Heavy Rain in Hawaii, September 22 to 23, 2005

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST THU SEP 22 2005

.SYNOPSIS...
WEAK TRADES WILL SLACKEN FURTHER ACROSS THE MAIN HAWAIIAN ISLANDS
INTO THE WEEKEND AS TROPICAL STORM JOVA MOVES FURTHER NORTHWEST. SEA
BREEZES WILL COMBINE WITH HIGH HUMIDITY AND UNSTABLE CONDITIONS TO
PRODUCE CLOUD BUILDUPS AND SHOWERS IN ISLAND INTERIORS...MAINLY IN
THE AFTERNOON. TRADES AND MORE TYPICAL WEATHER ARE EXPECTED TO
RETURN BY EARLY NEXT WEEK.

&&

.DISCUSSION...
WEATHER AROUND THE MAIN HAWAIIAN ISLANDS CONTINUED TO BE DETERMINED
MAINLY BY AN UPPER-LEVEL LOW TO THE NORTHWEST...AND TROPICAL STORM
JOVA TO THE EAST NORTHEAST. THE CPHC FORECAST TRACK FOR JOVA IN TURN
WAS INFLUENCED HEAVILY BY THE UPPER LOW AND AN UPPER HIGH FURTHER TO
THE NORTHEAST. THUS...ARGUABLY THE UPPER LOW COULD BE SAID TO BE
THE MORE INFLUENTIAL FEATURE. ALSO...A BROAD PLUME OF CLOUDS AND
TROPICAL MOISTURE SPREADING NORTH FROM THE ITCZ WAS POISED TO COVER
THE ISLANDS FROM THE BIG ISLAND TO OAHU.

THOUGH THE ATMOSPHERE WAS THERMODYNAMICALLY UNSTABLE ACROSS THE
STATE...CONVECTIVE DEVELOPMENT THIS EVENING HAS BEEN RELATIVELY
LIGHT. TRADE WINDS COMBINING WITH THE WIND FLOW AROUND THE NORTH
HALF OF JOVA PROBABLY HELPED TO DISRUPT SEA-BREEZE CIRCULATIONS MORE
FAVORABLE FOR AFTERNOON CONVECTION. ALSO...THE AFTERNOON SOUNDINGS
SHOWED VERY DRY AIR AND WEAK CAPPING ABOVE THE MOIST CLOUD LAYERS...
HINTING PERHAPS AT UPPER-LEVEL SUBSIDENCE AROUND JOVA. AS THE STORM
MOVES FURTHER NORTHWEST OVER THE NEXT 48 HOURS OR SO...CUTTING OFF
MOST OF THE TRADE WINDS...AND THE UPPER LOW ROTATES A VORTICITY
MAXIMUM OVER THE NORTHWEST PART OF THE STATE...SEA BREEZES SPRINGING
UP IN THE SLACK FLOW WILL DEVELOP CONVERGENCE THAT...TOGETHER WITH
THE THERMODYNAMIC INSTABILITY AND UPPER SUPPORT...WILL LIKELY
PRODUCE SIGNIFICANT CONVECTION...RAINFALL...AND POSSIBLY
THUNDERSTORMS OVER KAUAI AND OAHU ON FRIDAY. LOCALLY HEAVY RAINFALL
WILL REMAIN POSSIBLE THROUGHOUT THE STATE AS THE MOISTURE LINGERS
THROUGH THE WEEKEND...THOUGH TRADES BUILDING SOUTH OF JOVA WILL
START TO MOVE THE WEATHER REGIME TOWARD CLIMATOLOGY BY EARLY NEXT
WEEK. AT THIS TIME...NO WIDESPREAD FLOODING PROBLEMS ARE EXPECTED...
BUT VIGILANCE IS ADVISABLE.

ASSUMING JOVA FOLLOWS ITS FORECAST TRACK...AND THE UPPER LOW SLOWLY
MOVES OUT AS EXPECTED...THE NEXT BIG FORECAST PROBLEM MAY BE
TROPICAL STORM KENNETH. THE NHC FORECASTS KENNETH TO CROSS 140W INTO
THE CENTRAL PACIFIC ON SUNDAY. ANY EFFECTS OF KENNETH ON THE MAIN
HAWAIIAN ISLANDS REMAIN MORE THAN A WEEK AWAY...AND CONSEQUENTLY
IMPOSSIBLE TO FORECAST ACCURATELY AT THIS POINT.

&&

.MARINE...
EASTERLY SWELL FROM TROPICAL STORM JOVA HAVE BROUGHT SURF AT OR
ABOVE THE ADVISORY LEVEL OF 8 FEET TO EAST-FACING SHORES OF ALL THE
ISLANDS BUT NIIHAU AND LANAI. WE EXPECT THE SURF TO REMAIN AT OR
NEAR THE ADVISORY LEVEL THROUGH EARLY SATURDAY...THEN TO DECLINE
BELOW IT BY SUNDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FOR EAST-FACING SHORES OF KAUAI...OAHU...
MOLOKAI...MAUI...AND THE BIG ISLAND.

&&

RYSHKO