Prognostic Meteorological Discussion
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FXUS10 KWNH 221733
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1232 PM EST SUN JAN 22 2017

VALID JAN 22/1200 UTC THRU JAN 26/0000 UTC

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

12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

CLOSED LOW ACROSS THE LOWER MS VALLEY SUN WITH ASSOCIATED STRONG
SFC LOW LIFTING THROUGH THE MID-ATLANTIC MON...NEW ENGLAND ON TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

OVERALL MODELS REMAIN IN FAIRLY GOOD AGREEMENT SYNOPTICALLY WITH
THIS SYSTEM...ALTHOUGH SOME WAFFLING WITH THE EXACT TIMING AND LOW
POSITION CONTINUES. THE 0Z ECMWF AND 12Z NAM ARE A BIT CLOSER TO
THE COAST THAN THE 12Z GFS...WITH THE 12Z UKMET A BIT SLOWER THAN
THE CONSENSUS. HOWEVER ALL THE MODELS APPEAR TO BE WITHIN THE
RANGE OF PLAUSIBLE OUTCOMES...AND THUS A GENERAL MODEL BLEND
SHOULD HANDLE THE SYSTEM WELL FROM A SYNOPTIC STANDPOINT. BY
WEDNESDAY THE 12Z NAM DOES BECOME AN OUTLIER WITH ITS TRACK WELL
SOUTH OF NOVA SCOTIA...BUT BY THAT POINT SENSIBLE WEATHER IMPACTS
ON THE US WILL BE DECREASING.


LONGWAVE TROUGH OVER THE WEST COAST BY MON MORNING
DOWNSTREAM SURFACE LOW INTO THE PLAINS FOR TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z UKMET AND 0Z ECMWF THROUGH TUESDAY...MORE TOWARDS
THE 0Z ECMWF MEAN (OR A GFS/ECMWF COMPROMISE) BY TUESDAY NIGHT
INTO WEDNESDAY
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODELS CONTINUE TO SUPPORT STRONG OVERALL AGREEMENT TO THE
LONGWAVE TROUGH AS IT CROSSES INTO THE WESTERN US BY MONDAY NIGHT
(24/00Z). AS THE LONGWAVE TROUGH REACHES THE INTERMOUNTAIN
WEST...THIS SPURS LEE SURFACE CYCLOGENESIS AND THE FORMATION OF A
CLOSED UPPER LOW CROSSING NEB.  THE TWO BIGGEST OUTLIERS WITH THIS
SYSTEM ARE THE 0Z GEM AND 12Z NAM. THE 12Z NAM IS TOO FLAT AND
PROGRESSIVE WITH THE TROUGH/SHORTWAVE...RESULTING IN A WEAKER AND
QUICKER LOW THAN THE MAJORITY OF THE MODELS/ENSEMBLES. ON THE
OTHER HAND THE 0Z GEM IS MUCH SLOWER THAN THE CONSENSUS AND ALSO
APPEARS UNLIKELY. THAT LEAVES THE 12Z GFS/UKMET AND 0Z ECMWF AS
PLAUSIBLE MODEL OPTIONS. AGREE WITH THE OVERNIGHT SHIFT THAT
LEANING TOWARDS THE 0Z ECMWF AND 12Z UKMET IS THE BETTER OPTION AT
THIS TIME. THESE SOLUTIONS HAVE BEEN PRETTY CONSISTENT AND IN GOOD
AGREEMENT WITH EACH OTHER. THE 06Z GEFS MEAN IS ALSO FURTHER SOUTH
THAN THE DETERMINISTIC GFS AND CLOSER TO THE ECMWF/UKMET. THUS
WHILE I WOULD NOT COMPLETELY DISREGARD THE 12Z GFS...WOULD LEAN
MORE TOWARDS THE 12Z UKMET AND 0Z ECMWF. BY WEDNESDAY SPREAD IS
EVEN BIGGER...WITH THE GFS MUCH QUICKER AND FURTHER NORTH THAN THE
ECMWF/UKMET. BY THIS TIME GEFS/EC ENSEMBLE DATA SUGGESTS THAT
GOING MORE IN BETWEEN THE GFS/ECMWF IS THE BETTER OPTION. IN FACT
THE 0Z ECMWF MEAN IS PRETTY MUCH EXACTLY IN BETWEEN THE 0Z ECMWF
AND 12Z GFS LOW POSITION AT 12Z WED. THUS WOULD LEAN CLOSER TO THE
0Z ECMWF MEAN BY LATER TUESDAY NIGHT INTO WEDNESDAY...WHICH IS
PRETTY MUCH RIGHT IN BETWEEN THE 12Z GFS AND 0Z ECMWF SOLUTION.

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

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

CHENARD

$$





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