752
FXUS10 KWNH 201826
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EDT FRI SEP 20 2019
VALID SEP 20/1200 UTC THRU SEP 24/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF BLEND
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z UKMET TRENDED FASTER IN THE NORTHERN STREAM
AND NOW MATCHES THE NAM A MOST. THE ECMWF WAS VERY SIMILAR TO
PRIOR RUN AND THE 12Z GEFS. THE 12Z CMC SLOWED EVEN FURTHER. SO
OVERALL A GFS/ECWMF BLEND IS PREFERRED AT AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
THE STRONG SOUTHEASTERN RIDGE WILL CONTINUE TO BE STALWART IN
EFFORTS TO DEFLECT APPROACHING LARGER SCALE NORTHERN SHORTWAVE
TROUGHS. IN THE WEST, A COMPACT CLOSED LOW IN SE ID/N UT WILL
CONTINUE TO ADVANCE NORTHEAST BUT IS EMBEDDED IN A LARGER SCALE
DEEP LATITUDE TROF WITH AMPLIFYING ENERGY IN CANADA AS WELL AS A
JET STREAK THAT IS STARTING TO SLIDE ALONG THE WESTERN SIDE OF THE
TROF TO CARVE OUT THE TROF FURTHER SOUTH ACROSS THE FOUR CORNERS
REGION BY LATE SAT. THIS WILL SUPPORT MULTIPLE SURFACE
CIRCULATIONS ALONG THE HIGH PLAINS INTO MANITOBA. THE BINARY
INTERACTION INTERNALLY TO THE TROUGH CONTINUE TO LEAD TO THE
LARGEST SPREAD/UNCERTAINTY; HOWEVER, IT IS GETTING BETTER AGREED
UPON THROUGH THE ENSEMBLE SUITE. THE MAIN OUTLIERS CONTINUE TO
THE 12Z NAM WHICH IS NOT TOO BAD WITH THE INITIAL CLOSED LOW WAVE
EJECTING INTO THE PLAINS, BUT IS VERY STRONG WITH THE LINGERING
BASE ENERGY THAT ROLLS UP AND IS QUITE COMPACT/DEEP ROLLED UP BUT
ALSO FAST COMPARED TO OTHER GUIDANCE. THE OTHER MAIN OUTLIER IS
THE 00Z CMC WHICH SHOWS VERY STRONG NORTHERN STREAM VORT ENERGY
THAT LEADS TO A TIGHT/STRONG BINARY INTERACTION ACROSS THE
NORTHERN RED RIVER, LEADING TO A STRONG/SLOW TO WEAKEN OCCLUDED
SURFACE LOW. THE 12Z GFS SLOWED A BIT AND BECOMES A BIT MORE
COMPACT OVER THE GREAT LAKES BY DAY 3 BUT FALLS IN LINE WITH
TIMING OF THE ECMWF (WHICH MAY BE A BIT TOO COMPACT/DEEP BY 23.12Z
TOO, ESPECIALLY RELATIVE TO THE 00Z ECENS MEAN SUITE). STILL, FOR
THIS WAVE/DEEP FRONTAL ZONE ACROSS THE MIDWEST INTO THE SOUTHERN
PLAINS, A GFS/ECWMF/UKMET BLEND REMAINS PREFERRED AT AVERAGE
CONFIDENCE.
