Prognostic Meteorological Discussion
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000
FXUS10 KWNH 261716
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
116 PM EDT SUN MAR 26 2017

VALID MAR 26/1200 UTC THRU MAR 30/0000 UTC

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...CLOSED MID-LEVEL LOW WEAKENING INTO THE GREAT LAKES/NORTHEAST
THROUGH MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


...NORTHERN STREAM TROUGH EJECTING ACROSS THE NORTHERN
PLAINS/UPPER MIDWEST TODAY/MON AND REACHING THE ONTARIO/QUEBEC
BORDER TUES MORNING...
...POSSIBLE SHORTWAVE PHASING OVER NEW ENGLAND BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: BLEND OF THE 00Z UKMET AND 06Z GEFS MEAN
CONFIDENCE: BELOW AVERAGE

A COMPLEX INTERACTION OF SYSTEMS LEADS TO A LOW CONFIDENCE
FORECAST. WHILE THE 12Z GFS AND 00Z ECMWF APPEAR FAVORABLE WITH A
VORT MAX CROSSING THE CNTRL APPALACHIANS EARLY ON TUE...ENSEMBLE
SPREAD AND POOR RUN TO RUN CONTINUITY LOWERS CONFIDENCE WITH THE
NRN PORTION OF THE ENERGY INVOLVED DEVELOPING OVER SERN CANADA.
ENSEMBLE SCATTER LOW PLOTS SUPPORT A SURFACE LOW TRACK WEST OF THE
12Z GFS AND 00Z ECMWF TUE NIGHT/WED MORNING...WITH THE 06Z GEFS
MEAN AND 00Z ECMWF MEAN SUPPORTING A TRACK CLOSER TO THE 12Z
NAM/00Z UKMET. THE 12Z NAM HAS SOME UNDESIRABLE CHARACTERISTICS
WITH A FASTER/NORTHERN LEADING EDGE OF THE VORT TRACKING TO THE
SOUTH AND INTO THE ATLANTIC BUT MAY HAVE SOME USE ACROSS THE
NORTHEAST. AGAIN...CONFIDENCE IS VERY LOW WITH THIS SYSTEM.


...UPPER TROUGH CURRENTLY OVER THE CNTRL HIGH PLAINS AND WEAKENING
INTO THE OH VALLEY/NORTHEAST MON NIGHT/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS / 00Z ECMWF BLEND THROUGH 12Z/28
    00Z UKMET/06Z GEFS MEAN AFTER 12Z/28
CONFIDENCE: AVERAGE...BECOMING BELOW AVERAGE BY END OF PERIOD

THERE HAVE BEEN TRENDS IN THE GUIDANCE TO BE FASTER...OR CLOSER TO
THE 12Z GFS HERE...BUT THE 00Z CMC CONTINUES TO STAND OUT THE MOST
WITH A VORT MAX TRACK MUCH FARTHER SOUTH THAN THE REMAINING MODEL
CONSENSUS. THE GEFS/EC MEANS SUPPORT THE 12Z GFS/00Z ECMWF WITH A
TRACK NORTH OF THE 00Z CMC AND SOUTH OF THE 12Z NAM/00Z UKMET.
HOWEVER...POSSIBLE INTERACTION WITH A NRN STREAM SYSTEM MAKES FOR
A COMPLICATED FORECAST BEYOND 12Z/28. HERE...THE ENSEMBLE MEANS
SUPPORT A SHIFT TOWARD THE 00Z UKMET WHICH IS NEAR THE 06Z GEFS
MEAN AND 00Z ECMWF MEAN. SEE ABOVE SYSTEM FOR ADDITIONAL DETAILS.


...UPPER TROUGH/COLD FRONT REACHING THE WEST COAST TODAY...
...WEAKER NORTHERN STREAM TROUGH OVER THE NORTHWEST MON/TUES...
...CLOSED LOW EVOLUTION INTO THE SOUTHWEST MON/TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/00Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 12Z GFS CONTINUES TO TREND FASTER...TOWARD THE FASTER EDGE OF
THE ENSEMBLE SPREAD THROUGH TUE. WHILE THERE HAS BEEN SOME
CONVERGING OF SLOWER/FASTER ENSEMBLE GUIDANCE SINCE
YESTERDAY...THE GFS APPEARS TO BE TOO QUICK GIVEN THE
LATEST...SHRINKING ENSEMBLE DISTRIBUTION. A NON 12Z GFS CONSENSUS
IS PREFERRED ACROSS THE WRN U.S. UNTIL WED EVENING AT WHICH POINT
THE 00Z ECMWF PULLS AHEAD. AT 00Z/30...THE 00Z ECMWF IS FASTER
THAN ITS OWN ENSEMBLE MEAN BUT THE REMAINING MODELS APPEAR USABLE.
THE CLOSEST TO THE MIDDLE GROUND AND ENSEMBLE MEANS IS A BLEND OF
THE 12Z NAM AND 00Z UKMET THROUGHOUT THE SHORT RANGE PERIOD.


...COLD FRONT WEAKENING INTO BRITISH COLUMBIA ON TUES...
...ONSHORE FLOW INTO THE PACIFIC NORTHWEST THROUGH TUES NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM/GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

RELATIVELY MINOR ADJUSTMENTS MADE IN THE GUIDANCE OVER THE PAST
12-24 HRS SUPPORT THE MIDDLE GROUND REPRESENTED BY THE 12Z
NAM...12Z GFS AND 00Z ECMWF.


...SHORTWAVE/SURFACE LOW NEAR THE PACIFIC NORTHWEST BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE 12Z GFS APPEARS TOO AMPLIFIED WITH A SHORTWAVE APPROACHING THE
PACIFIC NORTHWEST GIVEN A LACK OF SUPPORT IN THE REMAINING
GUIDANCE. THE ENSEMBLE MEANS SUPPORT A TROUGH DEPTH AND SURFACE
LOW TIMING CLOSER TO THE 12Z NAM AND 00Z ECMWF. THE 00Z UKMET/CMC
HAVE TIMING AND DEPTH ISSUES UPSTREAM AT 00Z/30...DISPLACED FROM
THE CONSENSUS.

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

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

OTTO

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