Prognostic Meteorological Discussion
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056
FXUS10 KWNH 121653
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1153 AM EST FRI FEB 12 2016

VALID FEB 12/1200 UTC THRU FEB 16/0000 UTC

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

...AN EVALUATION OF THE 12Z NAM/GFS GUIDANCE ALONG WITH INITIAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...SHORT WAVE CROSSING PACIFIC NORTHWEST SAT TO THE GREAT LAKES/OH
VALLEY MON...

PREFERENCE: 12Z GFS/00Z ECMWF BLEND
FORECAST CONFIDENCE: AVERAGE

THE 12Z NAM APPEARS TO BE FASTER THAN THE MODEL CONSENSUS WITH THE
SHORT WAVE AS IT TRACKS FROM THE PACIFIC NORTHWEST EARLY SAT TO
THE WESTERN OH VALLEY SUN. THE 12Z GFS CLUSTERS WELL WITH THE 00Z
ECMWF/ECMWF MEAN WITH THE PLACEMENT OF THE SHORT WAVE OVER IA
SUN...WHILE THE 00Z UKMET APPEARS TO BE TOO FAST.

THERE IS SOME SPREAD ON THE PLACEMENT OF THE SURFACE BOUNDARY
ACROSS SD INTO NE SAT NIGHT INTO SUN...AND THIS COULD RESULT IN
DIFFERENCES IN THE PLACEMENT OF THE QPF MAXIMUM. THE SHORT WAVE
DRIVING THIS SYSTEM IS STILL OFF THE PACIFIC NORTHWEST COAST...SO
THERE MAY BE BETTER MODEL CONSENSUS ON SHORT WAVE TIMING AND
PLACEMENT OF THE SURFACE BOUNDARY AS THE SHORT WAVE GETS INTO THE
RADIOSONDE NETWORK.


..STRONG MID LEVEL ZONAL FLOW/LOW LEVEL ONSHORE FLOW PACIFIC
NORTHWEST SUN/MON...

PREFERENCE: BLEND OF THE 12Z GFS/00Z GEFS MEAN AND 00Z ECMWF/ECMWF
ENSEMBLE
FORECAST CONFIDENCE: AVERAGE

THE MID LEVEL FLOW BECOMES MORE ZONAL AND INCREASES IN THE SPEED
IN THE WAKE OF A SHORT WAVE CROSSING THE PACIFIC NORTHWEST COAST
SAT. WHILE THERE IS GENERALLY GOOD OVERALL MODEL AGREEMENT TO LIFT
HEIGHTS THROUGH SUN INTO MON...THERE ARE DIFFERENCES IN SPEED AS
TO HOW QUICKLY THIS OCCURS. WHILE THE 12Z NAM/GFS WERE NOT FAR
FROM THE CONSENSUS WITH RESPECT TO MID LEVEL HEIGHTS ACROSS THE
PACIFIC NORTHWEST...THERE ARE TIMING ISSUES...SO FOR NOW THESE
SOLUTIONS WERE NOT PREFERRED. THE PREFERRED SOLUTIONS LEANS MORE
HEAVILY ON THE ENSEMBLE OUTPUT (AS WELL AS THEIR DETERMINISTIC
RUNS).


...DEVELOPING LONG WAVE TROUGH OVER THE SOUTHERN PLAINS/GULF COAST
AND SURFACE DEVELOPMENT...

PREFERENCE:12Z GFS/00Z ECMWF BLEND
FORECAST CONFIDENCE: AVERAGE

THE 12Z NAM IS FLATTER AND FASTER THAN THE CONSENSUS AS THE LONG
WAVE TROUGH SHARPENS OVER THE SOUTHERN PLAINS AND WESTERN GULF
STATES LATE SUN NIGHT INTO MON (WHICH HAS BEEN THIS MODEL TREND
THE PAST THREE RUNS). SIMILARLY...THE UKMET APPEARS TO BE TOO FAST
WITH THE SPEED OF THE DEVELOPING LONG WAVE TROUGH (WHICH SEEMS TOO
FAST...GIVEN THE THE 00Z UKMET IS ALSO TRYING TO TAKE ON A
NEGATIVE TILT). THE 12Z GFS IS CLOSE TO THE 00Z ECMWF LONG WAVE
TROUGH POSITION...AND THESE SOLUTIONS OFFER THE BEST PLACEMENT FOR
NOW.

THE SURFACE LOW POSITIONS MIRROR THE ABOVE...SO THE SAME BLEND WAS
PREFERRED FOR THE SURFACE LOW POSITION.


...CLOSED MID LEVEL LOW MOVING FROM ONTARIO/QUEBEC ACROSS NORTHERN
NEW ENGLAND...
...SURFACE LOW OFF THE NORTHERN NEW ENGLAND COAST SAT/SUN...

PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
FORECAST CONFIDENCE: AVERAGE

THERE IS DECENT MODEL AGREEMENT WITH THE PLACEMENT AND STRENGTH OF
THE MID LEVEL VORTEX AS IT TRACKS FROM THE ONTARIO/QUEBEC BORDER
ACROSS ME. THE MAIN DIFFERENCES OCCUR WITH THE INITIAL SURFACE LOW
AS IT PASSES SOUTHEAST OF THE NORTHERN NEW ENGLAND COAST. THE
FOCUS WILL BE ALONG THE INVERTED TROUGH THAT REACHES BACK TOWARD
ME...WHERE THERE IS SOME SPREAD ON WHERE IT TOUCHES THE COAST. THE
PLACEMENT AFFECTS THE PLACEMENT OF THE QPF WITH THIS SYSTEM...SO A
BLEND OF THE 12Z GFS/00Z ECMWF WAS PREFERRED.

A SECONDARY LOW FORMS ON THE BOUNDARY SUN SOUTH OF NOVA SCOTIA.
THERE IS SOME SPREAD ON THIS FEATURE AS WELL...SO AT THIS POINT
THE ABOVEMENTIONED BLEND 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...

HAYES

$$





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