Prognostic Meteorological Discussion
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FXUS10 KWNH 041615
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1214 PM EDT FRI SEP 04 2015

VALID SEP 04/1200 UTC THRU SEP 08/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...SHORTWAVE CURRENTLY LIFTING THROUGH THE NORTHERN PLAINS...
...REACHING WESTERN ONTARIO ON SAT...

PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 24 HOURS
            NON-GFS CONSENSUS...AFTER 24 HOURS
CONFIDENCE: ABOVE AVERAGE

THERE IS MINIMAL MASS FIELD SPREAD OVER THE NEXT 24 HOURS WITH THE
CURRENT SHORTWAVE LIFTING NORTH-NORTHEAST THROUGH THE NORTHERN
PLAINS. HOWEVER..AS THE ENERGY REACHES CANADA AND MOVES INTO
WESTERN ONTARIO...THE 12Z GFS BECOMES A BIT OF A WEAKER
OUTLIER...WHICH ALSO TRANSLATES INTO A WEAKER SURFACE LOW
REFLECTION. THE 12Z NAM AND 00Z NON-NCEP MODELS ALL FAVOR A
RELATIVELY STRONGER AND MORE COMPACT SHORTWAVE/SURFACE LOW
EVOLUTION. A GENERAL MODEL COMPROMISE SEEMS REASONABLE THROUGH 24
HOURS...WITH A NON-GFS CONSENSUS THEREAFTER.


...SHORTWAVE EJECTING NORTHEAST FROM THE FOUR CORNERS...
...REACHING THE NORTHERN PLAINS ON SAT...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

A SHORTWAVE LIFTING NORTHEAST ACROSS THE FOUR CORNERS REGION THIS
MORNING WILL EJECT OUT INTO THE HIGH PLAINS EARLY SAT AND THEN
LIFT ACROSS THE NORTHERN PLAINS AND UPPER MS VALLEY. THE 12Z NAM
IS A MORE PROGRESSIVE AND SHARPER OUTLIER SOLUTION WITH THIS AS IT
CROSSES THE NORTHERN PLAINS AND UPPER MS VALLEY. WILL PREFER A
NON-NAM CONSENSUS.


...COMPACT MID-LEVEL LOW OVER MI...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE LATEST MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM GRADUALLY
DAMPENING OUT THIS WEEKEND OVER MI WITH SOME WEAK REMNANT ENERGY
OF IT ADVANCING DOWNSTREAM INTO SOUTHEAST ONTARIO AND SOUTHERN
QUEBEC. A GENERAL MODEL COMPROMISE WILL BE PREFERRED TO RESOLVE
ANY SMALLER SCALE DIFFERENCES.


...DEEP CYCLONE MOVING INTO SOUTH-CENTRAL CANADA...
...LINGERING TROUGHING ACROSS THE NORTHERN ROCKIES/NORTHWEST...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THERE IS REASONABLY STRONG AGREEMENT AMONG THE MODELS WITH THE
EVOLUTION OF THE DEEP TROUGH/CLOSED LOW THROUGH THE NORTHWEST AND
OUT ACROSS THE NORTHERN PLAINS AND INTO SOUTHERN CANADA THROUGH
THE WEEKEND AND INTO EARLY NEXT WEEK. THE MODELS AGREE IN ALLOWING
SOME SECONDARY SHORTWAVE ENERGY/TROUGHING TO DIG IN BEHIND THE
MAIN BATCH OF HEIGHT FALLS...BUT THE 12Z NAM APPEARS A LITTLE TOO
SHARP WITH THIS...AND THE 00Z UKMET IS A BIT TOO PROGRESSIVE. THE
STRONGER MODEL CLUSTERING TENDS TO RESIDE WITH THE 12Z GFS AND 00Z
ECMWF AND IS REASONABLY WELL SUPPORTED BY THE 00Z CMC...SO A BLEND
OF THE GFS AND ECMWF WILL BE PREFERRED.


...UPPER LOW RETROGRADING INTO THE SOUTHEAST...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THE MODELS AGREE IN RETROGRADING A BROAD UPPER LOW INTO THE
SOUTHEAST SUN AND MON WHILE ALSO BECOMING EXTENDED SOUTH INTO THE
GULF OF MEXICO. THE 12Z NAM APPEARS SLIGHTLY STRONGER THAN THE
GLOBAL MODELS WITH THE OVERALL TROUGH DETAILS AND ALSO IS A BIT
MORE DEVELOPED WITH AN AREA OF LOW PRESSURE OFF THE SOUTHEAST
COAST VERSUS THE MORE STRONGLY CLUSTERED AND SLIGHTLY WEAKER 12Z
GFS AND 00Z ECMWF. THE 00Z CMC ALSO SUGGESTS A SOMEWHAT STRONGER
SURFACE WAVE DEVELOPING OFF THE SOUTHEAST COAST. WILL PREFER THE
WEAKER CONSENSUS AS PER A BLEND OF THE GFS AND ECMWF.


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

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

ORRISON

$$




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