Prognostic Meteorological Discussion
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000 FXUS10 KWNH 210639 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 239 AM EDT TUE APR 21 2015 VALID APR 21/0000 UTC THRU APR 24/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INITIALIZATION ERRORS WITH THE NAM/GFS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. TROUGHING IN THE SOUTHWEST WEDNESDAY INTO FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THE GUIDANCE IS IN GOOD AGREEMENT HERE, THOUGH IT HAS SHOWN BAD CONTINUITY AS OF LATE. MEDIUM RANGE MENTIONS THAT DESPITE RECENT GUIDANCE VARIANCE, THE MODELS HAVE BEEN TRYING TO BRING THIS SYSTEM INTO THE SOUTHERN PLAINS IN THE 25/00Z TIME FRAME, WHICH THE MOST RECENT RUNS WOULD ACCOMPLISH. THE PREFERENCE IS FOR A GENERAL MODEL COMPROMISE WITH AVERAGE CONFIDENCE. DEEP CYCLONE APPROACHING THE NORTHWEST LATE THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSE TO THE ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THERE HAS BEEN A TREND TO THE SOUTH WITH THIS SYSTEM SINCE THE 12Z RUNS OF THE GUIDANCE, WHICH HAS LEFT THE 00Z GFS AS A NORTHWARD OUTLIER. DESPITE THE SHIFT ALOFT, VARIANCE REMAINS WITH THE SYSTEM`S SURFACE LOW. THE 00Z ECMWF SPLITS THE DIFFERENCE AT THE SURFACE AND IS PREFERRED WITH SLIGHTLY BELOW AVERAGE CONFIDENCE. CLOSED LOW MOVING ACROSS INTO SOUTHWEST CANADA THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CANADIAN/ECMWF COMPROMISE CONFIDENCE: AVERAGE AN AMPLIFIED RIDGE IN THE NORTHERN STREAM SHOULD ALLOW THIS SYSTEM TO SLIDE EASTWARD UNDER ITS BASE, SIMILAR TO THE BEHAVIOR OF THE NON-GFS GUIDANCE. PROGRESSION AND LATITUDE ISSUES REMAIN, WITH THE 00Z NAM THE SLOWEST AND THE UKMET THE QUICKEST -- THEIR USUAL BIASES. PREFER A COMPROMISE OF THE 00Z CANADIAN/00Z ECMWF WITH AVERAGE CONFIDENCE. DEEP CYCLONE MOVING ACROSS NEW ENGLAND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/CANADIAN/ECMWF/NAM COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 00Z UKMET IS QUICKER TO PROGRESS THE SYSTEM EASTWARD WHEN COMPARED TO THE OTHER GUIDANCE -- ITS USUAL BIAS. A COMPROMISE OF THE 00Z GFS/00Z NAM/00Z CANADIAN/00Z ECMWF SHOULD EFFECTIVELY DEAL WITH REMAINING DETAIL ISSUES WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH $$

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