Prognostic Meteorological Discussion
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000
FXUS10 KWNH 300642
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 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 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 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 00Z ECMWF...WHICH ARE
JUST A BIT FASTER THAN THEIR RESPECTIVE ENSEMBLE MEANS. THE 00Z
UKMET TIMING WAS ABOUT THE SAME...BUT THE MID LEVEL TROUGH WAS
STRONGER...AND THE 00Z CMC REMAINS JUST A BIT FASTER THAN THE
CONSENSUS.


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/00Z ECMWF/00Z 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). THE 00Z ECMWF HAS COME FURTHER NORTH WITH ITS
SHORT WAVE AND SURFACE LOW ALONG THE MID ATLANTIC COAST BY
01/00Z...AND REMAINS PART OF THE PREFERRED BLEND.  HOWEVER...THE
00Z GFS/UKMET COUPLET PROBABLY REPRESENTS THE MOST LIKELY TRACK OF
THE SURFACE LOW ACROSS THE MID ATLANTIC.

THE 00Z UKMET CAME IS A BIT FURTHER SOUTH THAN ITS PREVIOUS
RUNS...PLACING IT BETWEEN THE NORTHERN 00Z GFS POSITION AND
SLIGHTLY MORE SOUTHERN 00Z ECMWF POSITION WITH THE SURFACE LOW AS
IT CROSSES THE MID ATLANTIC COAST AROUND 01/00Z. AT THIS
POINT...BECAUSE OF THE SHIFT IN THE GFS AND ECMWF...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/00Z ECMWF/00Z 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 00Z ECMWF AND 00Z CMC WITH THE MID LEVEL TROUGH POSITION.
THE 00Z 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/00Z ECMWF
CONFIDENCE: SLIGHTLY BELOW 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. IN CONTRAST...THE 00Z ECMWF HAS SLOWED ITS
POSITION...RELATIVE TO ITS PREVIOUS SOLUTION AND IS NOW I BETTER
AGREEMENT WITH ITS 12Z ENSEMBLE MEAN POSITION. THE 00Z UKMET
SLOWED EVEN MORE WITH THE LONG WAVE TROUGH AND SURFACE FRONT...AND
NOW REPRESENTS THE WESTERNMOST EDGE OF THE MODEL ENVELOPE. THE 00Z
CMC WAS ALSO A TAD SLOWER...AND REMAINED SLOWER THAN CONSENSUS
WITH THE MID LEVEL AND SURFACE SYSTEMS.

GIVEN THAT BOTH THE GFS AND ECMWF HAS SHOWED SOME CHANGES WITH THE
00Z RUNS...THE CONFIDENCE IS DROPPED TO SLIGHTLY BELOW NORMAL.


SHORT WAVE CROSSING THE PACIFIC NORTHWEST INTO THE GREAT BASIN WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/00Z GFS/00Z CMC
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 00Z CMC
WAS SLOWER THAN ITS PREVIOUS RUNS WITH THIS FEATURE...AS HAS THE
00Z ECMWF. THE SLOWING TREND PLACES THE 00Z ECMWF/CMC COMBINATION
CLOSE TO THE 00Z GFS POSITION...RESULTING IN AN AD HOC CONSENSUS.
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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