Prognostic Meteorological Discussion
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FXUS10 KWNH 280501
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
101 AM EDT TUE MAR 28 2017

VALID MAR 28/0000 UTC THRU MAR 31/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...NORTHERN STREAM TROUGH CROSSING THE UPPER MIDWEST THROUGH MON...
...ENERGY CROSSING SOUTHEAST CANADA THROUGH TUES/WED...
...UPPER TROUGH OVER THE CNTRL PLAINS WEAKENING INTO THE OH
VALLEY/NORTHEAST MON NIGHT/TUES...
...POSSIBLE SHORTWAVE PHASING OVER NEW ENGLAND BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 36 HOURS
            BLEND OF THE 00Z GFS AND 12Z ECMWF...AFTER 36 HOURS
CONFIDENCE: ABOVE AVERAGE...BECOMING AVERAGE BEYOND 36 HOURS

A NORTHERN STREAM TROUGH CROSSING THE UPPER MIDWEST AND SOUTHERN
CANADA WILL AMPLIFY DOWNSTREAM ACROSS SOUTHEAST CANADA TUES AND
WED. MEANWHILE...A WEAKENING SOUTHERN STREAM TROUGH CROSSING THE
OH/TN VALLEYS WILL CONTINUE TO DAMPEN OUT AS IT MOVES
EAST-NORTHEAST INTO THE MID-ATLANTIC REGION ON TUES AND THEN
OFFSHORE. THIS WILL ALLOW SURFACE LOW PRESSURE TO ALSO CROSS THE
REGION. THE NORTHERN STREAM ENERGY BY TUES AND WED WILL BECOME
DOMINANT AND THERE IS EXPECTED TO BE A DEEP LAYER LOW CENTER
EVOLVING NEAR NOVA SCOTIA BY EARLY THURS. THIS ENERGY WILL ALSO
CAPTURE THE LOW PRESSURE CENTER ASSOCIATED WITH THE WEAKENING
SOUTHERN STREAM ENERGY AND THEN DEEPEN INTO A VERY STRONG LOW
CENTER SOUTHEAST OF CANADIAN MARITIMES ON THURS.

THE MODELS ARE IN GOOD AGREEMENT THROUGH 36 HOURS...BUT THEREAFTER
THE 12Z CMC BECOMES MORE PROGRESSIVE WITH THE LOW CENTER AND
EVENTUALLY THE 12Z UKMET TENDS TO BECOME MORE PROGRESSIVE AND DEEP
AS THE LOW LIFTS JUST SOUTHEAST OF NEWFOUNDLAND ON THURS. THE 00Z
GFS AND 12Z ECMWF TEND TO BE MUCH BETTER CLUSTERED WITH TIMING AS
THE SYSTEM MOVES OFFSHORE...BUT EVENTUALLY THE ECMWF BECOMES
PERHAPS A LITTLE TOO DEEP. AFTER A GENERAL MODEL COMPROMISE
THROUGH 36 HOURS...A BLEND OF THE 00Z GFS AND 12Z ECMWF WILL BE
PREFERRED.


...WEAK TROUGH OVER THE NORTHERN PLAINS/UPPER MIDWEST TUES/WED...
...STRONG CLOSED LOW EVOLUTION INTO THE SOUTHWEST ON TUES...
...EJECTING EAST ACROSS THE CENTRAL/SOUTHERN PLAINS WED...
...LIFTING THROUGH THE MID MS/TN/OH VALLEYS BY LATE THURS/FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET...THROUGH 60 HOURS
            BLEND OF THE 12Z UKMET/12Z ECMWF...AFTER 60 HOURS
CONFIDENCE: AVERAGE

THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE DEVELOPMENT OF A
RATHER STRONG UPPER TROUGH AND ASSOCIATED CLOSED LOW THAT WILL
DROP DOWN THROUGH THE SOUTHWEST AND INTO THE FOUR CORNERS REGION
THROUGH TUES. THE HEIGHT FALLS WILL BE ENCROACHING ON THE SOUTHERN
HIGH PLAINS BY WED AND THEN THE LOWER/MID MS VALLEY ON THURS ALONG
WITH A WELL-DEFINED LOW PRESSURE CENTER. THIS ENERGY WILL THEN
LIFT ACROSS THE OH/TN VALLEYS THURS NIGHT AND FRI. MEANWHILE...THE
MODELS SHOW A WEAKER NORTHERN STREAM COMPONENT OF THE ORIGINAL
TROUGH CROSSING THE NORTHWEST U.S. AND EJECTING OUT INTO THE
NORTHERN PLAINS TUES AND WED.

