882
FXUS10 KWNH 041852
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 PM EDT THU JUN 04 2020
VALID JUN 04/1200 UTC THRU JUN 08/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
...WAVY FRONT WITH LOW PRESSURE CROSSING THE GREAT LAKES TOWARDS
NORTHERN NEW ENGLAND THIS WEEKEND...
PREFERENCE: BLEND OF 12Z ECMWF/12Z NAM/12Z GFS
CONFIDENCE: AVERAGE
THE MODELS SHOW SIMILARLY TO ONE ANOTHER CONCERNING THE TIMING OF
A FRONT CROSSING THE GREAT LAKES FRI AND THE NORTHEAST SATURDAY.
WAVES OF LOW PRESSURE MAY DEVELOP ALONG THE FRONT AND THE 00Z-12Z
UKMET WERE OUTLIERS WITH THE LOW PRESSURE SEVERAL MB STRONGER THAN
OTHER SOLUTIONS, WHICH CHANGES THE FRONTAL TIMING. GIVEN GOOD
CLUSTERING AMONG THE 12Z ECMWF/12Z NAM/12Z GFS AND THEIR
RESPECTIVE ENSEMBLE MEANS, A BLEND OF THESE OPERATIONAL RUNS IS
PREFERRED.
...INITIAL CUT-OFF LOW OFFSHORE SOUTHERN CALIFORNIA, MOVING
ONSHORE FRIDAY AND INTO GREAT BASIN SATURDAY AND MONTANA SATURDAY
NIGHT...
PREFERENCE: BLEND OF THE 12Z ECMWF/12Z GFS/12Z UKMET
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A CUT OFF UPPER LOW WILL MOVE SLOWLY NORTHEAST FRIDAY AND MOVE
ONSHORE INTO SOUTHERN CALIFORNIA FRIDAY EVENING. THE LOW OPENS UP
AS IT MOVES INLAND WITHIN CONFLUENT FLOW AND BECOMES AN OPEN WAVE
AND DEAMPLIFIES AS IT MOVES NORTH ACROSS THE GREAT BASIN SATURDAY.
THE SHORTWAVE ENERGY MERGES WITH THE NORTHERN STREAM CLOSED LOW
OVER THE PACIFIC NORTHWEST, WITH THE MODELS SHOWING A 700-500 MB
WAVE AND SFC FLOW DEVELOPING IN MT SATURDAY, WITH THE SFC LOW
CROSSING INTO CANADA BY 12Z SUN IN MOST GUIDANCE.
EVEN THE LOW DEVELOPING IN ID AND MOVING INTO MT SAT HAS GOOD
CLUSTERING AMONG THE 12Z NAM/12Z GFS/00Z-12Z ECMWF/00Z-12Z UKMET.
THE GOOD CLUSTERING SUPPORTS A MODEL BLEND TO MITIGATE MINOR
TIMING AND LOCATION DIFFERENCES.
...CLOSED LOW OFF BRITISH COLUMBIA DRIFTING SOUTH THROUGH FRIDAY
NIGHT AND THEN OFF WASHINGTON/OREGON SATURDAY, MOVING EAST AND
ONSHORE SATURDAY NIGHT-SUNDAY...
PREFERENCE: 12Z GFS/12Z ECMWF/12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 12Z NAM/GFS/12Z UKMET/00Z-12Z ECMWF CLUSTER WELL WITH THE
CLOSED 500 MB LOW MOVING SOUTH OFFSHORE FROM BRITISH COLUMBIA
FRIDAY, THEN OFF WA/OR SATURDAY, THEN MOVING THE LOW ONSHORE
SATURDAY NIGHT, AND INTO THE NORTHERN ROCKIES SUNDAY. THERE IS
BETTER THAN USUAL CLUSTERING AMONG THESE MODELS AND THEIR
RESPECTIVE ENSEMBLE MEANS.
THE 12Z CANADIAN HAS TRENDED A BIT FASTER TO THE EAST, GETTING
CLOSER TO THE PRIMARY CLUSTER OF MODELS. THE CANADIAN IS STILL ON
THE WESTERN FRINGE OF THE MODEL 500 MB CLOSED LOW POSITIONS ON
SUNDAY. THEREFORE, THE PREFERENCE IS TOWARD A BLEND OF THE 12Z
GFS/12Z ECMWF/12Z UKMET. ONLY VERY MINOR CHANGES WERE NOTED WITH
THE 12Z ECMWF/12Z UKMET/12Z GFS COMPARED TO THEIR PRIOR CYCLES.
..TROPICAL CYCLONE CRISTOBAL
PREFERENCE: 15Z NHC ADVISORY
CONFIDENCE: REFER TO NHC PRODUCTS
THE 00Z ECMWF IS CLOSE TO THE OFFICIAL TRACK FOR T.S. CRISTOBAL
THROUGH DAY 2. THE 00Z CANADIAN AND 12Z GFS WERE SLIGHTLY FASTER
ON DAY 2 BUT SLOW DOWN ON DAY 3, TO MERGE MORE CLOSELY WITH THE
00Z ECMWF TRACK. THE 12Z ECWMF HAS SLOWED DOWN SEVERAL HOURS,
WITH CONFIDENCE IN THE NEW 12Z RUN LOW GIVEN THE BREAK IN
CONTINUITY FROM ITS ENSEMBLES AND OTHER MODELS. THE 12Z UKMET,
PREVIOUSLY ON THE EASTERN EDGE OF THE GUIDANCE SUITE, HAS TRENDED
WEST TOWARDS THE ECMWF/NAM/GFS/CANADIAN GLOBAL. THE 12Z NAM TAKES
A SHARP LEFT TURN 72-84 HOURS, BRINGING OUT OF ALIGNMENT WITH
OTHER MODEL SOLUTIONS AND THE OFFICIAL NHC TRACK.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
PETERSEN
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