Prognostic Meteorological Discussion
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FXUS10 KWNH 280652
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 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/GFS/UKMET/CMC AND ECMWF
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...NORTHERN STREAM TROUGH AMPLIFYING ACROSS SOUTHEAST CANADA...
...UPPER TROUGH WEAKENING ACROSS THE MID-ATLANTIC ON TUES...
...SURFACE LOW CROSSING MID-ATLANTIC...DEEPENING OFFSHORE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

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
SUFFICIENT AGREEMENT FOR A GENERAL MODEL COMPROMISE AT THIS POINT.


...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 UKMET AND 00Z ECMWF
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...THE DIFFERENCES ARE VERY MINOR THROUGH ABOUT 48 HOURS AT
THIS POINT. THEREAFTER...THE 00Z NAM AND EVENTUALLY THE 00Z CMC
BECOME A BIT SLOWER THAN THE MODEL CONSENSUS WITH THE FORWARD
PROPAGATION OF THE CLOSED LOW OFF TO THE EAST AS IT APPROACHES AND
MOVES THROUGH THE MID MS/TN/OH VALLEY REGION. THE 00Z ECMWF HAS
TRENDED A TAD SLOWER THAN ITS PREVIOUS RUN WITH THE FORWARD
PROPAGATION BUT IS IN VERY GOOD AGREEMENT WITH THE 00Z UKMET.
THESE TWO SOLUTIONS ALONG WITH THE 00Z GFS ARE A BIT FASTER THAN
THE NAM/CMC CAMP. HOWEVER...THE 00Z GFS GETS TO BE PROBLEMATIC IN
TIME...ESPECIALLY AFTER 60 HOURS AS IT IS MORE AGGRESSIVE TO DIG
ENERGY EAST-SOUTHEAST ACROSS THE LOWER MS VALLEY AND GULF COAST
STATES. THE GFS IS SHOWING CLEAR SIGNS OF CONVECTIVE FEEDBACK
ACROSS THIS REGION WHICH IS IN PART HELPING TO FOCUS ITS LOW
PRESSURE CENTER FARTHER SOUTH VERSUS THE MODEL CONSENSUS. GIVEN
THE LATEST TRENDS AND SPREAD...A BLEND OF THE UKMET AND ECMWF WILL
BE PREFERRED.


...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: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

GIVEN THE TRENDS OF THE UKMET AND CMC TOWARD THE RELATIVELY
STRONGER NAM/GFS/ECMWF SOLUTIONS...THE MODELS ARE NOW CLUSTERING
MUCH BETTER WITH THIS SYSTEM...AND THUS A GENERAL MODEL COMPROMISE
WILL BE PREFERRED.


...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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