MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1218 PM EST MON JAN 25 2016 VALID JAN 25/1200 UTC THRU JAN 29/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GFS/NAM EVALUATION INCLUDING PREFERENCES/CONFIDENCE LEVELS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SYSTEM IMPACTING THE PACIFIC NORTHWEST WEDNESDAY INTO THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE GUIDANCE IS GENERALLY IN GOOD AGREEMENT ON THE OVERALL PATTERN ACROSS THIS REGION. THE NAM/GEM MAY BE A BIT TOO SLOW WITH THE ARRIVAL OF THE SYSTEM AND PLUME OF MOISTURE. BY THURSDAY SPREAD BEGINS TO INCREASE WITH REGARDS TO HOW THEY HANDLE THE INDIVIDUAL SHORTWAVES AT THE BASE OF THE LARGE NORTHERN PACIFIC UPPER LOW. ENSEMBLE SPREAD ALSO INCREASES ACROSS THIS REGION AND WILL LIKELY TAKE SOME TIME FOR MODELS TO PICK UP ON THE DETAILS AND CONVERGE ON A SOLUTION GIVEN THE COMPLICATED SETUP. THUS FOR NOW WILL FAVOR A GENERAL CONSENSUS SOLUTION SINCE NO ONE PIECE OF GUIDANCE OR ENSEMBLE MEAN SEEMS SIGNIFICANTLY BETTER OR WORSE THAN ANY OTHER AT THIS TIME. SO WHILE CONFIDENCE IS HIGH ON THE WET PATTERN MOVING IN...CONFIDENCE IN THE EXACT TIMING AND DETAILS REMAINS LOW...ESPECIALLY BY LATER THURSDAY. SYSTEM MOVING FROM THE PACIFIC NORTHWEST ON TUESDAY...MOVING EASTWARD ACROSS SOUTHERN CANADA...THEN INTO THE NORTHERN PLAINS/UPPER MS VALLEY AND GREAT LAKES BY THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS AND 0Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE A SHORTWAVE WILL MOVE INTO THE PACIFIC NORTHWEST ON TUESDAY...AND WILL EVENTUALLY MERGE WITH A SHORTWAVE DIVING SOUTHEAST ACROSS ALBERTA. THE ALBERTA CLIPPER SHOULD THEN DIVE SOUTHEAST TOWARDS THE UPPER MS VALLEY AND GREAT LAKES WEDNESDAY INTO THURSDAY. INITIALLY MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM...WITH A GENERAL CONSENSUS PREFERRED. HOWEVER GUIDANCE BEGINS TO INCREASE IN SPREAD AS THE WAVES MERGE AND THE CLIPPER DIVES SOUTHEAST. DIFFERENCES IN THE TIMING HAVE DECREASED...BUT STILL SOME UNCERTAINTY WITH REGARDS TO HOW FAR NORTH/SOUTH THE LOW TRACKS. THE GEFS MEAN AND ECMWF ENSEMBLE MEAN ARE ACTUALLY IN QUITE GOOD AGREEMENT...AND SUGGEST A COMPROMISE BETWEEN THE 12Z GFS AND THE 0Z ECMWF IS THE MOST LIKELY SOLUTION AT THIS TIME. SYSTEM MOVING FROM THE MS VALLEY TO THE GREAT LAKES TODAY...INTO NEW ENGLAND ON TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON GEM CONSENSUS CONFIDENCE: ABOVE AVERAGE OVERALL THE GUIDANCE APPEAR TO BE HANDLING THIS SYSTEM WELL ON THE SYNOPTIC SCALE. THE GEM IS LIKELY TOO SLOW WITH THE SURFACE LOW AS IT MOVES ACROSS THE GREAT LAKES. THE GFS IS ALSO LAGGING THE OTHER GUIDANCE WITH THE LOW SPEED...BUT HAS BEEN TRENDING QUICKER...THUS CAN STILL BE CONSIDERED A USEFUL PIECE OF GUIDANCE FOR THIS SYSTEM ALONG WITH THE NAM/ECMWF AND UKMET. SYSTEM MOVING ALONG/NEAR THE GULF COAST INTO THE SOUTHEAST BY THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/GFS/NAM/UKMET CONSENSUS CONFIDENCE: SLIGHTLY BELOW AVERAGE MODEL SPREAD REMAINS QUITE LARGE WITH THIS SYSTEM. A COMPLEX SETUP...WITH ISSUES IN HOW MUCH ENERGY SHEARS OUT OF THE TROUGH CURRENTLY MOVING ACROSS THE PLAINS AND INTERACTS WITH THE SOUTHERN STREAM SHORTWAVE CURRENTLY MOVING THROUGH SOUTHERN CA. AND THEN HOW THIS SHORTWAVE ENERGY INTERACTS WITH NORTHERN STREAM ENERGY ASSOCIATED WITH THE CLIPPER SYSTEM MENTIONED ABOVE. THE GEM HANDLES THE ENERGY DIFFERENTLY THAN MOST OF THE OTHER GUIDANCE RESULTING IN A MUCH QUICKER AND PROGRESSIVE SYSTEM THAN THE OTHER GUIDANCE AND ENSEMBLE DATA...THUS IS CONSIDERED AN UNLIKELY SCENARIO. THE NEW 12Z GFS HAS ALSO TRENDED MORE PROGRESSIVE AND POSITIVELY TILTED WITH THE SOUTHERN STREAM WAVE...RESULTING IN A FURTHER EAST LOW TRACK. ON THE OTHER HAND THE ECMWF HAS CONSISTENTLY BEEN ON THE SLOWER/SOUTHWEST EDGE OF THE GUIDANCE ENVELOPE. THESE TWO DETERMINISTIC RUNS SEEM TO BE REPRESENTING THE TWO EXTREMES AT THIS TIME...WITH BOTH THE GEFS MEAN AND ECMWF MEAN IN BETWEEN AND IN CLOSER AGREEMENT WITH EACH OTHER. THUS PREFER SOMETHING CLOSE TO THESE MEANS...WITH THE 0Z UKMET AND 12Z NAM PROBABLY CLOSEST TO THIS MIDDLE GROUND SOLUTION AMONG THE DETERMINISTIC RUNS...GENERALLY BETWEEN THE 0Z ECMWF AND 12Z GFS DETERMINISTIC RUNS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... CHENARD