Prognostic Meteorological Discussion
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526
FXUS10 KWNH 121852
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM 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 GUIDANCE ALONG WITH FINAL
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/12Z 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 12Z
ECMWF/00Z ECMWF MEAN WITH THE PLACEMENT OF THE SHORT WAVE OVER IA
SUN...WHILE THE 12Z UKMET APPEARS TO BE TOO FAST AND FLAT BY THE
END OF DAY 3.

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/12Z GEFS MEAN AND 12Z ECMWF/00Z
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. LIKEWISE..THERE ARE SOME TIMING
ISSUES WITH THE 12Z UKMET/CMC AS THE FLOW TRANSITIONS FROM FAST
ZONAL TO MORE MID LEVEL RIDGING LATE IN THE PERIOD.

THE PREFERRED SOLUTION 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/12Z UKMET/12Z 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). THE 12Z GFS IS CLOSE TO THE 12Z ECMWF LONG
WAVE TROUGH POSITION...AND THE 12Z UKMET HAS SLOWED CONSIDERABLY
(ESPECIALLY WHEN COMPARED TO ITS PREVIOUS TWO RUN) TO NEARLY MATCH
THE 12Z GFS/12Z ECMWF TROUGH POSITION ON DAY 3. THE 12Z CMC
APPEARS TO BE TOO FAST WITH THE LONG WAVE TROUGH POSITION.

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/12Z 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/12Z 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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