REGARDING THE MUCH MORE SIGNIFICANT SOUTHERN STREAM CLOSED
LOW...SOME MEANINGFUL MODEL DIFFERENCES BEGIN TO SHOW UP AROUND 36
HOURS AS THE 12Z ECMWF BEGINS TO PROGRESS THE UPPER LOW A TAD
FASTER OFF TO THE EAST COMPARED TO THE MODEL CONSENSUS. THIS
CARRIES OVER THROUGH THE REMAINDER OF THE PERIOD AS THE ENERGY
EJECTS EAST ACROSS THE MID MS/TN/OH VALLEYS. THE 00Z NAM AND 12Z
CMC GRADUALLY TEND TO BECOME A BIT SLOWER THAN THE MODEL
CONSENSUS...BUT THE DIFFERENCES ARE NOT TOO SIGNIFICANT. THE 00Z
GFS AND 12Z UKMET ARE CLUSTERED IN THE MIDDLE...BUT THE GFS
FOCUSES PROBABLY TOO MUCH ENERGY FARTHER SOUTH AND CLOSER TO THE
CENTRAL GULF COAST REGION WHICH RESULTS IN ITS MUCH HEAVIER QPF
OVER THIS REGION AFTER 60 HOURS. IT SHOULD ALSO BE NOTED THAT
AFTER 60 HOURS THE 12Z ECMWF DOES GET MORE ENSEMBLE SUPPORT WITH A
SLIGHTLY MORE PROGRESSIVE SOLUTION. SO BASED ON THESE
COMPARISON...A BLEND OF THE 00Z GFS AND 12Z UKMET WILL BE
PREFERRED UP TO 60 HOURS...AND THEN A 12Z UKMET/12Z ECMWF BLEND
THEREAFTER.


...COLD FRONT WEAKENING INTO BRITISH COLUMBIA ON TUES...
...ONSHORE FLOW INTO THE PACIFIC NORTHWEST THROUGH TUES NIGHT...
...LOW PRESSURE ENTERING BRITISH COLUMBIA...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS HAVE COME INTO REASONABLY GOOD MASS FIELD AGREEMENT
WITH THIS SYSTEM...SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED.


...SHORTWAVE/SURFACE LOW NEAR THE PACIFIC NORTHWEST BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM/00Z GFS AND 12Z UKMET
CONFIDENCE: AVERAGE

THE 12Z UKMET AND 12Z CMC BOTH APPEAR TO BE A TAD TOO WEAK WITH
THIS APPROACHING SHORTWAVE/LOW CENTER. THE 00Z NAM/00Z GFS AND 12Z
ECMWF ARE ALL CLUSTERED AROUND A SOMEWHAT STRONGER AND BETTER
DEFINED LOW...AND THIS SLIGHTLY STRONGER CONSENSUS WILL BE
PREFERRED AS IT IS ALSO FAVORED BY THE LATEST GEFS MEAN AND ECENS
MEAN.



...VIGOROUS TROUGH DIGGING INTO THE WEST ON THURS/FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS AGREE IN DIGGING A STRONG UPPER TROUGH INTO THE WESTERN
U.S. ON THURS WHICH AMPLIFIES INTO A DEEP CLOSED LOW OVER THE
SOUTHWEST BY FRI. THE MODELS ARE IN VERY GOOD AGREEMENT...WITH THE
ONLY POSSIBLE EXCEPTION BEING THE 00Z GFS BY THE END OF THE PERIOD
WHICH HAS ITS UPPER LOW JUST TAD NORTH OF THE REMAINING AND VERY
WELL-CLUSTERED GUIDANCE. WILL FOR NOW FAVOR A GENERAL MODEL
COMPROMISE.

www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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