Prognostic Meteorological Discussion
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FXUS10 KWNH 281821
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
221 PM EDT SUN MAY 28 2017

VALID MAY 28/1200 UTC THRU JUN 01/0000 UTC

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

12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

UPPER TROUGH MOVING INTO THE WEST COAST TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A DEEP UPPER LOW WILL SHIFT NORTHEAST INTO THE SOUTHERN GULF OF AK
AT MILD SPACING TO RIDGING OVER ROCKIES THROUGH TUES.  ELONGATED
LEAD HEIGHT FALLS WILL SLOWLY SHIFT EASTWARD MON INTO TUES WHILE
MAIN FORCING IN THE WAVE LIFTS NORTH THROUGH THE EASTERN GULF OF
AK.  GUIDANCE IS FAIRLY AGREEABLE WITH THIS PLACEMENT/TIMING.  THE
DISAGREEMENT IS RELATED TO THE QUICK MOVING UNDERCUTTING SHORTWAVE
IN THE WESTERLY FLOW REACHING THE WEAKNESS ALONG THE WEST COAST
LATE TUES.  SMALL TIMING/ORIENTATION DIFFERENCES LEAD TO MILD
MODEL SPREAD IN THE DEPTH/INTENSITY OF THIS WAVE AND HOW WOUND UP
IT GETS.  THE 00Z ECMWF IS GENERALLY DEEPER INITIALLY THOUGH LESS
SHARP WHILE SHARPNESS TO THE TROF INCREASES FROM THE 00Z CMC TO
THE 12Z GFS, NAM AND SHARPEST 00Z UKMET BY 12Z WED.  THE NAM/UKMET
AND 00Z CMC ALL TEND TO STRETCH THE WAVE/HEIGHT FALLS THROUGH CA
TOWARD DEVELOPING WEAKLY CUT-OFF OVER THE SOUTHWEST BY 00Z THURS
THOUGH THE UKMET SEEMS THE MOST AGGRESSIVE AND OUT OF PLACE WITH
THIS S CALIFORNIA FEATURE WITH RESPECT TO THE OTHER
GUIDANCE/ENSEMBLE SOLUTIONS.

THE OVERALL ESSENCE/TIMING OF THE WAVE IS FAIRLY WELL AGREED
UPON...THOUGH CONFIDENCE IS REDUCED IN THE PRECISE DETAILS WHICH
CONTINUE TO VARY RUN TO RUN (AND WITHIN THE ENSEMBLE SUITE).
THESE SMALLER MESOSCALE DETAILS ARE IMPORTANT TO THE SENSIBLE
WEATHER/QPF...AND AS SUCH PLEASE REFER TO QPFPFD FOR ADDITIONAL
DETAILS/PREFERENCES. AS SUCH WILL PREFER A NON-UKMET BLEND THROUGH
THE ENTIRE WEST COAST AT FAIRLY GOOD CONFIDENCE FOR THE SYNOPTIC
SCALE/MASS FEATURE TIMING.  THOUGH WITH MODEST RUN TO RUN
VARIATION IN THE DETERMINISTIC AND ENSEMBLE MEMBERS KEYING ON THE
MESOSCALE DIFFERENCES WHICH LEAD TO POTENTIALLY IMPORTANT SENSIBLE
WX... CONFIDENCE IS REDUCED TO SLIGHTLY ABOVE AVERAGE OVERALL.

19Z UPDATE: THE 12Z UKMET HAS TRENDED TO MATCH THE 12Z NAM/GFS
FAIRLY WELL...WHILE THE 12Z CMC/ECMWF ARE MATCHED WELL TOO, JUST A
SHADE SHALLOWER ACROSS CA.  AS SUCH A GENERAL MODEL BLEND COULD BE
SUPPORTED THROUGH THE FORECAST PERIOD AT SLIGHTLY ABOVE AVERAGE
CONFIDENCE (BASED ON SIMILAR REASONING AS INITIAL PREFERENCE).


SHORTWAVE TROF TRACKING ACROSS THE OH VALLEY/WESTERN NY
SUNDAY/MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A SUBTLE POSITIVE TILT TROF EXTENDING FROM THE DEEP UPPER LOW OVER
WI/MN BACK TOWARD S KS WILL TRACK RAPIDLY ACROSS THE MID-MS VALLEY
TODAY THROUGH THE OH VALLEY MON MORNING INTO NEW ENGLAND LATE
MON/EARLY TUES.  WITH CONVECTIVE FEEDBACK ISSUES RESOLVED IN THE
UKMET...OVERALL GUIDANCE IS QUITE AGREEABLE THOUGH BY MONDAY THERE
ARE SOME SMALL TIMING DIFFERENCES WITH A SLIGHTLY DEEPER/SLOWER
REPRESENTATION OF THE TROF THROUGH ME NOTED IN THE 12Z NAM
COMPARED TO THE FASTER 06Z GFS/GEFS AND 00Z UKMET. THE 12Z GFS
SLOWED CONSIDERABLY ACROSS NEW ENGLAND MATCHING THE TIMING OF THE
12Z NAM AND THE 00Z ECMWF.  THE 00Z CMC IS THE CLEAR SLOWEST
OUTLIER.  AS SUCH A 12Z GFS/NAM AND ECMWF BLEND BLEND IS PREFERRED
AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: THE 12Z CMC TRENDED MUCH QUICKER AND MATCHES THE 12Z
ECMWF WHICH SHOWED A SLIGHT SLOWING TOWARD THE SHIFT MADE BY THE
GFS/NAM.  THE 12Z UKMET REMAINS QUICKER BY ABOUT 2-3 HOURS...WITH
LITTLE SIGNIFICANT SENSIBLE WX DEPARTURE ENOUGH SO TO SUPPORT A
GENERAL MODEL BLEND AT ABOVE AVERAGE CONFIDENCE.


