523
FXUS10 KWNH 191922
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
321 PM EDT THU SEP 19 2019
VALID SEP 19/1200 UTC THRU SEP 23/0000 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 ECMWF/CMC BLEND
EXCEPTION: INCLUDE THE 12Z NAM IN NORTHWEST/WEST DAY 3.
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z ECMWF/CMC BOTH TRENDED A BIT FASTER WITH THE
THE TROF LIFTING OUT OF THE ROCKIES INTO DAY 3, YET STILL MUCH
SLOWER THAN THE GFS/NAM. THIS APPEARS MORE LIKELY, THOUGH THE
UKMET HAS SIGNIFICANTLY SLOWED, PARTICULARLY WITH THE UPSTREAM
SHORTWAVE/JET STREAK DIGGING OUT THE INCREASINGLY POSITIVELY
TILTING BASE TO SAID TROF ACROSS THE CENTRAL ROCKIES/HIGH PLAINS
BY DAY 3. THIS SLOWING AND WESTWARD TREND IN THE SHORTWAVE
RIDGING BETWEEN THE NEXT APPROACHING SYSTEM, APPEARS TO NEGATIVELY
AFFECT THE UPSTREAM WAVE DEPTH AS WELL, DELAYING IT. AS SUCH,
WOULD PREFER TO REMOVE THE 12Z UKMET FROM THE INITIAL PREFERENCE.
OTHERWISE, THE NEW ECMWF/CMC FOR THE WEST ARE SIMILAR ENOUGH TO
CONTINUE A CMC/ECMWF/NAM BLEND FOR THE SECOND TROF IN THE WEST ON
DAY 3. CONFIDENCE IN THE BLEND REMAINS AVERAGE BUT SLIGHTLY
REDUCED COMPARED TO EARLIER GIVEN THE INCREASE IN
UNCERTAINTY/SPREAD BY THE END OF DAY 3 WITH BOTH WAVES.
---PRIOR DISCUSSION---
LARGE SCALE SYNOPTIC SETUP REMAINS CONSISTENT FOR THE PAST FEW
WEEKS, WITH A STRONG SOUTHEASTERN RIDGE WITH WESTERN TROUGHS
DEVELOPING AND LIFTING NORTHEASTWARD OVER THE NORTHWEST PERIPHERY.
THE CURRENT CONCENTRIC SHORTWAVE ENTERING THE GREAT BASIN IS
EXPECTED TO FOLLOW A SIMILAR PATTERN, CLOSING OFF CROSSING S ID
INTO THE NORTHERN ROCKIES SPURRING A SURFACE CYCLONE ACROSS THE
NORTHERN HIGH PLAINS BY FRIDAY MORNING. THE 12Z GFS AND NAM
SLOWED A BIT LIFTING OUT COMPARED TO PRIOR RUNS BUT BOTH CONTINUE
TO BE MUCH FASTER THAN THE 00Z ECWMF/UKMET/CMC AND EVEN THE GEFS
MEAN SLOWS COMPARED TO THE OPERATIONAL GFS RUNS. THIS SLOWER
SOLUTION IS MORE EXPECTED GIVEN THE PATTERN SETUP, ESPECIALLY WITH
A SUBTLE SHORTWAVE JET SPEED MAX ROTATING SOUTHWEST TO DELAY THE
BASE OF THE TROF LIFTING OUT AS WELL; DENOTED WELL IN THE ECMWF.
ADDITIONALLY, THE NEXT SHORTWAVE TROF APPROACHING WILL SUPPORT A
GREATER ELONGATION TOWARD THE SOUTH WITH SHARPER/EARLIER IMPACT TO
THE SHORTWAVE RIDGING BETWEEN IT AND THE EXITING SYSTEM. THIS
ALSO FAVORS THE ECMWF/UKMET AND CMC APPROACHING THE WEST COAST
LATE SAT INTO SUNDAY. HERE THE 12Z NAM MAY BE A BIT MORE USEFUL,
SHOWING GREATER TIMING/DEPTH PLACEMENT TO THE NON-GFS GUIDANCE.
AS SUCH A 00Z ECMWF/UKMET/CMC BLEND IS SUPPORTED THROUGH THE BULK
OF THE CONUS (PARTICULARLY THE NORTHERN STREAM). THERE IS MILD
SPREAD WITH THE WAVE LIFTING THROUGH THE NORTHERN PLAINS INTO
SOUTHERN CANADA, TO HAVE ONLY AVERAGE CONFIDENCE IN THIS BLEND.
..IMELDA.
LOW LEVEL CIRCULATION OF IMELDA AS BECOME A SE TO NW INVERTED TROF
WITH WEAK CLOSED LOW ALONG THE CONVECTIVE BAND WHERE LATENT HEAT
PRESSURE FALLS SUPPORT IT. THE MID-LEVEL CIRCULATION, HOWEVER
CONTINUES TO LIFT AWAY TOWARD THE NORTH FEELING SOME OF THE
HEIGHT-FALLS APPROACHING FROM THE WEST AND WESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE OVER THE SOUTHEAST. THE GLOBAL SCALE
DETERMINISTIC GUIDANCE IS FAIRLY AGREEABLE IN THE MASS FIELDS,
DEPICTING A HIGHLY SHEARED TOWARD THE NE WITH DEPTH REMAINING
SYSTEM. THE SURFACE WAVE IS EXPECTED TO BE OVERWHELMED BY ONSHORE
FLOW, AND INSTABILITY DRIVEN CONVECTION MAY KEEP THE MID-LEVEL
CIRCULATION A TAD FURTHER WEST THEN SOME OF THE EASTERN SOLUTIONS,
LIKE THE NAM/GFS. STILL, HI-RES CAMS SUPPORT SOMETHING CLOSE TO
THE ARW/ARW2 AND 12Z HRRR SOLUTIONS PARTICULARLY IN QPF.
HOWEVER, FOR LARGER SCALE MASS FIELDS, UKMET/ECMWF/CMC BLEND WILL
WORK ESPECIALLY GIVEN TIMING OF THE UPSTREAM HEIGHT-FALLS.
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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