High Surf in Hawaii, April 24 to 25, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST TUE APR 24 2007

.SYNOPSIS...
TRADE WINDS WILL REMAIN ON THE BREEZY SIDE THROUGH WEDNESDAY AS
STRONG HIGH PRESSURE PERSISTS TO THE NORTH OF THE MAIN HAWAIIAN
ISLANDS. TRADE WINDS WILL DECREASE THURSDAY AND THEREAFTER AS THE
HIGH MOVES AWAY TO THE EAST. A TRADE WIND DISTRIBUTION OF CLOUDS AND
SHOWERS WILL CONTINUE...FAVORING WINDWARD AND MAUKA AREAS. SOME
SHOWERS MAY BE BLOWN ACROSS LEEWARD AREAS AS WELL THROUGH WEDNESDAY.
TOTAL RAINFALL WILL BE LIGHT.

&&

.DISCUSSION...
THE LACK OF A STRONG INVERSION HAS ALLOWED CLOUDS AND DRIZZLE TO
REACH THE BIG ISLAND SUMMITS. BELOW FREEZING TEMPERATURES OVERNIGHT
MAY RESULT IN THIS DRIZZLE FREEZING UPON CONTACT WITH THE GROUND.
ANY FROZEN DRIZZLE WILL MELT AN HOUR OR TWO AFTER SUNRISE. A WINTER
WEATHER ADVISORY IS IN EFFECT FOR THE BIG ISLAND SUMMITS UNTIL 8 AM
HST.

A 1031 MB HIGH NEAR 31N151W DOMINATES THE CENTRAL NORTH PACIFIC
SOUTH OF THE STORM TRACK THIS MORNING. ASSOCIATED RIDGES EXTEND EAST
TO CENTRAL CALIFORNIA AND WEST TO 29N180. THE STEEP PRESSURE
GRADIENT BETWEEN THIS HIGH AND EQUATORIAL LOW PRESSURE IS
MAINTAINING TRADE WINDS IN THE 20 TO 30 MPH RANGE ACROSS HAWAIIAN
WATERS AND ACROSS EXPOSED LAND AREAS. WINDS ARE A BIT HIGHER IN THE
CHANNELS AND WHERE ISLAND TOPOGRAPHY FAVORS LOCALIZED ACCELERATION.
WIND ADVISORIES ARE IN EFFECT FOR THE HALEAKALA SUMMIT AREA OF MAUI
AND FOR LEEWARD KOHALA ON THE BIG ISLAND. BREEZY CONDITIONS WILL
CONTINUE THROUGH WEDNESDAY AS THE HIGH DRIFTS TOWARDS THE EAST BUT
REMAINS WEST OF 140W.

BY THURSDAY...THE HIGH WILL MOVE EAST OF 140W AND A WEAKNESS IN THE
SUBTROPICAL RIDGE WILL REPLACE IT TO THE NORTH OF THE ISLANDS. THE
PRESSURE GRADIENT WILL RELAX ACROSS THE ISLANDS AND WINDS WILL
DECREASE. GFS SHOWS THAT WHILE THE RIDGE WILL REMAIN NORTH OF THE
ISLANDS THROUGH THE FORECAST PERIOD...IT WILL NOT REGAIN THE
STRENGTH IT HAD DURING THE FIRST HALF OF THE WEEK. HOWEVER...THE 06Z
GFS SHOWS A SLIGHT INCREASE IN TRADES BY NEXT WEEKEND AS A 1024 MB
HIGH MOVES IN FROM THE WEST. WE SHOULD STAY IN TRADE WIND FLOW...SO
CLOUDS AND SHOWERS SHOULD CONTINUE TO FAVOR WINDWARD AND MAUKA
AREAS. LEEWARD AREAS MAY GET WET AS WELL FROM TIME TO TIME THROUGH
WEDNESDAY.

&&

.MARINE...
NORTHWEST SWELL IS DIMINISHING...BUT SLOWLY. WE WILL KEEP HIGH SURF
ADVISORIES UP UNTIL NOON TODAY. IN ADDITION...WE HAVE ISSUED HIGH
SURF ADVISORIES FOR EAST FACING SHORES OF THE ISLANDS AS OF 4 AM HST
FOR THE SLOPPY TRADE SWELL. SMALL CRAFT ADVISORIES WILL BE NEEDED
FOR ALL CHANNELS AND WATERS THROUGH EARLY WEDNESDAY MORNING.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...

SMALL CRAFT ADVISORY ALL COASTAL WATERS THROUGH EARLY WEDNESDAY
MORNING.

HIGH SURF ADVISORY NORTH AND WEST FACING SHORES OF NIIHAU KAUAI OAHU
MOLOKAI AND THE BIG ISLAND THROUGH NOON TODAY.

HIGH SURF ADVISORY NORTH FACING SHORES OF MAUI THROUGH NOON TODAY.

HIGH SURF ADVISORY EAST FACING SHORES UNTIL 6 AM HST WEDNESDAY KAUAI
OAHU MOLOKAI MAUI AND THE BIG ISLAND.

WIND ADVISORY UNTIL 4 PM HST WEDNESDAY FOR HALEAKALA SUMMIT.

WIND ADVISORY UNTIL 6 PM HST TODAY FOR LEEWARD KOHALA.

WINTER WEATHER ADVISORY UNTIL 8 AM HST TODAY FOR THE BIG ISLAND
SUMMITS.

&&

POWELL