High Surf in Hawaii, December 24 to 31, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST TUE DEC 24 2013

.SYNOPSIS...
MODERATE TO LOCALLY FRESH TRADE WINDS WILL CONTINUE TO BRING LOW
CLOUDS AND SHOWERS TO WINDWARD AND MAUKA AREAS OF THE ALOHA STATE
TODAY...ESPECIALLY OVER THE EASTERN END OF THE ISLAND CHAIN. A MORE
STABLE TRADE WIND WEATHER PATTERN IS EXPECTED TO PREVAIL FROM
TONIGHT INTO FRIDAY...FOLLOWED BY WET WEATHER ACCOMPANYING A COLD
FRONT MOVING DOWN ACROSS THE STATE THIS WEEKEND.

&&

.DISCUSSION...
THE TIGHTENING PRESSURE GRADIENT SOUTH OF AN EAST NORTHEAST TO WEST
SOUTHWEST ORIENTED SURFACE RIDGE LOCATED ABOUT 570 MILES NORTH OF
HONOLULU IS CAUSING TRADE WIND SPEEDS TO GRADUALLY INCREASE ACROSS
THE MAIN HAWAIIAN ISLANDS EARLY THIS MORNING. EVIDENCE FOR THIS
TIGHTENING OF THE PRESSURE GRADIENT INCLUDES 1 TO 2 MILLIBAR
PRESSURE RISES OVER THE PAST 24 HOURS AT MOST OBSERVATION SITES
ACROSS THE STATE.

ALOFT...THE AXIS OF A SHARP UPPER LEVEL TROUGH EXTENDS FROM NEAR 30N
144W THROUGH A POINT ABOUT 440 MILES EAST OF HILO TO 07N 153W. THIS
SYSTEM...WHICH CONTINUES TO PROPAGATE SLOWLY EASTWARD...IS STILL
CLOSE ENOUGH TO KEEP THE ATMOSPHERE SLIGHTLY UNSTABLE OVER THE
EXTREME EASTERN END OF THE ISLAND CHAIN. AT THE SAME TIME...UPPER
LEVEL RIDGING IS MOVING OVER THE ISLANDS FROM THE WEST...SO MORE
STABLE ATMOSPHERIC CONDITIONS ARE SLOWLY RETURNING TO THE WESTERN
ISLANDS. TRADE SHOWERS WILL REMAIN RELATIVELY ACTIVE THIS MORNING...
SO WINDWARD SHOWERS WILL REMAIN SLIGHTLY ENHANCED OVER THE EASTERN
END OF THE STATE. A FEW SHOWERS WILL SPREAD TO LEEWARD SECTIONS OF
THE SMALLER ISLANDS EARLY THIS MORNING.

SURFACE HIGH PRESSURE TO THE NORTH OF THE STATE WILL MAINTAIN
MODERATE TO LOCALLY FRESH TRADES THROUGH THURSDAY. WITH THE UPPER
LEVEL RIDGING MOVING IN FROM THE WEST...EXPECT INCREASINGLY STABLE
ATMOSPHERIC CONDITIONS TO DOMINATE THE WEATHER FROM LATER THIS
AFTERNOON THROUGH CHRISTMAS DAY AS THE UPPER LEVEL TROUGH CONTINUES
TO SHIFT EASTWARD. SCATTERED LIGHT TO MODERATE TRADE SHOWERS WILL
MAINLY AFFECT WINDWARD AND MAUKA AREAS. THE STRONGER TRADES MAY
CARRY A FEW BRIEF SHOWERS OVER TO LEEWARD SECTIONS OF SOME OF THE
SMALLER ISLANDS AT NIGHT...AND ISOLATED AFTERNOON SHOWERS MAY
DEVELOP OVER THE KONA SLOPES OF THE BIG ISLAND. OTHERWISE...EXPECT
MOSTLY DRY TRADE WIND WEATHER TO PREVAIL.

THE TRADE WINDS WILL BECOME DISRUPTED BY FRIDAY OR FRIDAY NIGHT AS A
FRONT APPROACHES KAUAI FROM THE NORTHWEST. THE FORECAST MODELS
INDICATE THIS FRONT WILL MOVE DOWN THE ISLAND CHAIN SATURDAY NIGHT
AND SUNDAY. THE MODELS APPEAR TO AGREE THAT THIS FRONT WILL BE
RATHER SHALLOW...SO WIDESPREAD HEAVY RAIN IS NOT EXPECTED.
HOWEVER...SUBTLE DIFFERENCES IN THE OUTPUT FROM THESE MODELS ARE
KEEPING THE DETAILS OF THIS FRONTAL PASSAGE UNCERTAIN AT THIS
TIME...SO STAY TUNED FOR UPDATES TO THE FORECAST AS WE GET CLOSER TO
THE WEEKEND.

