869
FXUS10 KWNH 111838
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 PM EDT THU JUN 11 2020
VALID JUN 11/1200 UTC THRU JUN 15/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..TROUGH AMPLIFYING ACROSS THE EAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: AVERAGE
19Z UPDATE:
THE NON-NCEP GUIDANCE, AS WELL AS THE 12Z GEFS MEAN ALL TRENDED
TOWARDS A LESS AMPLIFIED LONGWAVE TROUGH ACROSS THE EAST BY
SUNDAY. THIS APPEARS TO BE IN RESPONSE TO MORE SPLITTING OF
SHORTWAVE ENERGY LEADING TO LESS INTERACTION AND AN OVERALL WEAKER
EVOLUTION. THERE HAS BEEN LITTLE RUN-TO-RUN CONTINUITY NOW OF THE
PLACEMENT AND AMPLITUDE OF THE IMPORTANT SHORTWAVE/CLOSED LOW D3,
SO AM HESITANT TO SUGGEST A MAJOR CHANGE IN THE PREFERENCES UNTIL
MORE CONSISTENCY CAN ARISE. HOWEVER, THERE IS POTENTIAL FOR AN
OVERALL LESS AMPLIFIED SOLUTION, WHICH, SINCE THE ENTIRETY OF THE
NON-NCEP CAMP MOVED IN THAT DIRECTION, STILL SUPPORTS THE PREVIOUS
BLEND.
PREVIOUS DISCUSSION:
THREE DISTINCT SHORTWAVES WILL DIG INTO THE EAST FROM CANADA, EACH
ONE REINFORCING THE TROUGH WHICH IS LIKELY TO BECOME ANOMALOUSLY
DEEP BY MONDAY. THROUGH THE FIRST 60 HOURS, THE SPREAD IN
INTENSITY AND POSITION OF THESE SHORTWAVES IS MINIMAL, SO A
GENERAL BLEND SEEMS REASONABLE. HOWEVER, LATE D2 INTO D3, SATURDAY
INTO SUNDAY, THE MOST ROBUST SHORTWAVE BEGINS TO SLIDE SOUTHEAST
AND WILL EVENTUALLY CLOSE OFF ATOP THE OHIO VALLEY. THE NAM IS A
CLEAR OUTLIER DURING THIS EVOLUTION AS IT SHARPENS THE TROUGH WELL
WEST OF THE GLOBAL CONSENSUS LEADING TO A CLOSED LOW TOO FAR WEST,
AND ENHANCING QPF INTO THE APPALACHIANS. WHILE THERE IS SOME
EAST-WEST SPREAD IN THE POSITION OF THE TROUGH AXIS AND CLOSED LOW
BY D3, NOTABLY THE ENSEMBLE MEANS BEING A BIT EAST OF THE
DETERMINISTIC SOLUTIONS, THE SPREAD FOR D3 SEEMS WITHIN TOLERANCE
AND THE REMAINING GUIDANCE CAN BE INCLUDED IN THE PREFERENCE.
...LONGWAVE TROUGH OFF THE WEST COAST AND SHORTWAVE LIFTING
ONSHORE CALIFORNIA BY THE WEEKEND...
..CLOSED LOW DEVELOPING ACROSS THE NORTHERN ROCKIES SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM THROUGH 48 HOURS, ECMWF/ECENS/GEFS/UKMET
THEREAFTER
CONFIDENCE: SLIGHTLY BELOW AVERAGE
CLOSED LOW POSITIONED OFF BRITISH COLUMBIA WILL SPIN NEARLY IN
PLACE THROUGH FRIDAY, WHILE A SHORTWAVE ROUNDING THE BASE OF THE
LONGWAVE TROUGH EXTENDING SOUTH FROM THE BC CLOSED LOW WILL LIFT
ONSHORE CA LATE FRIDAY. THE NAM IS BY FAR A SLOW OUTLIER WITH THE
EASTWARD EJECTION OF THIS SHORTWAVE, LAGGING THE CONSENSUS AND ALL
OTHER AVAILABLE GUIDANCE TOO MUCH TO BE INCLUDED IN THE BLEND.
THEREAFTER, THE EVOLUTION BECOMES MESSY. THE SHORTWAVE LIFTING
FROM CA INTO THE GREAT BASIN WILL ENCOUNTER PROGRESSIVELY GREATER
SHEAR AS THE BC LOW BEGINS TO DIG SOUTHEASTWARD TOWARDS WA STATE.
THE NAM, WHICH WAS ALREADY SLOW, IS MUCH TOO STRONG WITH THIS
FEATURE SO CONTINUES TO BE REMOVED FROM THE BLEND. BY LATE D2 INTO
D3, THE GFS PRODUCES A PRONOUNCED JET STREAK ROTATING AROUND THE
BC LOW. WHILE A JET STREAK DEVELOPMENT SEEMS LIKELY, THE STRENGTH
OF THIS FEATURE IS MUCH STRONGER ON THE GFS THAN ANY OTHER
GUIDANCE, WHICH ALLOWS FOR BETTER UPPER VENTILATION AND A STRONGER
SURFACE LOW, MID-LEVEL IMPULSE, AND HEAVIER QPF. THE GFS THEN
CLOSES OFF A LOW WELL NORTH OF THE CONUS BORDER, VASTLY DIFFERENT
FROM THE NON-NCEP CAMP, AND MUCH FURTHER NORTH THAN ITS OWN
ENSEMBLE MEAN. WHILE THERE ARE SOME DISCREPANCIES INTO THE
AMPLITUDE OF THE TROUGH IN THE NW INTO D3, THE REMNANTS OF THE
OPENING BC LOW, THE NON-NCEP GUIDANCE IS WELL CLUSTERED OVERALL TO
THE ECENS/GEFS MEANS. THE CMC MAY BE A BIT STRONG WITH THE
REMAINING ENERGY, SO AFTER D2 THE PREFERENCE CHANGES TO THE 06Z
GEFS WITH THE 00Z ECENS/ECMWF/UKMET.
WEISS
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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