Prognostic Meteorological Discussion
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FXUS10 KWNH 241640
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1239 PM EDT FRI MAR 24 2017

VALID MAR 24/1200 UTC THRU MAR 28/0000 UTC

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

DIFFERENCES CONTINUE TO BE RATHER MINOR WITH THIS SYSTEM THROUGH
MONDAY MORNING. BEYOND MONDAY...THE POSITION OF THE FRONT IS MORE
A FACTOR OF THE NEXT SYSTEM DESCRIBED IN THIS DISCUSSION.


...CLOSED LOW EVOLUTION OVER THE CENTRAL PLAINS FRI...
...ENERGY CROSSING THE MID MS/OH VALLEYS THROUGH SAT...
...SYSTEM WEAKENING INTO THE GREAT LAKES BY SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 50/50 BLEND OF 12Z GFS AND 00Z ECMWF BLEND THROUGH SUN
            00Z ECMWF FROM SUN TO MON
CONFIDENCE: AVERAGE

LOOKING AT SATURDAY EVENING WITH THE MID-LEVEL TROUGH POSITION
OVER MISSOURI...THE GEFS ENSEMBLE MEMBERS HAVE TRENDED SLOWER
SINCE THE 00Z/23 CYCLE...WHICH IS OPPOSITE OF TRENDS PRIOR TO THE
00Z/23 CYCLE. STILL BY 12Z/26...THE 06Z GEFS AND 12Z GFS REMAIN
FASTER THAN THE REMAINING ENSEMBLE GUIDANCE. CONTINUING FORWARD IN
TIME THE 12Z GFS AND GEFS CONTINUE TO BE AHEAD OF THE PACK..BUT
MORE SO IN THE 12Z GFS. THE ECMWF MEAN HAS BEEN TRENDING FASTER BY
THIS POINT IN TIME...00Z/27 OVER THE GREAT LAKES REGION...OPPOSITE
OF ITS PREVIOUS TRENDS TO BE SLOWER.

A BLEND IN THE MIDDLE OF THE FASTER GFS AND SLOWER ECMWF IS
PREFERRED THROUGH SUN AT WHICH POINT THE 12Z GFS APPEARS TO BE A
BIT FAST COMPARED TO THE ENSEMBLE MEANS. THERE IS SOME SLOWER
GUIDANCE THAN THE 00Z ECMWF...BUT THE ENSEMBLE MEANS SUPPORT THE
TIMING OF THE 00Z ECMWF BEST. GIVEN THE INSTABILITY IN THE
ENSEMBLE TRENDS...PREFER TO STAY CLOSEST TO THE MEANS...MIDDLE
GROUND...AT THIS TIME.


...NORTHERN STREAM TROUGH/COLD FRONT CROSSING MONTANA TONIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODEL SHOW SIMILARLY WITH THIS SYSTEM.


...SOUTHERN STREAM COMPONENT OF UPPER LEVEL TROUGH OVER THE WEST
ON SAT...
...ENERGY EJECTING INTO THE CNTRL/SRN PLAINS SUN NIGHT/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z GFS APPEARS TO BE AN ALMOST OUTLIER...ON THE FAST END OF
THE ENSEMBLE SPREAD BY THE MID-LEVEL TROUGH AXIS MOVES EAST OF THE
PLAINS. THE 00Z CMC IS A SLOW OUTLIER. THE 06Z GEFS AND 00Z ECMWF
MEAN SUPPORT THE 00Z ECMWF POSITION OF THE TROUGH AND EMBEDDED
MID-LEVEL VORTICITY MAX WHICH IS IN THE MIDDLE OF THE TIMING
SPREAD. ONLY THE OFTEN LESS RELIABLE 12Z NAM AND 00Z CMC SUPPORT A
FARTHER SOUTH POSITION WITH THE VORTICITY MAX BY MON EVENING. SO
IT BREAKS DOWN TO THE TIMING OF THE FASTER 12Z GFS...SOMEWHAT
SLOWER 00Z UKMET AND MIDDLE GROUND 00Z ECMWF...WITH THE MIDDLE
GROUND PREFERRED GIVEN THE BEST ENSEMBLE SUPPORT.


...UPPER TROUGH/COLD FRONT REACHING THE WEST COAST SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/00Z UKMET AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM IS A BIT SHALLOWER WITH THE UPPER TROUGH AS IT ENTERS
THE WEST...THE 00Z CMC IS NOTICEABLY FASTER BUT THE 00Z
UKMET...00Z ECMWF AND 12Z GFS SHOW RELATIVELY GOOD AGREEMENT WITH
THE DEPTH AND TIMING OF THIS SYSTEM. FOR WHAT IS IS WORTH...THE
12Z GFS SPLITS THE DIFFERENCE BETWEEN THE SHARPER/DEEPER 00Z UKMET
AND SOMEWHAT SHALLOWER 00Z ECMWF.

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

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

OTTO

$$





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