Prognostic Meteorological Discussion
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000 FXUS10 KWNH 061847 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 146 PM EST SAT FEB 06 2016 VALID FEB 06/1200 UTC THRU FEB 10/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z MODEL GUIDANCE ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...UPPER TROUGH DIGGING THROUGH THE NORTHEASTERN GULF OF MX LATE TONIGHT... ...RAPIDLY DEEPENING SURFACE LOW LIFTING UP THE WESTERN ATLANTIC... FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE SPLIT FLOW REMAINS OVER THE CONUS WITH A PRONOUNCED SOUTHERN STREAM SHORTWAVE CURRENTLY MOVING THROUGH THE LOWER MS VALLEY. PRECIPITABLE WATER VALUES ARE RATHER LOW ACROSS THE GULF COAST AS A PREVIOUS FRONTAL PASSAGE SCOURED OUT MUCH OF THE TROPOSPHERIC MOISTURE. THIS SYSTEM IS FORECAST TO INTENSIFY ACROSS THE NORTHEASTERN GULF OF MX WHERE A CLOSED LOW DEVELOPS BY SUNDAY MORNING. ULTIMATELY THIS FORMS A SURFACE LOW OFF THE SOUTHEASTERN U.S. COAST WHICH IS EXPECTED TO RAPIDLY STRENGTHEN. THE 12Z NAM BEGINS ON THE FAR WESTERN SIDE OF THE SPREAD PER COMPARISONS WITH ENSEMBLE LOW PLOTS. THESE LATTER SCATTER DIAGRAMS SHOW DIFFERENT CAMPS SETTING UP WITH THE 00Z CMC MEMBERS BEING ON THE QUICKER SIDE WITH A BIT MORE CLUSTERING AMONG THE 00Z GEFS/ECMWF ENSEMBLE MEMBERS. AS THE SYSTEM ACCELERATES TOWARD THE NORTH-NORTHEAST...THE 12Z NAM/CMC ARE ON THE WESTERN SIDE OF THE MODEL SPREAD WITH THE ONLY SUPPORT FROM THE 09Z SREF MEAN. THROUGHOUT THE PERIOD...THE 12Z/00Z ECMWF/UKMET SHOW THE MOST AGREEMENT TOWARD THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS. WILL LEAN IN THE DIRECTION OF THESE SOLUTIONS HERE. ...NORTHERN STREAM FEATURE CLIPPING UPPER NEW ENGLAND EARLY SUNDAY... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE AMPLIFICATION TAKES PLACE OVER ONTARIO/QUEBEC WHICH DRAGS WEAK HEIGHT FALLS THROUGH UPPER SECTIONS OF NEW ENGLAND ON SUNDAY MORNING. THERE ARE SMALL-SCALE DIFFERENCES WITH THIS EVOLUTION BUT THESE DO NOT APPEAR TO BE DETRIMENTAL TO THE FORECAST. A GENERAL MODEL COMPROMISE APPEARS REASONABLE WITH THIS SYSTEM. ...PROGRESSIVE SHORTWAVE TRACKING FROM THE UPPER INTERMOUNTAIN WEST TO THE GREAT LAKES... ...EVENTUAL DEEP UPPER TROUGH ANCHORING THE EASTERN U.S. ON MONDAY/TUESDAY... ...ASSOCIATED SURFACE CYCLONES... FINAL PREFERENCE: BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE PROGRESSIVE HEIGHT FALLS MOVING THROUGH THE UPPER INTERMOUNTAIN WEST WILL EVENTUALLY REACH THE UPPER MIDWEST BY 07/1200Z WITH A CLOSED LOW EVOLVING DURING THIS PROCESS. THE PATTERN APPEARS TO BE REASONABLY RESOLVED THROUGH THE WEEKEND WITH ENSEMBLE LOW PLOTS INDICATING MINIMAL SURFACE CYCLONE SPREAD. THIS SOLUTION IS CENTERED OVER NORTHERN WI WITH SPREAD GRADUALLY INCREASING AS TIME MOVES ON. LIKE PRECEDING SYSTEMS...THE TROUGH WILL QUICKLY GAIN AMPLITUDE OVER THE MIDDLE MS VALLEY WITH THIS SHORTWAVE ENERGY ADVANCING TOWARD THE OH VALLEY/MID-ATLANTIC REGION. MODEL UNCERTAINTY CONTINUES TO INCREASE...PARTICULARLY WITH TIMING WITH THE 00Z GEFS/CMC ENSEMBLE MEMBERS ON THE QUICKER SIDE. THERE HAS BEEN A RECENT TREND IN 12Z GUIDANCE TO BE QUICKER THAN THEIR PRECEDING RUNS. REGARDING SURFACE DEVELOPMENT...WHILE THE INITIAL SURFACE LOW MIGRATES TOWARD THE LOWER GREAT LAKES EARLY NEXT WEEK...A SECONDARY AXIS OF LOW PRESSURE FORMS OVER THE LOWER MID-ATLANTIC. THE PAST FEW ENSEMBLE LOW PLOTS SHOW THE ECMWF ENSEMBLES HAVE SUPPORTED A LOW MOVING ALONG THE VA/NC BORDER ON MONDAY EVENING. THE 12Z ECMWF CONTINUES TO BE SOUTH OF ALL OTHER SOLUTIONS BUT IT DID MAKE A MOVE NORTHWARD. THIS KEEPS THE FORECAST SOUTH OF THE ENSEMBLE MEANS HOWEVER. OTHER GUIDANCE HAVE ALSO RECENTLY TRENDED NORTHWARD...PARTICULARLY THE 12Z GFS. NOT COMPLETELY SOLD ON ANY DETERMINISTIC SOLUTION GIVEN THE UNCERTAINTY IN THE PATTERN. THUS...WILL MAINTAIN THE PREVIOUS PREFERENCE. ...BROAD MID-LEVEL WEAKNESS EXTENDING OVER THE EASTERN SUBTROPICAL PACIFIC... FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF/UKMET FORECAST CONFIDENCE: AVERAGE HEIGHTS WILL QUICKLY BUILD OVER THE WESTERN U.S. SETTING UP AN IMPRESSIVE 588-DM RIDGE. TO THE SOUTH...MODELS SHOW A BROAD CYCLONIC CIRCULATION STRETCHING BETWEEN 20N AND 30N ACROSS THE SUBTROPICAL EASTERN PACIFIC. THIS EXTENSIVE AXIS OF VORTICITY IS FORECAST TO DRIFT EASTWARD TOWARD THE SOUTHERN GULF OF CA/SEA OF CORTEZ. THE 12Z NAM IS A BIT WEST OF THE CONSENSUS FORMED BY THE ENSEMBLE MEANS. THE BEST SUPPORT COMES FROM THE 12Z GFS/ECMWF/UKMET ALTHOUGH THE 12Z/00Z ECMWF SOLUTION MAY BE A TAD TOO ROBUST. WILL COMBINE THE SOLUTIONS FROM THESE THREE WHICH SHOULD TEMPER THE STRONGER 12Z/00Z ECMWF SOME. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER $$

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