW ENGLAND MON
COLD FRONT REACHING THE EAST COAST MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z ECMWF/12Z GFS
CONFIDENCE: AVERAGE

THERE IS REASONABLY GOOD AGREEMENT WITH THIS SYSTEM THROUGH MONDAY
EVENING ALTHOUGH THE NAM BEGINS TO STRAY FROM THE CONSENSUS WITH A
MUCH WEAKER SURFACE LOW OVER SRN QUEBEC. THE MAJORITY OF THE
MODELS HAVE TRENDED QUICKER WITH THE UPPER TROUGH INTO TUESDAY
MORNING...EXCEPT THE NAM WHICH HAS SLOWED SIGNIFICANTLY SINCE
YESTERDAY AND IS THE SLOWEST OF THE DETERMINISTIC MODELS.
CURRENTLY...THE ENSEMBLE MEANS ARE AHEAD OF THE NAM BUT SLIGHTLY
BEHIND THE 12Z GFS AND NEAR THE 12Z ECMWF. GIVEN A SLIGHTLY SLOWER
TREND IN THE 12Z ECMWF COMPARED TO ITS 00Z RUN...THE GFS/ECMWF
CONTINUE TO REPRESENT A GOOD MIDDLE GROUND WITH RESPECT TO THE
ENSEMBLE/DETERMINISTIC SPREAD...WITH THE 12Z UKMET/CMC NEAR THE
GFS.


SHORTWAVE CROSSING THE UPPER MS VALLEY/GREAT LAKES MON INTO TUE
SURFACE LOW CROSSING THE MID ATLANTIC STATES TUE NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 2/3 WEIGHT 12Z GFS AND 1/3 WEIGHT ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM IS THE FARTHEST NORTH WITH ITS MID-LEVEL SHORTWAVE OF
THE DETERMINISTIC MODELS AND OUTSIDE OF THE ENSEMBLE LOW SPREAD
WITH ITS SURFACE LOW BY TUE EVENING IN THE NRN MID-ATLANTIC
REGION. THE SURFACE LOW FROM THE 12Z GFS FITS IN VERY NICELY IN
THE MIDDLE OF THE ENSEMBLE LOW SPREAD BUT THE 00Z ECMWF IS ON THE
FAR SOUTHWEST EDGE OF THE ECMWF MEMBERS.

THE 12Z ECMWF ADJUSTED A BIT STRONGER COMPARED TO ITS 00Z RUN
WHICH APPEARS LIKE A GOOD CHANGE GIVEN THE 00Z ECMWF APPEARED A
BIT WEAK AND SLOW WITH THE MID-LEVEL SHORTWAVE...BUT THE 12Z GFS
HAS TRENDED STRONGER THAN THE AVERAGE DETERMINISTIC PIECE OF
GUIDANCE. THE 12Z CMC/UKMET IS A STRONG/FLAT OUTLIER RESPECTIVELY.
GIVEN FAVORABLE LOW PLACEMENT FROM THE 12Z GFS...THOUGH PERHAPS A
BIT TOO STRONG...IT IS RECOMMENDED TO BLEND THE 12Z GFS WITH 12Z
ECMWF...BUT WITH A LITTLE MORE WEIGHT ON THE GFS GIVEN THE ECMWF
IS NOT IN AS FAVORABLE OF A LOW LEVEL POSITION.


MID LEVEL TROUGH NEAR BAJA CA MON...CROSSING THE SOUTHERN PLAINS
TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PREFERENCE: 12Z GFS...12Z ECMWF...12Z CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z GFS IS A LITTLE WEAKER THAN THE AGREEABLE 12Z ECMWF/CMC
BUT ALL THREE SHOW A SIMILAR TIMING WITH THIS SHORTWAVE. THE 12Z
UKMET REMAINS THE SLOWEST AND IS NOT CONTAINED WITHIN THE ENSEMBLE
SPREAD. THE 12Z NAM IS NOT PREFERRED AS IT TAKES THE CORE OF THE
MID-LEVEL ENERGY...WHEN IT REACHES THE PLAINS TUE MORNING...NORTH
OF THE REMAINING CONSENSUS.


LONG WAVE TROUGH OFF THE PACIFIC NORTHWEST COAST MON
SHORTWAVE/COLD FRONT APPROACHING THE NORTHERN PLAINS TUE NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS SHOW GOOD AGREEMENT THROUGH DAY 2...00Z/01...AT WHICH
POINT SOME MINOR DIFFERENCES IN STRENGTH/TIMING APPEAR. THE
QUASI-AMPLIFIED NATURE OF THE NRN STREAM WOULD IMPLY THE 00Z CMC
IS TOO FAST BUT THE 12Z CMC HAS SLOWED TOWARD THE BACK EDGE OF THE
LATEST DETERMINISTIC GUIDANCE. BY WED EVENING...THE 12Z GEFS IS A
BIT SLOWER THAN THE 12Z GFS AND A BIT FASTER THAN THE ECMWF/EC
ENSEMBLES REGARDING THE 540 DM HEIGHT LINE...WITH A BLEND OF THE
TWO APPEARING TO BE THE MOST LIKELY SCENARIO AT THIS TIME. THE
GFS/ECMWF BLEND IS ALSO MOST AGREEABLE TO THE ENSEMBLE LOW
CLUSTERING SEEN FROM THEIR MOST RECENT RUN.


SHORT WAVE APPROACHING THE PACIFIC NORTHWEST EARLY WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z UKMET
CONFIDENCE: SLIGHTLY BELOW AVERAGE

CONFLICTING TRENDS MAKE FOR A DIFFICULT FORECAST WITH THIS FEATURE
BUT IT APPEARS THE 12Z NAM/GFS ARE TOO SLOW GIVEN REASONABLY GOOD
ENSEMBLE SPAGHETTI HEIGHT SUPPORT FOR A FASTER SOLUTION...NEAR THE
12Z ECMWF/00Z ECMWF MEAN. THE 12Z UKMET AGREES WITH THE 12Z ECMWF
BUT THE 12Z CMC CONTINUES TO BE ON THE WEAKER SIDE OF THE
GUIDANCE.


...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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