Prognostic Meteorological Discussion
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000
FXUS10 KWNH 010508
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1207 AM EST SUN MAR 01 2015

VALID MAR 01/0000 UTC THRU MAR 04/1200 UTC

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

00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


INITIAL UPPER LOW/TROUGH DRIFTING THROUGH CA/NV THRU MON
REMNANT MID-LEVEL ENERGY EJECTING ONTO THE CENTRAL PLAINS TUESDAY
ASSOCIATED SFC LOW / COLD FRONT MOVING OUT OF COLORADO EARLY TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: 12Z ECMWF/CMC...THROUGH 18Z TUE
CONFIDENCE: AVERAGE

500 MB TRENDS SINCE FRI EVENING SHOW MORE SEPARATION BETWEEN THE
INITIAL SHORTWAVE OVER SRN CALIFORNIA SUN/SUN NIGHT AND A
SECONDARY SHORTWAVE DROPPING DOWN THE WEST COAST WHICH IS
REFERENCED IN THE NEXT SECTION. AS THE FIRST REMNANT SHORTWAVE
REACHES THE CNTRL HIGH PLAINS TUE MORNING...THERE ARE RELATIVELY
SMALL PLACEMENT DIFFERENCES BUT THE 00Z NAM AND 12Z UKMET ARE
ALMOST OUTSIDE OF THE ENSEMBLE ENVELOPE WITH MID-LEVEL HEIGHTS BY
12Z/TUE AND WITH THE CORRESPONDING SURFACE LOW AND COLD FRONT. THE
12Z ECMWF/CMC ARE WELL WITHIN THE MIDDLE OF THE LATEST SPREAD AND
SHOULD BE USED THROUGH ABOUT 18Z TUE...AT WHICH POINT A NRN STREAM
UPPER TROUGH AND COLD FRONT DOMINATE THE SENSIBLE WEATHER ACROSS
THE CENTRAL AND EASTERN PART OF THE U.S. FOR WHICH USERS SHOULD
REFERENCE THE LAST SECTION IN THIS DISCUSSION...COLD FRONT PUSHING
THROUGH THE NRN PLAINS MONDAY INTO TUESDAY.


SECONDARY SHORTWAVE ENERGY DIVING SOUTHWARD ALONG THE WA/OR COAST
EARLY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: NON 12Z UKMET BLEND
CONFIDENCE: A LITTLE BELOW AVERAGE

THERE IS STRONG SUPPORT FOR THIS SHORTWAVE TO BE FARTHER OFFSHORE
THAN WHAT IS SHOWN BY THE UKMET THROUGH MON...WITH THE REMAINING
MODEL CONSENSUS IN REASONABLE AGREEMENT. THE MEANS AND
DETERMINISTIC GUIDANCE IS PREFERRED OUTSIDE OF THE 12Z UKMET.


DEVELOPING SFC FRONT FROM TEXAS TO THE OHIO VALLEY TODAY
NRN STREAM SHORTWAVE TRACKING FROM THE N-CNTRL U.S. ON SUN TO
  NEW ENGLAND ON MON
DEVELOPING SFC LOW OFF NEW ENGLAND EARLY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: 00Z NAM...00Z GFS...12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE GFS STILL APPEARS TO RETREAT LOW LEVEL COLD AIR ACROSS THE SRN
HIGH PLAINS TOO QUICKLY SUN MORNING...GIVEN GOOD AGREEMENT IN THE
REMAINING MODELS...BUT THIS FACTOR IS A NON-ISSUE FOR LATER IN THE
SHORT RANGE PERIOD. THERE ARE BASICALLY TWO CAMPS OF MODELS...ONE
THAT IS FARTHER WEST WITH A COASTAL FRONT ALONG THE EAST COAST AND
SUBSEQUENT SURFACE LOW DEVELOPMENT...AND ANOTHER CAMP FARTHER
EAST. CURRENTLY...THE SREF/GEFS/EC ENSEMBLES SUPPORT A
NAM/GFS/ECWMF BLEND OF MODELS...TOWARD THE MIDDLE OF THE SPREAD.
THE ENSEMBLES SUGGEST THE 12Z UKMET/CMC AND THE CMC ENSEMBLES ARE
TOO FAR EAST. THE BETTER CLUSTERING OF THE NAM/GFS/ECMWF ARE
PREFERRED AT THIS TIME.


COLD FRONT PUSHING THROUGH THE NRN HIGH PLAINS MONDAY INTO TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: 00Z NAM / 18Z GEFS MEAN BLEND
CONFIDENCE: BELOW AVERAGE

THE 00Z GFS AND 12Z ECMWF HAVE TRENDED FASTER WITH THIS TROUGH
OVER THEIR PAST FEW 12/00Z RUNS...WHICH IS A BREAK FROM PREVIOUSLY
SLOWER CONTINUITY. THE 12Z UKMET IS THE SLOWEST OF THE
DETERMINISTIC GUIDANCE AT THIS TIME...BUT THE GFS/ECMWF ARE ON THE
FASTER SIDE. ENSEMBLE MEANS SUPPORT SOMETHING SLOWER...WHICH
AFFECTS A COLD FRONT PROGRESSION INTO THE APPALACHIANS SOMETIME
NEAR TUE NIGHT. UNTIL SUBSEQUENT MODEL GUIDANCE COMES IN
CONSISTENTLY FASTER...WILL STAY MORE CONSERVATIVE ON THE
SPEED...WHICH ALSO AGREES WITH A HIGH AMPLIFIED UPPER PATTERN
TOWARD THE SLOWER SIDE. THE 12Z CMC IS REASONABLY CLOSE TO THE 00Z
NAM AND 18Z GEFS MEAN IDEA AS WELL.


...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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