MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 234 PM EDT WED APR 05 2017 VALID APR 05/1200 UTC THRU APR 09/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ IN THE SOUTHEAST, RECENT RAP, HRRR, AND THE 12Z NAM HAVE SHOWN A LOW BIAS IN PRECIPITABLE WATER VALUES ACROSS AL AND GA WHICH HAS SIGNIFICANTLY IMPACTED THEIR DAY 1 RAINFALL FORECASTS IN AND NEAR THE SOUTHEAST THROUGH AT LEAST 00Z. THE 12Z GFS HAS INITIALIZED THE PRECIPITABLE WATER FIELD IN THE SOUTHEAST BETTER, AND COMPARES REASONABLY TO RECENT RADAR IMAGERY DURING THE FIRST SIX HOURS OF ITS FORECAST. SEE THE UPCOMING DAY 1 QPF DISCUSSION AT 19Z FOR MORE INFORMATION ON THE DAY 1 PRECIPITATION FORECAST. DEEP CYCLONE MOVING OFFSHORE THE NORTHWEST FRIDAY LOW MOVING NEAR US/CANADIAN BORDER FRIDAY/SATURDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE HANDLES THESE SYSTEMS COMPARABLY. A COMPROMISE OF THE AVAILABLE GUIDANCE, SIMILAR TO THE PARALLEL VERSION OF THE NATIONAL BLEND OF MODELS, IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. LOW MOVING JUST OFFSHORE THE NORTHWEST WEDNESDAY/THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS COMPROMISE CONFIDENCE: NO BETTER THAN AVERAGE THE 12Z GFS LOSES THIS SYSTEM, WHICH THE OTHER GUIDANCE TAKE AS A WEAK LOW OFFSHORE THE NORTHWEST. THERE SHOULD BE ENOUGH SEPARATION BETWEEN THIS SYSTEM AND THE POWERFUL CYCLONE UPSTREAM FOR IT TO REMAIN INDEPENDENT UNTIL LANDFALL IN VANCOUVER ISLAND. A COMPROMISE OF THE 00Z UKMET/12Z NAM/00Z ECMWF/00Z CANADIAN STAYS WELL WITHIN THE UNUSUALLY LARGE GLOBAL ENSEMBLE CLUSTERING AND IS PREFERRED WITH CONFIDENCE NO BETTER THAN AVERAGE. SYSTEM MOVING INTO CALIFORNIA FRIDAY NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: AVERAGE A SHORTWAVE ROTATING UNDER THE BASE OF THE DEEP CYCLONE MOVING TOWARDS HAIDA GWAII IS BEING HANDLED DIFFERENTLY BY ALL THE GUIDANCE AS IT APPROACHES CALIFORNIA. THE 12Z NAM IS SHARPER WITH THE UPPER FEATURE THAN THE OTHER GUIDANCE. THE PATTERN IN WHICH THE SYSTEM IS EMBEDDED IS ONE OF LONG WAVELENGTH, WHICH WOULD FAVOR A BROADER SYSTEM, THUS RULING OUT THE NAM. THIS LEAVES THE 12Z ECMWF, 12Z CANADIAN, 12Z UKMET, AND 12Z GFS -- SIMILAR TO THE NATIONAL BLEND OF MODELS -- A COMPROMISE OF WHICH IS PREFERRED WITH AVERAGE CONFIDENCE. DEEP CYCLONE MOVING INTO THE NORTHEAST LATE THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE HANDLES THIS STRONG SYSTEM, WITH A CENTRAL PRESSURE CLOSE TO RECORD LOW SEA LEVEL PRESSURES FOR APRIL ACROSS SOUTH-CENTRAL AND NORTHWEST NY, COMPARABLY. A COMPROMISE OF THE AVAILABLE GUIDANCE, SIMILAR TO THE PARALLEL VERSION OF THE NATIONAL BLEND OF MODELS, IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH