Prognostic Meteorological Discussion
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FXUS10 KWNH 171857
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT FRI APR 17 2015

VALID APR 17/1200 UTC THRU APR 21/0000 UTC

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

12Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NOTE THAT THE 17/12Z CMC WAS NOT AVAILALBE FOR THIS DISCUSSION.

NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.



UPPER LOW CLOSING OFF IN NORTHERN MN EARLY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/00Z ECMWF COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z GFS IS FASTER WITH THE UPPER TROUGH REACHING THE NRN
PLAINS BY SUN MORNING...WITH THE 12Z UKMET SLOWEST/BACK TOWARD THE
WEST. THE ENSEMBLE MEANS SUPPORT A MIDDLE GROUND...CLOSEST TO THE
12Z NAM AND 00Z ECMWF WHICH FIT THE MIDDLE OF THE DETERMINISTIC
SPREAD. THE 12Z ECMWF MADE SOME SMALL AJUSTMENTS TO BE WEAKER
ALOFT AND NOW DIGS THE SHORTWAVE ENERGY A BIT FARTHER SOUTH THAN
ITS PREVIOUS CYCLE. THE 00Z ECMWF IS CONSIDERED A BETTER CYCLE
THAN THE 12Z ECMWF.


CLOSED LOW WEAKENING EWD FROM THE ROCKIES
  SURFACE LOW REACHING THE GREAT LAKES REGION SUN NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/GFS/ECMWF/UKMET COMPROMISE
CONFIDENCE: AVERAGE

THE 12Z ECMWF/UKMET MADE ADJUSTMENTS TOWARD THE 12Z NAM/GFS AND
NOW ONLY THE 00Z CMC APPEARS SIGNIFICANTLY DIFFERENT WITH THE
EVOLUTION OF THE CLOSED LOW FROM THE WEST AND SHOTWAVE ORIGINATING
FROM NRN MEXICO. ENSEMBLE SCATTER LOW PLOTS SUPPORT A
NAM/GFS/ECMWF/UKMET POSITION WITH A BLEND IN POSITION/STRENGTH
CLOSLY MATCHING THE ENSEMBLE MEANS.


*ENERGY ALOFT DROPPING DOWN THE CA COAST SAT/SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z CMC COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GUIDANCE SHOWS REASONABLY GOOD AGREEMENT WITH THIS SYSTEM
OUTSIDE OF THE 00Z CMC WHICH IS FARTHER OFFSHORE. A BLEND IN
STRENGTH OF THE NON 00Z CMC IS PREFERRED.


SHORTWAVE CROSSING NEW ENGLAND SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM / 12Z ECMWF BLEND
CONFIDENCE: ABOVE AVERAGE

THE 12Z GFS TRENDED MUCH WEAKER ALOFT AND HAS AN ILL DEFINED
SURFACE LOW NEAR MAINE...WHILE THE SREF/GEFS/EC MEANS SUPPORT MORE
OF A LOW LEVEL REFLECTION FROM THE UPPER WAVE THAN THE GFS
DEPICTS. THE 12Z UKMET IS WEAK...SIMILAR TO THE 12Z GFS AND WEAK
COMPARED TO THE ENSEMBLE MEANS...BUT THE 12Z NAM AND 12Z ECMWF
MAKE UP A GOOD COMPROMISE IN LINE WITH THE AGREEABLE ENSEMBLE
MEANS. GIVEN THE SHORT TERM NATURE OF THIS FEATURE AND THE GOOD
AGREEMENT SEEN IN THE ENSEMBLES...CONFIDENCE IS ABOVE AVERAGE.


...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

$$





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