Prognostic Meteorological Discussion
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FXUS10 KWNH 190642
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 AM EST FRI DEC 19 2014

VALID DEC 19/0000 UTC THRU DEC 22/1200 UTC

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

00Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT TO IMPACT THEIR FORECASTS.


SPLIT FLOW ACROSS THE NORTHERN TIER AND SOUTHERN PLAINS TODAY
WEAK SURFACE LOW TRACKING ALONG THE NORTHERN GULF OF MX
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z UKMET BLEND
CONFIDENCE: A LITTLE ABOVE AVERAGE

THE MAJORITY OF MODEL TRENDS HAVE BEEN FLATTER WITH A 500 MB
SHORTWAVE TROUGH TO TRACK ACROSS THE SRN PLAINS TODAY...RESULTING
IN A SLIGHT SRN SHIFT REGARDING A WEAK SURFACE LOW ALONG THE CNTRL
GULF COAST BY SAT MORNING. THE 00Z NAM/GFS/ECWMF/CMC SHOW SIMILAR
TIMING AND PLACEMENT ALONG WITH THE LATEST SREF/GEFS/EC MEANS
REGARDING THE LOW-MID LEVEL SHORTWAVE AND CORRESPONDING SURFACE
LOW...WHILE THE 00Z UKMET REMAINS SLIGHTLY AHEAD OF THE REMAINING
MODEL CONSENSUS.


WEAKENING NRN STREAM SHORTWAVE ENTERING THE PAC NW TODAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

MODELS SHOW SIMILARLY WITH THIS SYSTEM.


SERIES OF PACIFIC SHORTWAVES MOVING TOWARD THE NORTHERN ROCKIES
EVENTUAL SURFACE CYCLONE CROSSING THE DAKOTAS BY SUNDAY EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF / 00Z GFS BLEND
CONFIDENCE: A LITTLE BELOW AVERAGE

THROUGH F060 HOURS...12Z/21...THE MODELS SHOW DECENT AGREEMENT
WITH SHORTWAVE ENERGY ENTERING THE PACIFIC NORTHWEST BUT
DIFFERENCES ARISE AS TROUGH AMPLIFICATION BEGINS ACROSS THE PLAINS
DOWNSTREAM OF AN ANOMALOUS EAST-PACIFIC RIDGE FOR THE 22ND OF
DECEMBER. THE ECMWF HAS BEEN QUITE CONSISTENT BUT HAS MADE A SMALL
CHANGE FROM ITS 12Z RUN AND IS CURRENTLY JUST SOUTH OF THE MIDDLE
OF THE LATEST ENSEMBLE SCATTER LOW PLOTS BY 12Z/22...AND JUST
SOUTH OF THE LATEST GEFS/EC MEANS. IN ADDITION...THE LOW LEVEL LOW
IN THE 00Z ECMWF WEAKENED FURTHER FROM ITS 12Z RUN WHICH APPEARS
TO BE A STEP IN THE WRONG DIRECTION BY 12Z/22. HOWEVER...THE 12Z
ECMWF WHEN BLENDED WITH THE 00Z GFS LEADS TO A BETTER COMPROMISE
IN STRENGTH. THE 00Z GFS IS THE NEXT CLOSEST MODEL TO THE MORE
PREFERRED 12Z ECMWF...BUT POSITION-WISE...COULD BE A BIT SOUTH
WITH THE DEVELOPING SURFACE LOW ACROSS THE MIDWEST TUE MORNING.
LARGE ENSEMBLE SPREAD AND A SENSITIVE FLOW REGIME ACROSS THE
PACIFIC LOWERS CONFIDENCE A LITTLE BELOW AVERAGE.


MID-UPPER LEVEL TROUGH REACHING THE SRN PLAINS SUN MORNING AND
WEAKENING EWD INTO THE APPALACHIANS BY MON MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

A GFS/ECWMF COMBO FITS BEST WITHIN THE MIDDLE OF THE LATEST MODEL
SPREAD AND FITS CLOSEST TO THE ENSEMBLE MEANS. RUN TO RUN
CONTINUITY HAS BEEN DECENT WITH THE GFS/ECMWF AND WORST WITH THE
CMC...ENDING WITH ITS 00Z/19 RUN. CURRENTLY...THE 00Z NAM IS
FASTER WITH THIS FEATURE WHILE THE UKMET REMAINS SLIGHTLY MORE
AMPLIFIED.


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

OTTO

$$




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