Prognostic Meteorological Discussion
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000 FXUS10 KWNH 251829 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 128 PM EST SUN JAN 25 2015 VALID JAN 25/1200 UTC THRU JAN 29/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. MERGING SHORTWAVE MOVING INTO THE PLAINS WEDNESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE DETERMINISTIC GUIDANCE SHOWS MUCH LESS SPREAD THAN THE 00Z GLOBAL ENSEMBLE SPREAD WITH THIS SYSTEM. DUE TO THIS, PREFER A COMPROMISE OF THE 12Z ECMWF/12Z GFS, WITH THE LINGERING SPREAD IN THE GUIDANCE KEEPING CONFIDENCE AVERAGE. CLOSED LOW MOVING INTO THE WEST EARLY TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE IS IN GOOD AGREEMENT HERE. CLIPPER SYSTEM MOVING BY WISCONSIN MONDAY/TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE GUIDANCE SHOWS DECREASING SPREAD HERE, WITH THE 12Z GFS/12Z ECMWF SPLITTING THE DIFFERENCE IN THE DETERMINISTIC AND GLOBAL ENSEMBLE SPREAD. A 12Z GFS/12Z ECMWF COMPROMISE IS PREFERRED WITH AVERAGE CONFIDENCE CONSIDERING ITS QUICK PROGRESSION AND LINGERING MODEL SPREAD. CLIPPER-TYPE SYSTEM EVOLVING INTO A NOR`EASTER MON/TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: BELOW AVERAGE THERE REMAIN SOME SLIGHT EAST-WEST AND SLIGHT PROGRESSION ISSUES WITH THIS SYSTEM WHICH PLAY HAVOC WITH THE PRECIPITATION/WINTER WEATHER FORECAST. THE 12Z ECMWF, 12Z NAM, AND 12Z GFS HAVE WHAT APPEAR TO BE CONVECTIVE FEEDBACK BULL`S EYES CONTAMINATING THEIR SOLUTIONS -- THE 12Z UKMET/12Z CANADIAN ALSO SHOWS SIGNS OF GRID SCALE FEEDBACK. THE NAM/ECMWF BULL`S EYES OVER THE GULF STREAM OFFSHORE THE EAST COAST APPEAR TO CAUSE AN EASTWARD SHIFT IN THEIR 12Z SOLUTION AT THE SURFACE AND ALOFT ON (DAY 2 ON THE NAM AND DAY 3 ON THE ECMWF). THE GFS`S BULL`S EYE/QPF BOMB DRAGS ITS BOUNDARY LAYER WIND CIRCULATION ACROSS CAPE COD AND THE ISLANDS ON ITS 12Z RUN, MORE TO THE WEST OF THE OTHER GUIDANCE DESPITE ITS SURFACE PRESSURE PATTERN. THERE IS A CHANCE OF SOME WOBBLING/LOOPING OF THE CENTER OF THE SURFACE LOW DUE TO AN INVADING SHORTWAVE ROUNDING ITS SOUTHWEST SIDE ON TUESDAY, WHICH WOULD LEAD TO AN UNEVEN FORWARD PROGRESSION. THE 00Z GLOBAL ENSEMBLE GUIDANCE ENVELOPE OF SOLUTIONS MIRRORS THE ENVELOPE OF DETERMINISTIC SOLUTIONS AMONGST THE GFS, NAM, ECMWF, CANADIAN, AND UKMET. THERE IS NO OVERARCHING TREND SINCE THIS TIME YESTERDAY TOWARDS A QUICKER OR SLOWER SOLUTION, THOUGH THE NAM/GFS/ECMWF/UKMET HAVE TRENDED WESTWARD -- IN THE DIRECTION OF THE 12Z GFS. THE OCCASIONALLY SLOW/PLODDING 09Z SREF MEAN LIES IN THE MIDDLE OF THE DETERMINISTIC MODEL SPREAD, QUICKER THAN THE 12Z NAM/12Z ECMWF SOLUTIONS. SINCE NO SOLUTION CAN BE COMPLETELY DISCOUNTED WHEN USING THE SURFACE PRESSURE FIELD, 700 HPA HEIGHT FIELD, AND 500 HPA HEIGHT FIELD, FAVOR A COMPROMISE OF THE 12Z ECMWF/12Z UKMET/12Z CANADIAN/12Z GFS/12Z NAM, WHICH ROUGHLY RESEMBLES THE 09Z SREF MEAN AT 500 HPA AND THE SURFACE. FOR QPF AND WINTER WEATHER CHOICES, SEE OUR QPF AND WINTER WEATHER DISCUSSIONS AND GRAPHICS. ...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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