Prognostic Meteorological Discussion
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000
FXUS10 KWNH 220411
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1110 PM EST SAT JAN 21 2017

VALID JAN 22/0000 UTC THRU JAN 25/1200 UTC

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

00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

COMPACT CLOSED MID-LEVEL LOW REACHING THE UPPER MS VALLEY TONIGHT
AND WEAKENING OVER SOUTHERN CANADA THROUGH TUES MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS CONTINUE TO SHOW STRONG AGREEMENT WITH THIS SYSTEM;
ENOUGH SO TO CONTINUE A GENERAL MODEL BLEND AT ABOVE AVERAGE
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: 00Z GFS/12Z ECMWF BLEND THROUGH 24/00Z
            00Z GFS/NAM AND 12Z ECMWF BLEND AFTERWARD
CONFIDENCE: AVERAGE

LAST FOUR CYCLES OF ENSEMBLE SPREAD SHOWS SOME WAFFLING BACK AND
FORTH WITH RESPECT TO THE CENTER OF THE UPPER LOW THROUGH THE
SOUTHERN MID-ATLANTIC.  THE 12Z CYCLE SHIFTED A BIT FURTHER EAST
WITH THE 12Z ECMWF CENTER TO THE BULK OF ECENS MEMBERS.  THE 12Z
ECMWF SHOWS SOME HINT OF ITS LATER TERM BIAS OF BEING A BIT TOO
WOUND UP AND SLOW...THOUGH THE 12Z CMC REMAINS WELL ON THE
SOUTHEAST SIDE OF THE SOLUTIONS.  THE 12Z UKMET SHIFTED TOWARD THE
FASTER/WESTERN TRACK MAINLY AFTER 24/00Z DENOTED BY THE LAST DAY
OR SO OF THE GFS/GEFS MEMBERS...TYPICAL OF THE GFS THROUGH THE
NORTHEAST BY DAY 3.  THE 00Z NAM SHIFTED A BIT SLOWER TOWARD THE
12Z ECMWF AND BETWEEN THE GEFS/ECENS MEANS AS A VERY NICE
COMPROMISE BY DAY 3 OFF NOT TOO FAST AND NOT TOO SLOW BUT CLOSER
TO THE ENSEMBLE MEAN AS A WHOLE...THOUGH THE 00Z NAM SEEMS TO BE A
BIT TOO FAR SOUTH INITIALLY ON LATE SUNDAY GIVEN THE OTHERWISE
TIGHTER CONSENSUS OF THE GFS/UKMET/ECMWF AT THAT TIME.  THE 00Z
GFS SLOWED A BIT COMPARED TO PRIOR GFS/GEFS RUNS AND IS MORE
CONCENTRIC SHIFTING IT TO THE EAST MORE IN LINE WITH THE 00Z
NAM/12Z ECMWF.   ALL CONSIDERED A 00Z GFS/12Z ECMWF BLEND IS
PREFERRED THROUGH 24/00Z WITH INCLUSION OF THE 00Z NAM TO THE
BLEND THEREAFTER AT AVERAGE CONFIDENCE.


COLD FRONT REACHING THE WEST COAST TONIGHT
LONGWAVE TROUGH OVER THE WEST COAST BY MON MORNING
DOWNSTREAM SURFACE LOW INTO THE PLAINS FOR TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODELS CONTINUE TO SUPPORT STRONG OVERALL AGREEMENT TO THE
LONGWAVE TROF AS IT CROSSES INTO THE WESTERN US BY MONDAY NIGHT
(24/00Z).  THE INNER CORE/EMBEDDED SHORTWAVE THAT IS CURRENTLY
RAPIDLY DEEPENING NEAR 40N130W SHOWS GOOD AGREEMENT INITIALLY BUT
THIS BREAKS DOWN THE WAVE FILLS AND DROPS SOUTH ALONG THE SW OR/NW
CA COAST LINE INTO TUESDAY. THE 00Z NAM AND GFS BOTH CONTINUE TO
BE A BIT TOO FAST COMPARED TO THE BETTER CONTINUITY WITH THE
ECMWF/ECENS MEAN SOLUTION.

AS THE LONGWAVE TROF REACHES THE INTERMOUNTAIN WEST...THIS SPURS
LEE SURFACE CYCLOGENESIS AND THE FORMATION OF A CLOSED UPPER LOW
CROSSING NEB.  THE 00Z NAM IS A BIT MORE OPEN AND FLATTER YET
STRONG WITH THE SHORTWAVE ENERGY/JET STRUCTURE THROUGH THE
MIDWEST.  THIS SUPPRESSES THE SURFACE LOW WELL SOUTH OF THE
CURRENT ENSEMBLE CLUSTER.  THE GFS/GEFS CONTINUES TO BE FAST
TYPICAL OF THE DAY 3 BIAS ACROSS THE MIDWEST THOUGH THE 00Z GFS
RUN IS A TAD SLOWER.  THE 12Z CMC IS MUCH TOO SLOW EJECTING INTO
THE PLAINS TO BE CONSIDERED.  THE 12Z ECMWF/UKMET LIKE WITH THE
INNER CORE OFF THE WEST COAST IN DAY 1/2...SEEM TO BE MORE
LOGICALLY SHAPED AND TIMED WITH THE STEADY TIMING/PROGRESSION OF
THE TROF AS A WHOLE...SO DO NOT SEE MUCH REASON AT THIS TIME TO
BREAK FROM DAY-SHIFT`S PREFERENCE.  OVERALL PATTERN REMAINS FAIRLY
WELL AGREED UPON TO HAVE SLIGHTLY ABOVE AVERAGE CONFIDENCE IN THE
BLEND TO COME TO FRUITION.

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

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

GALLINA

$$




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