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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1659Z Jan 19, 2018)
 
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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
1159 AM EST FRI JAN 19 2018

VALID JAN 19/1200 UTC THRU JAN 23/0000 UTC

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

12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
...SOUTHERN STREAM WAVE EJECTING NORTHEAST FROM THE GULF OF
MEXICO...

PREFERENCE: 12Z GFS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
 
THE MODELS TAKE THE SOUTHERN STREAM CLOSED LOW/TROUGH OVER THE
WESTERN GULF COAST REGION GRADUALLY OFF TO THE EAST THROUGH THE
WEEKEND WHICH WILL ALLOW IT TO TRAVERSE THE REMAINDER OF THE GULF
COAST STATES. THE SYSTEM WILL WEAKEN AND BEGIN TO DAMPEN OUT BY
SUNDAY NIGHT AND MONDAY AS IT REACHES THE SOUTHEAST COAST AND
PUSHES OFFSHORE. BY LATER IN THE WEEKEND...THE 00Z UKMET/00Z CMC
AND 00Z ECMWF SOLUTION ALL BECOME A LITTLE MORE PROGRESSIVE AND
WEAKER THAN THE 12Z NAM/GFS SOLUTIONS. THE CMC OVERALL IS THE
WEAKEST...WITH THE NAM THE STRONGEST BY SUNDAY AND MONDAY. THE GFS
TENDS TO HAVE THE BETTER ENSEMBLE SUPPORT VIA THE 06Z GEFS MEAN
AND EVEN THE 00Z ECENS MEAN TO AN EXTENT WHICH SUGGESTS THE ECMWF
EVENTUALLY IS A BIT TOO PROGRESSIVE. WILL FAVOR THE GFS AT THIS
TIME WITH THIS SYSTEM.
 
 
...DEEPENING TROUGH MOVING INLAND ACROSS THE SOUTHWEST...
...ENERGY EJECTING NORTHEAST ACROSS THE PLAINS/MIDWEST...
...ATTENDANT SURFACE LOW LIFTING TOWARD THE GREAT LAKES...

PREFERENCE: GENERAL MODEL BLEND...THROUGH 48 HOURS
            12Z GFS...AFTER 48 HOURS
CONFIDENCE: AVERAGE

THE GUIDANCE AGREES IN TAKING A SOUTHERN STREAM TROUGH ACROSS CA
AND THROUGH THE SOUTHERN GREAT BASIN AND ADJACENT AREAS OF THE
SOUTHWEST U.S. THROUGH SATURDAY. THE SYSTEM IS THEN EXPECTED TO
AMPLIFY AND CLOSE OFF IN THE MID LEVELS OVER THE FOUR CORNERS
REGION SATURDAY NIGHT BEFORE EJECTING OUT ACROSS THE
CENTRAL/SOUTHERN HIGH PLAINS ON SUNDAY. THE STRONG HEIGHT FALLS
WILL DRIVE A WELL-ORGANIZED AREA OF LOW PRESSURE IN THE LEE OF THE
ROCKIES INVOLVING SOUTHEAST CO WHICH SHOULD THEN ADVANCE EAST
ACROSS SOUTHERN KS AND THEN LIFT NORTHEAST TOWARD THE GREAT LAKES
REGION SUNDAY NIGHT THROUGH MONDAY. THE MODEL MASS FIELD SPREAD IS
RATHER MINIMAL AS THE ENERGY TRAVERSES THE SOUTHWEST AND BROADER
FOUR CORNERS REGION...BUT AS THE SYSTEM REACHES THE
CENTRAL/SOUTHERN PLAINS...THE 12Z NAM BECOMES STRONGER THAN ANY
OTHER MODELS WITH ITS 500/700 MB REFLECTION AND TENDS TO LEAN A
BIT TOWARD THE FASTER SIDE OF THE GUIDANCE. THE 00Z ECMWF
MEANWHILE BECOMES THE SLOWEST SOLUTION AND IS ALSO A LITTLE SOUTH
OF THE MODEL CONSENSUS WITH ITS CLOSED LOW EVOLUTION ACROSS THE
MIDWEST THROUGH MONDAY. THE 12Z GFS IS A BIT FASTER AND ONLY A
LITTLE SLOWER THAN THE NAM. THE 00Z UKMET AND 00Z CMC ARE IN
BETWEEN THE SLOWER ECMWF AND FASTER GFS. THE 00Z ECENS MEAN
STRONGLY SUGGESTS THE ECMWF IS TOO SLOW BY THE END OF THE
PERIOD...AND THE 06Z GEFS MEAN IS A LITTLE FASTER THAN THE
OPERATIONAL GFS AND SUGGESTS THE RELATIVELY FASTER NAM IS WITHIN
THE REALM OF POSSIBILITIES. BASED ON ALL OF THIS...WILL SUGGEST A
GENERAL MODEL BLEND THROUGH 48 HOURS...FOLLOWED BY A SOLUTION AT
LEAST WEIGHTED STRONGLY TOWARD THE GFS THEREAFTER WITH MUCH
LOWERING WEIGHTING GIVEN TO THE ECMWF AND NAM BY COMPARISON.


...NORTHERN STREAM TROUGH CLIPPING THE NORTHERN PLAINS...

PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A WEAKER NORTHERN STREAM TROUGH COMING IN OFF THE PACIFIC OCEAN
TODAY WILL CROSS THE PACIFIC NORTHWEST AND TRAVERSE THE NORTHERN
PLAINS THROUGH SUNDAY. THE 12Z GFS AND 00Z ECMWF ARE REASONABLY
WELL CLUSTERED AND BEST APPROXIMATE THE MODEL CONSENSUS...AND SO A
BLEND OF THE GFS AND ECMWF WILL BE PREFERRED.


...UPPER TROUGH CROSSING INTO THE PACIFIC NORTHWEST BY SUNDAY...

PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE NEXT UPPER TROUGH COMING ACROSS THE NORTHEAST PACIFIC WILL
ARRIVE OVER THE NORTHWEST U.S. ON SUNDAY AND THEN BEGIN TO FLATTEN
OUT BY MONDAY OVER THE GREAT BASIN AND NORTHERN ROCKIES. THE 12Z
NAM TENDS TO BE THE STRONGEST OVERALL SOLUTION WITH THE TROUGH.
MEANWHILE...THE 00Z UKMET GRADUALLY APPEARS TO BE TOO SLOW. BETTER
MODEL CLUSTERING AND ENSEMBLE SUPPORT FAVORS THE 12Z GFS AND 00Z
ECMWF...SO A BLEND OF THE GFS AND ECMWF WILL BE PREFERRED.

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