&&

.AVIATION...
VFR CONDITIONS WILL PERSEVERE ACROSS THE HAWAIIAN ISLANDS
TODAY...THOUGH SHOWERS EMBEDDED IN THE TRADE WINDS WILL
AFFECT WINDWARD AND MOUNTAIN AREAS AT TIMES...BRINGING BRIEF MVFR
CEILING CONDITION. SOME OF THESE SHOWERS MAY REACH THE LEE AREAS OF
THE SMALLER ISLANDS AND MAY RESULT IN ISOLATED MVFR CEILING
CONDITIONS FOR THOSE AREAS.

AIRMET TANGO FOR LOW LEVEL TURB ACROSS MOUNTAIN AND IMMEDIATE
DOWNWIND AREAS WILL CONTINUE DUE TO THE MODERATE TRADES.

&&

.MARINE...
A SMALL CRAFT ADVISORY /SCA/ REMAINS IN EFFECT FOR STRONG TRADE
WINDS IN THE TYPICALLY WINDY WATERS ADJACENT TO THE ISLANDS OF MAUI
AND HAWAII COUNTIES. LITTLE CHANGE IN TRADE WIND STRENGTH IS
EXPECTED THROUGH WEDNESDAY. ALSO...COMBINED SEAS ARE EXPECTED TO
INCREASE TO THE SCA THRESHOLD LATER TODAY ACROSS COASTAL WATERS
EXPOSED TO A BUILDING WEST NORTHWEST SWELL AND TRADE WIND GENERATED
WAVES LATER TODAY. THESE ELEVATED SEAS WILL ARE FORECAST TO CONTINUE
OVER THESE WATERS AT LEAST THROUGH MID-WEEK.

THE WEATHER PATTERN ACROSS THE NORTHWEST PACIFIC IS DOMINATED BY A
STRONG NEARLY WEST TO EAST ORIENTED UPPER LEVEL JET STREAM FROM NEAR
JAPAN TO THE DATE LINE...WHICH TURNS TO THE NORTHEAST OVER THE NORTH
CENTRAL PACIFIC OCEAN. AS STORM SYSTEMS MOVE ALONG THIS TRACK OF THE
JET STREAM...THEIR CAPTURED FETCH GENERATES LARGE SWELLS FROM THE
WEST NORTHWEST. A LARGE WEST NORTHWEST SWELL HAS ARRIVED AT BUOY
51101...WHERE THE MOST RECENT READINGS SHOW A SWELL HEIGHT OF 9 TO
10 FEET WITH A PERIOD OF 19 SECONDS...WHILE THE HANALEI BUOY HAS A
SIGNIFICANT WAVE HEIGHT OF 6 FEET WITH A PERIOD OF 20 TO 22 SECONDS.
THIS WEST NORTHWEST SWELL WILL PRODUCE ELEVATED SURF ALONG MOST
NORTH AND WEST FACING SHORES OF THE SMALLER ISLANDS. AS A RESULT...A
HIGH SURF ADVISORY HAS BEEN ISSUED STARTING AT DAWN THIS MORNING FOR
RISING SURF ALONG NORTH AND WEST FACING SHOWERS OF NIIHAU...
KAUAI...OAHU AND MOLOKAI...AND FOR NORTH FACING SHORES OF MAUI.

THIS ELEVATED SURF WILL LIKELY PERSIST ALONG THESE NORTH AND WEST
FACING SHORELINES THROUGH FRIDAY...WITH SURF HEIGHTS POSSIBLY
APPROACHING THE HIGH SURF WARNING CRITERIA THURSDAY. A NEW
REINFORCING NORTHWEST SWELL IS EXPECTED THIS WEEKEND...WITH SURF
POSSIBLY APPROACHING THE HIGH SURF WARNING CRITERIA ALONG SOME
EXPOSED SHORELINES ON SATURDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL 6 AM HST WEDNESDAY FOR THE ALENUIHAHA AND
PAILOLO CHANNELS...MAALAEA BAY...AND WATERS SOUTH OF THE BIG ISLAND.

SMALL CRAFT ADVISORY FROM NOON TO 6 PM HST TUESDAY FOR KAUAI
NORTHWEST...KAUAI WINDWARD...AND KAUAI LEEWARD WATERS.

SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM HST WEDNESDAY
FOR THE OAHU AND MAUI COUNTY WINDWARD WATERS...AND FOR THE KAUAI AND
KAIWI CHANNELS.

HIGH SURF ADVISORY FROM 6 AM THIS MORNING TO 6 PM HST WEDNESDAY FOR
NORTH AND WEST FACING SHOWERS OF NIIHAU...KAUAI...OAHU...AND
MOLOKAI...AND FOR NORTH FACING SHORES OF MAUI.

&&

DISCUSSION/MARINE...HOUSTON
AVIATION...HUI