381
FXUS10 KWNH 081649
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1247 PM EDT WED APR 8 2020
VALID APR 8/1200 UTC THRU APR 12/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GREAT LAKES TO EAST COAST TROUGH AND LOW PRESSURE SYSTEM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/NAM/00Z ECMWF
CONFIDENCE: HIGH
A CLOSED LOW INITIALLY OVER MANITOBA WILL CONTINUE TRACKING
EASTWARD NORTH OF THE GREAT LAKES AND REACH NORTHERN NEW ENGLAND
BY 12Z FRIDAY, WITH A PAIR OF SHORTWAVE PERTURBATIONS PIVOTING
AROUND IT FROM THE UPPER MIDWEST TO THE EAST COAST. THIS WILL
SUPPORT A STRONG COLD FRONT REACHING THE EAST COAST THURSDAY
AFTERNOON AND A BIG SURFACE LOW NEAR MAINE BY FRIDAY MORNING. THE
OVERALL MODEL SUITE CONTINUES TO IMPROVE OVERALL. THE MAIN
DIFFERENCE IS WITH THE 12Z UKMET BEING A LITTLE STRONGER WITH THE
SURFACE LOW AND MORE AMPLIFIED WITH THE 500MB TROUGH AXIS.
SLOW MOVING CLOSED LOW ACROSS THE SOUTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/EC MEAN/12Z NAM
CONFIDENCE: MODERATE
A LARGE AND SLOW MOVING CUT-OFF CLOSED LOW IN THE SOUTHERN STREAM
SITUATED NEAR THE SOUTHERN CALIFORNIA COAST IS EXPECTED TO MAKE
LITTLE EASTWARD PROGRESS THROUGH FRIDAY EVENING, AND LIKELY MAKING
A SMALL CYCLONIC LOOP, BEFORE GRADUALLY TRACKING EASTWARD ACROSS
THE SOUTHERN ROCKIES AND EVENTUALLY THE WESTERN HIGH PLAINS OVER
THE UPCOMING WEEKEND. BOTH THE 6Z AND 12Z GFS RUNS ARE SLIGHTLY
FASTER IN EJECTING THE CLOSED LOW EASTWARD ACROSS THE SOUTHERN
ROCKIES AND ADJACENT HIGH PLAINS BY DAY 3. THE 12Z UKMET
RETROGRADES THE UPPER LOW FARTHER WEST DURING ITS CYCLONIC LOOP
WITH LITTLE ENSEMBLE SUPPORT. A BLEND OF THE 00Z ECMWF/00Z EC
MEAN/12Z NAM BEST REPRESENTS THE MODEL CONSENSUS.
UPPER LEVEL TROUGH AND COLD FRONT REACHING THE NORTHWEST BY END OF
THE WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF
CONFIDENCE: MODERATE-HIGH
SHORTWAVE ENERGY ALONG THE SOUTHERN COAST OF ALASKA WILL PROGRESS
EASTWARD TO THE YUKON TERRITORY, AND WITH THE ACCELERATING/EXITING
JET, THE UPSTREAM RIDGE WILL BREAK DOWN AND ALLOW FOR GREATER
PROPAGATION EAST AND THEN SOUTHWARD ACROSS SOUTHWESTERN CANADA.
THE HEIGHT-FALLS WILL OVERSPREAD THE LEE OF THE CANADIAN ROCKIES
AND THEN NORTHERN HIGH PLAINS, AND SUPPORT A SURFACE COLD FRONT TO
DROP SOUTHWARD ACROSS MONTANA AND THE DAKOTAS. THE MAIN
DIFFERENCES NOTED HERE ARE A MORE AMPLIFIED 12Z NAM WITH THE
TROUGH AXIS DROPPING SOUTH ACROSS THE NORTHERN ROCKIES, AND THE
12Z UKMET IS SLIGHTLY FASTER WITH THE PROGRESSION OF THE COLD
FRONT ACROSS THE NORTHERN PLAINS.
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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