MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 136 PM EST FRI JAN 31 2014 VALID JAN 31/1200 UTC THRU FEB 04/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z CMC/UKMET (12Z ECMWF NOT FULLY AVAILABLE) 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. ...SHORTWAVE REACHING THE WEST COAST OF FL BY FRIDAY EVENING... FINAL PREFERENCE: NON-12Z NAM MODEL CONSENSUS FORECAST CONFIDENCE: ABOVE AVERAGE AS SEEN ON WATER VAPOR IMAGERY...A WELL-DEFINED SHORTWAVE AND ITS ASSOCIATED MOISTURE PLUME WILL GRADUALLY SLIDE EASTWARD WITH THE SYSTEM GRADUALLY SHEARING APART OVER WESTERN FL. THE 12Z NAM APPEARS TO BE A HAIR FASTER THAN THE STRONGER CONSENSUS FORMING. THE RECOMMENDATION WILL BE TO DISREGARD THIS MODEL AND LEAN MORE TOWARD THE OTHER AVAILABLE DETERMINISTIC GUIDANCE. ...POSITIVELY-TILTED TROF MOVING THROUGH THE NORTHERN U.S. REACHING THE INTERIOR NORTHEAST BY 03/0000Z... FINAL PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF FORECAST CONFIDENCE: AVERAGE BROAD CYCLONIC FLOW ANCHORING ITSELF OVER MUCH OF CENTRAL/EASTERN CANADA WILL CARRY ANOTHER POTENT LONGWAVE TROF THROUGH THE NORTHERN TIER OF THE COUNTRY BY SATURDAY AFTERNOON. AS THE TROF DIGS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST...THE 12Z NAM SEEMS TO BE ON THE SLOWER SIDE WITH THE 09Z SREF MEAN SOMEWHAT AGREEING WITH THIS MORE WESTWARD SOLUTION. THE 12Z GFS/00Z ECMWF AGREE A BIT MORE WITH THE ENSEMBLE MEANS ALTHOUGH THE 12Z GFS MAY BE A TAD FAST GIVEN IT TRENDED IN THAT DIRECTION RELATIVE TO ITS PREVIOUS RUN. THIS TENDS TO FOLLOW SUIT WITH THE 540-DM SPAGHETTI PLOT WITH THE 00Z GEFS MEMBERS DEPICTING A SLIGHTLY FASTER SOLUTION. THIS HAS BEEN COMMONPLACE IN THE PREVIOUS FOUR SPAGHETTI PLOTS ALTHOUGH THE GAP HAS BEEN BRIDGED IN RECENT CYCLES. WILL CONTINUE TO SPLIT THE DIFFERENCE BETWEEN THEIR TWO IDEAS AND BLEND THE 12Z GFS/00Z ECMWF TOGETHER. ...PACIFIC ENERGY INITIALLY OVER THE DESERT SOUTHWEST EVENTUALLY ABSORBED BY THE NORTHERN STREAM... ...EVOLVING FRONTAL SYSTEM WITH EMBEDDED SURFACE WAVES... FINAL PREFERENCE: BLEND OF THE 12Z UKMET/00Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE A SERIES OF SHORTWAVES SLIDING THROUGH THE DESERT SOUTHWEST AND FOUR CORNERS REGION WILL GRADUALLY LIFT NORTH AND EAST EVENTUALLY BECOMING EMBEDDED WITHIN THE NORTHERN STREAM LONGWAVE TROF. DIFFERENCES ARE RATHER SUBTLE DURING THIS 24 TO 30 HOUR EVOLUTION SO WILL FOCUS MORE ON THE WELL-DEFINED COLD FRONT PUSHING EASTWARD. BY SATURDAY EVENING...THE 12Z GFS/GEFS MEAN AND THEIR ASSOCIATED LOW CENTER ARE FURTHER TOWARD THE NORTHEAST WHILE BEING QUICKER WITH THE FRONT. THE ENSEMBLE LOW PLOTS DO SHOW QUITE A BIT OF SPREAD WITH