Prognostic Meteorological Discussion
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000
FXUS10 KWNH 301843
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 PM EDT SAT JUL 30 2016

VALID JUL 30/1200 UTC THRU AUG 03/0000 UTC

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

...AN EVALUATION OF THE 12Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...


...SLOW-MOVING LONGWAVE TROUGH TRACKING FROM THE MS RIVER VALLEY
TOWARD NEW ENGLAND...
...AREA OF LOW PRESSURE FORMING OFF SOUTHERN NEW ENGLAND LATE
MONDAY...

FINAL PREFERENCE: A NON-12Z NAM MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A BROAD LONGWAVE TROUGH CURRENTLY EXTENDING FROM THE CORN
BELTS/UPPER GREAT LAKES DOWN TOWARD THE OZARKS WILL GRADUALLY
SHIFT ITS FOCUS TOWARD THE NORTH AND EAST OVER TIME. MULTIPLE
IMPULSES EMBEDDED WITHIN THE LONGER WAVELENGTH PATTERN SHOULD BE
FOCI FOR ACTIVE CONVECTION. TOWARD THE END OF THE WEEKEND...THE
12Z NAM SEEMS TO BE MORE AMPLIFIED COMPARED TO THE STRONGER MODEL
CLUSTERING. ITS SOLUTION IS ALSO DEEPER AND QUICKER AT THE SURFACE
FAVORING A MODEST AREA OF CYCLOGENESIS WELL OFF THE NEW ENGLAND
COAST. GIVEN THE REMAINING GUIDANCE ARE GENERALLY WITHIN THE
ENSEMBLE SPREAD...A NON-12Z NAM MODEL COMPROMISE APPEARS
REASONABLE.


...STRONG BAND OF HEIGHT FALLS MOVING ACROSS WESTERN/CENTRAL
CANADA...

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

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWED A ROBUST
POSITIVELY-TILTED UPPER LOW SPINNING OVER BRITISH
COLUMBIA/ALBERTA. THIS UPPER TROUGH WILL CONTINUE TO ADVANCE
EASTWARD GENERALLY STRADDLING THE INTERNATIONAL BORDER WITH
CANADA. MODELS EXHIBIT DIFFERENCES WITH THE NORTH/SOUTH PLACEMENT
OF THIS UPPER LOW WITH THE 12Z ECMWF/00Z ECMWF ENSEMBLE MEAN NORTH
OF THE STRONGER CONSENSUS. HOWEVER...MORE OF THE ISSUES RESIDE
ALONG THAT INTERFACE OF THE UPPER RIDGE ACROSS THE
SOUTHERN/CENTRAL PLAINS AND THE NEGATIVE ANOMALY OVER CENTRAL
CANADA. THE GUIDANCE SEEM TO AGREE THAT TWO PRIMARY WAVES WILL
MOVE EASTWARD ON MONDAY MORNING WITH ONE FEATURE MOVING AWAY FROM
THE FRONT RANGE OF THE CENTRAL ROCKIES WHILE THE OTHER TRACKS
ACROSS SOUTHEASTERN SD. UNCERTAINTY IS HIGH IN THIS REGIME SO WILL
LEAN IN THE DIRECTION OF HIGHER RESOLUTION MODEL OUTPUT. NOT
COMPLETELY SOLD ON THE 12Z NAM AT THIS POINT SO WILL TAKE A BLEND
OF THE 12Z GFS/ECMWF.


...TRAILING CLOSED LOW BARRELING THROUGH THE PACIFIC NORTHWEST BY
TUESDAY MORNING...
...ASSOCIATED FRONTAL ZONE/NORTHERN ROCKIES SURFACE LOW...

FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AS THE INITIAL UPPER TROUGH EJECTS ACROSS
SASKATCHEWAN/MANITOBA...A TRAILING CLOSED LOW BEGINS TO APPROACH
THE PACIFIC NORTHWEST COAST BY 02/0000Z. THROUGH TUESDAY
MORNING...THE MODELS HAVE MADE SOME ADJUSTMENTS TO THEIR PREVIOUS
FORECASTS. MOST NOTABLY...THE 12Z ECMWF/UKMET HAVE TRENDED IN THE
SLOWER DIRECTION...ESPECIALLY THE 12Z UKMET. THIS NOW PLACES THE
00Z ECMWF ENSEMBLE MEAN ON THE FAR EAST SIDE OF THE SPREAD. WILL
ADJUST THE PREFERENCE TO ACCOUNT FOR THE MORE RECENT SOLUTIONS BY
FAVORING A BLEND OF THE 12Z GFS/ECMWF WHILE LOWERING THE
CONFIDENCE.


RUBIN-OSTER


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

$$





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