Flash Flood Warning 30, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
930 AM HST MON DEC 31 2007

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL BRING THE THREAT OF HEAVY
RAIN SHOWERS TO THE BIG ISLAND AND MAUI COUNTY TODAY. BEHIND THE
TROUGH...INCREASING NORTHEAST TRADE WINDS ON KAUAI AND OAHU WILL
BRING SHOWERS MAINLY ACROSS SOGGY WINDWARD AND MAUKA AREAS TODAY. A
SHEAR LINE NEAR KAUAI TODAY WILL GRADUALLY WORK ITS WAY DOWN THE
ISLAND CHAIN TUESDAY AND DISSIPATES OVER THE CENTRAL ISLANDS DURING
THE MIDDLE OF THE WEEK.

&&

.DISCUSSION...AN UPPER TROUGH SITUATED ACROSS THE CENTRAL ISLANDS
THIS MORNING WITH HEAVY RAIN SHOWERS CONCENTRATED IN A SWATH FROM
SOUTHWEST MAUI ISLAND TO CENTRAL MOLOKAI ISLAND. THIS UPPER LOW HAS
SOME REFLECTION IN MID AND LOW LEVELS AS SHOWN IN RADAR IMAGERY AND
IS SHOWING LITTLE MOVEMENT OVER THE PAST SEVERAL HOURS. LIGHTNING
DETECTION SHOWED STRIKES OFFSHORE NORTHEAST OF MOLOKAI EARLIER THIS
MORNING INDICATING THE AREA OF BEST INSTABILITY ASSOCIATED WITH THE
SYSTEM AND HAVE ADDED ISOLATED THUNDERSTORMS TO THE FORECAST FROM
ROUGHLY THE NORTHERN END OF THE BIG ISLAND ACROSS MAUI TO MOLOKAI
AND SURROUNDING WATERS.

WITH THE TROUGH NOW STALLING OVER THE CENTRAL ISLANDS...THE REST OF
THE DAY WILL REFLECT SIMILAR CONDITIONS TO THE CURRENT SCENARIO.
THE BIG ISLAND WILL LIKELY SEE DEVELOPMENT OF SHOWERS LATER TODAY AS
DIFFERENTIAL HEATING DEVELOPS SEA BREEZE CONVERGENCE. FLASH FLOOD
WATCH AREA WILL REMAIN AS IS THROUGH THE DAY.

EXPECT THE WEATHER PATTERN TO QUIET DOWN THIS EVENING AND OVERNIGHT
AS THE TROUGH WEAKENS AND GETS PUSHED OUT OF THE CENTRAL ISLANDS BY
AN INCREASING NORTHEAST TRADE FLOW. THIS FLOW WILL BRING DOWN THE
REMNANTS OF A WEAKENING SHEAR LINE THROUGH KAUAI AND OAHU ON NEW
YEARS DAY. NOT MUCH SUPPORT WITH THIS LINE FOR MUCH MORE THAN
SCATTERED SHOWERS OVER THE WATERS AND MAYBE LEEWARD AND A SLIGHT
UPTICK IN WINDWARD PRECIP AMOUNTS.

A HIGH WILL TAKE UP A POSITION NORTH NORTHWEST OF THE STATE FOR THE
REST OF THE WEEK WITH MORE TYPICAL TRADE WIND WEATHER.

&&

.MARINE...MODERATE TO FRESH NORTHEAST WINDS WILL REQUIRE A SMALL
CRAFT ADVISORY TO BE EXPANDED TO COVER WATERS SURROUNDING OAHU AND
KAUAI INCLUDING THE KAIWI CHANNEL TODAY. 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...

FLASH FLOOD WATCH FOR MAUI COUNTY AND BIG ISLAND.

SMALL CRAFT ADVISORY FOR ALL WATERS SURROUNDING KAUAI AND OAHU.

&&

BRENCHLEY