Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13
000
FXUS10 KWNH 281647
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1246 PM EDT THU MAY 28 2015

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 FINAL MODEL PREFERENCES

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


NEW ENGLAND SHORTWAVE AND ASSOCIATED COLD FRONT EXITING BY FRIDAY
AFTERNOON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

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


SURFACE LOW PRESSURE CROSSING THE NORTHERN GREAT PLAINS INTO FAR
WESTERN GREAT LAKES/ONTARIO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF OPERATIONAL MODELS
CONFIDENCE:

A SURFACE LOW IS DEVELOPING IN MONTANA IN RESPONSE TO THE
DEEPENING NORTHERN STREAM TROF OVER SASKATCHEWAN.  GOOD CLUSTERING
OF THE OPERATIONAL MODELS EXIST WITH THE EVOLUTION OF THE SURFACE
AS IT MOVES ACROSS THE ONTARIO. THE 12Z NAM/GFS HAVE SHIFTED EVER
SO SLIGHTLY SOUTH AND EAST ALOFT AND AS SUCH THE SURFACE
REFLECTION IS A BIT WEAKER AND FURTHER WEST AS COMPARED TO THEIR
PRIOR RUNS AS WELL AS THE OTHER 00Z OPERATIONAL MODEL GUIDANCE
SUITE.  STILL THESE ARE VERY SUBTLE DIFFERENCES AND WITH THE
ELONGED SURFACE FRONTAL BOUNDARY WELL HANDLED CONNECTING UP TO THE
SURFACE WAVE EJECTING FROM THE CENTRAL ROCKIES LATER TODAY...A
GENERAL MODEL BLEND IS PREFERRED.


SHORTWAVE EJECTING FROM THE CENTRAL ROCKIES INTO THE PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF/00Z UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MAIN SHORTWAVE CURRENTLY LOCATED NEAR YELLOWSTONE SHIFTS
SOUTHEAST DAMPENING OUT AS IT PROGRESSES...WHILE OTHER WEAK
SHORTWAVES EJECT OUT OF THE BASE OF THE POSITIVELY TILTED AND
FILLING TROF.  A WEAK SURFACE LOW DEVELOPS ALONG THE COLORADO
FRONT RANGE THIS EVENING INTO THE CENTRAL GREAT LAKES BY FRIDAY
NIGHT/SATURDAY MORNING LEAVING A TRAILING WEAK FRONTAL BOUNDARY
THAT WILL REMAIN THE FOCUS OF SENSIBLE WEATHER FOR THE SHORT
RANGE. THE 12Z NAM INITIALLY LOOKS IN LINE WITH OTHER GUIDANCE
UNTIL OVER DEEPENING OF A SURFACE LOW IN IOWA SATURDAY
MORNING...LIKELY IN RESPONSE TO CONVECTIVE FEEDBACK AND SHOULD NOT
BE PREFERRED AFTER THIS TIME PERIOD.   THE 12Z GFS AND 00Z ECMWF
REMAIN IN GOOD AGREEMENT THROUGHOUT THE PERIOD WITH THE
PROGRESSION OF THE FRONT ACROSS THE CENTRAL U.S. INTO THE
MID-ATLANTIC BY DAY 3.


UPPER LEVEL LOW OVER BRITISH COLUMBIA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF
CONFIDENCE: ABOVE AVERAGE BEFORE 31/00Z....AVERAGE AFTERWARD

THE OPERATIONAL AND ENSEMBLE GUIDANCE ARE IN VERY GOOD AGREEMENT
WITH THE VERY SLOW PROGRESSION SOUTHEAST OF THE CUT-OFF LOW OVER
BRITISH COLUMBIA THROUGH SATURDAY NIGHT 30/18Z.  AFTER THAT TIME
PERIOD...THE STRONGER UPSTREAM FLOW BECOMES HIGHLY INFLUENTIAL AND
BEGIN TO MOVE THE OPENING LOW TOWARD THE EAST. THE 00Z UKMET AND
CMC APPEAR TO PROGRESSIVE WITH SHIFTING THE LOW FURTHER EAST WHICH
GOES AGAINST THE ENSEMBLE MODEL TRENDS AND SO ARE NOT PREFERRED.
THE 12Z GFS LOOKS IN LINE WITH PRIOR GUIDANCE AND IS PREFERRED
ALONG WITH THE 00Z ECMWF SOLUTION AS GOOD REPRESENTATIVES OF THE
00Z ECMWF ENSEMBLE MEAN...THOUGH THE SPREAD IN SOLUTIONS REDUCES
CONFIDENCE TOWARD THE END OF THE PERIOD.


WEAKENING PACIFIC CUT-OFF LOW PROGRESSING TO CENTRAL U.S. PACIFIC
COAST BY END OF THE PERIOD
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF
CONFIDENCE:  AVERAGE

WELL DEFINED CUT-OFF UPPER LOW NEAR 40N150W...WOBBLES IN DAY 1 BUT
BEGINS TO MOVE EAST AND SLOWLY FILL EVENTUALLY BEGINNING TO OPEN
UP AS IT AFFECTS THE U.S. WEST COAST BY DAY 3 WITH A SLIGHT
NEGATIVE TILT ORIENTATION.  THE 00Z CMC APPEARS TO BE THE MOST
SIGNIFICANT OUTLIER AS IT MUCH STRONGER AND HAS A LESSER NEGATIVE
ORIENTATION TO ITS TROF AND IS NOT FAVORED. THE 12Z NAM ALSO
APPEARS TOO FAST IN ITS SOLUTIONS.  SO WITH CONTINUED GOOD RUN TO
RUN CONSISTENCY FOR THE BOTH THE 12Z GFS AND 00Z ECMWF AND EACH
BEING GOOD REPRESENTATIONS WITHIN THE ENSEMBLE SPREAD...A BLEND OF
THE TWO OPERATIONAL RUNS IS CURRENTLY 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...

GALLINA

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.