Prognostic Meteorological Discussion
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000
FXUS10 KWNH 251848
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 PM EDT SAT MAR 25 2017

VALID MAR 25/1200 UTC THRU MAR 29/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...CLOSED LOW DIVING THROUGH EASTERN CANADA TODAY...
...COLD FRONT ADVANCING DOWN ACROSS THE GREAT LAKES/NORTHEAST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THERE ARE ONLY MINOR DIFFERENCES ASSOCIATED WITH THE HEIGHT FALLS
PUSHING THROUGH EASTERN CANADA AND WITH THE FRONT EXTENDING WWD
ACROSS THE EAST COAST...EVENTUALLY CONNECTING INTO A SURFACE LOW
ADVANCING TOWARD THE GREAT LAKES SUN NIGHT. A GENERAL MODEL
COMPROMISE IS PREFERRED.


...CLOSED LOW CROSSING THE MID MS/OH VALLEYS TONIGHT/SUN...
...SYSTEM WEAKENING INTO THE GREAT LAKES/NORTHEAST BY SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

OVER THE PAST 3 12Z/00Z ENSEMBLE CYCLES ENDING WITH THE 00Z/25
CYCLE...THE GEFS MEAN CONTINUED A SLOWER TREND WITH THE 500 MB LOW
SUN EVENING ACROSS THE OHIO VALLEY WHILE THE ECMWF MEAN HAS BEEN
CONSISTENT WITH TIMING. THE 12Z NAM/GFS REMAIN SLIGHTLY FASTER
THAN THE 00Z ECMWF MEAN AND ARE FARTHER NORTH WITH THE VORTICITY
MAX WITHIN THE MID-LEVEL LOW CENTER. THE GFS HAS BEEN CONSISTENTLY
NORTH WITH THE VORT CENTER WHILE THE ECMWF HAS BEEN CONSISTENTLY
SOUTH...WITH THE CORRESPONDING ENSEMBLE MEANS FOLLOWING SUIT WITH
THEIR DETERMINISTIC COUNTERPARTS. A BLEND OF THE 12Z GFS AND 00Z
ECMWF IS CLOSE ENOUGH TO A FAVORABLE MIDDLE GROUND...THROUGH
DIFFERENCES ARE MINOR.

19Z UPDATE...MINOR ADJUSTMENTS HAVE BEEN MADE WITH THE 12Z
ECMWF/UKMET/CMC IN THE DIRECTION OF THE 12Z NAM/GFS...SUCH THAT A
GENERAL MODEL COMPROMISE CAN BE PREFERRED.


...WEAKENING TROUGH/COLD FRONT OVER THE NORTHERN PLAINS TODAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


...NORTHERN STREAM TROUGH CROSSING THE PACIFIC NORTHWEST TODAY...
...EJECTING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST SUN/MON...
...REACHING THE ONTARIO/QUEBEC BORDER TUE EVENING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: 12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

THE MODELS ADVERTISE THE NORTHERN STREAM COMPONENT OF A LARGER
SCALE WESTERN U.S. TROUGH CROSSING THE PACIFIC NORTHWEST TODAY
WITH THE ENERGY THEN PROGRESSIVELY ADVANCING EASTWARD...GRAZING
THE NRN PLAINS AND UPPER MIDWEST SUN AND MON AND MOVING INTO SERN
CANADA FOR TUE. THE 12Z GFS STANDS OUT SIGNIFICANTLY IN THE
ENSEMBLES WITH A MORE AMPLIFIED TROUGH TOWARD THE SRN
ONTARIO/QUEBEC BORDER..ONLY SUPPORTED BY THE GEFS ENSEMBLES. A
BLEND OF THE 12Z ECMWF/UKMET IS RECOMMENDED HERE GIVEN THEIR
CLOSER AGREEMENT TO THE NON GEFS ENSEMBLE MEMBERS...AND NO
SIGNIFICANT ADJUSTMENT SEEN FROM THEIR PREVIOUS 00Z CYCLE.


