770
FXUS10 KWNH 131701
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT FRI MAR 13 2020
VALID MAR 13/1200 UTC THRU MAR 17/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED LOW DEVELOPING OVER PACIFIC NW THROUGH SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 00Z/16
NON-12Z GFS BLEND 00Z/16 - 00Z/17
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MODEL DIFFERENCES REMAIN SMALL UNTIL SUNDAY EVENING WHEN THE 12Z
GFS ENDS UP FARTHER SOUTH WITH THE 700-500 MB LOW OFF OF THE WEST
COAST. THE 12Z GFS IS NOT AN OUTLIER WHEN CONSIDERING THE
AVAILABLE ENSEMBLE GUIDANCE BUT GIVEN GREATER SUPPORT FOR A
NON-GFS SOLUTION BY SUNDAY, THE PRELIMINARY PREFERENCE WILL
EXCLUDE THE 12Z GFS AFTER 00Z/16.
...WEAKENING MID-LEVEL SHORTWAVE TRACKING THROUGH THE SOUTHWEST
TODAY, WEAKENING ACROSS THE MIDWEST LATE SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
ONLY MINOR TIMING/AMPLITUDE DIFFERENCES REMAIN WITH THE MID-LEVEL
SHORTWAVE AS IT TRACKS EAST THROUGH THE OH VALLEY. THE 12Z NAM, AS
WITH PREVIOUS CYCLES, CONTINUES TO LOOK TOO FAST, HOWEVER NOT BY A
LOT. A NON-12Z NAM BLEND OF GUIDANCE LOOKS REASONABLE WITH THIS
SYSTEM.
THERE ARE SOME LATITUDE DIFFERENCES WITH THE TRAILING FRONT ACROSS
THE SOUTHERN STATES BY SATURDAY INTO SUNDAY WITH A WEAKER SURFACE
LOW NOTED IN THE 12Z GFS TRACKING ACROSS THE MISSISSIPPI RIVER
VALLEY ALLOWING FOR A MORE SOUTHERN-PLACED WARM FRONT. THE GFS IS
NOT AN OUTLIER, BUT THERE IS LESS SUPPORT FOR IT AMONG THE
REMAINING DETERMINISTIC GUIDANCE. ENSEMBLE MEANS SUPPORT A MIDDLE
GROUND WHICH CAN BE REPRESENTED BY A GENERAL BLEND, REMOVING THE
FASTER TIMING OF THE 12Z NAM ACROSS THE EASTERN U.S.
...BASE OF LONGWAVE TROUGH OVER THE NORTH-CENTRAL U.S. BY MONDAY
EVENING...
..RELATED COLD FRONT ACROSS THE UPPER MIDWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z GFS BLEND
CONFIDENCE: AVERAGE
THE 12Z GFS STANDS OUT AS THE FASTER MODEL WITH THIS SYSTEM, A NON
12Z GFS BLEND WILL BE PREFERRED GIVEN THE REMAINING DETERMINISTIC
AND ENSEMBLE GUIDANCE (INCLUDING THE 06Z GEFS) IS SLOWER THAN THE
12Z GFS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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