Prognostic Meteorological Discussion
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000 FXUS10 KWNH 261851 PMDHMD 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 $$

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