Prognostic Meteorological Discussion
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FXUS10 KWNH 221713
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
112 PM EDT FRI AUG 22 2014

VALID AUG 22/1200 UTC THRU AUG 26/0000 UTC

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


UPPER TROUGHING MOVING FROM THE GREAT LAKES ACROSS THE NORTHEAST
COLD FRONT SINKING SWD THROUGH THE EAST COAST STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS / 00Z ECMWF BLEND
CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM CONTINUES TO INSIST ON STRONGER HEIGHT FALLS DIGGING
SWD DOWN ALONG THE EAST COAST OVER THE NEXT COUPLE OF DAYS AS
COMPARED TO THE GLOBAL MODEL CONSENSUS. THE NAM AS A RESULT
GENERALLY SENDS A COLD FRONT A LITTLE MORE QUICKLY SWD DOWN THE
ERN SEABOARD AS WELL AND INTO THE SOUTHEAST THROUGH THE WEEKEND.
THE STRONGER MODEL CLUSTERING ATTM FAVORS A 12Z GFS AND 00Z ECMWF
BLEND WHICH HAS THE BEST AGREEMENT WITH THE ENSEMBLE MEANS.


WEAKENING MID LEVEL DISTURBANCE LIFTING NEWD FROM THE SOUTHWEST
SFC LOW DEVELOPING OVER THE CENTRAL/NORTHERN PLAINS THRU 12Z/24
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: ABOVE AVERAGE

THE NAM HAS COME INTO BETTER AGREEMENT WITH THE OTHER MODELS BUT
IS NOTABLY NORTH/WEST WITH THE SURFACE LOW TRACKING NWD THROUGH
THE CNTRL AND NRN PLAINS SAT AND SAT NIGHT. THE REMAINING MODELS
MAKE UP A GOOD COMPROMISE WITH SUFFICIENT AGREEMNET TO SUPPORT A
NON 12Z NAM BLEND AS THE PREFERENCE. THESE DIFFERENCES WITH THE
DAKOTAS SURFACE LOW ARE


UPPER TROUGHING/CLOSED LOW DIGGING INTO THE WESTERN U.S. FOR FRI
AND SAT
SFC LOW MOVING INTO CANADA FROM THE N-CNTRL U.S. AFTER 12Z/24
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF/00Z UKMET
CONFIDENCE: AVERAGE

THE 06Z GEFS MEAN IS A BIT QUICKER THAN THE 00Z EC MEAN WITH THE
TRACK OF THE MID-LEVEL LOW INTO CANADA SUN NIGHT...BUT THERE HAS
BEEN SOME FLIP FLOPPING EAST/WEST BETWEEN THE 00Z AND 12Z CYCLES.
AT THE SURFACE...THE NAM DEPICTION OF THE SURFACE LOW APPEARS TOO
WEAK WHILE THE 12Z GFS POSITION IS A LITTLE WEST OF THE REMAINING
DETERMINISTIC/ENSEMBLE MEAN CONSENSUS REGARDING THE PRIMARY LOW.
HOWEVER...GIVEN THE FLIP FLOPPING SEEN IN THE ENSEMBLES...AND THE
FACT THAT THE GFS IS ONLY WEST OF THE ENSEMBLE MEANS FOR ABOUT A
12 HOUR PERIOD BETWEEN 12Z/24 AND 12Z/25...THE PREFERENCE IS TO GO
WITH A GENERAL COMPROMISE BETWEEN THE 12Z GFS...00Z ECMWF AND 00Z
UKMET. SUBTLE DIFFERENCES HOWEVER...WILL HAVE A SIGNIFICANT IMPACT
ON SENSIBLE WEATHER AND CONFIDENCE IN THE PREFERENCE ABOVE IS ONLY
AVERAGE AND SUBJECT TO CHANGE.


ADDITIONAL SHORTWAVE ENERGY DIGGING INTO THE NORTHWEST BY SUN AND
MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM...12Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS SHOW GOOD AGREEMENT UNTIL AROUND 12Z/25 WHEN LARGER
DIFFERENCES ARISE. THE 00Z UKMET AND 00Z CMC ARE MORE AMPLIFIED
OUT WEST WHILE THE NAM/GFS/ECMWF GENERALLY AGREE WITH THE MEANS.
TIMING AND PLACEMENT APPEAR GOOD OVERALL WITH THESE THREE MODELS
AS WELL.


...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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