Prognostic Meteorological Discussion
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FXUS10 KWNH 190458
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1258 AM EDT SUN OCT 19 2014

VALID OCT 19/0000 UTC THRU OCT 22/1200 UTC

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

...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

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


...STRONG LOBE OF VORTICITY EXITING THE VA CAPES BY 19/1200Z...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

WATER VAPOR IMAGERY INDICATED A POTENT SHORTWAVE WAS DIGGING INTO
UPSTATE SC WITH A PRONOUNCED TONGUE OF MID/UPPER-LEVEL DRY AIR
PUSHING INTO THE LOWER MID-ATLANTIC/CAROLINAS. DURING THE FIRST 12
HOURS OF THE PERIOD...THE 12Z CMC IS A HAIR FASTER SLIDING THE
VORTICITY OFF OF THE VA CAPES. HOWEVER...THESE DIFFERENCES SEEM TO
WASH OUT AS THE SYSTEM ATTAINS A NEGATIVE TILT WHILE LIFTING
OFFSHORE OF NEW ENGLAND. OVERALL INDIVIDUAL MODELS OFFER SUBTLE
DETAIL DIFFERENCES BUT IT IS DIFFICULT TO REJECT ANY ONE
DETERMINISTIC MODEL FROM THE SUITE. WILL SUGGEST A GENERAL MODEL
COMPROMISE IN THAT CASE.


...CLIPPER-LIKE SYSTEM CROSSING THE UPPER GREAT LAKES LATE SUNDAY
NIGHT...
...ASSOCIATED SURFACE WAVE/FRONTS...

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

THE NORTHERN STREAM WILL GAIN AMPLITUDE IN TIME AS BROAD MID-LEVEL
RIDGING SETS UP OVER THE ROCKIES EASTWARD INTO THE GREAT PLAINS.
THIS WILL ALLOW A CLIPPER-LIKE SYSTEM TO DIG THROUGH THE UPPER
GREAT LAKES BY LATE SUNDAY EVENTUALLY REACHING THE NORTHEASTERN
CONUS BY LATE MONDAY/EARLY TUESDAY. IT LOOKS LIKE THE 00Z NAM/GFS
AND 12Z ECMWF ARE FAIRLY CONSISTENT WITH ONE ANOTHER AND THE
ENSEMBLE MEANS WHILE THE 12Z CMC/UKMET DIFFER IN AMPLITUDE AND
TIMING. IN PARTICULAR...THE 12Z CMC IS MUCH MORE AMPLIFIED AND
WOULD BE ONE OF THE DEEPEST SOLUTIONS RELATIVE TO THE 564-DM
SPAGHETTI PLOT. BY 22/0000Z...THE ENSEMBLE MEANS DIFFER WITH THE
PLACEMENT OF THE SYSTEM AS IT SLOWLY CUTS OFF. THE 12Z GEFS
MEMBERS SUGGEST A MORE WESTWARD SOLUTION RELATIVE TO THE 12Z
ECMWF/CMC ENSEMBLE MEMBERS. THIS SPREAD LOOKS QUITE SIMILAR TO THE
00Z ENSEMBLE SUITE ALTHOUGH THERE IS BETTER AGREEMENT SEEN IN THE
12Z GEFS MEMBERS THAN PREVIOUS. INTERESTINGLY THE 00Z GFS HAS COME
IN LOOKING MORE LIKE THE 12Z ECMWF/ECMWF ENSEMBLE MEAN. WILL TAKE
THAT AS A TREND IN THE FASTER DIRECTION AND BLEND THE 00Z GFS/12Z
ECMWF SOLUTIONS.


