HAWAII EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 754 AM EDT TUE MAY 28 2013 VALID 00Z WED MAY 29 2013 - 00Z WED JUN 05 2013 AS OF 28/09Z...WATER VAPOR IMAGERY MAINTAINS A SET OF 'BOOK-END' UPPER-LEVEL CIRCULATIONS INVOF THE ISLANDS. ONE SYSTEM INVOF 20.6 175.7W WAS DRIFTING WESTWARD AND A SECOND...INVOF 22.8N 149.4W WAS DRIFTING NORTHWESTWARD. BOTH SYSTEMS WERE INITIALIZED AT THE 500 MB LEVEL IN THE 28/00Z H5 GEFS/EC ENSEMBLE MEANS PACKAGES AND THEIR SOLUTIONS AGREE WITH THE IDEA OF MAINTAINING WEAK CIRCULATIONS INTO THURSDAY (DAY 2) BEFORE LIFTING NORTHWARD...WITH AN UPPER-LEVEL RIDGE GRADUALLY BUILDING INTO THE FORECAST AREA FROM THE EAST. THAT RIDGE ANCHORS JUST NORTH AND NORTHEAST OF HAWAI'I THROUGH THE END OF THE FORECAST PERIOD (DAY7_4/12Z TO 5/00Z). GIVEN THAT THE 28/00Z DETERMINISTIC ECMWF/GFS WERE NOT INDICATING MUCH IN THE WAY OF VORTICITY/DYNAMICS AND MOISTURE AT 700 MBS...WHAT INFLUENCE THESE 'BOOK-END' SYSTEMS WILL HAVE ON THE ISLANDS IS LOCALIZED AT BEST...AND MORE SO...AFFECTING THE HIGHEST ELEVATIONS. THE WPC FORECAST PHILOSOPHY THROUGH DAY 7 IS TO FOLLOW AN EVEN BLEND OF THE 28/00Z GEFS/EC ENSEMBLE MEANS ALOFT AND AT THE SURFACE. THE GFS/ECMWF PACKAGES HAVE BEEN QUITE CONSISTENT WITH THE OVERALL FLOW PATTERN ACROSS THE NORTHERN PACIFIC EASTWARD INTO THE WESTERN ATLANTIC OCEANS. OVER THE PAST 3-4 CYCLES...LITTLE WAVERING OF THE FORECAST AND FOR THE MOST PART...LOOKS LIKE A SUMMER PATTERN WITH THE POLAR JET AXIS WELL NORTH OF 50N AND STRONG RIDGES IN THE SUBTROPICAL NORTHERN HEMISPHERE BETWEEN 20N-30N LATITUDES. VOJTESAK