349
FXUS10 KWNH 130512
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1211 AM EST WED NOV 13 2019
VALID NOV 13/0000 UTC THRU NOV 16/1200 UTC
..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORTWAVE TRACKING FROM THE NORTHWEST TO THE PLAINS BY WED AND
NORTHEAST ON THU...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.
...MID-LEVEL SHORTWAVE REACHING THE LOWER MISSISSIPPI VALLEY LATE
THURSDAY INTERACTING WITH A WEAKENING CLOSED LOW CROSSING SOUTHERN
TEXAS AROUND THE SAME TIME...
..CLOSED LOW DEVELOPMENT OVER THE SOUTHEAST BY LATE FRI
..CYCLOGENESIS OFF THE SOUTHEAST COAST ON FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 50% 00Z GFS, 25/25% 12Z ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
TWO SHORTWAVES ARE EXPECTED TO COME RATHER CLOSE TO ONE ANOTHER
ALONG THE CENTRAL GULF COAST THURSDAY NIGHT. ONE ORIGINATES FROM
NORTHERN MEXICO WHILE THE OTHER IS A NORTHERN STREAM WAVE FROM THE
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY. THE 12Z CMC SHOWS A
DIFFERENT TIMING WITH A SLOWER SOUTHERN WAVE AND FASTER NORTHERN
WAVE. MEANWHILE, THE 00Z NAM BEGINS TO SHOW STRONGER WITH THE
MID-LEVEL WAVE AND WINDS UP DEVELOPING A SURFACE LOW ALONG A
COASTAL FRONTAL BOUNDARY AND TRACKING THE LOW WELL NORTH OF THE
AVAILABLE ENSEMBLE/DETERMINISTIC GUIDANCE THROUGH THE WESTERN
ATLANTIC.
THE TIMING OF THE 12Z ECMWF'S 500 MB SHORTWAVE IS ON THE SLOW SIDE
OF THE ENSEMBLE SPREAD, BUT DOES NOT LOOK COMPLETELY UNREASONABLE,
ESPECIALLY WHEN BLENDED WITH THE SIMILAR 12Z UKMET POSITION. THE
RESULTING SURFACE LOW OFF OF THE SOUTHEAST U.S. IS STRONGEST IN
THE 12Z UKMET AND WEAKEST IN THE 12Z ECMWF WITH THE 00Z GFS IN THE
MIDDLE. A 3-WAY BLEND OF THE 00Z GFS/12Z ECMWF/12Z UKMET IS
CONSIDERED BEST AT THIS TIME WITH MORE WEIGHT TOWARD THE 00Z GFS.
...STRONG NORTHERN STREAM TROUGH BRUSHING THE NORTHEAST BY FRI
EVENING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
DESPITE SOME MINOR TIMING/DEPTH DIFFERENCES, THE MODELS SHOW
SIMILARLY WITH THIS SYSTEM.
...MID-LEVEL SHORTWAVES APPROACHING THE WEST COAST ON THU INTO
FRI...
...MID-LEVEL TROUGH REACHING THE NORTHERN ROCKY MOUNTAINS SATURDAY
MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND, TRANSITIONING TO A 12Z ECMWF/CMC
BLEND BY 12Z/16
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW GOOD AGREEMENT WITH A RELATIVELY WEAK MID-LEVEL
SHORTWAVE FORECAST TO REACH THE OREGON/CALIFORNIA COASTS ON
THURSDAY. A SECOND SHORTWAVE TO THE NORTH, FORECAST TO REACH
WASHINGTON EARLY FRIDAY, SHOWS SOME GREATER DIFFERENCES. THE 12Z
UKMET/CMC ARE FASTER WITH THE TIMING OF THIS WEAVE TO REACH THE
PACIFIC NORTHWEST.
DOWNSTREAM, HOWEVER, THE 12Z CMC SLOWS DOWN WITH THIS SYSTEM BY
SATURDAY MORNING WHILE THE 12Z UKMET REMAINS FASTER. MEANWHILE,
THE 00Z NAM/GFS SHOW GREATER AMPLIFICATION INTO THE WEST BY
SATURDAY MORNING RESULTING IN COLDER TEMPERATURES COMPARED TO THE
AGREEABLE ENSEMBLE MEANS AND 12Z ECMWF/CMC. THEREFORE, THE OVERALL
PREFERENCE WILL TRANSITION TO A 12Z ECMWF/CMC BLEND BY 12Z/16.
..CLOSED LOW DEVELOPMENT OFFSHORE SOUTHERN CALIFORNIA FRI NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z UKMET BLEND
CONFIDENCE: AVERAGE
THE MODELS SHOW MODERATE DIFFERENCES WITH THE TIMING OF A CLOSED
LOW OFFSHORE OF SOUTHERN CALIFORNIA BY SATURDAY MORNING. THE 12Z
UKMET STANDS OUT WITH A SLOWER TRACK COMPARED TO THE REMAINING
GUIDANCE, SO A NON 12Z UKMET BLEND WILL BE RECOMMENDED AT THIS
TIME.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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