Prognostic Meteorological Discussion
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000
FXUS10 KWNH 281643
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 PM EDT TUE MAR 28 2017

VALID MAR 28/1200 UTC THRU APR 01/0000 UTC

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

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

...NORTHERN STREAM TROUGH AMPLIFYING ACROSS SOUTHEAST CANADA...
...UPPER TROUGH WEAKENING ACROSS THE MID-ATLANTIC ON TUE...
...SURFACE LOW CROSSING MID-ATLANTIC...DEEPENING OFFSHORE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

OVERALL...MODELS REMAIN IN GOOD AGREEMENT WITH THE LARGER SCALE
FEATURES.


...WEAK TROUGH OVER THE NORTHERN PLAINS/UPPER MIDWEST TUE/WED...
...STRONG CLOSED LOW EVOLUTION INTO THE SOUTHWEST ON TUE...
...EJECTING EAST ACROSS THE CENTRAL/SOUTHERN PLAINS WED...
...LIFTING THROUGH THE MID MS/TN/OH VALLEYS BY LATE THU/FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

COMPARED WITH ITS 00Z RUN THE NAM IS MORE PROGRESSIVE WITH THE
UPPER LOW AS IT MOVES FROM THE CENTRAL PLAINS THROUGH THE MID MS
VALLEY LATE THU-EARLY FRI.  HOWEVER...DESPITE THE TREND...THE NAM
REMAINS ON THE SLOWER EDGE OF THE DETERMINISTIC GUIDANCE.  THIS
MAY BE PARTLY ATTRIBUTED TO THE LESS AMPLIFIED NORTHERN STREAM
TROUGH IT DEPICTS OVER THE NORTHERN PLAINS-UPPER MIDWEST.

THE GFS IS ALSO FASTER WITH THE TIMING OF THE UPPER LOW/TROUGH AS
IT MOVES ACROSS THE MID MS VALLEY EARLY FRI.  IN FURTHER CONTRAST
WITH ITS 00Z RUN THE GFS HAS BACKED OFF ON THE AMPLITUDE OF THE
ENERGY MOVING THROUGH THE BASE OF THE TROUGH OVER THE LOWER MS
VALLEY/NORTHERN GULF OF MEX EARLY FRI.  IT ALSO TRACKS THE SURFACE
LOW FURTHER TO THE NORTH FROM THE MID MS VALLEY INTO THE OH VALLEY
ON FRI.  WHILE DIFFERENCES IN TIMING STILL EXIST...THIS PUTS THE
GFS INTO BETTER AGREEMENT WITH THE 00Z ECMWF.  TO ACCOUNT FOR
CONTINUING TIMING DIFFERENCES...A COMPROMISE BETWEEN THE TWO IS
RECOMMENDED.


...VIGOROUS TROUGH DIGGING INTO THE WEST ON THU/FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE

THE 12Z NAM IS FASTER THAN ITS 00Z RUN DIGGING THE TROUGH
SOUTHEAST ACROSS THE PACIFIC NORTHWEST INTO THE GREAT BASIN ON
THU.  THIS PLACES ITS TROUGH AXIS ALONG THE EASTERN EDGE OF THE
LATEST DETERMINISTIC GUIDANCE FOR A PERIOD ON THU BEFORE CLOSING
OFF A LOW THAT SETTLES SOUTH INTO THE SOUTHWEST CLOSE TO THE OTHER
MODELS.

AS THE UPPER LOW SETTLES SOUTH INTO THE FOUR CORNERS REGION ON
FRI...THE GFS TRACKS THE LOW THE LOW A LITTLE FURTHER NORTHEAST OF
THE GREATER DETERMINISTIC MODEL CONSENSUS WITH LOWER MID-UPPER
LEVEL HEIGHTS EXTENDING OUT ACROSS THE CENTRAL HIGH PLAINS AND A
STRONGER SURFACE LOW DEVELOPING IN THE LEE OF THE CENTRAL ROCKIES.
 LACKING SUPPORT FROM THE DETERMINISTIC MODELS AND THE 06Z GEFS
MEAN...RECOMMEND LEANING AWAY FROM THIS SOLUTION FOR NOW TOWARD A
SOLUTION MORE IN LINE WITH THE 00Z ECMWF.  THIS WILL LIKELY BE
RE-EVALUATED ONCE THE REMAINDER OF THE 12Z DETERMINISTIC MODELS
AND THE GEFS MEAN BECOME AVAILABLE.


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

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

PEREIRA

$$




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