Prognostic Meteorological Discussion
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000
FXUS10 KWNH 300442
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1241 AM EDT MON MAR 30 2015

VALID MAR 30/0000 UTC THRU APR 02/1200 UTC

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

00Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY 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 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THERE IS GOOD MODEL AGREEMENT WITH THE SHORT WAVE TIMING THROUGH
MUCH OF DAY 1 (MON) AS IT TRACKS ACROSS THE GREAT LAKES INTO
SOUTHERN QUEBEC. THE EXCEPTION IS THE 00Z NAM...WHICH IS SLOWER
AND DEEPER THAN THE CONSENSUS...ITS PREVIOUS RUNS AND THE 21Z SREF
MEAN. THE 00Z GFS SLOTS IN WELL WITH THE 12Z ECMWF...WHICH ARE
JUST A BIT FASTER THAN THEIR RESPECTIVE ENSEMBLE MEANS.


SHORTWAVE CROSSING THE UPPER MS VALLEY/GREAT LAKES MON INTO TUE
SURFACE LOW CROSSING THE MID ATLANTIC STATES TUE NIGHT INTO WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF/12Z UKMET
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE 00Z NAM IS DEEPER AND FASTER THAN THE CONSENSUS WITH ITS SHORT
WAVE AND SURFACE LOW... ESPECIALLY DURING THE DAY 2/3 TIME FRAME
(TUE/WED). THE 00Z GFS CAME IN FASTER THAN THE CONSENSUS (AND
FASTER THAN ITS TWO PREVIOUS SOLUTIONS...AS WELL AS ITS ENSEMBLE
MEAN POSITION). IT IS STILL NORTH OF THE 12Z ECMWF...WHICH HAS
REMAINED CONSISTENT WITH ITS MORE SOUTHERLY SOLUTION FOR THE SHORT
WAVE AND ATTENDANT SURFACE LOW. SINCE THE DIFFERENCES BETWEEN THE
00Z GFS AND 12Z ECMWF HAVE INCREASED...THE 12Z UKMET WAS TOSSED
INTO THE PREFERENCE AS A MIDDLE GROUND BETWEEN THE TWO. AT THIS
POINT...BECAUSE OF THE SHIFT IN THE PREVIOUSLY CONSISTENT
GFS...CONFIDENCE FOR THIS SYSTEM HAS BEEN DROPPED TO SLIGHTLY
BELOW AVERAGE.


MID LEVEL TROUGH NEAR BAJA CA MON...CROSSING THE SOUTHERN PLAINS
TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PREFERENCE: 00Z GFS/12Z ECMWF/12Z CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 00Z NAM IS CLOSE TO THE CONSENSUS DAY 1 MOVING INTO DAY 2 WITH
THE POSITION OF THE MID LEVEL TROUGH TRACKING FROM BAJA CA THROUGH
THE SOUTHERN PLAINS...BUT BECOMES FASTER AND A BIT DEEPER LATER
DAY 2 INTO DAY 3 ACROSS THE TN VALLEY. THE 00Z GFS BLENDS WELL
WITH THE 12Z ECMWF AND 12Z CMC WITH THE MID LEVEL TROUGH POSITION.
THE 12Z UKMET REMAINED THE SLOWEST DETERMINISTIC SOLUTION (AS IT
HAS BEEN FOR THE PAST SEVERAL MODEL CYCLES).


LONG WAVE TROUGH OFF THE PACIFIC NORTHWEST COAST MON
SHORTWAVE/COLD FRONT APPROACHING THE NORTHERN PLAINS TUE NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z NAM REMAINS SLOWER AND DEEPER WITH THE LONG WAVE TROUGH
AND THE PLACEMENT OF THE FRONT APPROACHING THE NORTHERN PLAINS
LATE DAY 1 THROUGH DAY 3. THE 00Z GFS IS A BIT FASTER THAN ITS
PREVIOUS POSITION WITH THE BOTH THE MID LEVEL AND SURFACE
FEATURES...BUT STILL BLENDS WELL WITH THE 12Z ECMWF/12Z ECMWF
ENSEMBLE MEAN POSITIONS. THE 12Z UKMET STARTS OUT WITHIN THE MODEL
ENVELOPE...BUT SLOWS AND DEEPENS OVER SOUTHERN MANITOBA BY THE END
OF DAY 3 (LATE WED).


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

INCONSISTENCY AMONG MODELS (AND EVEN INDIVIDUAL MODEL RUNS) HAVE
BEEN THE NORM FOR THIS SYSTEM THE PAST COUPLE OF MODEL CYCLES. THE
00Z NAM CONTINUES ITS SLOWER TREND...AND THE 00Z GFS REMAINS ON
THE SLOWER SIDE OF THE GUIDANCE ENVELOPE (DESPITE SPEEDING UP ON
ITS 00Z SOLUTION...COMPARED TO THE PREVIOUS TWO RUNS). THE 12Z
ECMWF/12Z UKMET POSITION IS SUPPORTED REASONABLY WELL BY THE 12Z
ECMWF ENSEMBLE MEAN POSITION (WHICH IS FASTER THAN THE 00Z
NAM/GFS). HOWEVER...DUE TO CONFLICTING TRENDS IN THE
GUIDANCE...CONFIDENCE WITH THIS SYSTEM REMAINS BELOW NORMAL.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...


HAYES

$$




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