Prognostic Meteorological Discussion
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FXUS10 KWNH 210529
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 AM EDT MON AUG 21 2017

VALID AUG 21/0000 UTC THRU AUG 24/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

...DEEP UPPER TROUGH AMPLIFYING ACROSS THE GREAT
LAKES/NORTHEASTERN U.S. BY TUESDAY/WEDNESDAY...
...ATTENDANT SURFACE CYCLONE AND PROGRESSIVE COLD FRONT...

PREFERENCE: BLEND OF THE NAM/12Z ECMWF/00Z GEFS MEAN
FORECAST CONFIDENCE: AVERAGE

OVERALL...WITH RESPECT TO THE LARGER SCALE FEATURES...THE MODELS
ARE IN FAIRLY GOOD AGREEMENT THROUGH MUCH OF THE PERIOD.  BY EARLY
THU HOWEVER...THE 00Z GFS IS LESS AMPLIFIED WITH THE UPPER TROUGH
ACROSS THE OH VALLEY/MID ATLANTIC WHILE MAINTAINING A STRONGER
RIDGE ALOFT ACROSS FL AND THE EASTERN GULF.  THE GEFS MEAN
SUPPORTS A SOLUTION CLOSER TO THE NAM AND 12Z ECWMF.

...TUTT CELL SLIDING WESTWARD ACROSS THE GULF OF MX...

PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

OVERALL THE LATEST GUIDANCE REMAIN IN GENERALLY GOOD
AGREEMENT...SHOWING THIS SYSTEM MOVING WEST ACROSS THE NORTHERN
GULF BEFORE REACHING THE WESTERN GULF COAST ON TUE.

...POTENT IMPULSE LIFTING OUT OF THE SOUTHERN ROCKIES TOWARD THE
CENTRAL HIGH PLAINS...

PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: AVERAGE

OVERALL...THE MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE TIMING
OF THIS SYSTEM AS IT CONTINUES TO THE LIFT TO THE NORTHEAST TOWARD
THE CENTRAL PLAINS WHERE BY LATE TUE IT IS FORECAST TO CAPTURED BY
AN AMPLIFYING UPPER TROUGH.

...NEARLY QUASI-STATIONARY UPPER LOW LINGERING ACROSS
SOUTHERN/CENTRAL CA...

PREFERENCE: A NON-12Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

OVERALL THE MODELS REMAIN IN FAIRLY GOOD AGREEMENT.  THE 12Z
CANADIAN GLOBAL REMAINS THE ONLY SIGNIFICANT OUTLIER.  AS THE LOW
TRANSITIONS TO AN OPEN WAVE BY LATE WED...THE CANADIAN TAKES THE
SYSTEM FURTHER TO THE EAST THAN THE OTHER MODELS.

...AMPLIFIED FLOW REACHING THE PACIFIC NORTHWEST/BRITISH COLUMBIA
COAST BY MID-WEEK...

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/00Z GFS
FORECAST CONFIDENCE: AVERAGE

WITH RESPECT TO THE UPPER TROUGH AXIS MOVING ACROSS WESTERN CAN
AND THE PACIFIC NW EARLY THU...THE 00Z NAM AND UKMET ARE NOW ON
THE EASTERN EDGE OF THE GUIDANCE ENVELOPE.  THE 00Z GFS AND 12Z
ECMWF AND THEIR RESPECTIVE ENSEMBLE MEANS FALL CLOSE TO THE MIDST
OF THE CURRENT MODEL SPREAD...WHILE THE 12Z CANADIAN GLOBAL IS ON
THE WESTERN EDGE OF THE GUIDANCE.

www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

PEREIRA

$$





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