Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12
000
FXUS10 KWNH 170654
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 AM EST TUE JAN 17 2017

VALID JAN 17/0000 UTC THRU JAN 20/1200 UTC

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

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

CLOSED LOW REACHING THE SOUTHERN PLAINS TUE MORNING
SURFACE LOW TRACKING FROM THE SOUTHERN PLAINS TO THE UPPER GREAT
LAKES
TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

BOTH THE 00Z NAM AND GFS WERE CLOSE TO THE CONSENSUS WITH THE
POSITIONING OF THE MID LEVEL SYSTEM OVER THE CENTRAL PLAINS
EARLY...AND BOTH WEAKEN THE WAVE AS IT CROSSES INTO THE OH VALLEY
AND THE NORTHEAST DURING DAY 2.


SHORT WAVE CROSSING THE NORTHERN PLAIN AND UPPER GREAT LAKES
TUE...REACHING THE MID
ATLANTIC COAST WED AFTERNOON
SECONDARY SURFACE LOW DEVELOPMENT OFF SOUTHEAST NEW ENGLAND WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z ECMWF/00Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 00Z NAM IS SLOW WITH THE SHORT WAVE FROM THE MIDDLE OF DAY 1
THROUGH THE END OF DAY 2...WHEN COMPARED TO THE MODEL CONSENSUS.
HOWEVER...THE 00Z NAM IS CLOSE TO THE CONSENSUS WITH THE
DEVELOPMENT OF A SECONDARY LOW OFF THE SOUTHEAST NEW ENGLAND COAST
MIDDAY WED. THE 00Z CMC WAS EVEN SLOWER THAN THE 00Z NAM WITH THE
SHORT WAVE...YET LIKE THE 00Z NAM...THE SECONDARY SURFACE LOW
PLACEMENT WAS CLOSER TO THE TIGHTENING CLUSTER.

THE 00Z GFS HAS FINALLY SLOWED ITS MOTION OF THE SHORT WAVE...TO
BECOME MUCH BETTER ALIGNED WITH THE 00Z ECMWF/12Z ECMWF ENSEMBLE
MEAN/00Z UKMET DURING DAY 2. IN ADDITION...THE 00Z GFS PLACEMENT
OF THE SECONDARY LOW IS MUCH BETTER...JOINING A TIGHT CLUSTER WITH
THAT PLACEMENT.


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

AFTER REMAINING CLOSE TO THE MODEL CONSENSUS THROUGH DAY 2...THE
00Z NAM BECOMES FASTER THAN THE CONSENSUS WITH THE PLACEMENT OF
THE MID LEVEL LOW ACROSS THE MID MS VALLEY ON DAY 3. THE 00Z NAM
IS ON THE EASTERN EDGE OF THE GUIDANCE WITH THE MID LEVEL AND
ASSOCIATED SURFACE LOW. BY CONTRAST...THE 00Z GFS REMAINS CLOSE TO
THE CONSENSUS AS THE MID LEVEL SYSTEM CLOSED OFF OVER THE MID MS
VALLEY DURING DAY 3.

THE 00Z GFS IS CLOSE TO THE 00Z UKMET POSITION. THE 00Z ECWMF
CONTINUES THAT MODELS TREND OF A MORE WESTWARD PLACEMENT OF THE
CLOSED LOW (THOUGH IT STILL CLUSTERS WELL WITH THE 12Z ECMWF
ENSEMBLE MEAN POSITION). THE 00Z HAS SLOWED CONSIDERABLY WITH THE
MID LEVEL SYSTEM... AND NOW REPRESENTS THE WESTERN EXTENT OF THE
GUIDANCE ENVELOPE.

GIVEN THE OVERALL MODEL TREND TO PLACE THE MID LEVEL CLOSED SYSTEM
FURTHER WEST...THE PREFERRED MODEL BLEND REMAINS THE 00Z GFS/00Z
UKMET/00Z ECMWF...BUT SPREAD IS STILL WIDE ENOUGH TO HAVE LESS
THAN AVERAGE CONFIDENCE...ESPECIALLY ON DAY 3.


SHORTWAVES IN FAST FLOW ACROSS THE PACIFIC NORTHWEST MON/TUE
AMPLIFYING TROUGH REACHING THE WEST COAST WED/FOUR CORNERS REGION
THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z ECMWF/00Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 00Z NAM IS A BIT FASTER WITH THE MAIN PUNCH OF SHORT WAVE
ENERGY IN THE VERY FAST MID LEVEL FLOW ACROSS THE PACIFIC
NORTHWEST TUE/TUE NIGHT...BUT GIVEN THE SPEED OF THE FLOW...IT
DOES NOT APPEAR TO BE TOO FAR FROM THE MODEL CONSENSUS. THE 00Z
GFS IS CLOSE TO IT PREVIOUS POSITION WITH THE SHORT WAVE
ENERGY...AND THE 00Z GFS/00Z ECMWF CONTINUE TO FORM THE BEST
CONSENSUS WITH THIS ENERGY.

AS THE LONG WAVE TROUGH IS CARVED OUT OF SHORT WAVE ENERGY
DROPPING INTO ITS BASE OF THE WEST COAST...THE 00Z GFS BECOMES
SLOWER WITH THE MEAN TROUGH POSITION...MAINLY AFTER 19/12Z (A
TREND REINFORCED BY THE 00Z GEFS MEAN POSITION). THE DIFFERENCES
ARE MOST NOTABLE AFTER THE LONG WAVE TROUGH CROSSES CA AND STARTS
TAKING ON A NEGATIVE TILT OVER THE FOUR CORNERS AREA EARLY THU.

THE 00Z ECMWF AND 00Z UKMET STILL FORM THE BASIS FOR THE BEST
CONSENSUS WITH RESPECT TO THE PLACEMENT OF THE LONG WAVE TROUGH ON
DAY 3...THOUGH THERE ARE STILL SOME TIMING DIFFERENCES BETWEEN
THESE TWO SOLUTION AT THAT TIME.


CLOSED MID LEVEL LOW APPROACHING THE PACIFIC NORTHWEST EARLY THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A SHORT WAVE WITH ITS ORIGINS SOUTH OF THE ALEUTIANS ON DAY 2
CLOSES OFF NEAR 46N 133W BY THE END OF DAY 3. AS MIGHT BE EXPECTED
IN THE FAST MID LEVEL FLOW...THERE ARE SOME TIMING DIFFERENCES
DURING DAY 2 WITH THE SPEED OF THE SHORT WAVE...WITH THE 12Z ECMWF
GENERALLY FASTEST WITH THE SHORT WAVE JUST BEFORE IT CLOSES OFF.

BOTH THE 00Z NAM AND GFS ARE IN LOCK STEP WITH THE MODEL CONSENSUS
AS THE MID LEVEL SYSTEM CLOSES OFF. THE 00Z CMC SLOTTED INTO
BETTER AGREEMENT WITH THE CONSENSUS...AND THE 00Z UKMET WAS ONLY A
BIT SLOWER THAN THE CLUSTER BY THE END OF DAY 3. GIVEN THE
CLUSTERING OF THE MID LEVEL SYSTEMS IN A FAST MID LEVEL
FLOW...FORECAST CONFIDENCE IS SLIGHTLY ABOVE AVERAGE.
HOWEVER...TIMING DIFFERENCES IN THE FAST FLOW SHOULD BE
EXPECTED...SO FORECAST CONFIDENCE COULD CHANGE FOR LATER MODEL
RUNS.


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

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

HAYES

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.