Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10
000
FXUS10 KWNH 260639
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
138 AM EST MON JAN 26 2015

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

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

00Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


MID-LEVEL SHORTWAVE MOVING INTO BRITISH COLUMBIA MON NIGHT
SUBSEQUENT MOVEMENT INTO THE N-CNTRL U.S. EARLY THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS...00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE 00Z GFS AND 00Z ECMWF CONTINUE TO REPRESENT THE MIDDLE OF THE
LATEST DETERMINISTIC/ENSEMBLE SPREAD WITH A MID-LEVEL SHORTWAVE
FORECAST TO CROSS INTO SWRN CANADA TUE MORNING. THE 00Z NAM AND
00Z CMC ARE FLATTER...WHILE THE 00Z UKMET IS ON THE
STRONGER/DEEPER SIDE OF THE AVAILABLE GUIDANCE.


WEAKENING CLOSED LOW MOVING INTO CALIFORNIA EARLY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE THROUGH 12Z/28
    00Z ECMWF 12Z/28-12Z/29
CONFIDENCE: AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT HERE THROUGH 12Z/28 AT WHICH
POINT THE 12Z ECMWF HOLDS MORE SHORTWAVE ENERGY BACK TO THE WEST
ACROSS THE GREAT BASIN WHILE THE GFS FOCUSES MORE TOWARD THE FRONT
END OF THE SHORTWAVE TROUGH PROGRESSING ACROSS THE WEST. SEVERAL
OF THE MODELS HAVE TRENDED TOWARD THE 12Z ECMWF IDEA COMPARED TO
PREVIOUS CYCLES...BUT THE GFS HOLDS GOOD CONTINUITY FROM 00Z/25.
THE 00Z ECWMF TRENDED SOME TOWARD THE GFS...JUST ENOUGH SO THAT
THE 70/30 ECMWF/GFS BLEND RECOMMENDED EARLIER CAN BE REPALCED WITH
100 PERCENT 00Z ECMWF. THE ENSEMBLE MEANS REMAIN SPLIT ON THIS
IDEA.


WEAK CLIPPER PASSING THROUGH THE UPPER MISS VALLEY MON/TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT HERE.


CLIPPER-TYPE SYSTEM EVOLVING INTO A NOR`EASTER MON/TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM / 00Z ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE MODELS HAVE CONVERGED TOWARD A COMMON SOLUTION BUT AS IS
ALWAYS THE CASE WITH THESE BIG STORMS...SMALL DETAIL DIFFERENCES
RESULT IN LARGE IMPACT DIFFERENCES...ESPECIALLY WITH
PRECIPITATION. PREFERENCES LISTED HERE REFLECT MODEL POSITION AND
MASS FIELDS...BUT REFER TO WPC WINTER WEATHER AND QPF DESK
PRODUCTS FOR INFORMATION ON LIQUID EQUIVALENTS/SNOW.

THROUGH 12Z/27...THE 00Z NAM/GFS/ECMWF SHOW FAIRLY GOOD AGREEMENT
IN POSITION AND STRENGTH REGARDING THE SURFACE AND MID-LEVEL LOWS
BUT THE GFS IS SLIGHTLY WEAKER BY TUE MORNING. ENSEMBLE TRENDS AND
THE LATEST ENSEMBLE MEANS...INITIALIZED 12Z/25...SUPPORT THE
NAM/GFS/ECMWF COMBO.

BEYOND 12Z/27...A BLEND OF THE 00Z NAM/ECMWF APPEARS BEST AS THE
GFS LIFTS THE PRIMARY SURFACE LOW TO THE NORTH...QUICKER THAN
PREFERRED. HOWEVER...THE 21Z SREF MEAN...12Z EC MEAN AND 00Z NAM
ARE IN GOOD AGREEMENT AND SUPPORT A TRACK THAT IS FASTER TO DEPART
THE PRIMARY SURFACE LOW COMPARED TO THE 00Z ECMWF. THE 00Z ECMWF
DID ADJUST IN THE DIRECTION OF THE NAM/SREF/EC MEAN COMPARED TO
ITS 12Z RUN REGARDING POSITION/STRENGTH. THEREFORE...A BLEND OF
THE 00Z NAM AND 00Z ECMWF IS PREFERRED AS BOTH THE 00Z UKMET/CMC
APPEAR EITHER UNSUPPORTED IN POSITION OR STRENGTH.


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

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

OTTO

$$




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