Prognostic Meteorological Discussion
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FXUS10 KWNH 251733
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1232 PM EST SAT FEB 25 2017

VALID FEB 25/1200 UTC THRU MAR 01/0000 UTC

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

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

NEGATIVELY TILTED MID-LEVEL SHORTWAVE ACROSS THE NORTHEAST TONIGHT
  ALONG WITH ATTENDANT COLD FRONT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


FAST MOVING MID-LEVEL SHORTWAVE TRACKING FROM THE NRN PLAINS THIS
  EVENING TO THE GREAT LAKES SUN EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

CONTINUED CONVERGENCE OF MODEL SOLUTIONS REGARDING THE DEPTH AND
TIMING OF A SHORTWAVE PASSING OVER THE GREAT LAKES REGION SUN
EVENING INCREASES CONFIDENCE IN A GENERAL MODEL COMPROMISE. MODELS
THAT WERE IN THE MIDDLE OF THE SPREAD IN PREVIOUS CYCLES HAVE
EXHIBITED GOOD RUN TO RUN CONTINUITY.


SHORTWAVE SLIDING SOUTH OFF OF CALIFORNIA TODAY AND REACHING THE
  SRN PLAINS LATE SUN...SHEARING INTO CONFLUENT FLOW ACROSS THE
  CENTRAL U.S. MON INTO TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

THE MODELS SHOW ONLY MINOR DIFFERENCES THROUGH SUN NIGHT AS THE
WEAKENING WAVE REACHES THE SRN PLAINS. ALL OF THE MODELS SHOW
REASONABLY GOOD AGREEMENT THROUGHOUT BUT THERE ARE SOME SMALL
DIFFERENCES WORTH NOTING. THE 00Z CMC SHOWS GREATER INTERACTION
WITH THE AFOREMENTIONED SHORTWAVE AND A MORE ELONGATED FEATURE TO
ITS NORTH BY 00Z/27 WHEREAS THE 12Z NAM/GFS SHOW MORE SEPARATION.
THE END RESULT IS A MORE TRACKABLE WAVE IN THE 00Z CMC PAST 12Z/27
AND LESS SO IN THE 12Z GFS/NAM WITH THE 12Z GFS A BIT FASTER THAN
THE MODEL CONSENSUS.

GIVEN THE EXPECTED WEAK NATURE OF THE FEATURE AS IT CROSSES EAST
OF THE MISSISSIPPI...THE DIFFERENCES DESCRIBED ABOVE ARE
CONSIDERED MINOR ENOUGH THAT A GENERAL MODEL BLEND CAN BE UTILIZED
FOR THIS SYSTEM.


NEXT SHORTWAVE DROPPING OUT OF COASTAL BC TO THE NWRN U.S. COAST
  SUNDAY INTO MON WITH ADDITIONAL ENERGY FROM THE NW PHASING WITH
  OFFSHORE UPPER LOW THAT WILL SWING THROUGH SOUTHERN CA BY TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE GFS SLOWED THE PROGRESSION OF THE SHORTWAVE PASSING ACROSS THE
NORTHWEST U.S. SUN NIGHT COMPARED TO PREVIOUS RUNS TO NOW BE IN
GOOD AGREEMENT WITH THE REMAINING DETERMINISTIC MODELS. ALL OF THE
MODELS TRENDED EAST WITH THE REMNANT CLOSED LOW CURRENTLY
NORTHEAST OF HAWAII WITH ALL OF THE LATEST DETERMINISTIC GUIDANCE
IN GOOD AGREEMENT THROUGH 12Z/28 REGARDING THE BASE OF THE
LONGWAVE TROUGH OVER THE WEST COAST TUE MORNING. ONLY A FEW
ENSEMBLE MEMBERS FROM THE ECMWF/GEFS/CMC SHOW THE HAWAII LOW
LAGGING BEHIND THE CONSENSUS.

AT THE SURFACE...A LOW IS FORECAST TO TRACK ACROSS THE PLAINS
EARLY ON TUE AHEAD OF THE LEADING EDGE OF THE TROUGH AXIS SHIFTING
EAST AND SOME MINOR PLACEMENT DIFFERENCES WITH A SHORTWAVE ON THE
LEE SIDE OF THE MID-UPPER LEVEL TROUGH. ENSEMBLES SCATTER LOW
PLOTS SHOW THE GREATEST POTENTIAL FOR A SURFACE LOW 12Z/28 TO BE
FROM N-CNTRL TO NERN KS BUT SPREAD GOES AS FAR NORTH AS SOUTH
DAKOTA AND ONE OR TWO ECMWF MEMBERS IN NRN OKLAHOMA. THIS POSITION
IS NEAREST TO THE 12Z GFS...00Z ECMWF...BUT PERHAPS A TAD NORTH OF
THE GFS/ECMWF COMBO THROUGH 00Z/1.


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

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

OTTO


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