Prognostic Meteorological Discussion
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277
FXUS10 KWNH 220421
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1220 AM EDT SAT APR 22 2017

VALID APR 22/0000 UTC THRU APR 25/1200 UTC

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

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


SYSTEM MOVING THROUGH THE NORTHWEST INTO THE WEST
MONDAY INTO TUESDAY
~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 00Z NAM IS A BIT STRONGER THAN THE OTHER GUIDANCE WITH THIS
SYSTEM AS IT TRACKS THROUGH THE NORTHWEST INTO THE GREAT BASIN,
ONE OF ITS OLDER BIASES.  AS THE FLOW PATTERN IN WHICH IT IS
EMBEDDED IS ONE OF LOW AMPLITUDE, THE NAM IS LIKELY TOO STRONG
ALOFT. A COMPROMISE OF THE 12Z CANADIAN/12Z UKMET/00Z GFS/00Z NAM
APPEARS FINE, WHICH IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE.


SYSTEM MOVING INTO THE NORTHWEST SUNDAY NIGHT
SYSTEM MOVING BY THE CENTRAL US/CANADIAN BORDER MON/TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z UKMET NEARLY CLOSES OFF A 500 HPA CYCLONE ACROSS NORTHWEST
MN MONDAY NIGHT, WHICH IS QUITE A BIT STRONGER THAN THE REMAINDER
OF THE GUIDANCE.  AS THE FLOW PATTERN IN THE NORTHERN STREAM IS
ONE OF LOW AMPLITUDE, THE UKMET IS LIKELY TOO STRONG.  A
COMPROMISE OF THE 12Z ECMWF/12Z CANADIAN/00Z NAM/00Z GFS APPEARS
BEST, WHICH IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE.


DEEP CYCLONE IN THE SOUTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CANADIAN COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 12Z CANADIAN IS UP TO ITS OLD TRICKS, AND APPEARS TO FORM A
TROPICAL ENTITY IN THE FL STRAITS WHICH ROTATES INTO NC AS A
DEEPER CYCLONE THAN SEEN IN THE OTHER GUIDANCE.  IF THAT WEREN`T
ENOUGH, IT`S ALSO TOO FAR NORTH ALOFT BY LATE MONDAY/EARLY
TUESDAY, STRAYING FAR FROM THE DETERMINISTIC CONSENSUS.  A
COMPROMISE OF THE 00Z GFS/00Z NAM/12Z UKMET/12Z ECMWF IS PREFERRED
WITH ABOVE AVERAGE CONFIDENCE.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

ROTH
$$





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