Prognostic Meteorological Discussion
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544
FXUS10 KWNH 160439
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1138 PM EST SUN JAN 15 2017

VALID JAN 16/0000 UTC THRU JAN 19/1200 UTC

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

00Z NAM/GFS MODEL EVALUATION INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


CLOSED LOW REACHING THE SOUTHERN PLAINS MON MORNING
SURFACE LOW TRACKING FROM THE SOUTHERN PLAINS TO THE UPPER MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THERE IS FAIRLY GOOD MODEL AGREEMENT EARLY ON DAY 1 WITH THE
CLOSED MID LEVEL SYSTEM OVER THE SOUTHERN PLAINS...BUT THE 00Z GFS
REMAINS FASTER WITH THE CLOSED LOW AS IT OPENS UP INTO A WAVE
ACROSS THE WESTERN OH VALLEY BY THE BEGINNING OF DAY 2. BY
CONTRAST...THE 00Z NAM REMAINS CLOSE TO THE 12Z ECMWF...WHICH HAS
THE SUPPORT OF THE 12Z ECMWF ENSEMBLE MEAN. AT THE SURFACE...THE
00Z GFS REMAINS CLOSE TO THE CLUSTERING AS THE SURFACE WAVE
REACHES THE LOWER GREAT LAKES BY THE END OF DAY 2.

THE 12Z CMC/UKMET WERE FASTER WITH THE MID LEVEL WAVE BY THE END
OF DAY 2...BUT NOT QUITE AS FAST AS THE 00Z GFS. WITH THIS IN
MIND...THE PREFERENCE IS TO STAY CLOSE TO THE 00Z NAM/12Z ECMWF
BLEND...WHICH HAS SHOWN THE BEST CONTINUITY OVER THE PAST THREE
MODEL CYCLES. HOWEVER...GIVEN THE SPREAD IN THE GUIDANCE...
FORECAST CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE.


SHORTWAVE CROSSING THE NRN ROCKIES/NRN PLAINS SUN NIGHT/MON
INTERACTION WITH THE SHORT WAVE TRACKING FROM THE SRN PLAINS INTO
THE MIDWEST MON/TUE
SECONDARY SURFACE LOW DEVELOPMENT OFF SOUTHEAST NEW ENGLAND WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE 00Z NAM BECOMES FASTER WITH THE SHORT WAVE THAT TRACKS FROM
THE NORTHERN ROCKIES/NORTHERN PLAINS ON DAY 1...REACHING THE MID
ATLANTIC COAST DURING DAY 3. HOWEVER...THE 00Z NAM IS IN THE
BALLPARK WITH THE PLACEMENT OF THE SECONDARY LOW PRESSURE
DEVELOPMENT OFF THE SOUTHEAST NEW ENGLAND COAST DURING DAY 3. THE
00Z GFS IS EVEN FASTER WITH THE SHORT WAVE...AND IT IS MUCH FASTER
WITH THE SECONDARY SURFACE LOW PRESSURE DEVELOPMENT OFF THE
SOUTHEAST MA COAST.

BY CONTRAST...THE 12Z UKMET/CMC WERE SLOWER AND CLOSER TO THE
COAST (AS WELL AS DEEPER) WITH THE SURFACE LOW NEAR SOUTHEAST MA
ON DAY 3. GIVEN THE OVERALL PROGRESSIVE NATURE OF THE MID LEVEL
SUPPORT TRACKING FROM THE OH VALLEY OFF THE MID ATLANTIC/NEW
ENGLAND COAST...THE SLOWER SOLUTION APPEARS TO BE MORE UNLIKELY.

THE 12Z ECMWF HAS BEEN RELATIVELY CONSISTENT WITH THE PLACEMENT OF
THE DEVELOPING SURFACE LOW OFF THE SOUTHEAST MA COAST DURING DAY
3...AND IT IS CLOSE TO THE 00Z NAM POSITION. GIVEN THIS TENUOUS
CLUSTERING...THE MODEL PREFERENCE IS THE 00Z NAM/12Z ECMWF
BLEND...BUT GIVEN THE SPREAD (IN THE ENSEMBLE MEAN POSITIONS AS
WELL)...FORECAST CONFIDENCE REMAINS LESS THAN AVERAGE.


SOUTHWEST US AND NORTHERN MEXICO UPPER TROUGH MOVING INTO THE
SOUTHERN PLAINS WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE 00Z NAM IS CLOSE TO THE MODEL CONSENSUS WITH THE LONG WAVE
TROUGH AS IT CROSSES THE SOUTHWEST STATES AND NORTHERN MEXICO
THROUGH THE MIDDLE OF DAY 2....IT CLOSES AND BECOMES FASTER THAN
THE CONSENSUS BY THE END OF DAY 3. BY CONTRAST...THE 00Z GFS
REMAINS CLOSE TO THE CONSENSUS THROUGH THE PROCESSING OFF CLOSING
OFF IN THE MID LEVELS DURING DAY 3. IN FACT...THE 00Z GFS CLUSTERS
WELL WITH THE 18Z GEFS MEAN/12Z ECMWF/12Z ECMWF MEAN WITH RESPECT
TO THE CLOSED LOW...SO A 00Z GFS/12Z ECMWF BLEND IS THE PREFERRED
SOLUTION WITH THIS SYSTEM.


SHORTWAVES IN FAST FLOW ACROSS THE PACIFIC NORTHWEST MON/TUE
AMPLIFYING TROUGH REACHING THE WEST COAST WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW NORMAL

THERE IS STILL SOME SPREAD IN THE PLACEMENT OF THE SHORT WAVE
ENERGY IN THE FAST FLOW ACROSS BRITISH COLUMBIA AND THE PACIFIC
NORTHWEST THROUGH TUE (THIS IS NOT SURPRISING...GIVEN THE SPEED OF
THE MID LEVEL FLOW). THIS RESULTS IN A BELOW AVERAGE FORECAST
CONFIDENCE WITH RESPECT TO TIMING THE SHORT WAVES HERE. A BLEND OF
THE 00Z GFS/12Z ECMWF LOOKS REASONABLE...AS THESE SOLUTIONS ARE
CLOSE TO THE MIDDLE OF THE SPREAD.

AS SHORT WAVE ENERGY DROPS INTO A DEVELOPING LONG WAVE TROUGH OFF
THE WEST COAST DURING WED...MODEL SPREAD INCREASES DUE TO THE
SHORT WAVE TIMING. THE 00Z GFS WAS A TAD FASTER THAN THE CONSENSUS
(CONTINUING THIS MODELS TREND OF A FASTER MOVEMENT DURING DAY 3).
HOWEVER...IT IS NOT MUCH FASTER THAN A 18Z GEFS MEAN/12Z ECMWF/12Z
ECMWF ENSEMBLE MEAN BLEND...SO AT THIS POINT...A 00Z GFS/12Z ECMWF
BLEND IS PREFERRED.

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

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


HAYES

$$





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