Prognostic Meteorological Discussion
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FXUS10 KWNH 251841
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 PM EDT FRI JUL 25 2014

VALID JUL 25/1200 UTC THRU JUL 29/0000 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.


...SURFACE LOW TRACKING FROM THE NORTHERN/CENTRAL PLAINS TO THE
MIDDLE MS VALLEY THROUGH 26/1200Z...

FINAL PREFERENCE: 12Z NAM/GFS
FORECAST CONFIDENCE: AVERAGE

THIS SURFACE FEATURE IS ASSOCIATED WITH A BAROCLINIC ZONE
ATTEMPTING TO REDEVELOP EASTWARD AHEAD OF THE INCREASING MID LEVEL
WESTERLY FLOW ARRIVING FROM THE NORTHERN PLAINS AND PRAIRIE
PROVINCES. THE NAM AND GFS BOTH TRENDED FASTER IN MOVING THE UPPER
LOW ALONG THE BORDER WITH CANADA IN THE NEAR TERM. GIVEN HEALTHY
SUPPORT FROM 00Z GEFS MEMBERS AND PLACEMENT OF THE SYSTEM WITHIN
THE UPPER AIR NETWORK...THIS TREND WILL LIKELY STICK. THE 12Z
NAM/GFS/UKMET SHOW FAIR AGREEMENT IN THE PRECIPITATION
FIELD...WITH CONVECTIVE PRECIPITATION SWATHS EXPECTED IN THE 700
WARM ADVECTION PEAK OVER MI...850 MB PEAK OVER IL/IN...AND A NEW
SWATH GENERATING BENEATH A SHARP MID LEVEL SHORTWAVE OVER SD BY
SATURDAY MORNING. THE MORE GENEROUS UKMET OUTPUT MAY BE PREFERRED
OVER MI. THESE MODELS ALSO AGREE CLOSELY AT THE SURFACE.


...ANOMALOUS CLOSED LOW DROPPING FROM SOUTHERN SASKATCHEWAN INTO
THE UPPER GREAT LAKES...
...WELL-DEFINED COLD FRONT...

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

AS MENTIONED ABOVE...THERE IS A TREND TOWARD QUICKER PROGRESSION
OF THIS LOW IN THE 12Z NCEP GUIDANCE. THE 12Z/00Z UKMET...ALTHOUGH
SLOWER ALOFT...SHOWS RELATIVE AGREEMENT WITH THE NAM/GFS AT THE
SURFACE AND IN THEIR PRECIPITATION OUTPUT. MOVING INTO DAY 2...THE
MODEL SPREAD CONTINUES TO BUILD WITH THE 12Z NAM/GFS AND 12Z
GEFS/09Z SREF MEANS BEING MORE PROGRESSIVE THAN THE NON-NCEP
GUIDANCE. THE TIMING OF THE STRONG MID/UPPER WINDS WITH THE
PASSAGE OF THIS ROBUST SHORTWAVE WILL BE CRITICAL TO THE FORECAST
GIVEN THE HIGHER END IMPACTS OF HEAVY RAINFALL AND SEVERE WEATHER
POSSIBLE. THE DIFFERENCES BETWEEN THE TWO CAMPS HAS DIMINISHED A
BIT AFTER EVALUATING ALL OF THE AVAILABLE 12Z GUIDANCE. THE 12Z
ECMWF HAS DEFINITELY SPED UP LEAVING THE 00Z ECMWF ENSEMBLE MEAN
AS THE SLOWEST PIECE OF GUIDANCE. WILL STICK WITH THE PREVIOUS
PREFERENCE WHILE UTILIZING THE 12Z VERSION OF EACH.
CONFIDENCE WILL BE RAISED SLIGHTLY GIVEN THE MODEL DIFFERENCES
HAVE DIMINISHED.


...MEAN TROF ANCHORING NORTHEASTERN NORTH AMERICA...

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

A VERY ANOMALOUS HEIGHT PATTERN EVOLVES ACROSS MUCH OF THE EASTERN
THIRD OF THE COUNTRY WITH MODELS INDICATING 500-MB HEIGHTS MAY BE
AT LEAST 3 STANDARD DEVIATIONS BELOW CLIMATOLOGY FOR LATE JULY.
WHILE ALL GUIDANCE INDICATE THE PRESENCE OF THIS LONGWAVE
TROF...THEY DO VARY WITH THE DETAILS. MUCH OF THESE DIFFERENCES
ARE A RESULT OF THE TIMING OF THE AFOREMENTIONED SHORTWAVE DIGGING
THROUGH THE UPPER GREAT LAKES ON SATURDAY/SUNDAY. WILL MAINTAIN
THE SAME PREFERENCE AS THE PREVIOUS SECTION. GIVEN THE MODELS
AGREE ON THE SYNOPTIC PATTERN HERE...FEEL COMFORTABLE KEEPING THE
CONFIDENCE AT AVERAGE.


...SHORTWAVE APPROACHING NORTHERN CA BY SUNDAY...

FINAL PREFERENCE: 12Z NAM/UKMET/ECMWF
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ALONG THE WESTERN PERIPHERY OF AN EXPANSIVE MID/UPPER LEVEL RIDGE
ACROSS THE FOUR CORNERS/SOUTHERN PLAINS...A SHORTWAVE IS EXPECTED
TO APPROACH THE NORTHERN CA COAST EARLY SUNDAY. OVERALL...THE 12Z
NAM/ECMWF/UKMET FOLLOW THE WELL CLUSTERED ENSEMBLE MEANS MOST
CLOSELY. WITH THAT BEING THE CASE...ANY FORM OF COMBINATION OF THE
12Z NAM/ECMWF/UKMET SHOULD SUFFICE.


...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/BURKE

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