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000
FXUS10 KWNH 180447
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 AM EDT FRI APR 18 2014

VALID APR 18/0000 UTC THRU APR 21/1200 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 TROUGH REACHING NEW ENGLAND LATE FRI NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

OVERALL...MODELS SHOW GOOD AGREEMENT WITH THIS SYSTEM.


CLOSED MID LEVEL LOW FORMING OVER THE SOUTHEAST BY SAT MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  12Z CMC / 12Z ECMWF BLEND
CONFIDENCE:  AVERAGE

A DEFINITIVE SLOWING TREND EXISTS IN THE ENSEMBLE MEMBERS ACROSS
THE SOUTHEAST REGARDING THE UPPER TROUGH BY 00Z/SAT...WITH MUCH
SMALLER SPREAD NOW IN PLACE. THE LATEST DETERMINISTIC MODELS SHOW
SIMILAR 500 MB DEPICTIONS...BUT DIFFERENCES EXIST IN THE SURFACE
TO 700 MB LAYER. THE 12Z UKMET IS BY FAR THE WEAKEST
ALOFT...FOLLOWED BY THE 00Z NAM. THE PAST 2 RUNS OF THE
SREF/GEFS/EC MEANS SHOW GOOD CONTINUITY BUT THE SREF AND EC MEAN
ARE A BIT SOUTHWEST OF THE 18Z GEFS MEAN REGARDING THE 850 MB LOW
OVER THE SOUTHEAST. THE 00Z GFS IS ALSO A LITTLE NORTH OF THE
CONSENSUS. THEREFORE...PREFERRING TO BE A BIT SOUTH OF THE
GFS/GEFS GIVEN THE REMAINING MODEL GROUPING...A 12Z ECMWF/CMC
BLEND IS PREFERRED.


MID-LEVEL SHORTWAVE ENTERING THE PAC NW TODAY AND TRACKING ALONG
THE U.S.-CANADIAN BORDER THROUGH SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z GFS / 12Z ECMWF BLEND
CONFIDENCE:  AVERAGE

THERE ARE ONLY SMALL DIFFERENCES IN THE SURFACE LOW POSITION
TONIGHT...COMPARED TO YESTERDAY...BUT DIFFERENCES IN STRENGTH
STILL EXIST...MOSTLY BY SUN AS THE MID-LEVEL SHORTWAVE IS ALREADY
WELL INTO CANADA. THE 00Z NAM IS FLATTEST ALOFT...AND WEAKEST AT
THE SURFACE. THE GFS/ECMWF COMBO REPRESENT A GOOD MIDDLE GROUND
POSITION AND SHOW AGREEMENT WITH THE RELATIVELY WELL CLUSTERED
ENSEMBLE LOW PLOTS...BUT THE REMAINING NON-NAM GUIDANCE IS
REASONABLE AS WELL.


DEEP LAYERED TROUGH MOVING THROUGH THE SOUTHWEST INTO THE PLAINS
THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  NON-00Z NAM COMPROMISE
CONFIDENCE:  AVERAGE

THE NAM IS MUCH FLATTER WITH A DOWNSTREAM MID-LEVEL RIDGE OVER THE
SOUTHEAST BY MON MORNING...BUT OUTSIDE OF THE NAM...THERE IS
GENERALLY GOOD AGREEMENT. A NON-00Z NAM COMPROMISE IS PREFERRED.


MID-LEVEL SHORTWAVE REACHING THE PAC NW ON SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z GFS...12Z ECMWF...12Z UKMET BLEND
CONFIDENCE:  AVERAGE

SIMPLY PUT...THE GFS/ECMWF/UKMET MATCH THE ENSEMBLE MEANS AND EACH
OTHER THROUGHOUT THE WEEKEND INTO MONDAY WITH THIS SYSTEM...WHILE
THE NAM AND CMC SHOW A DIFFERENT IDEA.


CLOSED LOW IN THE GULF OF ALASKA BY MON MORNING
MOISTURE FEED INTO VANCOUVER ISLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  AVERAGE

BY MONDAY MORNING...THERE ARE SOME TIMING AND DEPTH DIFFERENCES IN
THE LATEST AVAILABLE GUIDANCE...BUT THEY ARE SMALL ENOUGH AT THIS
POINT TO PREFER A GENERAL MODEL COMPROMISE.


...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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