Prognostic Meteorological Discussion
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000
FXUS10 KWNH 230421
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1220 AM EDT SAT MAY 23 2015

VALID MAY 23/0000 UTC THRU MAY 26/1200 UTC

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

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


UPPER LOW DRIFTING ACROSS THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z UKMET IS THE ODD MODEL OUT, ADVERTISING TWO FEATURES FOR
THE PRICE OF ONE -- ONE THAT IS SOUTH OF MOST OF THE GUIDANCE
THROUGH MONDAY AND ANOTHER THAT EVOLVES OFFSHORE WA.  A COMPROMISE
OF THE 00Z GFS/00Z NAM/12Z CANADIAN/12Z ECMWF LOOKS GOOD HERE AND
FITS THE 12Z ECMWF/18Z GEFS MEAN SOLUTIONS, WHICH IS PREFERRED
WITH ABOVE AVERAGE CONFIDENCE.


CLOSED LOW MOVING THROUGH THE NORTHERN PLAINS MONDAY
PAIR OF SURFACE WAVES MOVING INTO SOUTHERN CANADA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CANADIAN/ECMWF COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ALOFT, THE 12Z UKMET IS THE WEAKEST MEMBER OF THE GUIDANCE.
DISCOUNTED THIS IDEA AS THE SYSTEM WOULDN`T ENTER CONFLUENT FLOW
ALOFT UNTIL IT EJECTED INTO SOUTHERN CANADA LATE MONDAY.  THE 00Z
NAM/00Z GFS STREAK A SURFACE LOW FROM MN QUICKLY INTO QUEBEC
TUESDAY MORNING, WHICH ENJOYS MINIMAL 12Z GLOBAL ENSEMBLE SUPPORT.
 OVERALL, A COMPROMISE OF THE 12Z CANADIAN/12Z ECMWF BEST FITS THE
12Z ECMWF/18Z GEFS ENSEMBLE MEAN SOLUTIONS, AND IS PREFERRED WITH
SLIGHTLY ABOVE AVERAGE CONFIDENCE.


SYSTEM MOVING INTO THE SOUTHERN PLAINS MON/TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CANADIAN/UKMET/ECMWF COMPROMISE
CONFIDENCE: AVERAGE

THE GUIDANCE GUIDES THIS SYSTEM FROM OFFSHORE OR THROUGH THE
SOUTHWEST SIMILARLY THROUGH SATURDAY NIGHT.  THEREAFTER, THE 00Z
GFS/00Z NAM OUTPACE THE REMAINDER OF THE GUIDANCE.  THIS SHORTWAVE
IS NAVIGATING AROUND THE SOUTHWEST PERIPHERY OF AN UPPER LOW WHICH
IS WEAKENING AS IT MOVES INTO SOUTHERN CANADA, WHICH MAY NOT BE
ABLE TO ACCELERATE THE SHORTWAVE ALONG BY MONDAY.  THE 12Z
ECMWF/18Z GEFS MEANS SUPPORT THE SLOWER 12Z CANADIAN/12Z UKMET/12Z
ECMWF SOLUTIONS, WHICH ARE PREFERRED WITH AVERAGE CONFIDENCE
CONSIDERING THE COMPLEXITY OF THE FLOW PATTERN IN ITS VICINITY.

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

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

ROTH
$$




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