Prognostic Meteorological Discussion
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000
FXUS10 KWNH 241701
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT THU JUL 24 2014

VALID JUL 24/1200 UTC THRU JUL 28/0000 UTC

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

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...SHEARING UPPER LOW ACROSS SOUTHEASTERN LA...

PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS
FORECAST CONFIDENCE: HIGH

THE LATEST WATER VAPOR IMAGERY DEPICTED CONTINUAL WEAKENING OF AN
UPPER LOW SWIRLING IN THE VICINITY OF SOUTHEASTERN LA. GUIDANCE AS
A WHOLE SUGGEST THIS TREND WILL CONTINUE WHICH SUPPORTS A GENERAL
MODEL CONSENSUS WITH THIS SYSTEM.


...SURFACE LOW CROSSING THE NORTHERN PLAINS THIS EVENING...

PRELIMINARY PREFERENCE: A NON-00Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MID-LEVEL ENERGY SLIDING EASTWARD ABOVE A BROAD RIDGE SITTING
ACROSS THE FOUR CORNERS REGION/SOUTHERN PLAINS WILL ALLOW AN AREA
OF LOW PRESSURE TO DEVELOP OVER THE NORTHERN PLAINS LATER THIS
AFTERNOON/EVENING. THROUGH 25/1200Z...THE ENSEMBLE LOW SCATTER
PLOTS DID NOT SHOW MUCH SPREAD WITH DECENT AGREEMENT NOTED IN THE
PAST FEW MODEL CYCLES. THE SURFACE WAVE SHOULD GRADUALLY WEAKEN BY
FRIDAY EVENING AS THE MID-LEVEL IMPULSE CONTINUES RACING TOWARD
THE EAST. WITH THE EXCEPTION OF THE 00Z CMC...THE MODELS ARE
WITHIN TOLERANCE OF THE SCATTER DEPICTED BY THE AFOREMENTIONED
ENSEMBLE LOW PLOT. WILL RECOMMEND A NON-00Z CMC MODEL COMPROMISE
GIVEN THIS ASSESSMENT.


...STRONG CLOSED LOW MOVING FROM THE PACIFIC NORTHWEST TOWARD
SOUTHERN SASKATCHEWAN...

PRELIMINARY PREFERENCE: BLEND OF THE 00Z ECMWF WITH THE 06Z
GEFS/00Z ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

ANOMALOUS UPPER LOW LIFTING OUT OF THE PACIFIC NORTHWEST TOWARD
SOUTHERN ALBERTA WILL MAINTAIN VERY LOW HEIGHTS FOR LATE JULY WITH
THE GUIDANCE SUGGESTING 500-MB HEIGHT DEPARTURES IN EXCESS OF 2
STANDARDIZED ANOMALIES. AS THE CLOSED SYSTEM MOVES ACROSS SOUTHERN
SASKATCHEWAN ON FRIDAY...THE FORWARD MOTION SHOULD BRIEFLY HALT
WHICH IS INDICATED BY ALL OF THE AVAILABLE GUIDANCE. SOME
UNCERTAINTY IS NOTED THEREAFTER WITH HOW QUICKLY THE SYSTEM OPENS
UP AND ACCELERATES DOWN TOWARD THE UPPER MIDWEST/GREAT LAKES. THE
09Z SREF MEAN IS DEFINITELY THE QUICKEST AMONG THE
DETERMINISTIC/ENSEMBLE GUIDANCE AND STRAYS FROM THE BETTER
CLUSTERING IN SPAGHETTI PLOTS. THE 06Z GEFS/00Z ECMWF ENSEMBLE
MEANS ARE IN STABLE AGREEMENT WITH SUPPORT FROM THE 00Z ECMWF.
MEANWHILE...THE 12Z GFS IS MUCH QUICKER THAN ITS MEAN SO DO NOT
FEEL COMPELLED TO INCLUDE IT IN THE PREFERENCE. WILL FAVOR A BLEND
OF THE 00Z ECMWF WITH THE ENSEMBLE MEANS TO ACCOUNT FOR THE
GROWING SPREAD.


...MEAN UPPER TROF ANCHORING THE NORTHEASTERN SECTOR OF NORTH
AMERICA...

PRELIMINARY PREFERENCE: A NON-00Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

A MEAN TROF WILL MAINTAIN A POSITION ACROSS THE EASTERN THIRD OF
THE COUNTRY FOR MUCH OF THE PERIOD WITH THE SYNOPTIC PATTERN BEING
REINFORCED BY THE WEEKEND AS THE UPPER TROF DIGS THROUGH THE UPPER
GREAT LAKES. THE MODELS ARE IN CLOSE AGREEMENT AS ONE BATCH OF
ENERGY SLIDES OFFSHORE WITH ADDITIONAL SHORTWAVES SPILLING IN
UPSTREAM. THE PREVIOUSLY MENTIONED IMPULSE TRACKING FROM THE
NORTHERN TIER INTO THE MIDDLE MS VALLEY/UPPER GREAT LAKES
EVENTUALLY HAS IMPACTS ON THE POSITION OF THE UPPER TROF. GIVEN
THE 00Z CMC DISAGREED WITH THE CONSENSUS IN THAT CASE...WILL NOT
INCLUDE IT IN THE PREFERENCE FOR THIS SYSTEM EITHER.


...SHORTWAVE APPROACHING NORTHERN CA BY 28/0000Z...

PRELIMINARY PREFERENCE: BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: AVERAGE

TOWARD THE END OF THE PERIOD...A SHORTWAVE IS EXPECTED TO REACH
THE NORTHERN CA COAST. THE GUIDANCE AGREE WITH THE IDEA OF THIS
FEATURE BUT VARY WITH PLACEMENT. WILL UTILIZE THE ENSEMBLE MEANS
GIVEN SUCH VARIABILITY.


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

RUBIN-OSTER

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