Prognostic Meteorological Discussion
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FXUS10 KWNH 211652
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1250 PM EDT SUN MAY 21 2017

VALID MAY 21/1200 UTC THRU MAY 25/0000 UTC

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

12Z PRELIMINARY MODEL EVALUATION/PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...CLOSED LOW CROSSING THE UPPER MS VALLEY AND GREAT LAKES TODAY...
...COLD FRONT MOVING ACROSS THE CENTRAL AND EASTERN U.S....
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE IN GOOD AGREEMENT WITH THE EVOLUTION OF THIS LARGE
SCALE SYNOPTIC SYSTEM. A GENERAL MODEL BLEND WILL BE PREFERRED TO
RESOLVE ANY LINGERING SMALLER SCALE DIFFERENCES.


...SHORTWAVE CROSSING THE GREAT BASIN/CENTRAL ROCKIES TODAY...
...EJECTING OUT INTO THE SOUTHERN PLAINS ON MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

OVERALL THERE REMAINS PRETTY GOOD MODEL AGREEMENT IN TRACKING A
RATHER WEAK SHORTWAVE FROM THE PACIFIC NORTHWEST TODAY SOUTHEAST
ACROSS THE GREAT BASIN AND CENTRAL ROCKIES ON SUN...AND THEN
GRADUALLY EJECTING OUT INTO THE SOUTHERN PLAINS ON MON AROUND THE
BASE OF THE LARGER SCALE TROUGH OVER THE MIDDLE OF THE COUNTRY.


...SHORTWAVE MOVING INTO MT EARLY MON AROUND THE BACKSIDE OF THE
UPPER MS VALLEY AND SOUTHERN CANADA CLOSED LOW...
...ENERGY AMPLIFYING OVER THE MIDWEST THROUGH TUES AND WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z UKMET AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS CONTINUE TO ADVERTISE A WELL-DEFINED SHORTWAVE DIGGING
SOUTHEAST ON MON ACROSS THE MT HIGH PLAINS AND THEN AROUND THE
SOUTHWEST FLANK OF THE LARGER SCALE UPPER MS VALLEY/SOUTHERN
CANADA CLOSED LOW BY TUES WITH THE ENERGY AMPLIFYING AS IT ARRIVES
OVER THE MIDWEST. THIS ENERGY EVENTUALLY HELPS DIG THE TROUGH OVER
THE CENTRAL PORTION OF THE COUNTRY BY TUES...AND WITH A NEW CLOSED
LOW EXPECTED TO EVOLVE EAST ACROSS THE MID MS VALLEY AND TOWARD
THE OH/TN VALLEYS THROUGH WED. THE 12Z NAM OVERALL GRADUALLY
APPEARS TO BE A BIT SLOW BY THE END OF THE PERIOD TO DEVELOP THIS
NEW CLOSED LOW EAST OUT OF THE MID MS VALLEY. THE 00Z CMC THOUGH
DIGS ENERGY LIKELY TOO FAR TO THE SOUTHEAST AND ALSO APPEARS TO BE
A BIT TOO WEAK. THE BETTER MODEL CLUSTERING AND ENSEMBLE SUPPORT
GENERALLY RESIDES WITH THE 00Z UKMET AND 00Z ECMWF SOLUTIONS FOR
THE TIME BEING...AS THE 12Z GFS MAY BE PIVOTING A LITTLE TOO MUCH
ENERGY AROUND THE BASE OF ITS TROUGH AND THROUGH THE SOUTHEAST BY
THE END OF THE PERIOD. THE 12Z GFS ALSO OVERALL BECOMES THE
STRONGEST SOLUTION AND HAS A DEEPER SURFACE LOW OVER THE OH VALLEY
COMPARED THE OTHER GUIDANCE. A BLEND OF THE UKMET AND ECMWF WILL
BE PREFERRED.


