974
FXUS10 KWNH 290427
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1226 AM EDT FRI MAY 29 2020
VALID MAY 29/0000 UTC THRU JUN 01/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
UPPER LEVEL TROUGH AND COLD FRONT ACROSS THE EASTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
THE UPPER LEVEL LOW THAT HAD BEEN TRACKING ACROSS THE
SOUTH-CENTRAL U.S. IS NOW IN THE PROCESS OF BECOMING ABSORBED AND
PHASING WITH AN AMPLIFYING NORTHERN STREAM TROUGH ACROSS THE GREAT
LAKES REGION. THIS WILL SUSTAIN THE PASSAGE OF A RATHER STRONG
COLD FRONT BY LATE MAY STANDARDS ACROSS THE EASTERN U.S. AND
EXITING THE EAST COAST ON SATURDAY, WITH A HIGH QUALITY AIRMASS
SETTLING IN BEHIND IT WITH COOLER TEMPERATURES AND MUCH LOWER
HUMIDITY. A REINFORCING SHORTWAVE WILL PIVOT AROUND THIS TROUGH
AND FURTHER AMPLIFY THE PATTERN ACROSS THE NORTHEAST STATES, AND
AN UPPER LEVEL RIDGE BUILDING IN BEHIND ACROSS THE PLAINS. THE
MODELS ARE ALL IN AGREEMENT ON THE PHASING OF THE TWO DISTURBANCES
THROUGH FRIDAY NIGHT, WITH ONLY MINOR DIFFERENCES NOTED
THEREAFTER. THE GFS IS ONLY SLIGHTLY FASTER WITH THE PROGRESSION
OF THE COLD FRONT ACROSS NEW ENGLAND, AND THE NAM SLIGHTLY MORE
AMPLIFIED WITH THE UPPER TROUGH ACROSS THE MID-ATLANTIC AND
NORTHEAST BY SUNDAY. THE DIFFERENCES ARE GENERALLY SMALL ENOUGH
TO SUPPORT A MULTI-DETERMINISTIC MODEL BLEND.
CLOSED UPPER LEVEL LOW THAT REACHES NORTHERN MEXICO ON FRIDAY AND
BECOMES SLOW MOVING THROUGH THE WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
AN UPPER LEVEL TROUGH INITIALLY OVER THE SOUTHERN PLAINS, MAINLY
EVIDENT AT THE 250MB LEVEL, WILL CONTINUE TO DROP SOUTHWARD TO
NORTHERN MEXICO BY FRIDAY NIGHT. IT WILL LIKELY BECOME TRAPPED
SOUTH OF THE BUILDING UPPER RIDGE OVER THE GREAT PLAINS, WITH
LITTLE IN THE WAY OF MOVEMENT. THERE SHOULD NOT BE MUCH OF A
SURFACE LOW REFLECTION WITH THIS TROUGH, HOWEVER. THE MODELS ARE
IN RELATIVELY GOOD AGREEMENT ON THE HANDLING OF THIS FEATURE, AND
THUS A GENERAL MODEL BLEND CAN BE INCORPORATED.
TROUGH EVOLUTION ALONG THE WEST COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH SATURDAY AFTERNOON, THEN
00Z NAM/GFS/12Z ECMWF BLEND
CONFIDENCE: MODERATE
A WELL DEVELOPED UPPER LEVEL LOW SITUATED NEAR 30N/125W WITH
SUBTROPICAL ORIGINS IS FORECAST TO REACH NORTHERN CALIFORNIA BY
MIDDAY SATURDAY, AND THEN EVOLVE INTO AN OPEN TROUGH AS IT LIFTS
NORTHWARD ACROSS THE PACIFIC NORTHWEST AROUND THE WESTERN SIDE OF
THE BUILDING RIDGE ACROSS THE PLAINS. A SECOND TROUGH BUILDS IN
WEST OF CALIFORNIA BY SUNDAY EVENING AS THE FIRST TROUGH LIFTS
NORTHWARD ACROSS WESTERN CANADA. IN TERMS OF THE MODEL EVOLUTION,
THE 12Z UKMET IS PORTRAYING A FASTER TRACK NORTHWARD ACROSS THE
PACIFIC NORTHWEST BY SATURDAY NIGHT, AND THE 00Z NAM AND GFS HOLD
ONTO THE CLOSED LOW THE LONGEST BEFORE BECOMING AN OPEN WAVE.
CONFIDENCE IS A LITTLE LOWER REGARDING THE SECOND DISTURBANCE OFF
THE CALIFORNIA COAST, WITH THE GFS/NAM/ECMWF SHOWING A STRONGER
500MB TROUGH COMPARED TO THE FLATTER CMC AND UKMET. THERE IS GOOD
OVERALL ENSEMBLE SUPPORT FOR THE STRONGER SET OF SOLUTIONS HERE,
AND A NAM/GFS/ECMWF BLEND WORKS WELL AND ALSO MAINTAINS EARLIER
FORECAST CONTINUITY.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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