Prognostic Meteorological Discussion
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FXUS10 KWNH 170652
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 AM EDT THU APR 17 2014

VALID APR 17/0000 UTC THRU APR 20/1200 UTC

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


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


UPPER TROUGH / SURFACE LOW WEAKENING ACROSS THE GREAT LAKES TODAY
AND REACHING THE NORTHEAST ON SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE 00Z UKMET/CMC HAVE COME INTO AGREEMENT WITH THE REMAINING
MODEL CONSENSUS ACROSS THE UPPER MIDWEST CONCERNING THE SURFACE
AND 850 MB LOW EARLY THIS MORNING. AFTER THE SURFACE LOW WEAKENS
INTO ONTARIO EARLY FRI MORNING...THE UPPER TROUGH BECOMES
REVITALIZED FROM THE NORTH AS THE SYSTEM APPROACHES THE NORTHEAST
FOR SATURDAY. THE LATEST 00Z MODEL SUITE NOW SHOWS ENOUGH
AGREEMENT REGARDING IMPACTS TO THE NORTHEAST U.S. TO PREFER A
GENERAL MODEL COMPROMISE.


CLOSED MID-LEVEL LOW FORMING OVER THE SOUTHEAST U.S. AT END OF WEEK
CORRESPONDING SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z ECMWF/UKMET COMPROMISE
CONFIDENCE:  BELOW AVERAGE

DETERMINISTIC AND ENSEMBLE SPREAD REMAINS WELL ABOVE AVERAGE FOR
THE RELATIVELY SHORT FORECAST TIME FRAME WITH THE EVENTUAL AND
LIKELY CLOSED LOW ACROSS THE SOUTHEAST. AS WE HEAD INTO EARLY
SATURDAY...THERE HAD BEEN A SLOWING TREND SEEN IN THE UKMET/CMC
THROUGH THEIR 12Z/16 RUNS BUT NOT MUCH OF A TREND SEEN IN THE
ECMWF. WITH THE ARRIVAL OF THE 00Z ECMWF/UKMET/CMC...THERE IS LESS
OF A DIFFERENCE IN TIMING BUT PERHAPS MORE WITH LATITUDE AND
STRENGTH. THE 00Z ECMWF DID SLOW A BIT FRI NIGHT COMPARED TO ITS
12Z/16 RUN...BUT IT MATCHES WELL WITH THE LONGITUDE OF THE 00Z
UKMET...WITH THE 00Z CMC STILL A BIT SLOWER THAN THE ECMWF/UKMET.

THE 00Z GFS IS EARLY TO CLOSE OFF A MID-LEVEL CENTER COMPARED TO
THE REMAINING GUIDANCE AND APPEARS TO BE SUFFERING FROM SOME
GRID-SCALE FEEDBACK WHICH IS A POSSIBLE REASON FOR WHY THE GFS IS
AHEAD MOST WITH THE TIMING OF THE UPPER TROUGH ACROSS THE
SOUTHEAST. THE GEFS IS SIMILAR TO THE GFS.

GIVEN SOME OF THE OBSERVED SLOWING TRENDS FROM EARLIER RUNS...AND
THE PLACEMENT OF THE LATEST 00Z MODEL SUITE OUTSIDE OF THE 00Z
NAM/GFS...THE PREFERENCE IS TO BE CLOSE TO THE LATEST ECMWF/UKMET
WHICH IS JUST A BIT SLOWER THAN THE MIDDLE OF THE 12Z/16 ENSEMBLE
MEMBERS.


UPPER TROUGH REACHING THE PACIFIC NORTHWEST TODAY AND FRI
AND REACHING SOUTH CENTRAL CANADA BY SAT NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z NAM/GFS/ECMWF COMPROMISE
CONFIDENCE:  AVERAGE

THE 00Z NAM AND 00Z ECMWF HAVE BETTER AGREEMENT WITH THE ENSEMBLE
MEANS IN BEING A BIT NORTH WITH THE TRACK OF THE VORTICITY CENTER
AS IT REACHES INTO S-CNTRL CANADA COMPARED TO THE 00Z
GFS/UKMET/CMC. HOWEVER...THE MODELS TO THE SOUTH HAVE ALL TRENDED
FROM A POSITION FURTHER NORTH COMPARED TO YESTERDAY. THEREFORE...A
BLEND OF THE NORTH/SOUTH SOLUTIONS IS PREFERRED...GIVEN THE
RELATIVELY SMALL SPREAD...BEST REPRESENTED BY A 00Z NAM/GFS/ECMWF
COMPROMISE. THE UKMET/CMC HAVE BEEN REMOVED FROM THE PREFERENCE
GIVEN THEIR SURFACE LOW PLACEMENT DOES NOT ALIGN WITH THE BETTER
ENSEMBLE LOW CLUSTERING SAT MORNING ACROSS S-CNTRL CANADA.


UPPER TROUGH REACHING THE SOUTHWEST U.S. FRI AND SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  00Z GFS/ECMWF/UKMET COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

DIFFERENCES ARE SMALL...BUT THE 00Z NAM APPEARS TO BE A BIT AHEAD
OF THE PACK WITH RESPECT TO THE UPPER TROUGH ACROSS THE SOUTHWEST.
ALSO...THE 00Z CMC TRENDED STRONGER WITH SHORTWAVE ENERGY IN THE
BASE OF THE UPPER TROUGH AND IS NOW A LITTLE SLOWER THAN THE
REMAINING MODEL CONSENSUS. THE 00Z ECMWF/UKMET DID NOT CHANGE MUCH
FROM THEIR PREVIOUS 12Z RUNS. THEREFORE...A 00Z GFS/ECMWF/UKMET
COMPROMISE IS PREFERRED GIVEN THEIR AGREEMENT AND SMALL RUN-TO-RUN
VARIANCE.


UPPER TROUGH REACHING THE PACIFIC NORTHWEST ON SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE:  GENERAL MODEL COMPROMISE
CONFIDENCE:  ABOVE AVERAGE

THE LATEST GUIDANCE SHOWS ONLY SMALL DIFFERENCES WITH THIS
SYSTEM...SO THEREFORE A GENERAL MODEL COMPROMISE IS PREFERRED.



...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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