Prognostic Meteorological Discussion
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000
FXUS10 KWNH 220645
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 AM EDT WED OCT 22 2014

VALID OCT 22/0000 UTC THRU OCT 25/1200 UTC

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

...AN EVALUATION OF ALL 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.


...UPPER LOW MOVING FROM THE MID-ATLANTIC TO COASTAL NEW ENGLAND
WEDNESDAY THROUGH FRIDAY...
...COASTAL SYSTEM AFFECTING THE NORTHEASTERN U.S...

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

A SLOW-MOVING CLOSED LOW WILL AFFECT A REGION STRETCHING FROM THE
MID-ATLANTIC UP TO NEW ENGLAND THROUGHOUT MUCH OF THE SHORT RANGE
PERIOD. WATER VAPOR IMAGERY SHOWS A MYRIAD OF EMBEDDED SHORTWAVES
SWIRLING AROUND THE UPPER LOW OVER THE MID-ATLANTIC. THE MODELS
DEPICT THIS FEATURE TRACKING OFFSHORE OF THE DELMARVA PENINSULA BY
MIDDAY WEDNESDAY BEFORE GRADUALLY LIFTING NORTHWARD. LIKE
YESTERDAY...THE 00Z GEFS/21Z SREF/12Z ECMWF ENSEMBLE MEANS ARE
FAIRLY CONSISTENT WITH ONE ANOTHER REGARDING THE SURFACE LOW TRACK
THROUGH THURSDAY. THE 00Z NAM IS WELL TO THE NORTH OF THIS CLUSTER
WHILE THE 00Z UKMET TAKES A MORE COASTAL POSITION. BY
24/0000Z...THE ENSEMBLE LOW SCATTER PLOT SHOWS THE 12Z ECMWF
ENSEMBLE MEMBERS ARE SLIGHTLY WEST OF THE 12Z GEFS MEAN. THERE IS
MUCH MORE SCATTER NOTED IN THE 12Z CMC ENSEMBLE MEMBERS.
EVENTUALLY THE SPREAD GROWS FURTHER BUT DOES REMAIN LOW ENOUGH TO
KEEP DETERMINISTIC MODELS IN THE SOLUTION. FEEL THE 00Z GFS/ECMWF
HAVE THE BEST HANDLE ON THE LOW TRACK AND STAY WITHIN THE CENTER
OF THE SPREAD THROUGHOUT THE PERIOD. IN ADDITION THEY HAVE SHOWN
REASONABLE CONTINUITY WITH THEIR PREVIOUS RUNS WHICH SLIGHTLY
RAISES THE FORECASTER CONFIDENCE. WPC WILL FAVOR A BLEND OF THE
00Z GFS/ECMWF.


....SPLIT FLOW ACROSS THE CENTER OF THE COUNTRY...

FINAL PREFERENCE: BLEND OF THE 00Z ECMWF WITH THE 12Z ECMWF
ENSEMBLE/00Z GEFS MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

AN AXIS OF HEIGHT FALLS MOVING THROUGH THE NORTHERN ROCKIES SHOULD
REACH THE NORTHERN PLAINS AND UP INTO SOUTHERN
SASKATCHEWAN/MANITOBA BY 23/0000Z. THIS IS WHERE THE FORECAST
BECOMES MORE NEBULOUS AS THE FLOW BECOMES MORE SPLIT IN NATURE.
THE 00Z ECMWF/UKMET ARE FARTHER TO THE SOUTH WITH THE SOUTHERN
SPLIT ACROSS THE MIDDLE MS VALLEY ON THURSDAY MORNING. THE BIG
QUESTION IS HOW DEVELOPED WILL THE SYSTEM BE WHICH MOVES EASTWARD
TOWARD THE UPPER GREAT LAKES/OH VALLEY ON FRIDAY/SATURDAY. THE 00Z
NAM APPEARS TO BE THE OUTLIER HERE SHOWING A MORE SHEARED SYSTEM
IN THE FORECAST. BESIDES THE UNCERTAINTY IN STRENGTH...THE DEPTH
AND TIMING OF THIS SYSTEM ARE ALSO VARIABLE. THE 576-DM SPAGHETTI
PLOT SHOWS A MAJORITY OF THE 12Z ECMWF ENSEMBLE MEMBERS SUPPORTING
A SLOWER SOLUTION THAT DIGS WELL INTO THE TN VALLEY.
MEANWHILE...THE 12Z GEFS MEMBERS ARE MORE PROGRESSIVE AND FLATTER
WHICH APPEARS TO BE WHAT THE 00Z GFS IS ALIASING...ALBEIT IN A
SLIGHTLY FASTER MANNER. THIS SEPARATION IN CAMPS IS NOTED IN THE
PAST TWO SPAGHETTI PLOTS DATING BACK TO THE 00Z GUIDANCE ON
OCTOBER 21. BY 25/1200Z...THE 00Z/12Z UKMET DROP A CLOSED LOW DOWN
TOWARD THE FL PANHANDLE WHICH APPEARS MORE EXTREME THAN ANY OTHER
DETERMINISTIC SOLUTION. THE 00Z/12Z ECMWF SEEM TO STAY AT THE
CENTER OF THE SPREAD RELATIVE TO THE FLATTER 00Z NAM/GFS AND
DEEPER 00Z/12Z UKMET. WILL INCORPORATE ENSEMBLE MEANS INTO THE
SOLUTION AS WELL GIVEN THE HIGH AMOUNT OF SPREAD.


