765
FXUS10 KWNH 131839
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 PM EDT TUE AUG 13 2019
VALID AUG 13/1200 UTC THRU AUG 17/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF OR NEAR THE ECMWF/GEFS
ENSEMBLE MEANS
CONFIDENCE: BELOW AVERAGE
..19Z UPDATE
ONLY MINOR CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES. PREVIOUS THINKING CONTINUES
TO APPLY, JUST REPLACING 00Z WITH 12Z.
..PREVIOUS DISCUSSION FOLLOWS
ZONAL FLOW ACROSS THE NORTHERN TIER OF THE U.S. STARTS OFF THE
PATTERN, TRANSITIONING TO A STRONG RIDGE IN THE SOUTHWEST AND
TROUGHING DOWNSTREAM ACROSS THE EASTERN HALF OF THE NATION BY
THURSDAY MORNING. DEAMPLIFICATION OF THE SOUTHWESTERN RIDGE OCCURS
BY THE WEEKEND AS MID-UPPER LEVEL TROUGHING MOVES INTO THE
NORTHWEST. WHILE THE MODELS AGREE WITH THE LARGE SCALE FLOW,
CONFIDENCE REMAINS LOWER THAN AVERAGE WITH SMALLER SCALE
SHORTWAVES WITHIN THE FLOW.
ACROSS THE EASTERN U.S., DIFFERENCES WITH AN 850 MB LOW DEVELOP ON
THURSDAY NEAR THE LOWER GREAT LAKES/OHIO VALLEY WITH THE 12Z NAM
FARTHEST SOUTH AND 00Z CMC FARTHEST NORTH. THE ENSEMBLE MEANS
SPLIT THE DIFFERENCE BUT WITH THE GEFS MEAN SOUTH OF THE ECMWF
MEAN. TRENDS AT 500 MB IN THE ENSEMBLES HAVE GENERALLY BEEN
SHIFTING SOUTH ACROSS THE EASTERN U.S. OVER THEIR PAST 4 CYCLES,
SO NEAR THE ENSEMBLE MEANS BUT TOWARD THE SOUTH SIDE SEEMS BEST.
THIS FAVORABLE POSITION IS NEAR THE 00Z ECMWF/12Z GFS. THE 00Z
UKMET STANDS OUT AS A FLATTER/WEAKER NORTHERN OUTLIER ACROSS THE
EAST.
ACROSS THE WESTERN U.S., SIGNIFICANT TRENDS TOWARD LESS TROUGHING
ACROSS THE WEST COAST WERE OBSERVED VALID FRIDAY MORNING.
DIFFERENCES IN THE DETERMINISTIC GUIDANCE LIE MORE WITH TIMING
THAN AMPLITUDE. A BLEND OF THE 12Z GFS AND 00Z ECMWF IS PREFERRED
FOR NOW GIVEN THEIR REPRESENTATION LYING IN THE MIDDLE OF THE
LATEST SPREAD.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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