418
FXUS10 KWNH 171612
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1211 PM EDT THU OCT 17 2019
VALID OCT 17/1200 UTC THRU OCT 21/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
RECORD DEEP SURFACE LOW IN NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
VERY STRONG AGREEMENT EXISTS WITH RECORD DEEP CYCLONE IN THE
NORTHEAST, ONLY THE 00Z CMC SLIGHTLY SHIFTS THE CENTER OF THE
SURFACE LOW TOWARD THE ENHANCING TRIPLE POINT OVER THE ST.
LAWRENCE WOBBLING IT FURTHER WEST. EACH OF THE OTHER GUIDANCE
SHOWS THE STRONG TRIPLE POINT BUT STILL RETAINS THE OLDER OCCLUDED
CENTER AS DOMINANT LIFTING THROUGH THE SEAWAY. THE CMC ROTATES
BACK TO THE CONSENSUS AFTER 30HRS, SO A GIVEN THE OTHERWISE SUPER
STRONG CONSENSUS THROUGH THE REMAINING MASS FIELDS, A GENERAL
MODEL BLEND IS SUPPORTED AT ABOVE AVERAGE CONFIDENCE.
DEEP LATITUDINAL WESTERN TROF PROGRESSING INTO THE PLAINS BY
FRI...SPURRING NORTHERN PLAINS SURFACE LOW BY LATE THURS/FRI AND
SOUTHERN PLAINS SURFACE LOW LATE FRI/SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
MODELS CONTINUE TO SHOW SOLID AGREEMENT FOR THE INITIAL
HEIGHT-FALLS/TROF CROSSING THE WEST TODAY AND DEVELOPING A
NORTHERN PLAINS SURFACE WAVE THAT LIFTS NORTHEAST INTO CANADA.
THE DEEP LATITUDE TROF, WILL ALSO SPUR A SECONDARY SURFACE WAVE
ACROSS THE SOUTHERN PLAINS THAT WILL ELONGATE/SHEAR ALONG THE
FRONTAL ZONE AS IT DROPS SOUTH AND THE BULK OF DRIVING ENERGY
LIFTS NORTH. AS THE NORTHERN PORTION OF THE WAVE CROSSES CENTRAL
CANADA, THE TRAILING TROF ACROSS THE GREAT LAKES SHOWS SOME MILD
MID-LEVEL DIFFERENCE, BASED MAINLY ON TYPICAL SLOW BREAK DOWN OF
THE ECMWF/CMC VS. THE FASTER BREAK DOWN IN THE UKMET/GFS. THIS IS
NOT MUCH OF IMPORTANCE TO THE SENSIBLE WEATHER ACROSS THE GREAT
LAKES, SO A GENERAL MODEL BLEND CAN BE SUPPORTED AT ABOVE AVERAGE
CONFIDENCE.
NW-SE ELONGATED SHORTWAVE ENTERING PAC NW SAT, CURLING INTO
COMPACT DEVELOPING CLOSED LOW IN LEE OF CENTRAL ROCKIES BY SUN
AFTERNOON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 20.00Z
12Z NAM AND 00Z ECMWF/CMC BLEND THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
IN THE WAKE OF THE INITIAL HEIGHT-FALLS (SEE SECTION ABOVE), THE
MID TO UPPER LEVEL FLOW IS FAIRLY FLAT AND VERY STRONG ACROSS THE
PACIFIC. THE NOSE OF THE APPROACHING JET WILL HELP TO SPUR A
STRONG SHORTWAVE THAT IS FAIRLY FLAT INITIALLY ENTERING THE
PACIFIC NW BY SAT. GUIDANCE IS IN STRONG AGREEMENT IN
PLACEMENT/TIMING OF THIS FEATURE, BUT AS THE SYSTEM CROSSES INTO
THE WESTERN CONUS AND STARTS TO AMPLIFY (MAINLY THE UPSTREAM JET
BUCKLES WITH A STRONG 150+ KT SPEED MAX ALONG THE SW PERIPHERY
OF THE WAVE. AS IT CROSSES THE CENTRAL ROCKIES, TIMING ISSUES
START TO OCCUR AS THE 12Z GFS JET ROUNDS THE BASE OF THE TROF
ALLOWING FOR FASTER VORTEX ROLL-UP INTO THE CENTRAL PLAINS BY
SUNDAY AFTERNOON, SPURRING A DEEPENING SURFACE CYCLONE. THE
REMAINING GUIDANCE AND ENSEMBLES (INCLUDING A BULK OF THE GEFS
MEMBERS) ARE SLOWER, WITH THE UKMET UNCHARACTERISTICALLY SLOW,
PERHAPS TOO SLOW WITHIN THE OTHERWISE TIGHTER ENSEMBLE MEMBERS.
AS SUCH AFTER 20.00Z, A 12Z NAM AND 00Z ECMWF/CMC BLEND IS
PREFERRED AT SLIGHTLY ABOVE AVERAGE CONFIDENCE (PRIOR, A GENERAL
MODEL BLEND IS SUFFICIENT).
POTENTIAL TROPICAL CYCLONE SIXTEEN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: PLEASE REFER TO 15Z NHC FORECAST
BEST PROXY: 12Z GFS/00Z UKMET UP TO 19.06Z; GFS/UKMET/00Z ECMWF
THEREAFTER
MOST OF THE GUIDANCE HAS FINALLY COME TO CONSENSUS WITH THE
NORTHERN CLOSED LOW ACROSS TX IN TERMS OF PLACEMENT, DEPTH, AND
SHAPE TO HAVE BETTER CONFIDENCE IN THIS PORTION OF THE STREAM.
THE TROPICAL/SUBTROPICAL STREAM IS STILL A BIT ELONGATED AND
HIGHLY DEPENDENT ON CONVECTIVE ENHANCEMENT TO THE MASS FIELDS, SO
THERE REMAINS MODERATE SPREAD. THE 12Z GFS AND 00Z UKMET ARE WELL
TIMED TO THE OFFICIAL NHC FORECAST EVEN EARLY IN THE FORECAST
PROCESS BUT STILL ON THE SOUTHEAST SIDE OF THE OFFICIAL TRACK.
THE 00Z ECMWF SHOWS STRONGER/TIGHTER BINARY INTERACTION BETWEEN
THE NORTHERN AND TROPICAL STREAMS DEEPENING THE SURFACE WAVE VERY
NEAR THE MOUTH OF THE MS RIVER BY 19.00Z WHICH IS NW OF THE TRACK.
AFTER 19.00Z, THE OFFICIAL FORECAST REMAINS DOMINANTLY NEAR THE
GFS/UKMET WITH SOME INCREASING WEIGHTING TOWARD THE ECWMF
ESPECIALLY AS THE WAVE REACHES NC/EAST COAST AT 21.00Z. THE 12Z
NAM REMAINS WEAK AND SLOW, AND CMC IS ALSO WEAK AND WELL SOUTH OF
THE TRACK TO NOT BLEND EITHER. SO, INITIALLY THE BEST PROXY TO
THE 15Z NHC FORECAST IS A 06Z GFS/00Z UKMET BLEND UP TO 19.06Z,
THEN INCORPORATE INCREASING INFLUENCE/PERCENTAGE TO THE 00Z ECMWF
AFTER 19.06Z.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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