Prognostic Meteorological Discussion
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000
FXUS10 KWNH 210639
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 AM EDT TUE APR 21 2015

VALID APR 21/0000 UTC THRU APR 24/1200 UTC

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

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


TROUGHING IN THE SOUTHWEST WEDNESDAY INTO FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT HERE, THOUGH IT HAS SHOWN BAD
CONTINUITY AS OF LATE.  MEDIUM RANGE MENTIONS THAT DESPITE RECENT
GUIDANCE VARIANCE, THE MODELS HAVE BEEN TRYING TO BRING THIS
SYSTEM INTO THE SOUTHERN PLAINS IN THE 25/00Z TIME FRAME, WHICH
THE MOST RECENT RUNS WOULD ACCOMPLISH.  THE PREFERENCE IS FOR A
GENERAL MODEL COMPROMISE WITH AVERAGE CONFIDENCE.


DEEP CYCLONE APPROACHING THE NORTHWEST LATE THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CLOSE TO THE ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THERE HAS BEEN A TREND TO THE SOUTH WITH THIS SYSTEM SINCE THE 12Z
RUNS OF THE GUIDANCE, WHICH HAS LEFT THE 00Z GFS AS A NORTHWARD
OUTLIER.  DESPITE THE SHIFT ALOFT, VARIANCE REMAINS WITH THE
SYSTEM`S SURFACE LOW.  THE 00Z ECMWF SPLITS THE DIFFERENCE AT THE
SURFACE AND IS PREFERRED WITH SLIGHTLY BELOW AVERAGE CONFIDENCE.


CLOSED LOW MOVING ACROSS INTO SOUTHWEST CANADA THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: CANADIAN/ECMWF COMPROMISE
CONFIDENCE: AVERAGE

AN AMPLIFIED RIDGE IN THE NORTHERN STREAM SHOULD ALLOW THIS SYSTEM
TO SLIDE EASTWARD UNDER ITS BASE, SIMILAR TO THE BEHAVIOR OF THE
NON-GFS GUIDANCE.  PROGRESSION AND LATITUDE ISSUES REMAIN, WITH
THE 00Z NAM THE SLOWEST AND THE UKMET THE QUICKEST -- THEIR USUAL
BIASES.  PREFER A COMPROMISE OF THE 00Z CANADIAN/00Z ECMWF WITH
AVERAGE CONFIDENCE.


DEEP CYCLONE MOVING ACROSS NEW ENGLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/CANADIAN/ECMWF/NAM COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 00Z UKMET IS QUICKER TO PROGRESS THE SYSTEM EASTWARD WHEN
COMPARED TO THE OTHER GUIDANCE -- ITS USUAL BIAS.  A COMPROMISE OF
THE 00Z GFS/00Z NAM/00Z CANADIAN/00Z ECMWF SHOULD EFFECTIVELY DEAL
WITH REMAINING DETAIL ISSUES WITH SLIGHTLY ABOVE AVERAGE
CONFIDENCE.


...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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