000 FXUS10 KWNH 100809 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 308 AM EST WED FEB 10 2010 VALID FEB 10/0000 UTC THRU FEB 13/1200 UTC ...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION INCLUDING THE NEW ECMWF AND PREFERENCES ANY INITIALIZATION ERRORS ARE DESCRIBED UNDER THE RELEVANT SYSTEM HEADINGS. ...UPPER LOW TRACKING EASTWARD FROM THE OHIO VALLEY... ...SURFACE LOW DEEPENING EAST OF DELMARVA/NEW JERSEY... PREFERENCE: 1/2 EACH NAM/UKMET RADAR AND SATELLITE TRENDS SHOW A SMALL BUT SIGNIFICANT LOW/MID LEVEL CYCLONIC VORTICITY CENTER MOVING EAST OF THE WASHINGTON DC AREA AT 00Z...WHICH IS NOT ADEQUATELY RESOLVED BY THE NAM BUT IS SLIGHTLY BETTER RESOLVED BY THE GFS...AND HAS MAGNIFIED THE NORTHWESTERN PERIPHERY OF THE DEVELOPING PRECIPITATION SHIELD. DESPITE SOME CONCERNS WITH MESOSCALE ASPECTS OF THE LOW PRESSURE AREA FORMING SOUTH OF DELMARVA...MODELS ARE IN LARGE SCALE AGREEMENT ALOFT AND AT THE SURFACE...WITH THE NEW ECMWF SIMILAR TO ITS PRIOR RUN IN REMAINING NEAR THE WESTERN EDGE OF THE SOLUTION ENVELOPE REGARDING THE DEEPENING LOW EAST OF NEW JERSEY THROUGH THE 1ST 24 HRS...WHILE THE NAM AND GFS TRENDED NORTHEASTWARD WITH THE LOW. THE UKMET IS WEST LIKE THE ECMWF BUT NOT AS MUCH WHILE THE CANADIAN IS LIKE THE NAM/GFS WITH THE GFS FARTHEST EAST. WITH LITTLE OR NO MODEL AGREEMENT FOR THE MORE WESTWARD ECMWF...AM SKEPTICAL TO RECOMMEND ITS SOLUTION. RATHER...RECOMMEND A SOLUTION NEAR THE CONSENSUS...WHICH IS A BLEND OF THE NAM/UKMET. ...UPPER LOW MOVING FROM CALIFORNIA TO THE GULF OF MEXICO THROUGH THE PERIOD... PREFERENCE: 40 PERCENT EACH ECMWF AND UKMET/20 PERCENT CANADIAN THE NEW ECMWF MAINTAINS GOOD CONTINUITY WITH ITS PRIOR RUN BY REMAINING FASTER THAN THE NAM/GFS CROSSING THE SOUTHWEST...WITH THE NAM THEN DRIFTING TOWARD THE SLOW EDGE OF THE GUIDANCE CROSSING THE GULF OF MEXICO AND GFS CATCHING UP TO THE ECMWF LATE IN THE PERIOD. HOWEVER...BOTH THE NAM AND GFS MAINTAIN MORE SEPARATION WITH THE NORTHERN STREAM...THUS PRODUCING A MORE SUPPRESSED OR SOUTHWARD SURFACE LOW IN THE GULF...WHEREAS THE ECMWF/UKMET/CANADIAN SHOW SOME DEGREE OF PHASING AND ALLOW THE LOW TO TRACK FARTHER NORTH AND ARE GENERALLY STRONGER WITH THE LOW EAST OF FLORIDA BY 84 HRS. THE CANADIAN IS MOST EXTREME WITH THE PHASING BUT HAS BACKED OFF SLIGHTLY FROM ITS PRIOR RUN. DIFFICULTY IN RESOLVING THE SPLIT-FLOW REGIME AT THIS TIME FRAME MAKES THIS A CHALLENGING FORECAST BEYOND JUST A COUPLE DAYS. HOWEVER...FOR NOW RECOMMEND EXCLUDING THE NAM...WHICH IS NEARLY A SLOW OUTLIER LATER IN THE PERIOD. MEANWHILE...IF