Prognostic Meteorological Discussion
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FXUS10 KWNH 041858
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EST WED MAR 04 2015

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

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

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF
AND GFS


...NORTHERN STREAM TROUGH DIGGING THROUGH THE MIDWEST/NORTHEAST...
...COLD FRONT SETTLING THROUGH THE EAST...
...SURFACE WAVE DEVELOPING ALONG THE FRONT AND IMPACTING THE
MID-ATLANTIC...

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

THE MODELS CONTINUE TO FORECAST A COLD FRONT ADVANCING
SOUTHEASTWARD OVER THE NEXT DAY OR SO DOWN THROUGH THE
MID-ATLANTIC AND SOUTHEAST AS ARCTIC HIGH PRESSURE NOSES SOUTH
DOWN THROUGH THE PLAINS AND MIDWEST. THE 12Z UKMET IS SLOWER THAN
THE GLOBAL MODEL CONSENSUS WITH THE FRONTAL PROGRESSION. THE 12Z
NAM AND 12Z GFS ARE GENERALLY A BIT FASTER TO DROP THE FRONT DOWN
TO THE SOUTH...AND BECOME MOST SUPPRESSED WITH THE FRONT. THE 12Z
GEM AND 12Z ECMWF ARE IN BETWEEN THE TWO CAMPS. MEANWHILE...A
SHORTWAVE TROUGH IS FORECAST TO BE DIGGING SOUTHEAST ACROSS THE
MIDWEST THROUGH THE PERIOD AND SHOULD CROSS THE OH VALLEY BY LATE
THURS AND THEN THE NORTHEAST THURS NIGHT. THE 12Z NAM IS THE
WEAKEST SOLUTION WITH THIS ENERGY...WITH THE REMAINING MODELS ALL
SLIGHTLY MORE AMPLIFIED. THE LATEST GEFS MEAN AND ECENS MEAN ARE
STRONGLY SUPPORTIVE OF THEIR RESPECTIVE DETERMINISTIC SOLUTIONS.
SO...BASED ON THIS WILL PREFER TO BLEND THE GFS AND ECMWF.


...CLOSED LOW/UPPER TROUGH REDEVELOPING OVER NORTHWEST MEXICO
THURS/FRI...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW ENERGY DIGGING BACK INTO PARTS OF THE FAR
SOUTHWEST U.S. AND THE BAJA PENINSULA BY THURS AND FRI. ASIDE FROM
THE 12Z UKMET...WHICH IS A BIT FARTHER WEST WITH THE CLOSED LOW ON
FRIDAY...THE DETERMINISTIC/ENSEMBLE GUIDANCE SHOWS GOOD AGREEMENT.
THEREFORE...A NON-UKMET CONSENSUS WILL BE PREFERRED.


...NORTHWEST FLOW IMPACTING THE NORTHERN TIER OF THE NATION FRI
AND SAT...
...EMBEDDED SHORTWAVE IMPULSES...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF...THROUGH 60 HOURS
            BLEND OF THE 12Z GEFS MEAN AND 00Z ECENS MEAN...AFTER
60 HOURS
CONFIDENCE: BELOW AVERAGE

THE MODELS ARE FORECASTING A SERIES OF SHORTWAVE IMPULSES THAT
WILL TRACK FROM THE GULF OF ALASKA TO TRACK INTO WESTERN CANADA
AND THEN SOUTHEAST IN A SHEARED FASHION DOWN ACROSS THE MIDWEST
AND INTO THE GREAT LAKES REGION THROUGH SAT. ALL OF THE MODELS
AGREE ON THE LARGER SCALE WITH DOMINANT NORTHERN STREAM FLOW...BUT
THERE ARE DIFFERENCES WITH RESPECT TO TIMING AND DEPTH OF
INDIVIDUAL SHORTWAVE IMPULSES. THE 12Z GFS AND 12Z ECMWF SHOW
REASONABLY GOOD AGREEMENT THROUGH ABOUT 60 HOURS WITH ENERGY THAT
DROPS SOUTHEAST ACROSS BRITISH COLUMBIA AND DOWN TOWARD THE
NORTHERN PLAINS. THE 12Z NAM IS A BIT STRONGER WITH THIS
ENERGY...WITH THE 12Z UKMET AND 12Z GEM A BIT FLATTER/SHEARED.
THEREAFTER...THE 12Z ECMWF SUGGESTS SOME SHORTWAVE AMPLIFICATION
OVER THE GREAT LAKES REGION WHICH IS SUPPORTED BY THE 00Z ECENS
MEAN AND 12Z GEM...HOWEVER...THE REMAINING MODELS ARE FLATTER
INCLUDING THE 12Z GEFS MEAN. WILL PREFER A BLEND OF THE 12Z GFS
AND 12Z ECMWF THROUGH 60 HOURS...AND LEAN TOWARD A CONSENSUS OF
THE ENSEMBLE MEANS THEREAFTER. CONFIDENCE IS LIMITED.


...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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