High Surf in Hawaii, December 14 to 17, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
650 AM HST FRI DEC 14 2007

.UPDATE...
UPDATED FORECASTS TO INCREASE POPS LEEWARD TODAY AS STRONG WINDS ARE
BLOWING MEASURABLE PRECIP INTO MOST GAGES. NUDGED WINDS UP SLIGHTLY
AS WELL...BUT FORECAST PHILOSOPHY REMAINS UNCHANGED.

&&

.SYNOPSIS...STRONG HIGH PRESSURE NORTH OF THE MAIN HAWAIIAN ISLANDS
WILL MAINTAIN STRONG TRADE WINDS THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK. WHILE CLOUDS AND SHOWERS WILL FAVOR WINDWARD AND MAUKA
AREAS...TRADE WINDS WILL BE STRONG ENOUGH TO PUSH BOTH ACROSS
LEEWARD AREAS AS WELL FROM TIME TO TIME.

&&

.DISCUSSION...THERE IS LITTLE CHANGE IN FORECAST PHILOSOPHY FROM
SEVEN HOURS AGO. A RIDGE OF SURFACE HIGH PRESSURE EXTENDS ACROSS THE
CENTRAL NORTH PACIFIC ROUGHLY ALONG 35N...WITH ANCHORING HIGHS NEAR
37N167W AND 37N135W. AS AN INTERVENING SURFACE TROUGH LIFTS OUT TO
THE NORTH...THE WESTERN HIGH...AT 1036 MB...WILL MOVE EAST AND MERGE
WITH THE HIGH FARTHER TO THE EAST. BY THIS AFTERNOON...A SINGLE 1036
MB HIGH NEAR 38N150W WILL BE THE DOMINANT WEATHER FEATURE IN THE
PACIFIC OCEAN SOUTH OF 40N BETWEEN THE MAINLAND AND THE DATELINE.
THE PRESSURE GRADIENT BETWEEN THIS HIGH AND EQUATORIAL LOW PRESSURE
WILL BE SUFFICIENTLY STEEP TO MAINTAIN STRONGER THAN NORMAL TRADE
WINDS ACROSS THE MAIN HAWAIIAN ISLANDS AND LOCAL WATERS THROUGH THE
WEEKEND AND INTO EARLY NEXT WEEK. SMALL CRAFT ADVISORIES ARE IN
EFFECT FOR ALL LOCAL WATERS...WITH A GALE WARNING IN EFFECT FOR THE
ALENUIHAHA CHANNEL. WIND ADVISORIES ARE IN EFFECT FOR HALEAKALA
SUMMIT...THE BIG ISLAND SUMMITS...AND FOR LEEWARD KOHALA ON THE BIG
ISLAND. LATEST SCATTEROMETER PASS SHOWS WINDS ABOVE SMALL CRAFT
ADVISORY THRESHOLD ACROSS ALL LOCAL WATERS...WITH 35 KT WINDS HINTED
AT WITHIN THE ALENUIHAHA CHANNEL. WE SEE NO REASON TO DROP WIND
ADVISORIES AND GALE WARNINGS ANYTIME SOON GIVEN THE EXPECTED SHIFT
OF THE SURFACE HIGH INTO AN INCREASINGLY FAVORABLE POSITION FOR
STRONG WINDS. GFS SHOWS THE HIGH WILL BE PUSHED SOUTHWARD BY MIDWEEK
NEXT WEEK AS TROUGHING IN THE MID-LATITUDES INTRUDES...SHIFTING THE
ZONE OF STRONGEST TRADES SOUTH OF THE MAIN ISLANDS. OUR TRADES WILL
WEAKEN SLIGHTLY AS A RESULT BUT MAY STILL STAY HIGH ENOUGH TO
REQUIRE SMALL CRAFT ADVISORIES FOR THE EASTERN CHANNELS. IN
SHORT...EXPECT WINDY CONDITIONS FOR THE NEXT SEVEN DAYS.

SATELLITE LOOPS SHOW SCATTERED TO BROKEN OPEN-CELLED CUMULUS
UPWIND OF THE ISLANDS ALL THE WAY TO 145W. WHILE WE EXPECT NO MAJOR
RAINMAKING WEATHER FEATURES TO AFFECT THE ISLANDS THROUGH THE
FORECAST PERIOD...THESE CLOUDS EMBEDDED IN THE TRADE FLOW WILL PILE
UP ALONG WINDWARD MOUNTAIN RANGES. WEAK TROUGHING ALOFT PREVENTS THE
FORMATION OF A CAPPING TRADE INVERSION...ALLOWING SHOWERS TO BECOME
BRIEFLY MODERATE TO HEAVY. THIS TROUGHING WILL PERSIST FOR AT LEAST
THE NEXT FEW DAYS. EXPECT CLOUDS AND SHOWERS TO FAVOR WINDWARD AND
MAUKA AREAS THROUGH THE NEXT SEVEN DAYS. TRADE WINDS WILL BE STRONG
ENOUGH TO PUSH CLOUDS AND SHOWERS ACROSS LEEWARD AREAS AS WELL FROM
TIME TO TIME. WE HAVE INCREASED POPS ACROSS WINDWARD AREAS TO
ACCOUNT FOR SLIGHTLY GREATER COVERAGE NOTED ON RADAR OVERNIGHT.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR HALEAKALA...BIG ISLAND SUMMITS AND KOHALA.
GALE WARNING IN EFFECT FOR THE ALENUIHAHA CHANNEL.
SMALL CRAFT ADVISORY IN EFFECT FOR ALL OTHER WATERS AND CHANNELS.
HIGH SURF ADVISORY FOR EAST FACING SHORES OF KAUAI OAHU MOLOKAI MAUI
AND THE BIG ISLAND.

&&

BIRCHARD/POWELL