Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center

 
 

 

Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   QPF
   PQPF
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/
Warnings

Satellite and Radar Imagery
   Satellite Images
   National Radar
Product Archive
WPC Verification
   QPF
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
   Development
WPC Overview
   About the WPC
   Staff
   WPC History
   Accomplishments
   Other Sites
   FAQs
Meteorological Calculators
Contact Us
   About Our Site
 
USA.gov is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
 
Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1855Z Dec 16, 2017)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 PM EST SAT DEC 16 2017

VALID DEC 16/1200 UTC THRU DEC 20/0000 UTC

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

12Z MODEL EVALUATION...WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...SHORTWAVE TROUGH EXITING THROUGH THE NORTHEAST TODAY/TONIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE LATEST MODELS ARE IN GOOD AGREEMENT WITH THE DETAILS OF THE
SHORTWAVE TROUGH CROSSING THROUGH THE NORTHEAST TODAY AND EXITING
THROUGH THE CANADIAN MARITIMES TONIGHT. A GENERAL MODEL BLEND WILL
BE PREFERRED.
 
 
...UPPER LEVEL LOW CURRENTLY OVER NORTHERN MEXICO...
...EJECTING NORTHEAST ACROSS THE SOUTHERN PLAINS BY TONIGHT...
...DEAMPLIFYING ON SUNDAY AS IT SHEARS DOWNSTREAM...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
PREFERENCE: NON-CMC BLEND 
CONFIDENCE: ABOVE AVERAGE 
 
THE 12Z CMC GRADUALLY BECOMES A LITTLE SLOWER THAN THE MODEL
CONSENSUS WITH THE UPPER LOW EJECTING NORTHEAST OUT OF NORTHERN
MEXICO AND THEN WEAKENING INTO AN OPEN WAVE BEFORE SHEARING OUT
OVER THE NEXT 24 TO 36 HOURS. THE REMAINING GUIDANCE IS GENERALLY
WELL CLUSTERED WITH THEIR TIMING AND DEPTH...SO WILL FAVOR A
NON-CMC BLEND AT THIS TIME.


...SHORTWAVE DIGGING SHARPLY THROUGH SOUTHERN CA...
...CLOSED LOW DEVELOPMENT OVER THE DESERT SOUTHWEST/NW MEXICO...
...EJECTING OUT ACROSS THE SOUTHERN PLAINS ON TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z UKMET AND 12Z ECMWF
CONFIDENCE: AVERAGE 
 
THE MODELS ARE IN VERY GOOD AGREEMENT DIGGING A SHORTWAVE TROUGH
DOWN THROUGH SOUTHERN CA TODAY AND THEN ACROSS THE NORTHERN BAJA
PENINSULA TONIGHT WHERE THE ENERGY SHOULD DEEPEN AND CLOSE OFF. A
CLOSED LOW CENTER IS THEN EXPECTED TO GRADUALLY PIVOT EAST ACROSS
FAR NORTHWEST MEXICO THROUGH MONDAY BEFORE THEN ADVANCING
DOWNSTREAM OUT ACROSS THE SOUTHERN PLAINS THROUGH TUESDAY. THE
HEIGHT FALLS WILL LIKELY INDUCE AT LEAST A WEAK AREA OF LOW
PRESSURE ACROSS THE SOUTHEAST TX COASTAL PLAIN BY LATE TUESDAY
WHICH SHOULD BE FOCUSED ALONG A FRONTAL ZONE. THE GUIDANCE IS IN
RATHER GOOD AGREEMENT UNTIL TUESDAY WHEN THE 12Z CMC BECOMES A
LITTLE SLOWER THAN THE REMAINING GUIDANCE. THE 12Z NAM ALSO
OVERALL APPEARS TO PERHAPS BE A TAD TOO SHARP AND A LITTLE TOO
AGGRESSIVE IN SUGGESTING SOME NEGATIVE TILT TO ITS TROUGH AXIS AT
THE END OF THE PERIOD. THE 12Z GFS IS NOW THE FASTEST
SOLUTION...WITH THE 12Z UKMET AND 12Z ECMWF NOW CLUSTERING
TOGETHER IN BETWEEN THE FASTER GFS AND SLOWER CMC. THE FASTER GFS
IS NOT WELL SUPPORTED BY THE 12Z GEFS MEAN WHICH ACTUALLY FAVORS
THE MODESTLY SLOWER UKMET/ECMWF CLUSTER. THEREFORE...BASED ON THE
LATEST TRENDS AND MORE AGREEABLE MODEL CLUSTERING...A BLEND OF THE
UKMET AND ECMWF WILL BE PREFERRED.