SURFACE LOW TRACKING OUT OF THE MID ATLANTIC MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

TRAILING EDGE OF TROF DESCRIBED BELOW CURRENTLY SPURRING WEAK
SURFACE LOW OVER S VA...THAT WILL LIFT NORTH ALONG THE EAST COAST
JUST SOUTH OF CAPE COD BEFORE SHIFTING EASTWARD OUT TO SEA.  AS
NOTED IN SECTION ABOVE...TIMING IS KEY AND THE 12Z GFS TRENDED
SLOWER THAN THE 06Z RUN TO BECOME A BIT DEEPER AND SHIFT MORE
CENTRALLY TO THE TIGHT ENSEMBLE CLUSTER THAT INCLUDES THE 00Z
ECMWF/UKMET.  THE 12Z NAM IS ALSO WELL CLUSTERED NEAR THE GFS. THE
00Z CMC IS A BIT SLOWER GIVEN A SLIGHTLY MORE AMPLIFIED TRAILING
SHORTWAVE ALOFT AND WHILE IT IS LESS PREFERRED THAN SAY THE
ECMWF/NAM OR GFS... IT IS CLOSE ENOUGH TO KEEP WITHIN THE
PREFERENCE TO BEST REPRESENT THE TIGHT ENSEMBLE CLUSTER.  AS SUCH
A GENERAL MODEL BLEND IS SUPPORTED AT ABOVE AVERAGE CONFIDENCE.

19Z UPDATE: BETTER TIMING/STRENGTH WITH THE 12Z CMC PROVIDES EVEN
TIGHTER CLUSTERING.  THE 12Z UKMET TRENDED A BIT QUICKER AND IS
BECOMES THE FASTEST SOLUTION BUT NOT ENOUGH TO REMOVE.   AS SUCH A
GENERAL MODEL BLEND PREFERENCE REMAINS AT ABOVE AVERAGE CONFIDENCE.


DEEP LAYERED CYCLONE WOBBLING ABOUT ONTARIO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/GFS/ECMWF BLEND
CONFIDENCE: ABOVE AVERAGE THROUGH 31/00Z
            SLIGHTLY ABOVE AVERAGE THEREAFTER

OVERALL PLACEMENT/DEPTH AND TRACK OF THE INNER CORE OF THE UPPER
LOW CONTINUES TO BE WELL AGREED UPON PARTICULARLY GIVEN THE UKMET
BACKING OFF THE STRONGER WAVE FROM THE OHIO VALLEY/GREAT LAKES
TODAY...REDUCING THE INSTABILITY OF THE ASYMMETRIC SHORTWAVES
LEADING TO A GREATER WOBBLE.   WHILE SHORT-TERM THROUGH TUES
CONTINUES TO BE AGREED UPON MODELS CONTINUE TO DIVERGE ON THE
HANDLING OF BINARY INTERACTION WITH COMPACT WAVE OVER NUNAVUT.
THE 00Z UKMET CONTINUES TO DESCEND FASTEST NEARING MN BY EARLY WED
MAKING IT LESS PREFERABLE.   THE 00Z CMC FAVORS A VERY
STRONG/CONSOLIDATED SHORTWAVE OVER THE PARENT LARGER VORTEX AND
WHILE IT IS WELL TIMED WITH THE ECMWF, IT IS CLEARLY MUCH STRONGER
WITH THE IMPACT EXTENDING FURTHER DOWNSTREAM AND WEST.  WHILE THE
12Z NAM/GFS BOTH LAG THE ECMWF TENDING TO SHEAR THE COMPACT
SHORTWAVE TIGHTER TO THE PARENT CIRCULATION AND SLOWER... THERE IS
REMAINING AGREEMENT WITH THE ENSEMBLE SUITE AND ITS OVERALL TREND
OVER THE LAST FEW CYCLES. AS SUCH WILL FAVOR A 12Z GFS/NAM AND 00Z
ECMWF BLEND AT AVERAGE CONFIDENCE (ABOVE AVERAGE UP TO 31/00Z)

19Z UPDATE: THE 12Z CMC CONTINUES TO FAVOR THE ARCTIC SHORTWAVE
OVER THE INNER CORE WHICH KEEPS THE TROF AMPLIFIED MUCH FURTHER
WEST THAN THE INITIAL PREFERENCE/THINKING.   THE 12Z UKMET HAS
TRENDED FAVORABLY TOWARD THE CONSENSUS IN NOT DRAWING THE ENTIRE
SHORTWAVE SOUTH INTO MN BY WED...BUT STILL SHEARS A LOBE OF IT
SOUTHWARD WHICH BEING SMALLER...DRAWS TIGHTER TO THE PARENT UPPER
LOW BUT STILL IS FAST CROSSING LK SUPERIOR AT 00Z ON
THURS...KEEPING IT FROM THE PREFERENCE. THE 12Z ECMWF TRENDED A
BIT SLOWER AND NOW HAS SIMILAR TIMING/EVOLUTION AS THE 12Z GFS.
AS SUCH WILL CONTINUE A 12Z NAM/GFS/ECMWF BLEND AT ABOVE AVERAGE
CONFIDENCE THROUGH 31/00Z AND SLIGHTLY ABOVE AVERAGE AFTER.


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


GALLINA

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