Prognostic Meteorological Discussion
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000
FXUS10 KWNH 231644
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 PM EDT TUE MAY 23 2017

VALID MAY 23/1200 UTC THRU MAY 27/0000 UTC

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

12Z NAM/GFS EVALUATION WITH INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...CLOSED UPPER LOW OVER THE UPPER MIDWEST DIGGING ACROSS THE
MIDDLE/LOWER MS VALLEY LATE WED...MOVING TO THE EAST COAST
THU...EXITING NEW ENGLAND FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

MODELS AGREE WELL THROUGH WED AS THE UPPER LOW DIGS TO A POSITION
OVER THE MIDDLE/LOWER MS VALLEY. MODELS  DIVERGE SLIGHTLY THU AND
FRI...AS SHORTWAVE ENERGY MOVING THROUGH THE BASE OF THE TROUGH
AFFECTS ITS DEVELOPMENT AND PROGRESSION. EVEN THEN...MODEL
AGREEMENT IS GOOD OVERALL SHOWING THAT THE UPPER TROUGH WILL TAKE
ON A NEGATIVE TILT ON THU...WITH THE UPPER LOW NEAR THE OHIO
VALLEY AND SHORTWAVE ENERGY/VORTICITY SWINGING THROUGH THE BASE OF
THE TROUGH OVER THE MIDDLE ATLANTIC. THE 12Z NAM AND THE 00Z RUNS
OF THE ECMWF...CMC...AND UKMET FORM A FAIRLY CLOSE SET OF
SOLUTIONS. THE 12Z GFS IS SIMILAR TO ITS 00Z RUN...AND IT REMAINS
THE MOST PROGRESSIVE OF THE MODEL SOLUTIONS. WHILE IT IS SOMETHING
OF AN OUTLIER COMPARED TO THE OTHER MODELS...THE DIFFERENCE IS NOT
THAT GREAT AND I WOULD BE RELUCTANT TO AUTOMATICALLY DISCOUNT IT.
THEREFORE A GENERAL MODEL BLEND IS RECOMMENDED.


...SUBTLE SHORTWAVE FEATURES AND SOUTHERN BRANCH JET MOVING ACROSS
THE SOUTHEAST TODAY...
...SURFACE LOWS TRAVERSING THE GULF COAST INTO THE SOUTHEAST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

WHILE SOME MINOR DIFFERENCES STILL EXIST...MODELS HAVE CONVERGED
ON SIMILAR SOLUTIONS WITH THIS ACTIVITY MOVING ACROSS THE
SOUTHEAST AND MID ATLANTIC. THUS A GENERAL MODEL BLEND SHOULD WORK
FINE.


...UPPER TROUGH MOVING ACROSS THE NORTHWEST THROUGH MID WEEK...
...DEVELOPING LONGWAVE TROUGH OVER THE WEST...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AN UPPER LOW OVER HAIDA GWAII WILL DIG SOUTHEAST ACROSS BRITISH
COLUMBIA TONIGHT...THEN MOVE SLOWLY EASTWARD ACROSS ALBERTA AND
SASKATCHEWAN WED AND THU. THE UPPER LOW WILL LEAVE A TRAILING
TROUGH MOVING SLOWLY EASTWARD OVER THE NORTHWEST TUE AND
WED...WITH ADDITIONAL SHORTWAVE ENERGY CARVING OUT A SOMEWHAT
DEEPER TROUGH OR CLOSED LOW OVER THE REGION THU AND FRI. MODELS
ARE INITIALLY IN VERY GOOD AGREEMENT WITH THIS SYSTEM. THE 12Z NAM
IS QUITE AGGRESSIVE WITH THE SHORTWAVE ENERGY...FORMING A CLOSED
LOW ALONG THE OR/ID BORDER LATE THU. THE 00Z RUNS OF THE CMC AND
UKMET SHOW THIS TENDENCY ALSO...BUT NOT QUITE AS STRONG. THE 12Z
GFS IS SIMILAR TO THE 00Z GFS...AND THEY BOTH MATCH WELL WITH THE
00Z ECMWF. FOR NOW A BLEND OF THE 12Z GFS AND 00Z ECMWF CONTINUES
TO LOOK LIKE THE MOST LIKELY SOLUTION.


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

MCDONNAL

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