Prognostic Meteorological Discussion
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000
FXUS10 KWNH 290648
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 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 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/00Z 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 00Z GEFS MEAN. THE 00Z UKMET
WAS FLATTER WITH THE WAVE...AND SUBSEQUENTLY FASTER INTO THE
CAROLINAS. 00Z CMC WAS MUCH SLOWER AND DEEPER WITH THE CLOSED MID
LEVEL SYSTEM ON FRI...AND REMAINED SLOWER AND DEEPER THROUGH SAT.
BECAUSE OF THIS A BLEND OF THE 00Z GFS/00Z 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
(INCLUDING THE 00Z ECMWF) WITH THIS WAVE...AND WAS CLOSER TO THE
00Z GEFS/12Z ECMWF ENSEMBLE MEAN. THE 00Z UKMET/CMC WERE ALSO
QUICKER WITH SHORT WAVE AS IT CROSSES SOUTHEAST CANADA FRI.
BECAUSE THE 00Z 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/00Z 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 00Z GEFS MEAN)...BUT IT
SLOWS AND DEEPENS LATE IN THE PERIOD AS WELL. THE 00Z GFS IS CLOSE
TO THE 00Z 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/00Z ECMWF/00Z CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE 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 00Z GEFS MEAN). THE 00Z ECMWF IS CLOSE TO THE
CONSENSUS THROUGH SAT INTO EARLY SUN...AND IT SLOWED ITS APPROACH
ACROSS ID LATE IN THE PERIOD (LOOKING MORE LIKE THE 00Z GFS).

THE 00Z UKMET WAS SLOWER AND FLATTER WITH THE SHORT WAVE...WHILE
THE 00Z CMC WAS CLOSE TO THE 00Z GFS/00Z ECMWF CONSENSUS. BECAUSE
OF THIS...IT WAS ADDED TO THE PREFERENCE. THIS ALLOWED FORECAST
CONFIDENCE TO RISE TO SLIGHTLY ABOVE AVERAGE.


LONG WAVE TROUGH AFFECTING CENTRAL AND SOUTHERN CA SAT INTO EARLY
SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z GEFS MEAN/00Z UKMET
CONFIDENCE: BELOW AVERAGE

BOTH THE 00Z NAM AND 00Z GFS WERE MUCH MORE AMPLIFIED WITH THE
SHORT WAVE ENERGY THAT AMPLIFIES ALONG THE CA COAST SAT...WHICH
THEN CROSSES SOUTHERN CA BY THE END OF THE PERIOD. BY
CONTRAST...THE 00Z ECMWF/12Z ECMWF MEAN/00Z CMC WERE MUCH LESS
AMPLIFIED AND PROGRESSIVE WITH THE WAVE...KEEPING FLATTER OVER THE
GREAT BASIN. THE DEPTH OF THE AMPLIFICATION APPEARS TO BE TIED TO
THE SHORT WAVE CROSSING THE NORTHERN ROCKIES AT ROUGHLY THE SAME
TIME.

MOST OF THE ENSEMBLE MEMBERS OF THE 00Z GFS/12Z ECMWF SUPPORT
THEIR RESPECTIVE SOLUTIONS. AT THIS POINT...GIVEN THE SUPPORT (TO
SOME DEGREE) OF THE 00Z NAM...THE MORE AMPLIFIED SOLUTION WAS
PREFERRED. HOWEVER...GIVEN THE SPLIT IN THE GUIDANCE...FORECAST
CONFIDENCE WAS BELOW AVERAGE.


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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