Prognostic Meteorological Discussion
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000
FXUS10 KWNH 290704
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 AM EDT FRI MAY 29 2015

VALID MAY 29/0000 UTC THRU JUN 01/1200 UTC

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

00Z MODEL EVALUATION INCLUDING FINAL MODEL PREFERENCES

***ONLY NEW MODEL TO COMPARE IN THIS DISCUSSION WAS CANADIAN GEM
DUE TO DATA FLOW PROBLEMS...


MODEL INITIALIZATION ERRORS DO NOT APPEAR TO BE SUFFICIENTLY LARGE
TO IMPACT THEIR FORECASTS OF LARGE-SCALE FEATURES.

NEW ENGLAND SHORTWAVE AND COLD FRONT EXITING BY THIS COMING
AFTERNOON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 00Z NCEP OPERATIONAL MODELS/CMC OR 28/12Z
ECMWF/UKMET
CONFIDENCE: ABOVE AVERAGE

VERY GOOD MODEL AGREEMENT EXISTS WITH THE EVOLUTION OF THE
WEAKENING SHORTWAVE AND ASSOCIATED COLD FRONT OVER NEW ENGLAND


SURFACE LOW CROSSING THE NORTHERN GREAT PLAINS INTO GREAT
LAKES/ONTARIO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~
PREFERENCE: BLEND OF 12Z OPERATIONAL MODELS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODEL CLUSTERING REMAINS GENERALLY GOOD WITH RESPECT TO THE SFC
LOW AND ASSOCIATED MID/UPPER LEVEL CIRCULATION IN THE DEEPENING
NORTHERN STREAM AS IT MOVES FROM THE GREAT LAKES REGION INTO
ONTARIO.  IT APPEARS THAT THE 00Z NCEP GUIDANCE AND CANADIAN
GLOBAL CONTINUED TO MAKE MINOR ADJUSTMENTS IN BOTH PLACEMENT AND
INTENSITY OF THE LOW BUT OVERALL NOT MUCH CHANGE AND THE IDEA IS
FOR A DEEPER LOW OVER QUEBEC BY 30/06Z.


SHORTWAVE EJECTING FROM THE CENTRAL ROCKIES INTO THE PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 29/00Z GFS...28/12Z GEFS MEANS AND THE ECMWF
ENS MEAN
CONFIDENCE: AVERAGE

THE MAIN SHORTWAVE CURRENTLY LOCATED NEAR YELLOWSTONE SHIFTS
SOUTHEAST DAMPENING OUT AS IT PROGRESSES...WHILE ANOTHER WEAK
SHORTWAVE EJECTS OUT OF THE BASE OF THE POSITIVELY TILTED AND
FILLING TROF IN NORTHEAST NEW MEXICO TODAY.  A WEAK SURFACE LOW
OVER SOUTHEAST CO AS OF THU EVENING SHOULD MAKE ITS WAY INTO THE
CENTRAL GREAT LAKES BY LATER TONIGHT/SATURDAY MORNING LEAVING A
TRAILING WEAK FRONTAL BOUNDARY THAT WILL REMAIN THE FOCUS OF
SENSIBLE WEATHER FOR THE SHORT RANGE.

THE 00Z NAM INITIALLY LOOKS IN LINE WITH OTHER GUIDANCE UNTIL OVER
DEEPENING OF A SURFACE LOW IN IOWA SATURDAY MORNING...WHICH MAKES
IT A SLOW/DEEP OUTLIER THROUGH MUCH OF THE REMAINING FORECAST.
PRESUMABLY THIS WAS THE RESULT OF THE NAM SUFFERING CONVECTIVE
FEEDBACK.  EVEN THE 28/12Z ECMWF APPEARS TO HAVE HAD PROBLEMS WITH
CONVECTIVE FEEDBACK FAIRLY EARLY IN THE SHORT RANGE PERIOD.
CONSIDERING THAT THE 28/12Z UKMET APPEARS TO BE TOO QUICK TO EJECT
THE ENERGY OUT OF THE TROF...IT LEAVES THE OPERATIONAL GFS AND THE
ENSMEAN FROM THE U.S. AND EUROPEAN CENTERS AS THE BEST CANDIDATES.
 FIGURE THAT A BLEND OF THOSE MODELS SHOULD HELP MITIGATE SOME OF
THE TIMING AND PLACEMENT DIFFERENCES WHICH REMAIN.


WEAKENING PACIFIC CUT-OFF LOW PROGRESSING TO CENTRAL U.S. PACIFIC
COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~
PREFERENCE: BLEND OF 29/00Z GFS...28/12Z ECMWF/UKMET
CONFIDENCE:  AVERAGE

WELL DEFINED CUT-OFF UPPER LOW NEAR 40N150W...WOBBLES A BIT TODAY
BUT BEGINS TO MOVE EAST.  THIS SET OF MODEL RUNS STILL SUGGEST TAT
IT WILL BE OPENING UP AS IT APPROACHES THE U.S. WEST COAST BY DAY
3 WITH A SLIGHT NEGATIVE TILT ORIENTATION.

GIVEN FAIRLY GOOD RUN TO RUN CONTINUITY OF THE GFS...SEE LITTLE
REASON TO CHANGE THE PREVIOUSLY STATED PREFERENCE FOR THE GFS AND
THE PREVIOUS RUNS OF THE ECMWF/UKMET.


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

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

BANN

$$





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