...SOUTHERN STREAM WAVE ARRIVING ACROSS SOUTHEAST TX ON MON...
...ADDITIONAL SHORTWAVE ENERGY MOVING ACROSS THE GULF
COAST/SOUTHEAST MON/TUE...
...SURFACE LOWS TRAVERSING THE GULF COAST INTO THE SOUTHEAST
TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z UKMET AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS REMAIN IN AGREEMENT IN BRINGING A SOUTHERN STREAM WAVE
ACROSS NORTHERN MEXICO AND EASTWARD INTO TX BY EARLY MON. AS THIS
ENERGY...ALONG WITH ADDITIONAL ENERGY DROPPING SOUTHEAST AROUND
THE BASE OF THE CENTRAL U.S. TROUGH... INTERACTS WITH A STALLED
FRONT NEAR THE SOUTHEAST TX COAST...ONE OR MORE WAVES OF LOW
PRESSURE SHOULD DEVELOP ALONG THIS FRONT AND THEN ADVANCE
EAST-NORTHEAST AND JUST INLAND ACROSS THE CENTRAL GULF COAST
BEFORE THEN LIFTING NORTHEAST UP ACROSS THE INTERIOR SOUTHEAST
U.S. AND MID-ATLANTIC IN AN ELONGATED FASHION THROUGH LATE TUES
AND EARLY WED.

THE 12Z GFS AND TO A LESSER EXTENT THE 12Z NAM APPEAR TO POSSIBLY
BE A BIT TOO PROGRESSIVE WITH THE LEAD ENERGY/SURFACE WAVE THAT
TRAVERSES THE GULF COAST STATES MON NIGHT AND ON UP ACROSS THE
MID-ATLANTIC REGION BY EARLY TUES. THE 12Z NAM ALSO APPEARS TO BE
PERHAPS EARLY IN THE PERIOD A BIT TOO STRONG AND TOO FAR NORTH
WITH ITS LOW TRACK. THE 00Z UKMET/00Z CMC AND 00Z ECMWF ARE ALL
RELATIVELY SLOWER BUT ALSO A TAD MORE SUPPRESSED WHICH HAS THE
SUPPORT OF THE 06Z GEFS MEAN. IN THE WAKE OF THE LEAD LOW CENTER
WILL BE ANOTHER WAVE THAT TRAVERSES THE GULF COAST STATES LATER
TUES WHICH THEN CONSOLIDATES FARTHER NORTH TOWARD THE INTERIOR
MID-ATLANTIC ON WED. THE NAM AND GFS BOTH ARE NOT NEARLY AS
AGGRESSIVE AS THE UKMET/CMC/ECMWF CAMP WITH THE LOW PRESSURE AREA
OVER THE MID-ATLANTIC COASTAL PLAIN ON WED. WILL FAVOR THE
NON-NCEP CAMP WITH THIS SOUTHERN STREAM ENERGY AND THE WAVES GIVEN
A BIT BETTER RUN TO RUN CONTINUITY...WITH A PREFERENCE MAINLY
TOWARD A BLEND OF THE UKMET AND ECMWF.


...UPPER TROUGH MOVING ACROSS THE PACIFIC NORTHWEST ON TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

A RATHER STRONG UPPER TROUGH IS EXPECTED TO BE DIGGING SOUTHEAST
TOWARD THE PACIFIC NORTHWEST ON TUES FROM THE GULF OF AK. THIS
ENERGY WILL ADVANCE INLAND AND CROSS THE NORTHERN ROCKIES ON WED.
A STRONG COLD FRONT WILL ALSO BEGIN CROSSING THE NORTHERN
INTERMOUNTAIN REGION. THE 12Z GFS IS A TAD MORE PROGRESSIVE TOWARD
THE END OF THE PERIOD WITH THE TROUGH EVOLUTION...AND THE 00Z
UKMET APPEARS PERHAPS A BIT TOO SLOW. THE 12Z NAM/00Z CMC AND 00Z
ECMWF ARE CLUSTERED IN THE MIDDLE. OF THESE SOLUTIONS...THE 00Z
ECMWF APPEARS TO BE CLOSEST TO THE MODEL CONSENSUS...AND THIS WILL
BE THE MODEL PREFERENCE.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

ORRISON

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