Prognostic Meteorological Discussion
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FXUS10 KWNH 291857
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT WED MAR 29 2017

VALID MAR 29/1200 UTC THRU APR 02/0000 UTC

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

FINA 12Z MODEL EVALUATION...INCLUDING THE ECMWF
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...STRONG CLOSED LOW CROSSING THE CENTRAL/SOUTHERN PLAINS...
...ADVANCING EAST THROUGH THE MID MS/TN/OH VALLEYS BY THU/FRI...
...ENERGY CROSSING THE MID-ATLANTIC BY FRI NIGHT...
...TROUGH CROSSING THE NORTHERN TIER STATES WED THROUGH FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF
CONFIDENCE: AVERAGE

COMPARED TO ITS 00Z RUN...BY EARLY FRI THE NAM IS FASTER WITH THE
UPPER LOW AS IT MOVES FROM THE MID MS INTO THE LOWER OH VALLEY.
THIS OCCURS AROUND THE SAME TIME THAT THE NAM ALSO STARTS TO TREND
MORE AMPLIFIED WITH THE NORTHERN STREAM TROUGH TO THE NORTH.
THESE TRENDS CONTINUE THROUGH EARLY SAT AS THE LOW MOVES OFF OF
THE MID ATLANTIC COAST AND THE NORTHERN STREAM TROUGH MOVES INTO
THE NORTHEAST.

THE GFS SHOWS A TREND SIMILAR TO THE NAM AND IT TOO IS FASTER THAN
ITS 00Z RUN WITH THE UPPER LOW AS IT MOVES FROM THE MID MS TO THE
LOWER OH VALLEY.  IN ADDITION...IT IS FURTHER TO THE NORTH THAN
THE 00Z RUN WITH THE MID-UPPER LEVEL CENTER AS IT MOVES ACROSS THE
OH VALLEY ON FRI.

THE 12Z UKMET...WHICH HAD BEEN ONE OF THE SLOWEST DETERMINISTIC
MODELS OVERNIGHT...HAS TRENDED FASTER...MOVING INTO BETTER
AGREEMENT WITH THE MODEL CONSENSUS.  FOLLOWING THE SAME
TREND...THE CANADIAN GLOBAL IS ALSO FASTER THAN ITS PREVIOUS RUN.
HOWEVER...IT MOVES TO THE SLOWER SIDE OF THE DETERMINISTIC
GUIDANCE AS THE SYSTEM MOVES ACROSS THE OH VALLEY/MID ATL REGION.
THE 12Z ECMWF CONTINUED THE TREND...AND SIMILAR TO THE GFS IT
TRENDED FURTHER TO THE NORTH WITH THE MID-UPPER LEVEL CENTER AS IT
MOVES ACROSS THE OH VALLEY.

THE GFS/ECMWF CLUSTER FAIRLY WELL INTO EARLY FRI.  THEN DESPITE
THE GENERAL TREND IN THE DETERMINISTIC GUIDANCE TOWARD A FASTER
SOLUTION...THE GFS APPEARS A LITTLE TOO FAST WITH THE MID-UPPER
LEVEL LOW/TROUGH...ESPECIALLY LATE IN THE PERIOD.  BY EARLY SAT AS
THE MID-UPPER LOW MOVES REACHES THE NORTHERN MID ATL...THE GFS IS
ALONG THE LEADING EDGE OF THE DETERMINISTIC GUIDANCE.  IT THEN
TRACKS THE ASSOCIATED SURFACE FURTHER TO THE SOUTH OFF OF THE
COAST THAN THE OTHER MODELS.  THE NAM IS MORE AMPLIFIED AND TRACKS
THE MID-UPPER LOW FURTHER TO THE SOUTH ACROSS THE OH VALLEY.  AS
THE SYSTEM MOVES OFFSHORE...THE NAM MOVES OUT AHEAD OF THE GFS AND
DEPICTS A MORE NEGATIVELY-TILTED MID-UPPER LEVEL TROUGH AND IN
TURN A SURFACE LOW THAT TRACKS CLOSER TO THE NEW ENGLAND COAST
THAN THE OTHER DETERMINISTIC MODELS ON SAT.  THAT SAID...RECOMMEND
LEANING CLOSE TO THE ECMWF WHICH FALLS NEAR THE MIDST OF THE MODEL
SPREAD.


...VIGOROUS TROUGH DIGGING INTO THE WEST ON THU...
...STRONG CLOSED LOW OVER THE FOUR CORNERS BY FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF
CONFIDENCE: AVERAGE

THE NAM SHOWS GOOD RUN-TO-RUN CONTINUITY WITH ITS 00Z
RUN...HOWEVER BY LATE FRI THE NAM STARTS TO BECOME A SIGNIFICANT
OUTLIER WITH RESPECT TO THE UPPER LOW POSITION...MOVING EAST AND
THEN NORTHEAST OF THE GREATER MODEL CONSENSUS.

THE GFS ALSO SHOWS FAIRLY GOOD RUN-TO-RUN CONTINUITY...HOWEVER AS
THE LOW DROPS INTO THE FOUR CORNERS REGION LATE FRI IT SHOWS A
MORE ELONGATED STRUCTURE...WITH MORE AMPLIFIED ENERGY LIFTING
NORTHEAST OF THE CENTER AND LOWER MID-UPPER LEVEL HEIGHTS
EXTENDING OUT ACROSS THE CENTRAL HIGH PLAINS.  LACKING A GOOD DEAL
SUPPORT FROM THE LATEST DETERMINISTIC GUIDANCE...AS WELL AS THE
12Z GEFS MEAN...RECOMMEND LEANING AWAY FROM THIS SOLUTION TOWARD
ONE MORE SIMILAR TO THE 00Z ECMWF.


...NORTHERN STREAM TROUGH/FRONT CROSSING THE NORTHERN PLAINS FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

THE NEXT NORTHERN STREAM TROUGH WILL CROSS THE NORTHERN PLAINS BY
FRI ALONG WITH A WEAK COLD FRONT. THERE IS SUFFICIENT MASS FIELD
CLUSTERING DESPITE SOME MINOR TIMING/DEPTH DIFFERENCES TO GO WITH
A GENERAL MODEL COMPROMISE AT THIS POINT.


...NORTHERN STREAM TROUGH MOVING ACROSS WESTERN CANAD ON SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

AS WITH THE PREVIOUSLY NOTED SYSTEM...THE LATEST DETERMINISTIC
MODELS ARE FAIRLY WELL-CLUSTERED...SUPPORTING A GENERAL BLEND AT
THIS POINT.

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

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

PEREIRA

$$





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