Flash Flood Warning 27, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SUN DEC 30 2007

.SYNOPSIS...INCREASED SHOWER ACTIVITY CAN BE EXPECTED ACROSS OAHU
AND MAUI COUNTY OVERNIGHT AS A WEAK TROUGH LINGERS OVER THE CENTRAL
ISLANDS. A WEAK SHEAR LINE IS EXPECTED TO REACH KAUAI TONIGHT AND
THEN STALL AND DISSIPATE OVER THE CENTRAL ISLANDS DURING THE MIDDLE
OF THE WEEK. LIGHT WINDS ARE EXPECTED TONIGHT BUT WILL GRADUALLY
INCREASE FROM A NORTHEAST DIRECTION AS WE ENTER THE NEW YEAR. A
TYPICAL TRADE WIND PATTERN OF WINDWARD AND MAUKA SHOWERS IS EXPECTED
FOR THE START OF 2008.

&&

.DISCUSSION...THE TAIL END OF A FRONTAL BOUNDARY ASSOCIATED WITH A
DEEPENING LOW IN THE GULF OF ALASKA WAS JUST NORTHWEST OF KAUAI THIS
EVENING. FORECAST MODELS CONTINUE TO SHOW THIS FEATURE STALLING
NORTH OF KAUAI TONIGHT AND MONDAY. IT WILL SLOWLY DISSIPATE AS IT
MOVES TOWARD THE CENTRAL ISLAND TUESDAY AND WEDNESDAY. MODERATE
NORTHEAST WINDS ARE EXPECTED TO SLOWLY FILTER ACROSS THE ISLAND
CHAIN AS THE SHEAR LINE PASSES. A HIGH WILL TAKE UP A POSITION NORTH
NORTHWEST OF THE STATE...NORTHEAST WINDS WILL FILTER ACROSS THE
ISLANDS AND TYPICAL TRADE WIND WEATHER IS EXPECTED FOR FIRST WEEK OF
2008.

AN INTERESTING PATTERN IS SEEN ON RADAR AND SATELLITE IMAGERY.
NORTHERLY FLOW AS TAKEN OVER THE ISLAND OF KAUAI THIS EVENING.
FURTHER DOWN THE CHAIN...A WEAK CIRCULATION APPEARED TO BE CENTERED
BETWEEN OAHU AND MOLOKAI. SHOWERS ARE SEEN MOVING TOWARD THE
EAST...NORTH OF MOLOKAI AND OAHU...WHILE SHOWERS ARE SEEN MOVING
WESTWARD SOUTH OF THESE ISLANDS. FORECAST MODELS PICKED UP ON THIS
FEATURE AND SHOWS THE CIRCULATION WEAKENING TONIGHT AND SHIFTING IT
SOUTH ON MONDAY.  SHOWERS ASSOCIATED WITH THIS FEATURE WILL CONTINUE
TO AFFECT THE CENTRAL ISLANDS TONIGHT.

MOUNTAIN SURFACE OBSERVATIONS ON MAUNA KEA ARE REPORTING
TEMPERATURES IN THE LOWER TO MID 20S. MOISTURE UP THERE IS PRETTY
HIGH WITH RELATIVE HUMIDITIES NEAR SATURATION. ALSO WITH MORE
MOISTURE MOVING INTO THAT REGION...THERE COULD BE A POSSIBILITY OF A
LIGHT DUSTING OF SNOW AT THE HIGHER ELEVATIONS.

WILL SEND OUT AN EVENING UPDATE TO REFLECT CHANGES IN THE GRIDS TO
ACCOUNT FOR INCREASED SHOWER ACTIVITY OVER THE CENTRAL ISLANDS AND
THE POSSIBILITY OF LIGHT PRECIPITATION ON THE SUMMITS.

&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINS UP DUE TO SEAS GENERATED FROM THE
STRONG TRADES THIS PAST WEEK. ALSO THE HIGH SURF ADVISORY WAS
EXTENDED THROUGH TONIGHT SINCE SEAS ARE STILL HIGH. A COUPLE OF
MODERATE SIZE NORTH NORTHWEST SWELLS ARE EXPECTED THIS WEEK WITH THE
FIRST ARRIVING TUESDAY AND THE SECOND ON THURSDAY. THIS MAY CAUSE
SEAS TO REMAIN AROUND THE 10 FOOT SMALL CRAFT ADVISORY THRESHOLD
ESPECIALLY OVER WATERS NORTH OF THE ISLANDS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...

SMALL CRAFT ADVISORY FOR ALL HAWAIIAN WATERS.

HIGH SURF ADVISORY FOR EAST FACING SHORES.

&&

ELAU