Prognostic Meteorological Discussion
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000
FXUS10 KWNH 260501
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 AM EDT THU MAY 26 2016

VALID MAY 26/0000 UTC THRU MAY 29/1200 UTC

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

00Z INITIAL MODEL EVALUATION WITH PREFERENCES/CONFIDENCE LEVELS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


SYSTEM MOVING FROM THE SOUTHWEST INTO THE PLAINS THU-SUN
INTERACTING WITH SHORTWAVE ENERGY ACROSS THE NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CONSENSUS OF THE 0Z GFS AND 12Z ECMWF/UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AS OF 12Z THIS MORNING WILL HAVE A SHORTWAVE NEAR THE FOUR CORNERS
REGION AT THE BASE OF THE LARGE SCALE TROUGH...AND A COUPLE OTHER
SHORTWAVES MEANDERING ACROSS THE NORTHERN PLAINS. THE SOUTHERN
SHORTWAVE IS EXPECTED TO EJECT INTO THE ROCKIES AND PLAINS
THURSDAY AND FRIDAY...EVENTUALLY INTERACTING WITH THE SLOW MOVING
SHORTWAVES ACROSS THE NORTHERN PLAINS. INITIALLY MODELS ARE IN
PRETTY GOOD AGREEMENT ON THE SYNOPTIC SCALE WITH THE SOUTHERN
SHORTWAVE EJECTING INTO THE PLAINS. HOWEVER BY FRIDAY BEGIN TO SEE
DIFFERENCES IN HOW THE VARIOUS MODELS INTERACT THIS FEATURE WITH
THE ENERGY OVER THE NORTHERN PLAINS. THE 0Z GFS IS THE MOST
AGGRESSIVE IN MERGING THESE WAVES INTO AN ELONGATED VORTICITY
AXIS...WITH THE ECMWF KEEPING THEM MORE SEPARATE. THE 12Z ECMWF IS
ALSO THE QUICKEST IN EJECTING ALL THIS ENERGY INTO CANADA. THE 12Z
ECMWF IS CONSIDERABLY QUICKER THAN ITS PREVIOUS RUNS AND ALSO IS
FASTER THAN ITS ENSEMBLE MEAN. THUS OVERALL THINK BOTH THE 0Z GFS
AND 12Z ECMWF HAVE ISSUES IN THE HANDLING OF THESE FEATURES. THE
12Z UKMET PROBABLY REPRESENTS A GOOD CONSENSUS SOLUTION
SYNOPTICALLY. WILL RECOMMEND A CONSENSUS OF THE 12Z UKMET/ECMWF
AND 0Z GFS FOR THESE SYSTEMS WHICH REPRESENTS A MIDDLE GROUND
SOLUTION.

THE 12Z GEM ENDS UP THE SLOWEST WITH THE THE SHORTWAVE ACROSS THE
PLAINS BY FRIDAY/SATURDAY...WHICH ALSO HAS IMPACTS ON ITS SURFACE
FEATURES. IT LIES ALMOST OUTSIDE THE ENSEMBLE SPREAD AND IS THUS
NOT RECOMMENDED AT THIS TIME. THE 0Z NAM ALSO ENDS UP A BUT
SLOWER/SOUTH WITH THIS WAVE BY SATURDAY AND ALSO APPEARS TO BE AN
OUTLIER.


...SYSTEM MOVING FROM THE GREAT LAKES BY MAINE FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL CONSENSUS
CONFIDENCE: ABOVE AVERAGE

MINOR DIFFERENCES EXIST WITH THE SHORTWAVE AND SURFACE FEATURE
MOVING TO THE NORTH OF MAINE ON FRIDAY. IN GENERAL THE DIFFERENCES
WITHIN THE GUIDANCE APPEAR TO BE WITHIN THE USUAL MARGIN OF ERROR
AT THIS TIME PERIOD...THUS A MODEL BLEND SHOULD SUFFICE.


...UPPER LOW DRIFTING E OF FLORIDA
CONVECTIVE LOW TRACKING N OF BAHAMAS FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/0Z GFS CONSENSUS
CONFIDENCE: AVERAGE

BY 12Z SUNDAY THE 12Z ECMWF/UKMET AND 0Z GFS ARE IN VERY GOOD
AGREEMENT IN THE POSITION OF THE CONVECTIVE LOW OFF THE SC COAST.
HOWEVER THEY DIFFER IN HOW THEY GET IT IN THAT POSITION...WITH THE
GFS/UKMET FURTHER NORTH INITIALLY THAN THE ECMWF. SEE NO REAL
STRONG EVIDENCE TO PREFER ONE OVER ANOTHER AT THIS TIME...THUS
WILL PREFER A CONSENSUS OF THE 12Z ECMWF AND 0Z GFS. WILL LEAN
AGAINST 0Z NAM WHICH APPEARS TOO SLOW...AND THE 12Z GEM WHICH
APPEARS TO QUICK AND NORTH WITH THE SYSTEM.


...UPPER LOW/TROUGH OVER THE NORTHWEST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: MODEL CONSENSUS
CONFIDENCE: AVERAGE

AN UPPER LOW IS EXPECTED TO SET UP ACROSS THE NORTHWEST THURSDAY
INTO SATURDAY. THERE IS A DECENT AMOUNT OF SPREAD WITH REGARDS TO
HOW INDIVIDUAL SHORTWAVES WITHIN THE LOW/TROUGH INTERACT WITH EACH
OTHER AND IMPACT THE SHAPE/ORIENTATION OF THE BROADER TROUGH.
GIVEN THE MULTIPLE PIECES OF ENERGY INVOLVED...LOW CONFIDENCE
EXISTS ON THE EXACT DETAILS. AND THUS SEE NO STRONG REASON TO
PREFER ONE MODEL OVER ANOTHER AT THIS TIME...WITH A GENERAL
COMPROMISE PREFERRED.


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

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

CHENARD

$$





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