...SOUTHERN STREAM UPPER TROUGH OVER THE WESTERN U.S. TODAY...
...ENERGY EJECTING INTO THE CNTRL/SRN PLAINS SUN NIGHT/MON...
...SYSTEM WEAKENING INTO THE OH VALLEY MON NIGHT/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAREST TO THE 12Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z GFS STILL APPEARS TOO FAST HERE GIVEN THE LATEST ENSEMBLE
DISTRIBUTION ALTHOUGH IT HAS TRENDED SLOWER WITH ITS 12Z CYCLE
COMPARED TO EARLIER RUNS. THE 12Z CMC IS ANOTHER MODEL THAT STANDS
OUT AGAINST THE OTHERS AND HAS LITTLE TO NO SUPPORT. NEAR THE 12Z
ECMWF...WHICH ADJUSTED A TAD FASTER FROM ITS 00Z RUN...IS
RECOMMENDED WITH THE 12Z UKMET ADJUSTING FASTER GIVEN THE LATEST
ENSEMBLE GUIDANCE.


...UPPER TROUGH/COLD FRONT REACHING THE WEST COAST SUN...
...CLOSED LOW EVOLUTION INTO THE SOUTHWEST MON/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z NAM/12Z CMC BLEND
CONFIDENCE: AVERAGE

THE MODELS SHOW RELATIVELY CLOSE TO ONE ANOTHER UNTIL MON AT WHICH
POINT MINOR DIFFERENCES SHOW UP. THE BIGGEST DIFFERENCE THOUGH IS
LIKELY TOWARD THE END OF THE SHORT RANGE...ON MONDAY...WHEN THE
12Z NAM/GFS DEVELOP A CLOSED LOW WHILE THE 00Z ECMWF/UKMET/CMC ARE
A BIT SLOWER TO DEVELOP THIS SYSTEM. THERE APPEARS TO BE ENOUGH
SEPARATION FROM THE NRN STREAM AND ENOUGH ENERGY DIGGING TO ALLOW
A CLOSED LOW TO DEVELOP. GIVEN THIS SCENARIO...SLOWER IS LIKELY
BETTER...AND THE 00Z ECMWF IS A BIT FASTER TO PROGRESS ITS CLOSED
LOW EAST INTO THE SOUTHWEST. THE 00Z ECMWF MEAN IS A TAD SLOWER
THAN THE 00Z ECMWF BUT NEAR THE 12Z GFS IS RECOMMENDED AT THIS
TIME...WITH SUPPORT FROM A SHIFT IN THE ENSEMBLES WITH THE 00Z/25
CYCLE LED BY THE 00Z/06Z GEFS MEAN.

19Z UPDATE...THE 12Z ECMWF/UKMET/CMC TRENDED SLOWER...CLOSING OFF
A LOW SOONER THAN THEIR EARLIER RUN...BUT THE ADJUSTMENTS MADE IN
THE 12Z ECMWF AND UKMET ARE NOT QUITE FAR ENOUGH TO BE NEAR THE
PREFERRED 12Z GFS.


...COLD FRONT WEAKENING INTO BRITISH COLUMBIA ON TUE...
...ONSHORE FLOW INTO THE PACIFIC NORTHWEST THROUGH TUE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS / 12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

AMPLITUDE DIFFERENCES EXIST WITH THIS SYSTEM...AND WHEN
DISCOUNTING THE DEEPER...NEAR OUTLIER 00Z CMC...THE 12Z GFS AND
12Z ECMWF SEEM TO REPRESENT TWO LIKELY BUT SOMEWHAT DIFFERENT
SOLUTIONS CONCERNING DEPTH. A BLEND OF THE TWO IS RECOMMENDED FOR
NOW TO MAXIMIZE POTENTIAL FOR VERIFICATION...WITH THE 12Z ECMWF
ADJUSTING A LITTLE TOWARD THE 12Z GFS.


www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

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