Prognostic Meteorological Discussion
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000
FXUS10 KWNH 200640
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 AM EDT SUN APR 20 2014

VALID APR 20/0000 UTC THRU APR 23/1200 UTC

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


00Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00Z GFS SURFACE DEWPOINTS APPEAR TO BE INITIALIZED 5-10 F TOO HIGH
AHEAD OF A COLD FRONT EXTENDING FROM THE UPPER MIDWEST INTO THE
CNTRL PLAINS. THIS IS CAUSING GFS FORECAST PRECIPITABLE WATER
VALUES TO BE TOO HIGH AT LEAST EARLY IN THE FORECAST PERIOD FROM
NRN KANSAS INTO WISCONSIN...AND POSSIBLY TOO WET WITH QPF.

OTHERWISE...NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE
THEIR SHORT RANGE FORECASTS.


DEEP UPPER TROUGH DEPARTING THE SOUTHEAST TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE MODELS SHOW REASONABLE AGREEMENT SUCH THAT A GENERAL MODEL
COMPROMISE CAN BE USED TO IRON OUT ANY SMALLER SCALE DETAIL
DIFFERENCES.


BROADENING UPPER LEVEL TROUGH THE CNTRL U.S. TODAY/MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE MODELS SHOW REASONABLE AGREEMENT SUCH THAT A GENERAL MODEL
COMPROMISE CAN BE USED TO IRON OUT ANY SMALLER SCALE DETAIL
DIFFERENCES.


WEAK MID-LEVEL SHORTWAVE PASSING JUST NORTH OF MAINE ON MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

SMALL TIMING DIFFERENCES EXIST WITH THE 00Z NAM/GFS A BIT FASTER
WITH THE ASSOCIATED COLD FRONT THROUGH THE NORTHEAST COMPARED TO
THE 12Z ECMWF/UKMET/CMC. THE CORRESPONDING ENSEMBLE MEANS ARE
SIMILAR TO THEIR PARENT MODELS...BUT DIFFERENCES ARE SMALL ENOUGH
THAT A BLEND OF THE TWO CAMPS CAN BE USED.


COLD FRONT PASSING THROUGH THE PLAINS ON MON...EASTERN U.S. ON TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z ECMWF / 00Z GFS BLEND
CONFIDENCE:  AVERAGE

THE 00Z NAM IS THE SLOWEST DETERMINISTIC PIECE OF GUIDANCE WITH
THE COLD FRONT AND IS ALSO WEAKER WITH THE SHORTWAVE TRACKING
ACROSS SRN ONTARIO/QUEBEC. THE 00Z GFS IS A BIT FAST WITH THE COLD
FRONT COMPARED TO THE REMAINING MODELS BUT THE 00Z UKMET/CMC ARE
LIKELY TOO SLOW WITH THE TRACK OF THE SURFACE LOW SHOWING LITTLE
CHANGE FROM THIER 12Z RUNS. THE SREF/GEFS/EC MEANS SUPPORT A
SOLUTION CLOSE TO THE 12Z ECMWF AND 00Z GFS...BUT WITH MORE WEIGHT
TOWARD THE SLOWER ECMWF COLD FRONT. THE 00Z ECMWF ADJUSTED
SLIGHTLY IN THE DIRECTION OF THE 00Z GFS...SO AN EVEN BLEND OF THE
TWO 00Z MODELS IS PREFERRED.


DEEP UPPER TROUGH MOVING THROUGH THE WEST TUE/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z GFS / 12Z ECMWF COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE MODELS SHOW VERY GOOD AGREEMENT UNTIL AROUND TUE...WHEN SOME
DIVERGENCE IN SOLUTIONS BEGINS. THE NAM IS SLIGHTLY AHEAD OF THE
PACK...WHILE THE 12Z CMC FALLS TO BECOME THE SLOWEST DETERMINISTIC
MODEL. THE GFS AND ECMWF APPEAR TO HAVE HELD THE BEST RUN-TO-RUN
CONTINUITY (CONSIDERING 12/00Z RUNS ONLY)...WITH THE 12Z UKMET
CLOSE TO THESE TWO MODELS EXCEPT BY WED MORNING WITH A SURFACE LOW
FARTHER OUT INTO THE PLAINS THAN THE GFS/ECMWF OR ENSEMBLE MEANS
DEPICTION. THE 00Z ECMWF IS QUICKER AT THE END OF THE SHORT RANGE
PERIOD...12Z/23...IN SWINGING THE SRN PORTION OF THE WEST COAST
TROUGH INTO THE NRN PLAINS WITH THE EC/GEFS/SREF MEANS AND THE
REMAINING 00Z MODEL CONSENSUS SUPPORTING A SOLUTION AWAY FROM THE
00Z ECMWF. DIFFERENCES ARE SMALL HOWEVER.


...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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