Prognostic Meteorological Discussion
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263
FXUS10 KWNH 270448
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 AM EDT SAT MAY 27 2017

VALID MAY 27/0000 UTC THRU MAY 30/1200 UTC

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

00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...WEAK MID LEVEL SHORTWAVE/SURFACE LOW TRACKING FROM THE OH
VALLEY TO THE MID ATLANTIC ON SAT ...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

BOTH THE 00 UTC NAM AND GFS ARE A LITTLE SLOWER THAN THEIR 12 UTC
RUNS WITH THE SURFACE LOW AS IT TRACKS EAST FROM THE OH VALLEY
INTO THE MID ATLANTIC REGION SAT MORNING.  THERE ARE SOME SLIGHT
TIMING DIFFERENCES WITH THIS SYSTEM AS THE LOW STARTS TO MOVE OFF
OF THE VA/NC COAST...WITH THE 12 UTC ECMWF AND CANADIAN GLOBAL
BOTH SLIGHTLY FASTER...BUT OVERALL...THE LATEST DETERMINISTIC
GUIDANCE IS IN GENERALLY GOOD AGREEMENT.


...UPPER LOW MOVING SLOWLY FROM WESTERN MANITOBA INTO THE UPPER
GREAT LAKES ON MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/12 UTC ECMWF
CONFIDENCE: AVERAGE

THE 00 UTC NAM HAS REMAINED CONSISTENT WITH ITS 12 UTC RUN.  EARLY
TUE...THE 00 UTC GFS LIFTS THE LOW FURTHER TO THE NORTH INTO
NORTHERN ONTARIO THAN THE 12 UTC GFS WAS SHOWING.  THE NAM IN
COMPARISON TO THE OTHER DETERMINISTIC RUNS STARTS TO BECOME A
RELATIVELY DEEP OUTLIER ON MON AS THE LOW MOVES ACROSS THE GREAT
LAKES AND BEGINS TO LIFT BACK TO THE NORTH INTO ONTARIO.
OVERALL...THE 00 UTC GFS AND 12 UTC ECMWF HANDLE THIS SYSTEM
SIMILARLY.

...UPPER TROUGH OVER NORTHERN ROCKIES/INTERMOUNTAIN WEST DIGGING
ACROSS CENTRAL ROCKIES SAT...
...WEAK SURFACE LOW AND FRONTAL BOUNDARY ACROSS THE LOWER/MIDDLE
MS VALLEY SAT NIGHT/SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET COMPROMISE
CONFIDENCE: AVERAGE

THE NAM AND GFS HAVE SHOWN GOOD RUN-TO-RUN CONTINUITY WITH THEIR
12 UTC RUNS AND OVERALL THE LATEST DETERMINISTIC GUIDANCE IS IN
GENERALLY GOOD AGREEMENT.  THE BIGGEST EXCEPTION AT THIS POINT IS
THE 12 UTC UKMET...WHICH SHOWS A MORE AMPLIFIED MID LEVEL
SHORTWAVE/SURFACE LOW TRACKING NORTHEAST ALONG THE OH VALLEY INTO
THE LOWER GREAT LAKES REGION ON SUN.

...UPPER TROUGH APPROACHING THE NORTHWEST TUE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

OVERALL...THE MODELS ARE IN GENERALLY GOOD AGREEMENT WITH THIS
SYSTEM.

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

PEREIRA

$$





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