...INITIAL ENERGY CROSSING THE NORTHWESTERN CONUS...EVENTUAL TROF
OVER THE NORTHERN GREAT LAKES...
...POTENT SYSTEM APPROACHING THE PACIFIC NORTHWEST BY EARLY
SATURDAY...

FINAL PREFERENCE: INITIAL SYSTEM: BLEND OF THE 00Z
GFS/ECMWF...SECOND SYSTEM: BLEND OF THE 00Z GEFS/12Z ECMWF
ENSEMBLE MEANS
FORECAST CONFIDENCE: AVERAGE FOR THE FIRST SYSTEM/SLIGHTLY BELOW
AVERAGE FOR THE SECOND SYSTEM

THE FIRST BATCH OF ENERGY WITH THIS SYSTEM WILL ADVANCE THROUGH
THE PACIFIC NORTHWEST DURING THE NEXT 24 TO 36 HOURS. EVENTUALLY
THIS UPPER TROF WILL TRANSLATE EASTWARD ACROSS SOUTH-CENTRAL
CANADA WHILE DRAGGING HEIGHT FALLS INTO THE UPPER MIDWEST/GREAT
LAKES LATE IN THE PERIOD. THE 00Z NAM IS BY FAR THE MOST AMPLIFIED
SOLUTION WITH LITTLE SUPPORT FROM THE ENSEMBLE MEANS. THE OTHER
REMAINING 00Z GUIDANCE SHOW STRONG SIMILARITIES TO ONE ANOTHER
WITH DETAIL DIFFERENCES WITH THE CORE OF THE UPPER LOW. WHILE THE
00Z CMC/UKMET ARE REASONABLE SOLUTIONS...WILL FAVOR THE 00Z
GFS/ECMWF GIVEN THE WAY THEY HANDLE THE LOWER HEIGHTS ACROSS
CENTRAL CANADA.

IN THE WAKE OF THIS INITIAL SYSTEM WILL BE A MUCH MORE AMPLIFIED
TROF NEARING THE PACIFIC NORTHWEST BY EARLY SATURDAY. THE 00Z NAM
IS A SLOW OUTLIER BUT HAS GAINED AT LEAST SOME MARGINAL SUPPORT
FROM THE 00Z ECMWF WHICH HAS TRENDED MUCH SLOWER. THE 00Z/12Z
UKMET CONTINUE TO REMAIN ON THE OTHER SIDE OF THE SPECTRUM BEING
QUICKER. THE 564-DM SPAGHETTI PLOT SHOWS ONLY MODEST SPREAD WITH
THIS FEATURE AS GENERAL AGREEMENT IS NOTED BETWEEN THE GEFS/ECMWF
ENSEMBLE MEMBERS. OVERALL THE CONFIDENCE HAS DECREASED WITH THIS
SYSTEM GIVEN THE FLIP-FLOPPING OF SOME OF THE DETERMINISTIC
MODELS. WILL LEAN ON THE ENSEMBLE MEANS IN THIS CASE.


...FRONTAL ZONE STALLED ALONG THE FL KEYS THROUGHOUT THE PERIOD...

FINAL PREFERENCE: A NON-00Z NAM/CMC MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

MODELS SHOW A STATIONARY BOUNDARY LINGERING ACROSS SOUTH FL AND
DOWN ACROSS THE FL KEYS THROUGHOUT MUCH OF THE PERIOD. THE
GUIDANCE SHOW SOME VARIABILITY IN THE PLACEMENT AND TIMING OF
WAVES TRACKING ALONG THIS BOUNDARY. IN PARTICULAR...THE 00Z NAM IS
A FARTHER TO THE NORTH WHICH CARRIES HEAVY RAINFALL UP INTO A
MAJORITY OF SOUTH FL. ON THE OTHER SIDE OF THE EQUATION IS THE 00Z
CMC WHICH HAS TRENDED SOUTHWARD WHICH CARRIES THE HEAVY RAINFALL
TOWARD THE BAHAMAS. WILL FAVOR A NON-00Z NAM/CMC MODEL COMPROMISE
FOR THIS AREA.



...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

RUBIN-OSTER

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