Prognostic Meteorological Discussion
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000
FXUS10 KWNH 270449
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1149 PM EST THU FEB 26 2015

VALID FEB 27/0000 UTC THRU MAR 02/1200 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.


UPPER LOW NEAR THE CALIFORNIA COAST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM / 12Z ECMWF COMPROMISE
CONFIDENCE: AVERAGE

TRENDS IN THE DETERMINISTIC/ENSEMBLE GUIDANCE HAS BEEN FOR THIS
SYSTEM TO BE SLOWER TO MAKE ITS WAY EAST AND SETTING UP SLIGHTLY
FARTHER OFFSHORE THE COAST OF CALIFORNIA. THE LATEST ENSEMBLE
SPREAD FAVORS THE MIDDLE TO DEEPER SIDE OF THE DETERMINISTIC
GUIDANCE WHICH IS AWAY FROM THE 00Z GFS. THE DIFFERENCES IN UPPER
LOW PLACEMENT ARE RELATIVELY SMALL...BUT FOR NOW...WILL FAVOR A
BLEND MORE OFFSHORE THAN THE GFS...BEST REPRESENTED BY THE
NAM/ECWMF.


DEVELOPING FRONT FROM THE SRN/CNTRL HIGH PLAINS TO THE GREAT LAKES
  ON SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF COMPROMISE
CONFIDENCE: A LITTLE BELOW AVERAGE

THERE ARE SUBTLE DIFFERENCES WITH THE POSITION OF A DEVELOPING
FRONTAL BOUNDARY ON SUN...STRETCHING FROM THE SRN/CNTRL HIGH
PLAINS...ENEWD ACROSS THE MISSISSIPPI. THE 12Z CMC IS THE MOST
DIFFERENT WITH RESPECT TO HIGH PRESSURE PLACEMENT ACROSS THE LOWER
48 AND THE GFS/UKMET MORE NORTHWEST WITH THE FRONT AND NAM/ECMWF
FARTHER SOUTH. DIFFERENCES ARE PARTIALLY RELATED TO A SHORTWAVE
DROPPING INTO THE GREAT LAKES SUN NIGHT AND THE RIDGE ORIENTATION
ACROSS THE SRN/SERN CONUS. AT THIS TIME...SPLITTING THE DIFFERENCE
BETWEEN THE TWO MAIN CAMPS IS PREFERRED...BUT WITH LOWER THAN
AVERAGE CONFIDENCE GIVEN THE SUBTLE DIFFERENCES IN PLACE.


SHORTWAVE TROUGH/COLD FRONT IN THE N-CNTRL U.S. SUN AND REACHING
  THE NORTHEAST BY MON MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS...12Z ECMWF...12Z UKMET COMPROMISE
CONFIDENCE: AVERAGE

THE NAM IS THE FLATTEST WITH THE SHORTWAVE BY SUN EVENING AND THE
ENSEMBLE SPREAD WOULD FAVOR A DEPTH BETWEEN THE DEEPER
GFS/ECMWF/UKMET AND SOMEWHAT FLATTER 12Z CMC. THE MODELS ARE
SIMILAR WITH TIMING...BUT THE CMC MUCH LESS DEFINED WITH THE
TRAILING BOUNDARY AND A BIT FASTER. FOR NOW...WILL GO WITH THE
AGREEABLE GFS/ECMWF/UKMET.


SHORTWAVE/COLD FRONT REACHING THE NORTHWEST EARLY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: BELOW AVERAGE

THIS TROUGH IS FORECAST TO OCCUR DOWNSTREAM OF A PRONOUNCED UPPER
RIDGE OFF OF THE WRN COAST OF NORTH AMERICA. CURRENTLY...THE
MODELS SHOW REASONABLE AGREEMENT GIVEN THE DAY 3 TIME FRAME...AND
A GENERAL MODEL COMPROMISE WILL BE PREFERRED FOR NOW...WITH
DETAILS AND LARGER DIFFERENCES LIKELY TO EVOLVE OVER TIME.

...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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