280
FXUS10 KWNH 170653
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 AM EDT SUN MAY 17 2020
VALID MAY 17/0000 UTC THRU MAY 20/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
07Z UPDATE: FOR TS ARTHUR, THE 00Z ECMWF REMAINS THE FAVORED MODEL
PROXY TO THE OFFICIAL NHC TRACK WHILE THE 00Z UKMET ALSO OFFERS A
SIMILAR TRACK. FOR THE DEVELOPING CUT-OFF LOW, THE TREND CONTINUES
TO BE FOR A SOUTHWARD/SOUTHWESTWARD DRIFT OVER THE LAST FEW MODEL
CYCLES, WITH A NOTABLE SHIFT SEEN IN THE ECMWF AND UKMET. THIS NOW
PUTS THE GFS ON THE NORTHERN/NORTHEAST SIDE OF MODEL SPREAD, WHILE
THE NAM REMAINS ON THE SOUTHERN SIDE.
TROPICAL STORM ARTHUR
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NATIONAL HURRICANE CENTER OFFICIAL TRACK
BEST MODEL PROXY: 12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
TROPICAL STORM ARTHUR FORMED LATE YESTERDAY EVENING OFF THE
SOUTHEAST FLORIDA COAST AND IS FORECAST TO TRACK NORTHWARD TOWARD
THE OUTER BANKS BY EARLY NEXT WEEK BEFORE TURNING NORTHEASTWARD
AWAY FROM THE MID-ATLANTIC. THE INTERACTION OR LACK THEREOF WITH
AN APPROACHING MID-LEVEL CLOSED LOW WILL HELP DETERMINE THE
NORTHWARD OR NORTHEASTWARD STEERING MOTION OF ARTHUR AND THROUGH
ABOUT 18.00Z, GUIDANCE IS IN REASONABLE SHAPE. BEYOND THAT TIME
FRAME, THE MODELS DIFFER ON THE LONGITUDINAL DIRECTION WITH THE
LATEST GFS WEST OF THE CONSENSUS AND TAKES ARTHUR JUST ONSHORE
CAPE HATTERAS BY MONDAY MORNING. MEANWHILE, THE ECMWF/UKMET OFFER
A SLIGHTLY WEAKER SOLUTION THAT ALLOWS THE SYSTEM TO PULL EASTWARD
AND IS JUST TO THE RIGHT OF CONSENSUS AND OFFICIAL TRACK. THE BEST
PROXY TO THE OFFICIAL NHC TRACK IS THE 12Z ECMWF WITH SOME
INCLUSION OF THE 12Z UKMET ACCEPTABLE THROUGH MOST OF THE PERIODS.
FOR THE LATEST AND OFFICIAL FORECAST INFORMATION, SEE UPDATES FROM
THE NATIONAL HURRICANE CENTER.
SHORTWAVE TRACKING THROUGH GREAT LAKES, BECOMING CUT-OFF CLOSED
LOW OVER TN/OH VALLEYS EARLY NEXT WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 00Z ECMWF, 00Z UKMET BLAND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
MID-LEVEL SHORTWAVE ENERGY TRACKING THROUGH THE NORTH-CENTRAL
PLAINS AND UPPER MIDWEST EARLY THIS MORNING WILL DEEPEN AND CLOSE
OFF AS IT SLOWS OVER THE LOWER GREAT LAKES AND OHIO VALLEY EARLY
NEXT WEEK. FORECAST GUIDANCE HAS STRUGGLED WITH THE EVOLUTION OF
THIS SYSTEM, TYPICAL OF CUT-OFF LOWS. ALL OF THE GUIDANCE HAS
CONVERGED ON AN IDEA TO TAKE THE LOW FURTHER SOUTH THAN EAST
COMPARED TO PREVIOUS MODEL RUNS AND NOW SHOW THE CENTER OF THE LOW
REACHING THE TENNESSEE RIVER VALLEY BY THE END OF THE PERIOD. A
COMPROMISE OF THE GFS/ECMWF/UKMET APPEARS THE MOST STABLE
RUN-TO-RUN AS WELL AS MIRRORS THE ENSEMBLE MEANS THE MOST. THE NAM
SHOWED A SOLUTION THE FURTHEST TO THE SOUTH, WHICH WHILE NOT OUT
OF THE QUESTION, DID NOT FIT THE MODEL ENVELOPE SPREAD AS MUCH.
GIVEN THE LARGER THAN AVERAGE MODEL AND RUN TO RUN SPREAD,
FORECAST CONFIDENCE IS SET TO SLIGHTLY BELOW AVERAGE.
DEEP UPPER LEVEL TROUGH DEVELOPING ALONG THE WEST COAST BY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
LARGE, LONGWAVE TROUGHING EXPECTED TO MOVE FROM THE EASTERN
PACIFIC ONSHORE TOWARD THE INTERIOR WESTERN U.S. BY THE END OF THE
FORECAST PERIOD. THE MODEL GUIDANCE CONTINUES TO SHOW ABOVE
AVERAGE CONSISTENCY IN THE DEVELOPING OMEGA BLOCK PATTERN. AS
SUCH, A GENERAL MODEL BLEND SHOULD MORE THAN SUFFICE FOR MASS
FIELD PURPOSES.
SOUTHERN STREAM TROUGH TRACKING FROM TEXAS AND ALONG THE GULF COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
WEAK MID-LEVEL SHORTWAVE ENERGY SKIRTING ACROSS THE SOUTHERN
PLAINS IS FORECAST TO REACH THE SOUTHEAST U.S. BEFORE BECOMING
ABSORBED INTO THE LARGER CUT-OFF LOW DISCUSSED ABOVE. UNTIL THAT
HAPPEN, THE MODEL AGREEMENT IS AVERAGE AND OVERALL THE LATEST
GUIDANCE SHOWS FAIRLY GOOD CONSISTENCY SUCH THAT A GENERAL MODEL
BLEND IS PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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