Prognostic Meteorological Discussion
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000
FXUS10 KWNH 010705
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 AM EDT SUN MAY 01 2016

VALID MAY 01/0000 UTC THRU MAY 04/1200 UTC

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

==============================================
00Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...FRONTAL ZONE AND SHORTWAVES EJECTING FROM THE SOUTHWEST AND
PLAINS TOWARD THE EAST COAST...
...NORTHERN STREAM SHORTWAVE SETTLING INTO THE MEAN LONGWAVE
TROUGH BASE OVER THE PLAINS/SOUTHEAST...

PREFERENCE: 00Z ECMWF
CONFIDENCE: BELOW AVERAGE

THOUGH THERE ARE A NUMBER OF SHORTWAVES...THE FLOW OVER THE
CENTRAL AND EASTERN U.S. IS MORE BROADLY CHARACTERIZED BY A STORM
TRACK TAKING IMPULSES OUT OF THE SOUTHWEST AND THE PLAINS TOWARD
THE EAST COAST. A MEAN LONGWAVE TROUGH AXIS REMAINS ESTABLISHED
OVER THE CENTRAL U.S. THROUGH DAY 3...AS NORTHERN AND SOUTHERN
STREAM WAVES CONVERGE DOWNSTREAM OF A NORTHERN ROCKIES RIDGE. THE
FIRST NOTEWORTHY SHORTWAVE AND SURFACE LOW REFLECTION ARE HANDLED
SIMILARLY BY MOST OF THE MODELS...TRACKING TOWARD THE MID ATLANTIC
BY MONDAY AND THEN TOWARD THE COAST OF NEW ENGLAND MONDAY NIGHT.
THE GFS/ECMWF/UKMET COULD BE USED WITH CONFIDENCE. THE NAM WAS
DECENT IN THE UPPER LEVELS...BUT ITS SURFACE LOW TRACK IS SOUTH OF
THE RATHER STEADY MODEL CONSENSUS. THE CANADIAN ALSO LAGS BEHIND
THAT CONSENSUS ON DAY 3.

BACK FARTHER WEST...THE MODEL TRENDS AND SPREAD PRESENT SOME
CHALLENGES. IF VIEWED AT FACE VALUE...THE 00Z OPERATIONAL MODELS
CLUSTER AROUND A UKMET/CANADIAN SOLUTION...WITH A 04/12Z TROUGH
AXIS INTO GEORGIA AND NO TRAILING SHORTWAVE OVER THE LOWER
MISSISSIPPI VALLEY. FOR THE UKMET THIS WAS A REMARKABLE
CHANGE...AS THE 12Z RUN HAD SUPPORTED THE ECMWF AND PREVIOUS
THINKING WHICH HELD ONTO ENERGY RELATED TO A SMALL BUT PRONOUNCED
SHORTWAVE THAT WILL DROP OUT OF CANADA MONDAY MORNING AND MAY DIG
INTO THE LOWER MISSISSIPPI VALLEY LATE TUESDAY. THE GFS HAS BEEN
CONTINUALLY UNDERPLAYING THIS FEATURE...AS SPAGHETTI PLOTS REVEAL
THE GFS TO BE AT ONE EXTREME. UNFORTUNATELY...THE RUN TO RUN
CHANGES IN THE OTHER MODELS ALSO FAIL TO INSPIRE CONFIDENCE.
GENERALLY...IN A STREAM PHASING SITUATION...AS THIS
IS...DOWNSTREAM OF THE NORTHERN ROCKIES RIDGE...THE ECMWF TENDS TO
DO A BETTER JOB OF MAINTAINING THE IDENTITY OF INDIVIDUAL
FEATURES...WHEREAS THE GFS IS SO QUICK TO PHASE THE STREAMS. THE
GEFS IS SOMEWHAT SUPPORTIVE OF THE ECMWF...OR AT LEAST IS
SUPPORTIVE OF THE ECMWF ENSEMBLE MEAN...HOLDING MORE ENERGY BACK
ACROSS THE SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY DAY 3. FOR
THESE REASONS...WE WILL CONTINUE TO HEDGE TOWARD THE ECMWF...WHILE
NOTING THAT THE 00Z ECMWF DID SHARE THE OVERALL MODEL TREND OF
GETTING THE LEADING TROUGH AXIS CLOSER TO GEORGIA BY THE END OF
THE SHORT RANGE. THEREFORE...OUR CHOICE OF THE ECMWF DOES
PARTIALLY EMBRACE THE TRENDS...WHILE HEDGING TOWARD THE SYNOPTIC
PATTERN AND CONTINUITY FROM PREVIOUS CYCLES.


...DEEP UPPER TROUGH APPROACHING THE WEST COAST ON TUES...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

THE MODELS AGREE IN DEVELOPING A FULL-LATITUDE TROUGH OVER THE
EASTERN PACIFIC OCEAN...AND THIS WILL APPROACH THE WEST COAST ON
TUESDAY. THE GUIDANCE IS IN RELATIVELY GOOD AGREEMENT AND HAS
SHOWN SOME STABILITY FROM RUN TO RUN. THE MAIN ODDITY WAS THE 12Z
UKMET WHICH DEPICTED A SHARP SHORTWAVE TROUGH AT THE BASE OF THE
LARGER SCALE TROUGH BY LATE TUESDAY. THE 00Z BACKED OFF OF THIS
IDEA ENOUGH THAT THE UKMET COULD BE LUMPED WITH THE OTHER
MODELS...FORMING A STRONG CONSENSUS.


...DEEP GREAT LAKES TROUGH DEVELOPING MON/TUE...

PREFERENCE: BLEND OF 00Z NAM/ECMWF/UKMET
CONFIDENCE: ABOVE AVERAGE

THE PATTERN TRENDS TOWARD A DEVELOPING OMEGA BLOCK THAT SPANS THE
ENTIRE U.S. BY DAY 3 INTO THE MEDIUM RANGE PERIOD. THIS WILL
INCLUDE A CLOSED LOW DIGGING IN AND FEEDING INTO THE BROAD MEAN
WEAKNESS/TROUGH OVER THE GREAT LAKES AND EASTERN U.S. TUESDAY.
MODELS ARE PRETTY AGREEABLE ON THE LARGE SCALE...THOUGH THE 00Z
GFS WAS A BIT QUICK....AND THE 00Z CANADIAN DEPICTED THE SURFACE
LOW DISPLACED SOUTH AND WEST OF CONSENSUS. THE 00Z NAM/ECMWF/UKMET
ARE BEST SUPPORTED...ESPECIALLY AT SURFACE...BY THE ENSEMBLE
SURFACE LOW PLOTS SEEN OVER MULTIPLE MODEL CYCLES. THE 00Z GFS
TRENDED TOWARD THE CONSENSUS...AND COULD NEARLY BE INCLUDED IN OUR
PREFERENCE.

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

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

BURKE
$$




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