Prognostic Meteorological Discussion
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000
FXUS10 KWNH 191858
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT FRI SEP 19 2014

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

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

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...REMNANTS OF ODILE...

PREFERENCE: BLEND OF 12Z NAM/GFS/ECMWF/UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE LOWER TO MIDDLE LEVEL REMNANTS OF PACIFIC TROPICAL CYCLONE
ODILE...DEFINED AS EITHER A SMALL CIRCULATION OR SHEAR AXIS...ARE
FORECAST TO STALL OVER EASTERN NM AND WEST TX...TRAPPED WITHIN A
BUILDING UPPER LEVEL RIDGE. THE CANADIAN CONTINUES AS THE MOST
NOTABLE OUTLIER...ESPECIALLY WITH RESPECT TO QPF PLACEMENT.


...CLOSED LOW INITIALLY OVER CALIFORNIA...

PREFERENCE: ANY OF THE 12Z OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

FEW MODEL DIFFERENCES EXIST HERE. THE 00Z UKMET WAS SLIGHTLY
FASTER THAN CONSENSUS IN EJECTING THIS SYSTEM TOWARD THE NORTHERN
HIGH PLAINS ON MONDAY. THE 12Z RUN MOVED TOWARD CONSENSUS.


...UPPER TROUGH DIGGING INTO THE EASTERN U.S THIS WEEKEND...
...SURFACE LOW DEVELOPING OFF THE SOUTHEAST U.S. COAST SATURDAY...

PREFERENCE: BLEND OF 12Z GFS/ECMWF
CONFIDENCE: AVERAGE

THE ONLY STRONG OUTLIER HERE IS THE CANADIAN...WHICH BRINGS
COASTAL LOW PRESSURE ONSHORE DURING PARTS OF ITS JOURNEY FROM THE
CAROLINAS TOWARD NEW ENGLAND. THE CONSENSUS OVER MULTIPLE MODEL
CYCLES IS FOR A POSITION FARTHER OFFSHORE AND REMAINING OFFSHORE
WHILE BEING ABSORBED BY SYNOPTIC LOW PRESSURE OVER NEW ENGLAND.
RECENT GFS AND GEFS FORECASTS...AS WELL AS THE UKMET...HAVE
SUPPORTED THESE IDEAS. THE 00Z ECMWF WAS SIMILAR...ALTHOUGH IT
LOST ANY SENSE OF THE COASTAL LOW BEYOND SUNDAY MORNING. THE 12Z
ECMWF TRENDED TOWARD THE GFS AT THE SURFACE. JUDGING BY RECENT
ENSEMBLE SPREAD...THE ECMWF MAY BE A BIT STRONG WITH THE ENERGY IN
THE BASE OF THE UPPER TROUGH OVER THE MID ATLANTIC BY MONDAY...BUT
THE UKMET WAS EVEN DEEPER. THE GFS...ON THE OTHER HAND...IS
SLIGHTLY WEAK AND MORE PROGRESSIVE. THE NAM FAVORS THE ECMWF
ALOFT...BUT WAS SLOWER WITH THE COASTAL LOW - THIS KEPT THE NAM
OUT OF OUR PREFERENCE. HERE WE COULD DEFAULT TO RECOMMENDING THE
GEFS AND ECMWF ENSEMBLE MEANS...BUT A SIMPLE BLEND OF THE
OPERATIONAL GFS/ECMWF SHOULD ALSO PRODUCE A SOLUTION
REPRESENTATIVE OF THE ENSEMBLE CONSENSUS.


...DEEP TROUGH LEANING INTO THE PACIFIC NORTHWEST...

PREFERENCE: ANY OF 12Z NAM/GFS/ECMWF/UKMET
CONFIDENCE: ABOVE AVERAGE

A DEEP LONGWAVE TROUGH OFFSHORE SHOULD HAVE LITTLE IMPACT THROUGH
SUNDAY NIGHT/MONDAY MORNING...BUT MODELS DO BRUSH THE PACIFIC NW
COAST WITH LOW PRESSURE ASSOCIATED WITH A LEAD SHORTWAVE THIS
WEEKEND. MOST OF THE 12Z MODELS WERE CONSISTENT WITH A RECENT
TREND TOWARD GREATER AMPLIFICATION WITHIN THE BASE OF THE TROUGH
OFFSHORE...AND BETTER DEFINITION OF THE LEAD SHORTWAVE AND
ASSOCIATED WEAK HEIGHT FALLS OVER THE PACIFIC NORTHWEST. WHEN
CONSIDERING SHORTWAVES EMBEDDED IN THE LARGER TROUGH...THE
CANADIAN MOVED OUT OF PHASE WITH THE OTHER MODELS BY THE END OF
THE SHORT RANGE PERIOD...MONDAY.

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

BURKE
$$




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