Prognostic Meteorological Discussion
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000
FXUS10 KWNH 241848
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 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 MODEL EVALUATION...INCLUDING FINAL 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 12Z ECMWF BLEND THROUGH SUN
            12Z 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 12Z 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 12Z/00Z ECMWF BEST. GIVEN THE INSTABILITY IN THE
ENSEMBLE TRENDS...PREFER TO STAY CLOSEST TO THE MEANS...MIDDLE
GROUND...AT THIS TIME. ONLY MINOR CHANGES WERE SEEN IN THE 00Z
ECMWF/UKMET/CMC RELATIVE TO THEIR PREVIOUS CYCLES AND ANY
ADJUSTMENTS MADE...WERE SLOWER IN THE UKMET/CMC WHILE THE ECMWF
REMAINED ABOUT THE SAME.


...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/ECMWF/CMC
CONFIDENCE: AVERAGE

THE 12Z NAM IS A BIT SHALLOWER WITH THE UPPER TROUGH AS IT ENTERS
THE WEST AND THE 12Z UKMET IS NOTICEABLY SHARPER BY 00Z/28. THE
12Z GFS/ECMWF/CMC SHOW RELATIVELY GOOD AGREEMENT WITH THE DEPTH
AND TIMING OF THIS SYSTEM. THE 12Z GEFS AND 00Z ECMWF MEAN ARE
SLOWER THAN THE 12Z CMC FOR MONDAY BUT THE ENSEMBLE MEANS SUPPORT
SOME ADJUSTMENT FASTER OR SLOWER...BUT NOT THE DEPTH OF THE 12Z
UKMET.

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

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

OTTO

$$




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