Issued by NWS
000 FXUS10 KWNH 231841 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 141 PM EST MON NOV 23 2009 VALID NOV 23/1200 UTC THRU NOV 27/0000 UTC ...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR INGEST... FINAL 12Z MODEL EVALUATION INCLUDING THE ECMWF MODEL INITIALIZATION ERRORS DO NOT APPEAR TO BE LARGE ENOUGH TO HAVE A SIGNIFICANT IMPACT ON THE FORECAST. ...SYSTEM EDGING INTO THE WEST ON THU... PREFERENCE: GFS/CANADIAN GLBL COMPROMISE WITH THE SFC WAVE... GFS/UKMET BLEND ALOFT BY THU THE GFS IS SLIGHTLY FASTER THAN THE NAM WITH LEADING HGT FALLS ALOFT... WHILE THE NAM IS SOMEWHAT WEAKER AND A LITTLE FASTER THAN THE GFS WITH THE SFC WAVE THAT REACHES THE PAC NW COAST BY F84 LATE THU. ADDING THE 12Z UKMET/CANADIAN GLBL SOLNS YIELD A RELATIVE CONSENSUS THAT BRINGS A WAVE NEAR THE OREGON COAST BY F84 LATE THU... ALBEIT WITH A NEARLY 10 MB SPREAD ON DEPTH. STILL THE NEW 12Z ECMWF IS AN EXTREMELY DEEP OUTLIER COMPARED TO OTHER SOLNS AND ON THE SLOW EDGE OF GUIDANCE INCLUDING THE 00Z ECMWF ENSEMBLE MEAN. THE 00Z ECMWF WAS ON THE SLOW EDGE OF GUIDANCE AS WELL. THERE IS ENOUGH OF A STRONGER TREND IN GUIDANCE TO LEAN AWAY FROM THE LATEST SREF/GEFS/ECMWF ENSEMBLE MEANS WHICH MAY BE TOO WEAK DUE TO NOT ACCOUNTING ADEQUATELY FOR IMPORTANT SMALLER SCALE DETAILS. PREFER A COMPROMISE BETWEEN THE GFS/CANADIAN GLBL FOR THE SFC FCST. THE GFS/CMC MAY BE A LITTLE TOO FAST WITH PORTIONS OF THE MID LVL TROF... SO WILL RECOMMEND A GFS/UKMET BLEND ALOFT. ...SFC LOW TRACKING FROM THE PLAINS INTO THE GRTLKS... ...UPR TROF/ASSOC SFC FRONT REACHING THE NRN PLAINS TUE... PREFERENCE: COMPROMISE AMONG NAM/UKMET/CANADIAN GLBL/ECMWF... EXCEPT EXCLUDING THE NAM ALONG EAST COAST BY LATE WED-THU DURING THE DAY WED THE NAM SHOWS MORE EWD AMPLITUDE THAN THE GFS AND MOST OTHER SOLNS WITH THE LEADING SHRTWV TROF THAT CROSSES AREAS FROM THE ERN GRTLKS SEWD. THEN THE GFS IS FARTHER SWWD AND WEAKER THAN THE NAM WITH THE TRAILING UPPER LOW THAT REACHES THE OH VALLEY/GRTLKS BY THU. AS A RESULT THE OVERALL TROF AXIS IN THE GFS ENDS UP FARTHER WWD THAN THE NAM FCST. DIFFS ALOFT CAUSE THE NAM TO BECOME DEEPER THAN THE GFS WITH THE SFC LOW AS IT TRACKS INTO THE GRTLKS. WHILE THE 06Z/00Z GEFS MEANS AND SOME 09Z SREF MEMBERS OFFER SOME DEGREE OF SUPPORT FOR THE GFS HANDLING OF THE SECOND SYSTEM... THE UKMET/CANADIAN GLBL AND FAIRLY CONSISTENT ECMWF SHOW A MID LVL CLOSED LOW TRACK CLOSER TO THE NAM. HOWEVER MODEL/ENSEMBLE CONSENSUS INDICATES