Prognostic Meteorological Discussion
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018
FXUS10 KWNH 120701
PMDHMD

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

VALID FEB 12/0000 UTC THRU FEB 15/1200 UTC

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

...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...CLIPPER SYSTEM/DEVELOPING SURFACE LOW AFFECTING THE CAROLINAS
ON FRIDAY...

PREFERENCE: GENL MODEL BLEND
FORECAST CONFIDENCE: ABOVE AVERAGE

MODELS ARE TIGHTLY CLUSTERED WITH CLIPPER SYSTEM THAT WILL QUICKLY
MOVE ACRS THE TN VALLEY BY EARLY FRI...INDUCING A SFC LOW THAT
WILL INTENSIFY AND MOVE RAPIDLY NEWD AWAY FROM THE CAROLINA COAST
DURING THE DAY FRI.  A GENL MODEL BLEND IS RECOMMENDED GIVEN SMALL
MODEL SPREAD.


...COLD UPPER VORTEX SWEEPING THE NORTHEAST THIS WEEKEND...
...POLAR FRONT/SURFACE CYCLONE CROSSING ME...

PREFERENCE: BLEND OF THE NAM/00Z UKMET/00Z EC
FORECAST CONFIDENCE: AVERAGE

MODELS SHOW REASONABLY CLOSE AGREEMENT IN DRIVING STG UPR LOW OVER
ERN CANADA SEWD WITH WEAKENING UPR LOW TRACKING ACRS MAINE SAT
NIGHT. IN ADVANCE OF THE UPR LOW...MODELS AGAIN ARE FAIRLY WELL
CLUSTERED IN SWINGING STG VORT ENERGY NEWD FROM THE SRN GT LAKES
TO A POSITION OFF THE NEW ENGLAND COAST SAT MRNG.  INITIAL SFC
WAVE ALONG ARCTIC FRONT IS FCST TO WEAKEN AS IT MOVES TOWARD
MAINE..BUT A STG SFC TROF DVLPS BETWEEN IT AND STGR OFFSHORE LOW
EAST OF NOVA SCOTIA FRI NIGHT SAT ACRS SRN/ERN MAINE. SUBTLE
DIFFERENCES EXIST WHERE THIS LOW LEVEL TROF AXIS SETS UP BUT ALL
MODELS SUGGEST ENHANCED PCPN THREAT NEAR COASTAL MAINE WITH THIS
FEATURE.  THE 00Z NAM MATCHED UP FAIRLY CLOSELY WITH THE UKMET/EC
WHICH WERE SLIGHTLY PREFERRED OVER THE GFS WHICH WAS SLIGHTLY
NORTH OF THE CONSENSUS.


...PROGRESSIVE SHORTWAVE PUSHING FROM THE PACIFIC NORTHWEST THRU
THE NRN PLAINS/UPR MS VALLEY AND GREAT LAKES...

PREFERENCE: NON-NAM BLEND
FORECAST CONFIDENCE: AVERAGE

UPR TROF OFF THE PAC NW COAST IS EXPECTED TO OPEN UP RAPIDLY AS IT
MOVES INTO THE PAC NW FRI/FRI NIGHT WITH WEAKENING S/WV
ACCELERATING THRU THE NRN ROCKIES AND ACRS THE NRN PLAINS/UPR MS
VALLEY REGION SAT INTO SUN.  MODELS HAVE STRUGGLED WITH THIS
ENERGY AS IT EMERGES THRU THE NRN ROCKIES INTO THE PLAINS WHICH
MAINLY AFFECTED AXIS OF DOWNSTREAM WAA/OVERRUNNING SNOWS THRU THE
DAKOTAS AND UPR MS VALLEY.  THE 18Z GFS APPEARED TO BE A SLIGHT
NORTHERN OUTLIER WITH THE PCPN SHIELD AND SUBSEQUENT LOW DVLPEMENT
GIVEN NWD SHIFT OF VORT MOVING THRU THE DAKOTAS IN RESPONSE TO
SLOWER MOVING VORT ENERGY OF NRN CANADA.  THE 00Z LOOKS REASONABLE
THROUGH DAY 2 AND CLUSTERED FAIRLY CLOSE TO EARLIER EC/UKMET
GUIDANCE BUT LOOKS TO AGAIN SHIFT ENERGY A TAD TOO FAR NORTH BY
THE END OF THE DAY 3 PD ACRS THE UPR MS VALLEY.  A SLIGHTLY MORE
SUPPRESSED 00Z GFS SOLN WOULD ALIGN BETTER WITH MOST OF THE
NON-NAM GUIDANCE.

....SHARPENING UPR TROF THRU THE SRN PLAINS AND ACCOMPANYING SFC
LOW DVLPMENT...

PREFERENCE:NON-NAM BLEND
FORECAST CONFIDENCE...AVERAGE

00Z NAM OFFERS A FLATTER AND QUICKER SOLN WITH SRN PORTION OF S/WV
ENERGY DIGGING SEWD THRU THE CNTL/SRN PLAINS SUN NIGHT INTO MON
MRNG.  BOTH THE 00Z GFS AND 00Z EC SHOW ABOUT 20 TO 30 KT STGR JET
LEVEL WINDS DIGGING INTO THE BACKSIDE OF THE TROF FROM SW
CANADA/NW U.S. BY 12Z MON WHICH PROBABLY ACCOUNTS FOR THE
DIFFERENCE NOTED IN THE FLATTER AND MORE PROGRESSIVE NAM SOLN.
ONLY THE SREF MEAN SUPPORTS THE OPERATIONAL NAM HERE WITH MOST 00Z
GUIDANCE SUPPORTING A SLOWER/SHARPER UPR TROF THRU THE SRN PLAINS.
 PREFERENCE HERE IS FOR A NON-NAM BLEND.

..DVLPG STG ONSHORE FLOW EVENT ACRS THE PAC NW SAT NIGHT INTO MON
MRNG...

PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS/GFS/NAM
FORECAST CONFIDENCE: AVERAGE

THE BEGINNING OF A MULTI-DAY ONSHORE FLOW EVENT INTO THE PAC NW
BEGINS ON SAT AS WAVY FRONTAL BNDRY BECOMES ALIGNED WITH
INCREASINGLY ZONAL FLOW OVER TOP OF BUILDING ERN PAC RIDGE OFF THE
CA COAST.  BOTH OPERATIONAL AND ENSEMBLE CLUSTERING OF THE 558DM
HEIGHT LINE IS FAIRLY TIGHT ACRS WA STATE ON SAT WITH LONG FETCH
OF DEEP MSTR EXPECTED TO FOCUS INTO WA STATE THRU MON MRNG.  AN
ENSEMBLE APCH ALONG WITH THE 00Z NAM/GFS ARE PREFERRED TO SMOOTH
OUT SMALLER SCALE TIMING DIFFERENCES WITH FEATURES IN FAST FLOW
OVER THE RIDGE WHICH WILL AFFECT INTENSITY OF PCPN SURGES INTO THE
PAC NW/NRN INTERMOUNTAIN REGION.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

SULLIVAN

$$





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