Prognostic Meteorological Discussion
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000
FXUS10 KWNH 200430
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1129 PM EST FRI DEC 19 2014

VALID DEC 20/0000 UTC THRU DEC 23/1200 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 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


SRN STREAM SHORTWAVE EXITING OFF OF THE MID-ATLANTIC COAST TODAY
WEAK SURFACE LOWS IN THE NRN GULF OF MEXICO AND OFF THE SE COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z GFS COMPROMISE
CONFIDENCE: ABOVE AVERAGE

MODELS SHOW SIMILARLY WITH THESE SYSTEMS...BUT THE 00Z GFS IS
CLOSER TO THE SOUTHEAST COASTLINE LATER TODAY WITH A WEAK FRONTAL
WAVE COMPARED TO THE REMAINING DETERMINISTIC/ENSEMBLE GUIDANCE.
OUTSIDE OF THAT SMALL DETAIL...THERE ARE NO MAJOR DIFFERENCES
BETWEEN THE LATEST GUIDANCE.


UPPER TROUGH AXIS OVER NEW ENGLAND SUN AFTERNOON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


LOW AMPLITUDE SHORTWAVE PASSING THROUGH THE NRN PLAINS TODAY/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

MINOR MODEL DIFFERENCES CAN BE RESOLVED WITH A GENERAL MODEL
COMPROMISE.


SERN U.S. FRONT AND POSSIBLE WEAK WAVE OFF OF THE EAST COAST ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 00Z GFS...12Z ECMWF...12Z UKMET
CONFIDENCE: AVERAGE

DETERMINISTIC AND ENSEMBLE TRENDS SINCE YESTERDAY BEST SUPPORT THE
12Z ECMWF WHICH IS CLOSE TO THE 00Z GFS AND 12Z UKMET. IT APPEARS
THAT THE 00Z NAM IS TOO FAR NORTH AND THE 12Z CMC IS MUCH FARTHER
OUT TO SEA CONCERNING A WEAK SURFACE LOW ALONG A FRONT PROGGED
JUST OFF THE EAST COAST THIS MON.


EVOLVING LONGWAVE TROUGH OVER THE MIDDLE OF THE COUNTRY
SURFACE LOW MOVING INTO THE N-CNTRL U.S. ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF
CONFIDENCE: A LITTLE BELOW AVERAGE

BOTH THE ECMWF AND UKMET HAVE HELD GOOD CONTINUITY SINCE THEIR
12Z/18 CYCLES...BUT THE UKMET APPEARS TO BE A BIT FASTER/EAST THAN
IDEAL GIVEN THE SLOWING TRENDS SEEN IN THE ENSEMBLE SPAGHETTI
HEIGHT PLOTS. THIS IS TRUE WITH THE EVOLVING UPPER TROUGH AND
SURFACE LOW EXPECTED TO MOVE OUT OF THE WEST AND ACROSS THE
N-CNTRL U.S. ON MON. ENSEMBLE SPREAD IS SHRINKING BUT ENOUGH OF A
SPREAD REMAINS TO KEEP CONFIDENCE A BIT BELOW AVERAGE.


POTENTIAL SHORTWAVE NEARING BRITISH COLUMBIA MON NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS...12Z ECMWF
CONFIDENCE: BELOW AVERAGE

DESPITE SOME RECENT CONVERGENCE...IT IS UNCLEAR WHAT DEGREE OF
SHORTWAVE ENERGY WILL MAKE IT OVER A STRONG E-PAC RIDGE BY TUE
MORNING. CURRENTLY...A BLENDED SOLUTION OF THE 00Z GFS AND 12Z
ECMWF FITS BEST WITH THE MIDDLE OF THE LATEST SPREAD AND CLOSEST
TO THE 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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