...SHEARING MID-LEVEL IMPULSE ACROSS THE SOUTHERN/CENTRAL PLAINS...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

AN UPPER LOW WHICH WAS INITIALLY OVER THE DESERT SOUTHWEST HAS
BEGUN TO SHEAR ACROSS THE FOUR CORNERS REGION. WHAT REMAINS OF
THIS SYSTEM CONSISTS OF FRACTURED MID-LEVEL IMPULSES OVER THE
FRONT RANGE OF THE ROCKIES ALONG WITH THE SOUTHERN HIGH PLAINS.
MODELS SUGGEST THIS DISSIPATING BATCH OF ENERGY WILL EVENTUALLY
JOIN THE LONGWAVE TROF ACROSS THE MS VALLEY BY LATE SUNDAY. GIVEN
THE REASONABLE AGREEMENT NOTED IN THE GUIDANCE...A GENERAL MODEL
COMPROMISE APPEARS REASONABLE HERE.


...CLOSED LOW CURRENTLY APPROACHING NORTHERN BAJA CA...
...REACHING NORTHERN MX BY MIDDAY MONDAY...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AN UPPER LOW CURRENTLY SPINNING SOUTH OF SAN DIEGO CA WILL
CONTINUE TO SLOWLY MIGRATE EASTWARD IN TIME WITH GRADUAL WEAKENING
EXPECTED. THROUGH 21/0000Z...THE MODELS ARE IN NEAR AGREEMENT WITH
THE EVOLUTION OF THIS SYSTEM AS IT SHEARS OVER NORTH-CENTRAL MX.
PERHAPS THE 12Z CMC IS A TAD WEAKER BUT THIS DIFFERENCE DOES NOT
APPEAR TOO DETRIMENTAL TO THE FORECAST. RESIDUAL ENERGY SHOULD
REACH FAR WEST TX BY 22/0000Z WITH A VARIETY OF SHEARED SOLUTIONS
DEPICTED. WILL SUGGEST A GENERAL MODEL COMPROMISE TO HANDLE THESE
GENERAL DIFFERENCES.


...STRONG UPPER TROF REACHING THE WEST COAST BY MONDAY EVENING...
...FRONTAL SYSTEM CROSSING THE HIGH PLAINS BY MID-WEEK...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET
FORECAST CONFIDENCE: BELOW AVERAGE

A POTENT UPPER TROF CROSSING 140W WILL MARCH EASTWARD IN TIME
NEARING THE WEST COAST BY MONDAY AFTERNOON WITH ONE KEY SHORTWAVE
APPROACHING THE NORTHERN CA COAST BY 21/0000Z. AT THIS POINT...THE
WELL CLUSTERED ENSEMBLE MEANS WOULD SUGGEST THE 00Z NAM/GFS ARE
TOO SLOW WITH THIS INITIAL WAVE. THIS IS DEFINITELY NOTED BY
21/1200Z WITH THE 00Z NAM/GFS OVER WESTERN NV WHILE THE 12Z
ECMWF/UKMET/CMC ARE UP IN WESTERN ID. BY LATER IN THE PERIOD...THE
12Z CMC IS MORE AGGRESSIVE DIGGING A SHORTWAVE INTO THE DESERT
SOUTHWEST. PLAN ON STAYING CLOSER TO THE 12Z ECMWF/UKMET WITH
POTENTIAL CHANGES BASED ON THE ARRIVAL OF ADDITIONAL 00Z GUIDANCE.
CONFIDENCE IS NOT GREAT GIVEN THE LARGE SPREAD AMONG THE
DETERMINISTIC MODELS.


...NEXT PACIFIC SYSTEM NEARING VANCOUVER ISLAND ON WEDNESDAY
MORNING...

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

AS THE INITIAL PACIFIC SYSTEM ADVANCES INTO THE ROCKIES/HIGH
PLAINS...THE UPPER FLOW BEGINS TO FLATTEN OUT WITH MORE OR LESS
ZONAL FLOW SETTING UP IN THE WAKE. THE 12Z CMC APPEARS QUITE FAST
AS ENSEMBLE MEANS ARE FAVORING A SLOWER EASTWARD PROGRESSION OF
THIS JET ENERGY. THE MODEL SPREAD IS RATHER HIGH SO FOR NOW WILL
LEAN ON THE ENSEMBLE MEANS.


...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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