221
FXUS10 KWNH 180701
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SAT JUL 18 2020
VALID JUL 18/0000 UTC THRU JUL 21/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 60 HOURS
NON-NAM/UKMET D3
CONFIDENCE: AVERAGE
07Z UPDATE: 00Z NAM AND 00Z UKMET ARE STRONG OUTLIER BOTH WITH THE
CONVECTIVELY ENHANCED SHORTWAVE LEADING TO DEEPER TROUGHING IN THE
MIDDLE OF THE COUNTRY ON D3, AS WELL AS WITH AN IMPULSE LIFTING
OUT OF THE GULF OF MEXICO TOWARDS LA/TX AT THE SAME TIME. WHILE
THE LARGE SCALE FLOW IS GENERALLY AGREEABLE EVEN BEYOND D2, THE
CONSENSUS OF THE OTHER MODELS IS IN MUCH BETTER ALIGNMENT WHEN
REMOVING THE MORE AMPLIFIED SOLUTIONS REPRESENTED BY THE NAM AND
UKMET.
PREVIOUS DISCUSSION:
NORTHERN TIER OF THE CONUS WILL REMAIN ACTIVE WITH FAST FLOW ATOP
AN EXPANSIVE MID-LEVEL RIDGE COVERING MUCH OF THE LOWER 48. WITHIN
THE FLOW ATOP THE RIDGE, THE PRIMARY CONCERN IS A MID-LEVEL
SHORTWAVE DRIVING A COLD FRONT ACROSS THE COUNTRY FROM THE
NORTHERN PLAINS THIS MORNING, TO OFF THE NEW ENGLAND COAST TUESDAY
MORNING. ALONG THIS FRONT, A WAVE OF LOW PRESSURE IS ALSO LIKELY
TO DEVELOP AND MOVE NORTHEAST THROUGH THE GREAT LAKES SUNDAY.
GUIDANCE IS IN VERY GOOD AGREEMENT WITH THE PLACEMENT AND
INTENSITY OF MOST FEATURE THROUGH THE FIRST 48-60 HOURS.
THEREAFTER, SOME SPREAD BEGINS TO DEVELOP WITH A SHORTWAVE PROGGED
TO DROP OUT OF THE NORTHERN ROCKIES MONDAY MORNING AND THEN BECOME
CONVECTIVELY ENHANCED LATE MONDAY INTO THE CENTRAL PLAINS. AS THIS
OCCURS, IT MAY ENHANCED THE LONGWAVE TROUGH AMPLITUDE AND BEGIN TO
BREAK DOWN THE RIDGE. BY DAY 3, TIMING AND INTENSITY OF THESE
SMALLER SCALE FEATURES, ESPECIALLY WHEN CONVECTIVELY ENHANCED, CAN
BE TROUBLESOME. THE LARGE-SCALE FEATURES ARE GENERALLY WELL
ALIGNED SO A GENERAL MODEL BLEND STILL SHOULD BE REASONABLE INTO
D3. HOWEVER, BOTH THE NAM AND UKMET SUGGEST SOME TROPICAL MOISTURE
WITH A WEAK MID-LEVEL WAVE COULD BE PULLED NORTHWARD TOWARDS THE
GULF COAST ON D3, ASSOCIATED WITH SOME STRONGER TROUGHING INTO THE
RIDGE. AT THIS POINT THESE ARE OUTLIERS SO SHOULD BE USED WITH
CAUTION, BUT IT APPEARS THEIR SOLUTIONS ARE DUE HEAVILY TO THE
EVOLUTION OF THIS AFOREMENTIONED SHORTWAVE, FOR WHICH LARGE-SCALE
EVOLUTION REMAINS WELL ALIGNED. SO FOR NOW A GENERAL MODEL BLEND
IS REASONABLE, BUT SOME LESSER WEIGHT ON THE NAM/UKMET MAY LEAD TO
A MORE COMPROMISED SOLUTION, ESPECIALLY FOR THE CENTRAL PLAINS AND
GULF COAST, BY TUESDAY.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
WEISS
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