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
000
FXUS10 KWNH 260650
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 AM EST FRI DEC 26 2014

VALID DEC 26/0000 UTC THRU DEC 29/1200 UTC

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

...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS OF THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...INITIAL SHORTWAVE LIFTING FROM THE CENTRAL PLAINS TO THE UPPER
MIDWEST...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

WATER VAPOR IMAGERY SHOWED A BROAD UPPER TROF SINKING TOWARD THE
FOUR CORNERS REGION WITH SEVERAL BATCHES OF VORTICITY SEEN
CIRCULATING ABOUT THE REGION. THE NORTHERN MOST IMPULSE CURRENTLY
SPREADING LIGHT/MODERATE SNOW ACROSS AREAS OF NORTHEASTERN
CO/SOUTHEASTERN WY/NE PANHANDLE WILL SHIFT ITS FOCUS NORTHEASTWARD
IN TIME. MODELS ARE UNANIMOUS IN FLATTENING OUT THE SHORTWAVE AS
IT PROGRESSES THROUGH MN/WI ON FRIDAY AFTERNOON BEFORE MOVING INTO
SOUTHERN ONTARIO BY NIGHTFALL. THE SOLID AGREEMENT WARRANTS A
GENERAL MODEL COMPROMISE.


...FULL-LATITUDE TROF SLIDING EASTWARD ACROSS THE CONUS THIS
WEEKEND...
...PROGRESSIVE COLD FRONT/WAVE OF LOW PRESSURE CROSSING THE GREAT
LAKES...

FINAL PREFERENCE: THROUGH 28/1200Z...BLEND OF THE 00Z
GFS-PARALLEL/ECMWF...THEREAFTER: BLEND OF THE 00Z ECMWF WITH THE
00Z GEFS/12Z ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: AVERAGE

AS THE LEAD MID-LEVEL ENERGY MOVES TOWARD THE UPPER MIDWEST BY
FRIDAY EVENING...THE AFOREMENTIONED TROF ACROSS THE SOUTHWESTERN
U.S. WILL GRADUALLY ADVANCE EASTWARD. THE CORE OF LOWER HEIGHTS
ARE FORECAST TO BE LOCATED OVER THE FOUR CORNERS REGION ON
26/1800Z. MODELS SUGGEST THE LEADING EDGE OF THE HEIGHT FALLS WILL
LIFT NORTHEASTWARD TOWARD THE MIDDLE MS VALLEY/GREAT LAKES REGION
ON SATURDAY. THERE IS MINIMAL ENSEMBLE SPREAD WITH THE RESULTANT
AREA OF LOW PRESSURE MOVING THROUGH THE GREAT LAKES MIDDAY
SATURDAY. THE BEST CLUSTERING IS WITH THE SLIGHTLY FASTER SOLUTION
FEATURING THE 00Z NAM/GFS/GFS-PARALLEL/UKMET. THE 00Z ECMWF WHICH
HAD BEEN SLOWER HAS MOVED IN THE DIRECTION OF THE PREVIOUSLY
MENTIONED CLUSTER. THIS KEEPS THE PREVIOUS PREFERENCE AS
REASONABLE.

WHILE THE INITIAL WAVE MOVES THROUGH THE GREAT LAKES...THE
REMAINING PORTION OF THE UPPER TROF IS FORECAST TO EJECT EASTWARD
CROSSING THE RIO GRANDE BY SUNDAY MORNING. THE 00Z CMC/UKMET STILL
LOOK SLOW BUT THEY DO AT LEAST HAVE COMPANY IN THE 00Z NAM. LATER
IN THE PERIOD...THERE ARE SOME TIMING DIFFERENCES BETWEEN THE 0OZ
GFS/GFS-PARALLEL AND 00Z ECMWF WITH THE 00Z GFS BEING THE QUICKEST
SOLUTION WHILE THE 00Z ECMWF UNDERGOES A BIT MORE AMPLIFICATION.
THROUGH DAY 2/SUNDAY MORNING...A COMBINATION OF THE 00Z
GFS-PARALLEL/ECMWF APPEARS REASONABLE BUT WILL BEGIN TO
INCORPORATE THE MORE STABLE ENSEMBLE MEANS INTO THE MIX ON DAY 3.
THAT IS...A BLEND OF THE 00Z ECMWF WITH THE 00Z GEFS/12Z ECMWF
ENSEMBLE MEANS.


...STRONG SHORTWAVE REACHING THE PACIFIC NORTHWEST BY LATE
SATURDAY...
...SURGE OF ARCTIC AIR INTO THE WEST...

FINAL PREFERENCE: BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

MODELS SHOW A STOUT UPPER RIDGE SETTING UP ACROSS THE EASTERN
PACIFIC AT THE START OF THE PERIOD. BY SATURDAY...A PRONOUNCED
SHORTWAVE IS FORECAST TO DIG SOUTHWARD FROM THE GULF OF AK
CARRYING STRONG HEIGHT FALLS INTO THE STATE OF WA BY SATURDAY
EVENING. AS THE SYSTEM PROPAGATES SOUTH AND EAST...THE 00Z
CMC/UKMET ARE EAST OF THE MODEL CONSENSUS. ONE NOTABLE THING IS
RUN-TO-RUN CONTINUITY OF THE MODELS HAS NOT BEEN STELLAR WHICH
MAKES A BLEND OF THE ENSEMBLE MEANS A BIT MORE PLAUSIBLE HERE. FOR
INSTANCE...THE 00Z ECMWF JUST TRENDED WEST OF ITS ENSEMBLE MEAN.
WILL PLAN ON A BLEND OF THE 00Z GEFS/12Z ECMWF ENSEMBLE MEANS
UNTIL THE DETERMINISTIC MODELS SHOW BETTER CONTINUITY. WILL LOWER
THE CONFIDENCE ACCORDINGLY.


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

RUBIN-OSTER

$$




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