561
FXUS10 KWNH 290442
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1240 AM EDT WED APR 29 2020
VALID APR 29/0000 UTC THRU MAY 02/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PLAINS TO EAST COAST STORM SYSTEM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/12Z UKMET/12Z ECMWF
CONFIDENCE: MODERATE
THE OVERALL UPPER LEVEL PATTERN OVER THE CENTRAL AND EASTERN U.S.
WILL BECOME MORE AMPLIFIED OVER THE NEXT COUPLE OF DAYS AS AN
UPPER LEVEL RIDGE BUILDS ACROSS THE ROCKIES AND WESTERN HIGH
PLAINS. HEIGHT FALLS ON THE EASTERN SIDE OF THE RIDGE IS
SUPPORTING A RAPIDLY DEVELOPING CLOSED LOW OVER THE MIDWEST AND
DEEPENS FURTHER AS IT REACHES THE OHIO VALLEY REGION BY THURSDAY.
AS THE MAIN SURFACE LOW OVER MICHIGAN OCCLUDES BY THURSDAY NIGHT,
A SECONDARY SURFACE LOW FORMS OVER THE MID-ATLANTIC AND LIFTS
NORTHWARD AS THE UPPER LEVEL TROUGH ACQUIRES SOME NEGATIVE TILT.
BEYOND 00Z THURSDAY, THE 00Z GFS BECOMES A LITTLE FASTER WITH
SHORTWAVE ENERGY PIVOTING AROUND THE UPPER LOW, AND FARTHER NORTH
WITH THE UPPER LOW BY 00Z FRIDAY. THE CMC REMAINS A LITTLE WEAKER
WITH THE LOW. THE UKMET, NAM, AND ECMWF ARE RELATIVELY WELL
ALIGNED AND CLOSE TO THE ENSEMBLE MEANS, SO A BLEND OF THESE THREE
SOLUTIONS SHOULD WORK WELL AS A STARTING POINT.
MULTIPLE SHORTWAVES AFFECTING THE PACIFIC NORTHWEST TO THE
NORTHERN PLAINS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z EC MEAN/00Z NAM
CONFIDENCE: MODERATE
THERE WILL BE THREE INDIVIDUAL SHORTWAVES THAT WILL AFFECT THE
WEST COAST THROUGH THE END OF THE WEEK AND EVENTUALLY FLATTEN THE
WESTERN U.S. RIDGE SOME IN THE PROCESS. THE LEAD SHORTWAVE
REACHES SOUTHERN BRITISH COLUMBIA THURSDAY MORNING, FOLLOWED BY A
FLATTER WAVE REACHING NORTHERN CALIFORNIA AND OREGON THURSDAY
AFTERNOON. THESE EVENTUALLY PHASE INTO A STRONGER TROUGH OVER
SOUTH-CENTRAL CANADA AND THE NORTHERN PLAINS BY FRIDAY EVENING.
THE THIRD SHORTWAVE APPROACHES THE PACIFIC NORTHWEST COAST BY
FRIDAY NIGHT ASSOCIATED WITH AN UPPER LOW OVER THE NORTHEAST
PACIFIC.
THE 18Z GEFS MEAN SHOWS LESS DEFINITION TO THE LEAD SHORTWAVE
ACROSS BRITISH COLUMBIA, AND THEN THE NAM BECOME SLIGHTLY MORE
AMPLIFIED. THERE ARE AMPLITUDE DIFFERENCE WITH THE TROUGH
CROSSING THE PACIFIC NORTHWEST, WITH THE ECMWF AND CMC NOT AS
STRONG AS THE UKMET/GFS/NAM, AND THE GFS IS WEAKER WITH THE
DOWNSTREAM RIDGE AXIS. BUT SATURDAY MORNING, THE GFS IS SLIGHTLY
STRONGER AND FARTHER SOUTH WITH THE LOW OVER MANITOBA, AND THE CMC
SLIGHTLY FASTER WITH THE SURFACE FRONT ACROSS THE NORTHERN PLAINS.
MODEL AGREEMENT IS GOOD OVERALL WITH THE SYSTEM APPROACHING THE
PACIFIC NORTHWEST LATER IN THE WEEK.
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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