Prognostic Meteorological Discussion
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FXUS10 KWNH 011853
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
152 PM EST SUN MAR 01 2015

VALID MAR 01/1200 UTC THRU MAR 05/0000 UTC

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

12Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


INITIAL UPPER LOW/TROUGH
ASSOCIATED SFC LOW / COLD FRONT MOVING OUT OVR THE CNTRL PLAINS
TUE TO GRT LAKES BY WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 01/12Z ECMWF AND 01/12Z GFS
CONFIDENCE: AVERAGE

THE MODELS STILL SHOW MORE SEPARATION BETWEEN THE INITIAL
SHORTWAVE OVER SOUTHERN CA TODAY AND TONIGHT WITH A SECOND
SHORTWAVE TROF DROPPING SOUTH ALONG THE WEST COAST OF NORTH
AMERICA. THE NAM HAS BEEN STRUGGLING WITH THE INTENSITY AND
PLACEMENT OF THE SHORTWAVES.  IT HAS FAIRLY DECENT AGREEMENT WITH
OTHER MODELS INTO LATE MONDAY NIGHT/EARLY TUESDAY NIGHT BEFORE IT
AMPLIFIES A TROF DROPPING SOUTH FROM CANADA WHERE THE EC/GFS DO
NOT.  IN THE BROADEST SENSE...THE ECMWF AND GFS HAD BEST RUN TO
RUN CONTINUITY.  ONE AREA WHERE THE TWO MODELS DIVERGED WAS ACROSS
PARTS OF THE CENTRAL/SOUTHERN PLAINS WHERE THE ECMWF WAS NOT AS
FAR SOUTH AS THE GFS WITH THE TAIL END OF THE FRONT.  THE UKMET
TRACKS WELL WITH THE ECMWF UNTIL THE SURFACE LOW REACHES THE
SOUTHERN GREAT LAKES LATE WEDNESDAY...WHILE THE SURFACE FRONT WAS
SOUTH OF THE EC IDEA.  THE DIFFERENCE SEEMS TO REVOLVE AROUND THE
STRENGTH OF THE SFC HIGH...WITH THE GFS BEING SOME 3 TO 5 MB
STRONGER.  THE CANADIAN WAS BACK NEAR THE ECMWF.

A COMPROMISE BETWEEN THE GFS/ECMWF SHOULD HELP SPLIT THE
DIFFERENCE BETWEEN THE TWO...AND GET CLOSE TO A UKMET/CANADIAN
CONSENSUS.


SECONDARY SHORTWAVE ENERGY DIVING SOUTHWARD ALONG WEST COAST OF
NORTH AMERICA MONDAY
CROSSING BACK INTO SOUTHWEST STATES LATE TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z UKMET/NAM BLEND
CONFIDENCE: AVERAGE

THERE IS STRONG SUPPORT FOR THIS SHORTWAVE TO BE FARTHER OFFSHORE
THAN WHAT IS SHOWN BY THE UKMET AND NAM THROUGH MON...WITH THE
REMAINING MODEL CONSENSUS IN REASONABLE AGREEMENT.


ADDITIONAL SHORTWAVE ENERGY DROPPING OUT OF CANADA INTO
NORTHERN/WESTERN U.S. BY WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON NAM
CONFIDENCE: AVERAGE

THE NAM AND ECMWF/GFS ARE IN PRETTY GOOD AGREEMENT WITH THE MID
LEVEL FLOW PATTERN AS ENERGY COMES OUT OF CANADA LATE TUESDAY
NIGHT.  THAT IS WHEN THE MODEL SOLNS REALLY BEGIN TO DIVERGE AS
THE NAM TAKES THE LEAD SHORTWAVE AND AMPLIFIES IT SIGNIFICANTLY
OVER ID AND DROPS A POTENT WAVE INTO UT/NE AZ.  THIS IDEA HAS
LITTLE SUPPORT FROM OTHER MODELS...WHICH TEND TO KEEP THE ENERGY
IN THE NORTHERN STREAM.


NRN STREAM SHORTWAVE TRACKING FROM THE N-CNTRL U.S. TO NEW ENGLAND
ASSOCIATED COLD FRONT PUSHING THROUGH THE NRN HIGH PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 01/12Z GFS...01/12Z ECMWF BLEND
CONFIDENCE: AVERAGE

AGREE WITH PREVIOUS FORECASTER THAT WHILE THE GFS MAY RETREAT COLD
AIR TOO QUICKLY ACROSS THE SOUTHERN PLAINS...IT IS PRETTY MUCH A
NON FACTOR DURING LATER PERIODS OF THE SHORT RANGE.  WE DO NOTE
THAT THE TWO CAMPS OF MODELS SOLN...ONE THAT IS FARTHER WEST WITH
A COASTAL FRONT ALONG THE EAST COAST AND SUBSEQUENT SURFACE LOW
DEVELOPMENT...AND ANOTHER CAMP FARTHER EAST. CURRENTLY...THE
SREF/GEFS/EC ENSEMBLES SUPPORT A NAM/GFS/ECWMF BLEND OF MODELS.
THE UKMET AND CANADIAN WERE ALSO CLUSTERED IN PRETTY MUCH THE SAME
AREA. WILL STILL RECOMMEND THE GFS/ECMWF.

...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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