Prognostic Meteorological Discussion
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000
FXUS10 KWNH 221848
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 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 FINAL 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 ECMWF/UKMET THROUGH TUESDAY...CLOSER TO THE 12Z
ECMWF BY 12Z WED.
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 WELL AS WITH THE WEAKENING AREA OF LOW PRESSURE MOVING
SOUTH OFF THE COAST. 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.

19Z UPDATE: THE 12Z ECMWF DID TREND SLIGHTLY NORTH WITH THE
SURFACE LOW OVER THE PLAINS...AND IS NOW IN VERY CLOSE AGREEMENT
TO THE 12Z UKMET. WILL CONTINUE TO PREFER THE FURTHER SOUTH
ECMWF/UKMET THROUGH TUESDAY GIVEN THEIR CONSISTENCY AND THE FACT
THAT THE 12Z GEFS MEAN CONTINUES TO BE FURTHER SOUTH THAN THE
DETERMINISTIC GFS. AGAIN NOT ENTIRELY DISMISSING THE GFS...BUT
PREFERRING SOMETHING CLOSER TO A 70/30 BLEND TOWARDS THE
ECMWF/UKMET.

THE 12Z ECMWF DID INDEED TREND A BIT QUICKER/NORTH BY 12Z WED AND
IS NOW IN LINE WITH THE 0Z ECMWF MEAN POSITION. IN FACT THE NEW
12Z ECMWF APPEARS PRETTY MUCH RIGHT IN THE MIDDLE OF THE
DETERMINISTIC AND ENSEMBLE SPREAD...THUS WOULD LEAN OUR
PREFERENCES TOWARDS THE 12Z ECMWF BY DAY 3.


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

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

CHENARD

$$





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