Prognostic Meteorological Discussion
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000
FXUS10 KWNH 201856
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 PM EST FRI JAN 20 2017

VALID JAN 20/1200 UTC THRU JAN 24/0000 UTC

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

12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


SHORTWAVE TROUGH OVER THE OHIO VALLEY TODAY...WEAKENING NEWD
  THROUGH EARLY SAT MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


COMPACT CLOSED MID-LEVEL LOW ADVANCING THROUGH THE CNTRL PLAINS
  TODAY AND REACHING THE UPPER MS VALLEY SAT NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

TRENDS IN THE 12Z NAM/GFS SHOW A QUICKER DEPARTURE OF THE CLOSED
LOW AS IT REACHES THE UPPER MISSISSIPPI VALLEY. GIVEN THESE
ADJUSTMENTS ARE IN THE F036-FO48 HR TIME FRAME...OR RELATIVELY
SHORT TERM...AND ROOM IN THE ENSEMBLE GUIDANCE TO ADJUST
QUICKER...THIS TREND MAY BE SEEN IN THE REMAINING ECMWF/UKMET/CMC
GUIDANCE WHEN THEIR 12Z RUNS ARRIVE. A BLEND OF THE FASTER 12Z GFS
AND SLOWER 00Z ECMWF IS PREFERRED FOR NOW TO TREND IN THE
DIRECTION OF THE QUICKER GUIDANCE.

19Z UPDATE...THE 12Z ECMWF/UKMET/CMC FOLLOWED THE LEAD OF THE
NAM/GFS TO SPEED UP THROUGH 00Z/23. GIVEN THE STRONG SUPPORT FOR
THIS ADJUSTMENT BY ALL OF THE 12Z MODELS...AND GENERAL GOOD
AGREEMENT...A GENERAL MODEL BLEND IS PREFERRED.


HEIGHT FALLS ACROSS THE WEST TODAY...CLOSED LOW ACROSS THE LOWER MS
  VALLEY SUN WITH ASSOCIATED STRONG SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS...12Z ECMWF...12Z UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

DESPITE TRENDING SLOWER FROM PREVIOUS RUNS...THE 12Z NAM CONTINUES
TO BE QUICKER THAN MOST GEFS/EC/CMC ENSEMBLE MEMBERS WITH AN
EXPECTED CLOSED LOW DEVELOPING OVER THE SRN PLAINS SUN. IT IS
CONSIDERED UNLIKELY TO VERIFY. THE REMAINING MODELS ARE IN FAIR
AGREEMENT BUT THERE ARE DIFFERENCES WORTH NOTING. THE 00Z ECMWF IS
MUCH STRONGER WITH THE RESULTING 850/700 MB LOWS BY 12Z/23 OVER
THE MID-ATLANTIC REGION. THE 12Z GFS APPEARS TO LIFT THE CLOSED
LOW FASTER/FARTHER NORTH BY 00Z/24 AND IS ALSO NOTABLY WARMER AT
850 MB ACROSS OH/PA GIVEN A MORE NORTH-SOUTH ELONGATION TO THE 850
MB LOW NOT SEEN IN THE OTHER MODELS. THE 00Z UKMET IS A BIT SLOWER
WITH THE TIMING OF THE PROGRESSION OF THE LOW. WHILE NO MODEL
APPEARS IDEAL THROUGHOUT THE F036-FO84 HR TIME FRAME...A BLEND OF
THE 12Z GFS...00Z ECMWF AND 00Z UKMET APPEARS MOST REASONABLE WITH
RESPECT TO THE ENSEMBLE DISTRIBUTION AND TRENDS.

19Z UPDATE...THE 12Z ECMWF WEAKENED FROM ITS PREVIOUS CYCLE...NOW
SHOWING TWO LOW CENTERS...MORE SIMILAR TO THE 12Z GFS WITH WARMER
LOW LEVELS ACROSS PA/NY BY MON. THE 12Z UKMET LOOKS SIMILAR TO ITS
PREVIOUS RUN AND SO A GFS/ECMWF/UKMET BLEND REMAINS THE PREFERRED
COMPROMISE.


COLD FRONT REACHING THE WEST COAST SAT NIGHT AND LONGWAVE TROUGH
  OVER THE WEST COAST BY MON MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

THE LATEST GUIDANCE CONTINUES TO SHOW A STRONG LOW DEVELOPING OFF
OF THE WEST COAST ON SUN WITH DIFFERENCES IN TIMING AND PLACEMENT
NOTED. THERE IS RELATIVELY TIGHT ENSEMBLE CLUSTERING WITH THE
EVOLUTION OF THIS SYSTEM AND ALL OF THE DETERMINISTIC GUIDANCE IS
WITHIN REASON HERE. THE MID-LEVEL LOW HAS NO SIGNIFICANT
DIFFERENCES AMONG THE NAM/GFS/ECMWF/UKMET/CMC GUIDANCE WITH A
GENERAL BLEND RECOMMENDED AT THIS TIME TO IRON OUT INDIVIDUAL
DIFFERENCES.

19Z UPDATE...THERE HAVE BEEN MINOR ADJUSTMENTS IN THE 12Z
ECMWF/UKMET/CMC TO SHOW THE 12Z GFS FARTHER OFFSHORE WITH THE LOW
BY MON OFF OF THE WEST COAST...BUT ALL OF THE MODELS REMAIN
SIMILARLY CLUSTERED AND WITHIN THE ENSEMBLE SPREAD.

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

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

OTTO

$$




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