Heavy Rain in Hawaii, February 19, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN FEB 19 2006

.SYNOPSIS...
BRIEF HEAVY SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS TONIGHT
WILL GIVE WAY TO MORE TYPICAL TRADE WIND SHOWERS MONDAY AND
THEREAFTER THROUGH THE FORECAST PERIOD. HIGH CLOUDS ALONG THE
SOUTHEAST FLANK OF AN UPPER LOW FAR NORTHWEST OF KAUAI WILL REMAIN
WITH US THROUGH MONDAY.

&&

.DISCUSSION...
OUR AIRMASS REMAINS UNSTABLE THIS EVENING...WITH MODERATE TO
BRIEFLY HEAVY SHOWERS POPPING UP ACROSS WINDWARD OAHU AND PORTIONS
OF WINDWARD MOLOKAI AND MAUI. THERE HAVE BEEN SPORADIC RAIN GAGE
ALARMS FOR 1 TO 1.2 INCH PER HOUR RAINFALL RATES AT WAIHEE PUMP AND
AHUIMANU ON WINDWARD OAHU WITHIN THE PAST TWO HOURS. THESE TWO
STATIONS HAVE SEEN 3 AND 5.5 INCHES OF TOTAL
RAINFALL...RESPECTIVELY...OVER THE PAST 24 HOURS. OTHER WINDWARD
OAHU GAGES HAVE SEEN GENERALLY BETWEEN 1 AND 3 INCHES OF TOTAL
RAINFALL OVER THE PAST 24 HOURS.

A BROAD BAND OF BROKEN TO OVERCAST HIGH CLOUDS LIES ACROSS THE MAIN
HAWAIIAN ISLANDS...ALONG THE SOUTHEAST FLANK OF AN UPPER LOW FAR
NORTHWEST OF KAUAI AND ALONG THE NORTHERN FRINGE OF AN UPPER RIDGE
SOUTH OF THE ISLAND CHAIN. THUNDERSTORMS AT LONG RADAR RANGE...110
TO 115 MILES NORTHEAST OF OAHU...MARK A ZONE OF UPPER DIVERGENCE AS
UPPER NORTHWESTERLIES EAST OF THE UPPER LOW SPLIT FROM UPPER
EASTERLIES WRAPPING AROUND THE NORTH SIDE OF THE RIDGE. THESE
THUNDERSTORMS SHOULD POSE NO THREAT TO THE ISLANDS AS THEY MOVE WEST
WITH THE SPLIT UPPER FLOW. HIGH CLOUD COVER ACROSS THE ISLANDS
SHOULD DECREASE MONDAY AS MODELS SHOW A RETURN TO A MORE ZONAL FLOW
PATTERN ALOFT.

LINGERING INSTABILITY ACROSS THE ISLANDS WILL KEEP THE THREAT OF
BRIEF HEAVY SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS WITH US
OVERNIGHT...MOSTLY OVER AND NEAR KAUAI AND OAHU. AFTER
TONIGHT...SHOWERS SHOULD BEGIN TO ASSUME A TRADE WIND
DISTRIBUTION...FAVORING WINDWARD AND MAUKA AREAS. TRADE WINDS WILL
BE SLOW TO RECOVER STRENGTH THROUGH THE WEEK...HOWEVER...BECAUSE
ANOTHER LOW NORTHEAST OF THE ISLANDS WILL KEEP THE PRESSURE
GRADIENT ACROSS THE ISLANDS RATHER SLACK.

GRIDS HAVE BEEN CHANGED FOR A SLIGHT CHANCE OF THUNDERSTORMS FOR
KAUAI...OAHU AND SURROUNDING WATERS THROUGH TONIGHT.

A DENSE FOG ADVISORY CONTINUES FOR THE BIG ISLAND SUMMITS TONIGHT AS
THE FOG THICKENS. BASED ON THE MAUNA KEA AND MAUNA LOA WEB
CAMS...THERE WERE SEVERAL BREAKS IN THE FOG DURING THE DAY
SUNDAY...BUT EXPECT VISIBILITIES TO DECREASE AGAIN TONIGHT.

&&

.MARINE...
A GALE BETWEEN CALIFORNIA AND THE ISLANDS PRODUCED A
SWELL THAT IS HITTING THE EAST-FACING SHORES. COMPUTER MODELS
FORECAST THE SWELL TO REMAIN HIGHER THAN NORMAL THROUGH MONDAY. SURF
WILL GRADUALLY DROP BELOW THE 8 FEET ADVISORY LEVEL THROUGH THE DAY
MONDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST MONDAY FOR EAST FACING SHORES OF
KAUAI OAHU MOLOKAI MAUI AND THE BIG ISLAND.

DENSE FOG ADVISORY UNTIL 10 AM HST MONDAY FOR BIG ISLAND SUMMITS.
&&

POWELL