IT WERE NOT FOR CONCERNS WITH HOW FAST THE GFS IS ACROSS THE PACIFIC NORTHWEST EARLIER IN THE PERIOD...THE GFS MIGHT BE CONSIDERED A REASONABLE SOLUTION ACROSS THE SOUTHEAST. HOWEVER...ITS SOLUTION IS ALSO CONSIDERED QUESTIONABLE DUE TO UPSTREAM CONSIDERATIONS. THIS LEAVES ALL NON-NCEP GUIDANCE AS VIABLE ALTERNATIVES...WHICH INCORPORATES SOME DEGREE OF PHASING WITH THE NORTHERN STREAM...WITH THE CANADIAN STRONGEST BUT NOT ENTIRELY UNREASONABLY...ESPECIALLY GIVEN THE RECENT HISTORY WITH SOUTHERN STREAM SYSTEMS THIS WINTER SEASON. ...SHORTWAVE TROUGH GRAZING THE PACIFIC NORTHWEST TDY/TNGT... PREFERENCE: NAM OR ECMWF THE NAM AND ECMWF ARE COMPARABLE...WHILE THE GFS IS SLIGHTLY FASTER AND LESS AMPLIFIED. THUS...DUE TO CONSENSUS RECOMMEND EITHER THE NAM OR ECMWF. ...2ND SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST THU NGT... PREFERENCE: NAM OR ECMWF GUIDANCE IS NEARLY EVENLY SPLIT REGARDING TIMING...WITH THE NAM/ECMWF SLOWER AND GFS/NEW UKMET FASTER. SREF/GEFS MEANS ARE IN BETWEEN...BUT WITH EARLIER PREFERENCES FOR AN EARLIER SHORTWAVE TROUGH (MENTIONED ABOVE) FAVORING SLOWER TIMING...AND THE POSSIBILITY THAT THE GFS IS BEGINNING TO SHOW SOME OF FAST BIAS AT THIS TIME FRAME...PREFER A SOLUTION TOWARD THE SLOWER SIDE OF THE GUIDANCE. ...3RD SHORTWAVE TROUGH NEARING THE PACIFIC NORTHWEST FRI... PREFERENCE: GFS OR ECMWF THE NAM IS CONSIDERED A SLOW OUTLIER WITH ARRIVAL OF THIS SYSTEM ALONG THE COAST WITH THE GFS/ECMWF OTHERWISE IN GOOD AGREEMENT. ...SHORTWAVE TROUGH MOVING FROM THE UPPER MIDWEST TO THE OHIO VALLEY THU NGT/FRI... PREFERENCE: GFS OR ECMWF THE NEW ECMWF HAS TRENDED FASTER...WHICH NOW MAKES THE NAM A SLOW OUTLIER...WHICH ALSO IS CONSISTENT WITH THE NAM`S SLOWER TIMING WITH A SOUTHERN STREAM SYSTEM INFLUENCING THE DEEP SOUTH DURING THIS PERIOD. OTHERWISE...GOOD MODEL AGREEMENT EXISTS CONCERNING STRENGTH AND TIMING. ...SMALL UPPER LOW NEARING THE DAKOTAS FRI... PREFERENCE: UKMET OR HALFWAY BETWEEN THE GFS/ECMWF THE NEW ECMWF HAS TRENDED SLOWER LATE IN THE PERIOD AND NOW AGREES WITH THE UKMET AND IS ONLY SLIGHTLY FASTER AND WEAKER THAN THE GFS...WHILE THE NAM IS SLOWEST BUT SUPPORTED BY THE CANADIAN. TRENDS HAVE BEEN ERRATIC OVER THE LAST COUPLE OF RUNS MAKING A MODEL CHOICE DIFFICULT. FOR NOW...RECOMMEND LEANING TOWARD THE CONSENSUS...WHICH IS ABOUT MIDWAY BETWEEN THE GFS AND ECMWF...OR CLOSEST TO THE UKMET. ...MODEL TREND GRAPHICS AT WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... ...500 MB FORECAST AT WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... JAMES $$