THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


MODEL DIAGNOSTIC DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EST SUN FEB 26 2017

VALID FEB 26/1200 UTC THRU MAR 02/0000 UTC

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

12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

FAST MOVING MID-LEVEL SHORTWAVE TRACKING THROUGH THE NWRN GREAT
  LAKES TONIGHT INTO ONTARIO BY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


SHORTWAVE SWINGING THROUGH THE SOUTHWEST TODAY AND REACHING THE
  SRN PLAINS LATE TONIGHT BEFORE HEADING INTO CONFLUENT FLOW
  ACROSS THE CENTRAL U.S. LATE MON INTO TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

RUN TO RUN CHANGES IN THE MODELS HAVE BEEN RATHER SMALL SINCE
YESTERDAY. WHILE MINOR DIFFERENCES REMAIN WITH THE EVOLUTION OF
MID-LEVEL SHORTWAVE ENERGY ACROSS THE PLAINS TONIGHT AND INTO THE
OHIO VALLEY FOR MON...THE BIGGER DIFFERENCES ARE WITH
PRECIPITATION AND MESOSCALE BOUNDARIES DRIVEN BY CONVECTIVE
PRECIPITATION EARLY MON MORNING ACROSS THE LOWER MS VALLEY. GIVEN
THIS...USERS WILL BE REFERRED TO THE QPFPFD FOR INFORMATION
REGARDING PRECIPITATION WHILE A GENERAL MODEL COMPROMISE WILL BE
PREFERRED IN THIS DISCUSSION FOR MODEL MASS FIELDS.


NEXT SHORTWAVE DROPPING SOUTH OFF OF THE NWRN U.S. COAST TODAY
  AND EXITING INTO THE N-CNTRL U.S. TUE MORNING
MERGING ENERGY FROM COASTAL BRITISH COLUMBIA AND REMNANT OFFSHORE
  OFFSHORE UPPER LOW INTO NWRN MEXICO BY TUE MORNING
STRENGTHENING SURFACE LOW INTO THE GREAT LAKES TUE NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: IN GENERAL: 12Z ECMWF/12Z GFS BLEND THROUGH 00Z/01
            COLD FRONT: 12Z ECMWF/12Z GFS THROUGH 00Z/01
                        12Z ECMWF 00Z/01-00Z/02
	    SURFACE LOW: 12Z ECMWF/UKMET BLEND 00Z/01-00Z/02
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A SOMEWHAT COMPLEX EVOLUTION OF 3 SHORTWAVES INTO THE WRN U.S.
THROUGH TUE MAKES FOR A SENSITIVE EVOLUTION FROM THE ROCKIES INTO
THE PLAINS. A LEADING SHORTWAVE IS CURRENTLY OFF OF THE PACIFIC
NORTHWEST COAST AND IS EXPECTED TO DEAMPLIFY INTO SOUTH DAKOTA BY
TUE MORNING. MEANWHILE...SHORTWAVE ENERGY DROPPING SOUTH ALONG THE
BRITISH COLUMBIA COAST ON MON WILL LIKELY INTERACT TO SOME DEGREE
WITH A REMNANT CLOSED LOW...TURNED SHEARED VORTICITY MAX...INTO
NWRN MEXICO BY EARLY TUE...RESULTING IN A LARGE...NEUTRALLY
ORIENTED TROUGH AXIS EXTENDING FROM THE NRN PLAINS TO THE SRN
ROCKIES BY TUE NIGHT.

THE BIGGEST DIFFERENCES THROUGH TUE ARE WITH THE SHORTWAVE
APPROACHING NWRN MEXICO EARLY TUE...WITH THE 12Z CMC SLOWER AND
00Z UKMET A BIT QUICKER THAN THE CONSENSUS. THE RESULT IN THE 12Z
CMC IS A LESS AMPLIFIED TROUGH OVER THE WEST LATE TUE. FARTHER
NORTH...THERE ARE TIMING DIFFERENCES WITH THE 12Z GFS AT THE
LEADING EDGE OF THE ENSEMBLE CONSENSUS AND IS FASTEST WITH THE
TIMING OF THE RESULTING COLD FRONT MOVING ACROSS THE MIDDLE MS
VALLEY TUE NIGHT. CONCERNING THE SURFACE LOW...THE MIDDLE OF THE
ENSEMBLE SCATTER LOW PLOTS SUPPORTS A POSITION BETWEEN THE 12Z GFS
AND 00Z ECMWF UNTIL ABOUT 00Z/01 AT WHICH POINT THE 12Z GFS BEGINS
TO LIFT FARTHER NORTH INTO SERN CANADA WHILE A VAST MAJORITY OF
ENSEMBLES ARE SOUTH. THE ENSEMBLES ALSO SHOW THE 00Z ECMWF A BIT
SLOW WITH THE FRONT AND THE 00Z ECMWF MEAN A BIT FASTER BUT STILL
SLOWER THAN THE 12Z GFS COLD FRONTAL TIMING. THE 12Z ECMWF FRONTAL
TIMING LOOKS SLOW UNTIL ABOUT 00Z/01 AT WHICH POINT IT SPED UP
RELATIVE TO ITS PREVIOUS RUN AND APPEARS REASONABLE ON WED.

THE END RESULT IS A BLEND OF COLD FRONTAL TIMING BETWEEN THE 12Z
GFS AND 00Z ECMWF THROUGH ABOUT 00Z/01 AND TRANSITIONING TO THE
12Z ECMWF FROM 00Z/01 TO 00Z/02. HOWEVER WITH THE SURFACE LOW...A
12Z GFS...12Z ECMWF BLEND WILL WORK THROUGH ABOUT 00Z/01 WITH A
12Z ECMWF/UKMET BLEND WORKING FROM 00Z/01 TO 00Z/02.


LOW AMPLITUDE SHORTWAVE CLIPPING THE NRN ROCKIES WED MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: AVERAGE

THE ENSEMBLE SPAGHETTI PLOTS SUPPORT THIS FEATURE STAYING A LOW
AMPLITUDE WAVE BUT THERE ARE MINOR TIMING DIFFERENCES WITH THE 12Z
NAM ON THE FASTER EDGE OF THE LATEST GUIDANCE. AT THIS POINT IN
TIME...WILL FAVOR SOMEWHERE NEAR THE MIDDLE OF THE SPREAD GIVEN
POSSIBLE UPSTREAM DIFFERENCES IN FUTURE CYCLES AFFECTING THE
POSITION OF THIS WAVE. THE MIDDLE IS BEST REPRESENTED BY A NON 12Z
NAM BLEND WITH PERCEIVED FAVORABLE ADJUSTMENTS MADE FROM THE 12Z
CMC INTO THE NON NAM CLUSTER OF SOLUTIONS. WHILE THE 12Z GFS
REMAINS A BIT FASTER THAN THE 12Z ECMWF/UKMET/CMC...THE NAM STANDS
OUT FROM THE NON 12Z NAM GUIDANCE.

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

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

OTTO






Last Updated: 151 PM EST SUN FEB 26 2017