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FXUS10 KWNH 241833
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
232 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 CMC/UKMET/ECMWF ALONG WITH FINAL
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...

FINAL 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...

FINAL PREFERENCE: A NON-12Z/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 12Z/00Z CMC...THE MODELS ARE
WITHIN TOLERANCE OF THE SCATTER DEPICTED BY THE AFOREMENTIONED
ENSEMBLE LOW PLOT. WILL RECOMMEND A NON-12Z/00Z CMC MODEL
COMPROMISE GIVEN THIS ASSESSMENT.


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

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/GEFS MEAN
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

AN 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 12Z GEFS MEAN HAS TRENDED A BIT
FASTER BUT SEEMS TO MATCH THE SHIFT EASTWARD NOTED IN THE LATEST
12Z ECMWF. FROM THE PREVIOUS ISSUANCE...THE 12Z GFS WAS NOTED TO
BE TOO QUICK WHICH CONTINUES TO BE THE CASE AFTER EVALUATING THE
LATEST GUIDANCE. WILL GO AHEAD AND FAVOR THIS TREND AND REMOVE THE
00Z ECMWF ENSEMBLE MEAN AS IT NOW APPEARS TOO SLOW. THE SUGGESTED
BLEND IS A MIX OF THE 12Z ECMWF/GEFS MEAN.


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

FINAL PREFERENCE: A NON-12Z/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 12Z/00Z CMC DISAGREED WITH THE CONSENSUS IN THAT CASE...WILL
NOT INCLUDE THEM IN THE PREFERENCE FOR THIS SYSTEM EITHER.


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

FINAL PREFERENCE: BLEND OF THE 12Z 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. ADDITIONALLY...RUN-TO-RUN
CONTINUITY HAS NOT BEEN GREAT OVERALL. WITH THIS BEING THE
CASE...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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