....SHORTWAVE ENTERING WEST SUNDAY, AND DIGGING TO CLOSED LOW IN
GREAT BASIN BY LATE MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/CMC AND 12Z GFS BLEND (MASS)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE (MASS)
19Z UPDATE: THE 12Z ECMWF JOINED THE GFS WITH A STRONGER AND
EASTWARD TRACKING LORENA, BUT A BIT SLOWER AND LEFT OF THE GFS,
ALLOWING FOR GREATER MOISTURE FLUX (TYPICAL SPLIT OF THE GFS/ECMWF
IN TIMING) AND SO LEADS TO INCREASED QPF SPREAD STILL IN THE
SOUTHWEST BY DAY 3. HOWEVER, THE NORTHERN STREAM TROF TRENDED A
BIT SLOWER AND CLOSED THE LOW NEARLY ALIGNED WITH THE GFS TO HAVE
INCREASED CONFIDENCE TOWARD THIS EVOLUTION. YET THE UKMET REMAINS
WEAK AND THEREFORE SHIFTS EAST RELATIVE TO THE OTHER GUIDANCE. THE
CMC SHOWS SOME SIMILARITY TO THE PRIOR RUN AND THE 00Z ECMWF. IT
IS A BIT NORTH AS IT CLOSES OFF THE LOW, BUT IN GOOD
PROXIMITY/EVOLUTION TO KEEP THE INITIAL PREFERENCE THOUGH STILL
WEIGHTING TOWARD THE ECMWF/GFS. CONFIDENCE REMAINS SLIGHTLY ABOVE
AVERAGE IN MASS FIELDS BUT SLIGHTLY BELOW IN THE QPF/MOISTURE FEED
GIVEN THE VARIANCE IN THE DETERMINISTIC GUIDANCE.
---PRIOR DISCUSSION---
FURTHER UPSTREAM, THE NEXT SHORTWAVE ENERGY CONTINUES TO REMAIN
AGREED UPON AND WITH STILL SOME LINGERING/SLOWER PRIOR WAVE, A
SHARPER WAVELENGTH RIDGE BUILDS BETWEEN TO ALLOW FOR THE NEXT WAVE
TO STRETCH NORTH TO SOUTH AND EVENTUALLY START TO CLOSE OFF OVER
THE S GREAT BASIN TO LOWER COLORADO RIVER VALLEY. THE NAM BEING
FAST WITH THE PRIOR WAVE, DOES NOT BLOCK ENOUGH TO STRETCH SOUTH
ENOUGH AND IS NOT A CLOSED OFF. THE 00Z UKMET APPEARS TO BE A BIT
TOO FAST, WHICH IS A BIT IN LINE WITH ITS BIAS, GIVEN A WEAKER
DOWNSTREAM RIDGE AXIS. OVERALL, THE MASS FIELDS SUPPORT A 12Z GFS
AND 00Z ECMWF/CMC BLEND; HOWEVER, COMPLICATIONS WITH MOISTURE
ASSOCIATED WITH TC LORENA WILL LEAD TO LARGE DIFFERENCES IN QPF.
THE 12Z GFS, BEING VERY STRONG WITH LORENA AND LIFTING IT THROUGH
THE SEA OF CORTEZ, BRINGS MOISTURE TOWARD THE REGION FASTER AND
WILL BE SHUNTED SOUTHEAST GIVEN INFLUENCES FROM THE LINGERING TAIL
END OF THE PRIOR TROF. GIVEN THE PLACEMENT AND STRENGTH OF
LORENA, IT MAY BE ONTO SOMETHING, AS THE OTHER GUIDANCE, KILLS
LORENA IN FAVOR OF TC MARIO. THE ECMWF, CMC ON THE OTHER HAND,
HAVING KILLED OFF LORENA, ALLOW FOR DEEPER MOISTURE PUMPING BACK
INTO THE DESERT SW BY THE END OF DAY 3, AND THEREFORE SUGGEST
GREATER CONVECTIVE ACTIVITY AHEAD OF THIS DEEPENING CLOSED LOW.
AT THIS TIME, THE NHC FORECAST PREFERENCE IS TILTED TOWARD THE
ECWMF/CMC, BUT AGAIN WITH THE GFS THE ONLY DETERMINISTIC (ALONG
WITH A MUCH WEAKER NAM), MAY HAVE A BETTER HANDLE ON THE CURRENT
ASSIMILATION TO THE GUIDANCE. CONFIDENCE IN THE NORTHERN STREAM
EVOLUTION IS SLIGHTLY ABOVE AVERAGE, BUT THIS UNCERTAINTY WITH QPF
IS BELOW AVERAGE.
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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