 
...SHORTWAVE TRAVERSING THE NORTHERN ROCKIES/PLAINS TODAY/SUNDAY...
...ENERGY DAMPENING OUT OVER THE GREAT LAKES/NORTHEAST BY MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
 
THE NORTHERN PORTION OF THE SHORTWAVE TROUGH THAT CAME INTO THE
PACIFIC NORTHWEST LAST NIGHT WILL MOVE ACROSS THE NORTHERN ROCKIES
TODAY AND ACROSS THE NORTHERN PLAINS ON SUNDAY. ON MONDAY THE
ENERGY WILL BEGIN TO DAMPEN OUT AS IT CROSSES THE GREAT LAKES
REGION AND THE NORTHEAST. A WEAK AREA OF LOW PRESSURE ALONG A
FRONTAL ZONE OVER THE CENTRAL PLAINS/MIDWEST WILL BREAK AWAY AND
CROSS PARTS OF THE GREAT LAKES AND NORTHEAST AS THIS ENERGY
CROSSING THE NORTHERN TIER OF THE COUNTRY. DIFFERENCES WITH THIS
SYSTEM ARE SMALL SCALE AND MAINLY NOTED WITH THE 12Z UKMET AND 12Z
ECMWF FAVORING A SLIGHTLY STRONGER REMNANT SHORTWAVE FEATURE THAT
CROSSES THE NORTHEAST...VERSUS THE WEAKER 12Z NAM/12Z GFS AND 12Z
UKMET. THE FLOW DOES BECOME QUITE ZONAL ACROSS THE REGION BY
MONDAY WHICH WOULD TEND TO SUPPORT A WEAKER/SHEARED SOLUTION...BUT
FOR NOW WILL RECOMMEND A GENERAL MODEL BLEND TO RESOLVE THE
SMALLER SCALE DIFFERENCES.


...AMPLIFYING NORTHERN STREAM TROUGH OVER SOUTHERN CANADA MONDAY...
...ENERGY DIGGING ACROSS THE MIDWEST/GREAT LAKES BY TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE 

THE MODELS TAKE SHORTWAVE ENERGY THAT ARRIVES ACROSS NORTHERN
BRITISH COLUMBIA FROM THE GULF OF AK AND DIGS IT AGGRESSIVELY
SOUTHEAST OVER THE NEXT FEW DAYS WHICH ALLOWS A RATHER STRONG
NORTHERN STREAM TROUGH TO CROSS SOUTHERN CANADA AND THE NORTHERN
U.S. WITH IMPACTS ACROSS THE NORTHERN PLAINS/MIDWEST AND GREAT
LAKES THROUGH MONDAY AND TUESDAY. A STRONG COLD FRONT WILL
ACCOMPANY THESE HEIGHT FALLS. THE MODELS ARE IN RATHER GOOD
AGREEMENT WITH THE LARGE SCALE DETAILS OF THE TROUGH AND THE COLD
FRONT. THE UKMET WHICH HAD BEEN TRACKING ITS SURFACE LOW SOUTH OF
THE MODEL CONSENSUS HAS TRENDED A BIT FARTHER NORTH WITH ITS 12Z
CYCLE AND IS NOW IN LINE WITH THE MULTI-MODEL CONSENSUS. WILL
PREFER A GENERAL MODEL BLEND AS A RESULT.


...DEEP UPPER TROUGH/CLOSED LOW CROSSING THE GULF OF AK MONDAY...
...ENERGY DIGGING SHARPLY INTO THE PACIFIC NORTHWEST ON TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE 

THE MODELS TAKE A NORTHERN STREAM SHORTWAVE TROUGH OVER THE GULF
OF AK AND AMPLIFY IT SOUTHEAST TOWARD THE PACIFIC NORTHWEST ON
TUESDAY WHICH ALLOWS FOR SOME STRONG HEIGHT FALLS TO ARRIVE IN
CONJUNCTION WITH A DEEPENING AREA OF LOW PRESSURE. THIS LOW
PRESSURE WAVE MOVES ACROSS NORTHWEST WA BY LATE TUESDAY. THE
MODELS ARE WELL CLUSTERED WITH TIMING AND DEPTH UNTIL TUESDAY WHEN
SOME DIFFERENCES ARE NOTED. THE 12Z ECMWF TRENDED A BIT MORE
PROGRESSIVE WITH ITS LATEST RUN AND IS CLOSE TO THE MODEL
CONSENSUS AS THE ENERGY ARRIVES ACROSS THE NORTHWEST. THE 12Z
UKMET THOUGH HAS SET ITSELF OUT AS BEING THE STRONGEST SOLUTION AT
THE SURFACE AND ALOFT BY TUESDAY...AND IS LIKELY TOO STRONG BASED
ON THE LATEST ENSEMBLE GUIDANCE. THE 12Z NAM FOR ITS PART LOOKS TO
BE A TAD TOO WEAK WITH ITS SURFACE LOW. THE 12Z CMC ALSO NOW
APPEARS TO BE TRACKING ITS SURFACE LOW A TAD TOO FAR SOUTH AS IT
APPROACHES WA STATE. THE BETTER MODEL CLUSTERING AND ENSEMBLE
SUPPORT WOULD SUGGEST A BLEND OF THE GFS AND ECMWF AND THAT WILL
BE THE PREFERENCE.


MODEL TRENDS AT www.wpc.ncep.noaa.gov/html/model2.shtml
500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

ORRISON