THE LOW PLACEMENT SO WILL NOT FOCUS TOO MUCH ON THE DETAILS OF WHERE THE SURFACE CYCLONE IS LOCATED. A MAJORITY OF THE MODELS SEEM TO FAVOR A SOMEWHAT SLOWER SOLUTION INCLUDING THE 00Z ECMWF ENSEMBLE MEAN. WPC WILL FAVOR THIS IDEA WITH THE 12Z UKMET/00Z ECMWF ENSEMBLE MEAN BEST SUIT THIS PARTICULAR SOLUTION. ...SHORTWAVE CROSSING THE SOUTHERN HIGH PLAINS EARLY SUNDAY AND REACHING THE MID-ATLANTIC BY MONDAY... ...DEVELOPING SURFACE LOW MOVING THROUGH FROM THE TN VALLEY TOWARD THE LOWER MID-ATLANTIC... FINAL PREFERENCE: BLEND OF THE 12Z CMC/UKMET WITH THE 00Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE AN AREA OF HEIGHT FALLS TRACKING FROM SOUTHERN CA TOWARD THE SOUTHERN TIP OF NM THROUGH SUNDAY MORNING IS EXPECTED TO LIFT NORTHEASTWARD AS THE MID-LEVEL FLOW TURNS MORE SOUTHWESTERLY ACROSS THE EASTERN HALF OF THE COUNTRY. THE 12Z NAM IS SLOWER THAN THE OTHER MODELS WHICH INCLUDES THE ENSEMBLE MEANS. A HOST OF DIFFERENCES EMERGE FURTHER DOWNSTREAM PRIMARILY WITH THE AMPLITUDE OF THE WAVE AND ASSOCIATED SURFACE LOW DEVELOPMENT. THE 12Z CMC/UKMET HAVE BOTH TRENDED TOWARD A SHARPER SHORTWAVE WHICH IS MORE IN ACCORDANCE WITH THE 00Z ECMWF ENSEMBLE MEAN BUT STILL NOWHERE NEAR AS AGGRESSIVE AS THE 00Z ECMWF. WOULD LIKE TO ACCOUNT FOR THIS GROWING TREND HERE AND INCORPORATE THE 12Z CMC/UKMET INTO THE MIX WHILE MAINTAINING THE 00Z ECMWF ENSEMBLE MEAN IN THE PREFERENCE DUE TO THE LARGE AMOUNT OF UNCERTAINTY IN THE FORECAST. ...CLOSED LOW INITIALLY NEAR 40N/130W AFFECTING SOUTHERN CA SOMETIME LATE SUNDAY... FINAL PREFERENCE: BLEND OF THE 12Z UKMET/00Z ECMWF FORECAST CONFIDENCE: AVERAGE A CLOSED LOW AROUND 40N/130W ON SUNDAY MORNING WILL GRADUALLY BECOME MORE OF AN OPEN WAVE AS TIME PROCEEDS FORWARD WITH THE SYSTEM NEARING THE SOUTHERN CA COAST BY SUNDAY EVENING. THE 12Z NAM/09Z SREF MEAN ARE A BIT SLOWER RELATIVE TO THE REASONABLE CONSENSUS TO THE SOUTH. INTO EARLY NEXT WEEK...THE 12Z GFS BEGINS TO DIG THE ENERGY WELL TO THE SOUTH AND WEST OF THE ENSEMBLE MEANS...INCLUDING THE 12Z GEFS MEAN. WILL LEAN MORE TOWARD THE SOLID AGREEMENT SUGGESTED BY THE 12Z UKMET/00Z ECMWF. ...AXIS OF MID-LEVEL HEIGHT FALLS MOVING THROUGH THE PACIFIC NORTHWEST EARLY MONDAY... FINAL PREFERENCE: BLEND OF THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: BELOW AVERAGE A SYSTEM DROPPING DOWN FROM WESTERN CANADA IS EXPECTED TO AFFECT THE PACIFIC NORTHWEST BY EARLY MONDAY. OVERALL...THE SOLUTIONS ARE QUITE VARIABLE WITH A LOT OF UNCERTAINTY WITH THE PRECISE TRACK OF THIS SYSTEM. GIVE SUCH UNCERTAINTY...WILL STAY ON THE CONSERVATIVE SIDE FAVORING A GENERAL BLEND OF THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER