Prognostic Meteorological Discussion
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000
FXUS10 KWNH 230651
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 AM EDT SUN JUL 23 2017

VALID JUL 23/0000 UTC THRU JUL 26/1200 UTC

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

00Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


...SYSTEM APPROACHING THE PACIFIC NORTHWEST LATE TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 00Z CMC ADJUSTED CLOSER TO THE REMAINING AGREEABLE
DETERMINISTIC MODELS WITH A MID-LEVEL CLOSED LOW TRACKING EASTWARD
INTO BRITISH COLUMBIA ON MONDAY INTO TUESDAY. ONLY MINOR
DIFFERENCES REMAIN IN THE LATEST SUITE OF DETERMINISTIC GUIDANCE.
ENSEMBLE SPREAD HAS DRAMATICALLY SHRUNK COMPARED TO YESTERDAY AND
AGREES WITH THE 00Z BLEND OF GUIDANCE.


...SYSTEM MOVING THROUGH SOUTH-CENTRAL CANADA MONDAY/TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 00Z UKMET TRENDED A LITTLE SLOWER COMPARED TO ITS 12Z RUN
REGARDING THE MID-LEVEL SHORTWAVE AND ASSOCIATED COLD FRONT
TRACKING EAST ACROSS SOUTHERN CANADA EARLY THIS WEEK HOWEVER THE
UKMET REMAINS ON THE FASTER SIDE OF THE MODELS WITH THIS SYSTEM
THROUGH WED. BETTER DETERMINISTIC/ENSEMBLE SUPPORT EXISTS FOR A
NON 00Z UKMET BLEND WITH THIS SYSTEM. ENSEMBLE TRENDS HAVE ALSO
BEEN SLOWER SINCE YESTERDAY.


...UPPER LOW NEAR CALIFORNIA SUNDAY-TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ONLY MINOR DIFFERENCES EXIST WITH THIS SYSTEM SO A GENERAL MODEL
BLEND IS PREFERRED TO SMOOTH OUT SMALLER SCALE DIFFERENCES.


...SHORTWAVE MOVING ACROSS THE GREAT LAKES SUN/NORTHEAST MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/00Z NAM BLEND
CONFIDENCE: AVERAGE

THE 00Z GFS SURFACE LOW DEPICTION TO MOVE OFF OF THE MID-ATLANTIC
COAST MONDAY IS WEAKER THAN THE REMAINING DETERMINISTIC CONSENSUS
AND DISPLACED TO THE SOUTH. THE ENSEMBLE SCATTER LOW PLOTS HAVE
SHOWN GROWING AGREEMENT WITH EACH CYCLE AND CURRENTLY RESIDE
CLOSEST TO THE 00Z NAM AND 00Z ECMWF. WHILE THE 00Z UKMET/CMC HAVE
SHOWN SOME ADJUSTMENT TOWARD THE 00Z NAM/ECMWF IDEA AT VARIOUS
FORECAST HOURS...THE 00Z ECMWF/NAM ARE CLOSEST TO THE BETTER
ENSEMBLE CLUSTERING AT ALL TIMES. THIS SURFACE LOW IS LIKELY THE
BIGGEST DIFFERENCE NOTED WITH THE MASS FIELDS OF THIS SYSTEM.


www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

OTTO

$$




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