Prognostic Meteorological Discussion
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FXUS10 KWNH 290445
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 AM EDT THU JUN 29 2017

VALID JUN 29/0000 UTC THRU JUL 02/1200 UTC

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

00Z NAM/GFS MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


WEAKENING MID LEVEL TROUGH OVER THE WESTERN GULF...WHICH LIFTS
ACROSS THE CENTRAL GULF COAST THU/FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z NAM IS FAIRLY CLOSE WITH THE MID LEVEL SYSTEM AS IT
CROSSES LA/MS THU...BUT IT BECOMES FLATTER AND FASTER WITH THE
SHORT WAVE AS IT CROSSES THE MID ATLANTIC STATES FRI. THE 00Z GFS
IS CLOSER TO THE CONSENSUS AND ITS 18Z GEFS MEAN. THE 12Z CMC IS A
BIT FASTER WITH THE WAVE ACROSS THE CAROLINAS FRI/SAT...AND A BIT
STRONGER. BECAUSE OF THIS A BLEND OF THE 00Z GFS/12Z ECMWF WAS
PREFERRED...BUT THE CONFIDENCE IS ONLY AVERAGE...DUE MAINLY TO
TIMING DIFFERENCES FRI INTO SAT.


SHORT WAVE/SURFACE LOW MOVES ACROSS THE UPPER GREAT LAKES
THU...THEN DISSIPATES ACROSS ONT/QUE FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 00Z NAM WAS STRONGER WITH THE SHORT WAVE AS IT CROSSES THE
UPPER GREAT LAKES THU...BEFORE WEAKENING AS IT CROSSES
ONTARIO/QUEBEC FRI. THE 00Z GFS WAS CLOSER TO THE CONSENSUS WITH
THIS WAVE...AND WAS CLOSER TO THE 18Z GEFS/12Z ECMWF ENSEMBLE
MEAN. THE 12Z UKMET/CMC WERE ALSO QUICKER WITH SHORT WAVE AS IT
CROSSES SOUTHEAST CANADA FRI. BECAUSE THE 12Z NAM IS STRONGER AND
FASTER WITH THE WAVE...IT WAS NOT INCLUDED IN THE PREFERENCE.


MID LEVEL LOW CROSSING THE NORTHERN PLAINS THU/FRI INTO GREAT
LAKES FRI/SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z NAM WAS SLOWER AND DEEPER WITH THE MID LEVEL SYSTEM AS IT
CROSSES THE NORTHERN PLAINS...AS ADDITIONAL SHORT WAVE ENERGY
DROPS INTO IT...SLOWING IT DOWN. BY CONTRAST...THE 00Z GFS IS
CLOSER TO THE CONSENSUS (AS WELL AS ITS 18Z GEFS MEAN)..BUT IT
SLOWS AND DEEPENS LATE IN THE PERIOD AS WELL. THE 00Z GFS IS CLOSE
TO THE 12Z ECMWF THROUGH MUCH OF THE EVOLUTION OF THE MID LEVEL
WAVE...SO THESE TWO MODELS WERE CHOSEN AS THE PREFERRED BLEND.
HOWEVER...DUE TO THE TIMING DIFFERENCES OF THE SHORT WAVE ENERGY
DROPPING INTO THE WESTERN PORTION OF THE MID LEVEL WAVE...FORECAST
CONFIDENCE IS ONLY AVERAGE.


SHORT WAVE REACHING THE PACIFIC NORTHWEST LATE FRI...MOVING INTO E
OR/SW ID SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE 00Z NAM WAS CLOSE TO THE CONSENSUS WITH THE SHORT WAVE FROM
THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES. THE 00Z GFS IS
CLOSE ACROSS THE PACIFIC COAST AS WELL...BUT SLOWS NOTICEABLY
ACROSS SOUTHEAST OR/SOUTHWEST ID BY THE END OF THE PERIOD (EVEN
SLOWER THAN THE 18Z GEFS MEAN). THE 12Z ECMWF IS CLOSE TO THE
CONSENSUS THROUGH SAT INTO EARLY SUN...AND IT IS CLOSER TO THE 12Z
ECMWF ENSEMBLE MEAN AS WELL. GIVEN THE TIMING DIFFERENCES...A
BLEND OF THE 00Z GFS/12Z ECMWF WAS PREFERRED...BUT THE UPSTREAM
TIMING DIFFERENCES RESULTED IN AVERAGE FORECAST CONFIDENCE.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

HAYES

$$




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