THE NAM COULD BE A FRACTION DEEP WITH THE CORE OF THE SYSTEM... AND IS LIKELY TOO AGGRESSIVE WITH LEADING HGT FALLS ALOFT NEAR THE EAST COAST BY WED-THU. AS FOR NAM/GFS TRENDS... THE NAM HAS DISPLAYED A FASTER TREND OVER THE PAST DAY. THE GFS HAS ADJUSTED MODESTLY FASTER VERSUS 06Z/00Z RUNS BUT REMAINS SLOWER THAN YDAYS 12Z GFS. THESE TRENDS ALONG WITH CURRENT CONSENSUS SEEM TO FAVOR LEANING MORE TO THE NAM THAN GFS EXCEPT FOR LEADING HGT FALLS NEAR THE EAST COAST... WITH AN ULTIMATE PREFERENCE BEING A NAM/UKMET/CANADIAN GLBL/ECMWF COMPROMISE TO LEAN AWAY FROM THE GFS FCST AND TO MITIGATE SOMEWHAT EXTREME TRAITS OF THE NAM AT SOME FCST HRS. ...LOW PRESSURE DEVELOPING NEAR THE EAST COAST WED-THU... PREFERENCE: COMPROMISE AMONG CANADIAN GLBL/UKMET/ECMWF DUE TO THE NAM BEING FASTER TO BRING HGT FALLS ALOFT TO THE EAST COAST... THE NAM IS FARTHER N/NE THAN THE GFS WITH WRN ATLC LOW PRESSURE. THE NAM IS ON THE NERN EDGE OF THE CURRENT MODEL/ENSEMBLE SPREAD AND WILL BE DISCOUNTED SINCE ITS MID LVL SOLN ALSO DOES NOT COMPARE WELL TO OTHER SOLNS. MEANWHILE THE AVERAGE OF REMAINING MODEL/ENSEMBLE GUIDANCE IS SLIGHTLY SWWD OF THE GFS... WITH THE UKMET/CANADIAN GLBL/ECMWF ALL IN CLOSE PROXIMITY BY LATE THU BUT WITH THE UKMET DEEPER THAN OTHER SOLNS. WITH FURTHER SUPPORT FROM THE 12Z GEFS MEAN... PREFER AN AVERAGE AMONG THE CANADIAN GLBL/UKMET/ECMWF. ...SYSTEM OFF THE MID ATLC/NORTHEAST COAST MON-WED... PREFERENCE: CANADIAN GLBL/ECMWF COMPROMISE THE GFS GRADUALLY TRACKS THE SYSTEM FARTHER N/E VERSUS THE NAM. LATEST MODEL/ENSEMBLE SOLNS DISPLAY ENOUGH SPREAD TO INCLUDE BOTH THE GFS AND NAM AS POTENTIAL SOLNS. PROGRESSIVE SWLY FLOW ALOFT COULD FAVOR FASTER TIMING THAN THE NAM... BUT THE 12Z ECMWF HAS ADJUSTED SLOWER FROM ITS PREVIOUS RUN TO A NAM-LIKE SOLN. THE UKMET IS ALSO FAIRLY SLOW BUT IS WEAKER THAN OTHER GUIDANCE WITH THE LEADING MID LVL SHRTWV ENERGY. MEANWHILE THE CANADIAN GLBL/REG GEM INDICATE POTENTIAL FOR A SLIGHTLY STRONGER SYSTEM THAN OTHER SOLNS DURING TUE-TUE NIGHT... WITH AN INTERMEDIATE TRACK. THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS LEAN TO THE MIDDLE OR SLOWER PORTION OF THE GUIDANCE SPREAD. GIVEN THE SPREAD AND CONTINUITY CHANGES IN RECENT GUIDANCE PREFER A MODERATE SOLN REPRESENTED BY A CANADIAN GLBL/ECMWF COMPROMISE. ...MODEL TREND GRAPHICS AT WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... ...500MB FORECASTS AT WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... RAUSCH $$
