Prognostic Meteorological Discussion
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FXUS10 KWNH 190646
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 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 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.


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

FINAL 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 LATEST 00Z CMC SEEMS TO HAVE SLOWED DOWN
SLIGHTLY CARRYING IT CLOSER TO THE CONSENSUS AS THE BATCH OF
VORTICITY EXITS THE VA CAPES. 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...

FIANL PREFERENCE: MODEL COMPROMISE BETWEEEN THE 00Z ECMWF/UKMET
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/ECMWF ARE FAIRLY CONSISTENT WITH ONE ANOTHER AND THE
ENSEMBLE MEANS THROUGH LATE MONDAY WHILE THE 00Z CMC DIFFERS IN
AMPLITUDE AND TIMING. 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. IT DOES APPEAR A VAST MAJORITY OF
THE LATEST 00Z MODELS HAVE TRENDED TOWARD THE 00Z GEFS MEAN
SOLUTION WHICH IS A LITTLE SLOWER. WILL FAVOR THIS IDEA AND LEAN
ON A MODEL COMPROMISE BETWEEN THE 00Z ECMWF/UKMET.


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

FINAL 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...

FINAL 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 00Z/12Z CMC ARE 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...

FINAL PREFERENCE: BLEND OF THE 00Z ECMWF/UKMET
FORECAST CONFIDENCE: SLIGHTLY 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 00Z
ECMWF/UKMET ARE UP IN WESTERN ID. MEANWHILE...THE 00Z CMC IS
MUDDLED SOMEWHERE IN THE MIDDLE...CLOSER TO THE NCEP CLUSTER. BY
LATER IN THE PERIOD...THE 00Z CMC IS MORE AGGRESSIVE DIGGING A
SHORTWAVE INTO THE FOUR CORNERS REGION. IT APPEARS THE 00Z
ECMWF/UKMET STAYED CLOSE ENOUGH TO THEIR PREVIOUS MODEL CYCLES TO
MAINTAIN THE PREVIOUS PREFERENCE. CONFIDENCE WILL BE RAISED
SLIGHTLY GIVEN THIS FACT.


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

FINAL PREFERENCE: BLEND OF THE 00Z 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. SUCH A FLOW REGIME IS
CHARACTERIZED BY QUITE A BIT OF MODEL SPREAD SO WILL MAINTAIN THE
CONTINUITY OF THE PRIOR ISSUANCE.


...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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