Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5
000
FXUS10 KWNH 251852
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT TUE APR 25 2017

VALID APR 25/1200 UTC THRU APR 29/0000 UTC

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

12Z MODEL EVALUATION WITH FINAL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...CONSOLIDATING CYCLONE MOVING UP THE EAST COAST THROUGH THU...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE ENSEMBLE SCATTER LOW PLOTS HAVE SHOWN A GRADUAL TREND TO THE
NORTH OVER THE PAST 3-4 12Z/00Z CYCLES...AND WHILE THERE ARE SOME
MINOR PLACEMENT DIFFERENCES WITH THE SURFACE AND MID-LEVEL LOW
TRACKING NEAR THE NEW ENGLAND COAST...THE BIGGEST DIFFERENCE MAY
BE WITH THE PLACEMENT OF THE 500 MB LOW BY 00Z/28 WITH THE 12Z NAM
DISPLACED FARTHER OFFSHORE COMPARED TO THE REMAINING MODEL
GUIDANCE. OUTSIDE OF THE 12Z NAM...GOOD MODEL AGREEMENT EXISTS
WITH THIS SYSTEM.


...SURFACE CYCLONE REACHING THE PACIFIC NORTHWEST TODAY/TONIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


...LOW AMPLITUDE SHORTWAVE REACHING THE PACIFIC NORTHWEST WED
MORNING AND REACHING THE SRN/CNTRL PLAINS FOR THU NIGHT...
...WEAK SURFACE LOW TRACKING INTO THE MIDWEST ON FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE MODELS SHOW MINOR DIFFERENCES WITH THIS SYSTEM AS IT KICKS OUT
INTO THE PLAINS REGARDING MID-LEVEL HEIGHTS AND THE SURFACE LOW
WEAKENING FROM THE SRN PLAINS TOWARD THE MISSISSIPPI VALLEY.
DESPITE MODEL DIFFERENCES...ENSEMBLE SPAGHETTI HEIGHTS AND SCATTER
LOW PLOTS DO NOT SHOW ANY DETERMINISTIC RUN TO BE AN OUTLIER AND
THERE IS BROAD ENOUGH AGREEMENT WITH THIS SYSTEM TO RECOMMEND A
GENERAL MODEL COMPROMISE.


...SHORTWAVE DROPPING INTO DEVELOPING LARGE SCALE TROUGH ACROSS
THE INTERMOUNTAIN WEST FRI/SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS / 12Z ECMWF BLEND
CONFIDENCE: BELOW AVERAGE

ENSEMBLE SPAGHETTI HEIGHTS SHOW MODEST SPREAD EVOLVING ACROSS THE
WRN U.S. THROUGH FRI WITH LARGE DIFFERENCES SEEN IN THE 552 DAM
HEIGHT. THE PREFERENCE FOR NOW WILL BE TO STAY TOWARD THE MIDDLE
OF THE SPREAD. THE 12Z GFS IS A BIT DEEPER THAN THE OVERALL MODEL
CONSENSUS AND ITS 12Z ENSEMBLE MEAN ACROSS THE SOUTHWEST REGARDING
THE MID-LEVEL TROUGH...WHILE THE 12Z ECMWF REMAINS CONSISTENT WITH
ITS PREVIOUS RUNS KEEPING THE FEATURE A BIT FURTHER NORTH AND
WEAKER. A GFS/ECMWF BLEND IS PREFERRED TO PLACE THE TROUGH IN THE
MIDDLE OF THE ENVELOPE OF ENSEMBLE SOLUTIONS BUT CONFIDENCE IS LOW
GIVEN THE BROAD NATURE OF THIS SYSTEM.


...SYSTEM MOVING NORTHWARD THROUGH THE PLAINS INTO SE CANADA ON
THU...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND OF THE 12Z MODELS
CONFIDENCE: AVERAGE

A PORTION OF THIS SYSTEM IMPACTS THE N-CNTRL U.S. TUE NIGHT INTO
WED WITH A 500 MB VORT CENTER AND CORRESPONDING 850 MB LOW. WHILE
THE 12Z NAM APPEARS REASONABLE WITH ITS PLACEMENT...IT IS
DISPLACED SLIGHTLY WEST OF THE ENSEMBLE MEANS 12Z/26. THE 12Z
ECMWF IS SHOWING GOOD CONSISTENCY WITH ITS PREVIOUS RUNS AND
REMAINS CLOSE TO THE ENSEMBLE MEANS...AND THE 12Z UKMET AND CMC
HAVE COME INTO BETTER AGREEMENT WITH THE CONSENSUS THAN THEIR
PREVIOUS RUNS SHOWED.

FARTHER SOUTH...A NEGATIVELY TILTED SHORTWAVE IS FORECAST TO SWING
ACROSS THE MISSISSIPPI VALLEY WED NIGHT AND THE DISTANCE BETWEEN
THIS FEATURE AND THE CLOSED LOW HAS IMPACTS FOR LATER IN THE
FORECAST. THE 12Z UKMET AND CMC SOLUTIONS AGAIN HAVE COME INTO
BETTER AGREEMENT WITH THE 12Z GFS AND 12Z ECMWF...WHICH LEAVES THE
12Z NAM LOOKING LIKE SOMETHING OF AN OUTLIER. IT SHOULD BE NOTED
THAT THERE IS STILL CONSIDERABLE MODEL SPREAD IN THE SURFACE LOW
AND IMPLIED FRONTAL POSITIONS...SO CONFIDENCE REMAINS ONLY AVERAGE
WITH THE EVOLUTION OF THE UPPER SYSTEM AND SURFACE COLD FRONT
MOVING THROUGH THE OHIO VALLEY INTO THE MID-ATLANTIC REGION FOR
THU/FRI. A BLEND OF THE 12Z MODELS THAT EXCLUDES THE NAM LOOKS
BEST.


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

OTTO/MCDONNAL

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.