High Surf in Hawaii, September 27 to 28, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
744 AM HST THU SEP 27 2012

.UPDATE...
INCREASED CHANCE OF RAIN FOR WINDWARD BIG ISLAND THIS MORNING AS
CLOUDS AND SHOWERS WILL CONTINUE.

&&

.SYNOPSIS...
TRADE WINDS WILL CONTINUE THROUGH THE WEEK AS HIGH PRESSURE
REMAINS FAR NORTH OF THE STATE. CLOUDS AND PASSING SHOWERS WILL
AFFECT MAINLY WINDWARD AND MAUKA AREAS...WITH ISOLATED SHOWERS
LEEWARD. WINDS WILL BECOME LIGHT AS A FRONT STALLS NORTHWEST OF
THE AREA. A LAND AND SEA BREEZE REGIME WILL DOMINATE OVER THE
SMALLER ISLANDS SUNDAY AND MONDAY.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS AN MIDDLE TO UPPER LEVEL TROUGH ORIENTED
NORTHEAST TO SOUTHWEST EXTENDING ACROSS KAUAI. AT THE SURFACE...HIGH
PRESSURE IS CENTERED FAR TO THE NORTH-NORTHEAST AND IS DRIVING
MODERATE TRADE WINDS OVER HAWAII. 12Z SOUNDINGS FROM HILO AND LIHUE
SHOW INVERSIONS AROUND 6 TO 8 KFT...WITH PRECIPITABLE WATER /PW/
VALUES 1.2-1.3 INCHES. RADAR SHOWERS WIDELY SCATTERED RAIN SHOWERS
MOVING ACROSS THE HAWAIIAN ISLANDS EARLY THIS MORNING. THESE SHOWERS
ARE MOSTLY HITTING THE WINDWARD AND MOUNTAIN AREAS. EXPECT THESE
PASSING SCATTERED SHOWERS TO DECREASE BY MID-MORNING AND GIVE WAY TO
MOSTLY SUNNY SKIES THROUGH THE REST OF THE DAY.

CURRENT NUMERICAL MODEL RUNS ARE SHOWING THIS MODERATE TRADE WIND
WEATHER PATTERN TO CONTINUE THROUGH FRIDAY NIGHT. THERE SHOULD BE
ENOUGH LOW-LEVEL MOISTURE EMBEDDED IN THE TRADE WIND FLOW TO KEEP
RAINFALL CHANCES NEAR NORMAL VALUES. WINDWARD AND MAUKA AREAS SHOULD
EXPECT TO HAVE THE MAJORITY OF THE PASSING SHOWERS AND WILL OCCUR
MOSTLY DURING THE NIGHTTIME HOURS. ISOLATED SHOWERS WILL BE POSSIBLE
FOR LEEWARD AREAS TOO AT NIGHT...BUT MOSTLY FOR THE UPPER SLOPES.
TRADE WINDS SHOULD REMAIN AROUND MODERATE LEVELS THROUGH FRIDAY WITH
A WEAKENING TREND EXPECTED SATURDAY AND SUNDAY.

DURING THE WEEKEND...MODELS SHOW A COLD FRONT AND SURFACE LOW MOVING
IN FROM THE NORTHWEST. THIS SYSTEM WILL WEAKEN THE HIGH PRESSURE
NORTH OF OUR AREA AND SLIDE THE RIDGE OVER THE HAWAIIAN ISLANDS. THE
FRONT IS NOT EXPECTED AT THIS TIME TO CROSS OVER ANY OF THE MAIN
ISLANDS...BUT IT WILL VEER THE BACKGROUND WIND FLOW TO THE SOUTH AND
SOUTHEAST SUNDAY AND INTO EARLY NEXT WEEK. THE LIGHTER WINDS UNDER
THE RIDGE WILL LEAD TO ONSHORE SEA BREEZES DURING THE AFTERNOONS AND
OFFSHORE LAND BREEZES AT NIGHT. UNDER THIS TYPE OF CONVECTIVE
PATTERN...CLOUDS AND SHOWERS WILL BE MOST ACTIVE ACROSS INTERIOR AND
LEEWARD SECTIONS DURING THE AFTERNOONS...WITH CLEARING CONDITIONS
OVERNIGHT. THE AIRMASS REMAINS RELATIVELY STABLE...SO HEAVY SHOWERS
ARE NOT EXPECTED. THE FRONT IS EXPECTED TO STALL NEAR KAUAI AND THEN
BE PUSHED BACK TO THE NORTHWEST BY THE RIDGE DURING THE MIDDLE OF
NEXT WEEK.

&&

.AVIATION...
A BATCH OF MOISTURE FOCUSED ACROSS WINDWARD BIG ISLAND WILL BRING
MVFR CIGS AND VIS AT PHTO AND WILL PRODUCE MT OBSC THROUGH MUCH OF
THE MORNING. AIRMET SIERRA IS CURRENTLY IN PLACE THROUGH NOON.
OTHERWISE...VFR WILL DOMINATE ACROSS LEEWARD SITES...WHILE ISOL
MVFR CIGS WILL BE CONFINED TO WINDWARD SLOPES AND PHNY AT TIMES.

AIRMET TANGO FOR LOW LVL TURB REMAINS IN EFFECT THROUGH NOON AND
WILL LIKELY BE EXTENDED THROUGH THE AFTERNOON. THIS AIRMET MAY BE
DROPPED BY EVENING.

&&

.MARINE...
A SOUTH SWELL WILL BUILD TODAY AND BRING ADVISORY LEVEL SURF TO
SOUTH FACING BEACHES. THIS SWELL WILL PEAK TONIGHT AND FRIDAY
MORNING...THEN DIMINISH THROUGH THE WEEKEND.

A SMALL CRAFT ADVISORY /SCA/ REMAINS IN EFFECT THROUGH 600 PM HST
TODAY OVER THE TYPICALLY WINDIER AREAS NEAR MAUI AND THE BIG ISLAND.
THE ASCAT SCATTEROMETER PASS FROM EARLY THIS MORNING SHOWED
MARGINAL SCA WINDS OVER THESE AREAS. WIND SPEEDS ARE EXPECTED TO
GRADUALLY WEAKEN THROUGH FRIDAY.

A NORTH-NORTHWEST SWELL WILL ARRIVE FRIDAY AND WILL PEAK SATURDAY
PRODUCING MODERATE-SIZED SURF ALONG NORTH AND WEST FACING SHORES.
THIS SWELL WILL CONTINUE SUNDAY...AND SLOWLY DIMINISH NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST FRIDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU SOUTH SHORE-WAIANAE COAST-MOLOKAI-
LANAI MAKAI-KAHOOLAWE-MAUI LEEWARD WEST-MAUI CENTRAL VALLEY-
WINDWARD HALEAKALA-LEEWARD HALEAKALA-KONA-SOUTH BIG ISLAND-BIG
ISLAND NORTH AND EAST.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS EVENING FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

&&

FOSTER...DISCUSSION
MORRISON...UPDATE AND MARINE
WROE...AVIATION