High Surf in Hawaii, January 15 to 17, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT JAN 15 2011

.SYNOPSIS...
THE WEATHER WILL REMAIN TRANQUIL DURING THE OVERNIGHT HOURS. THE
COLD FRONT WEST OF THE AREA WILL REACH KAUAI BY MID-DAY SUNDAY. THE
FRONT WILL PRODUCE NUMEROUS SHOWERS...ISOLATED THUNDERSTORMS AND A
TEMPORARY BOOST IN WINDS AS IT MOVES DOWN THE ISLAND CHAIN THROUGH
MONDAY. EASTERLY TRADE FLOW WILL STRENGTHEN GRADUALLY MID-WEEK AND
PERSIST INTO THE FOLLOWING WEEKEND AS HIGH PRESSURE BUILDS FAR TO
THE NORTHEAST. A VERY LARGE WEST NORTHWEST SWELL WILL PRODUCE LARGER
THAN NORMAL SURF AND COASTAL FLOODING FOR MANY NORTH AND WEST FACING
AREAS TONIGHT THROUGH MONDAY.

&&

.DISCUSSION...
ONLY ISOLATED LIGHT SHOWERS CAN BE SEEN ON CURRENT RADAR IMAGERY.
SHOWER ACTIVITY SHOULD REMAIN MINIMAL AS INCREASED SUBSIDENCE FROM
UPPER LEVEL RIDGING IS BRINGING INCREASING STABILITY. THE 00Z UPPER
AIR SOUNDING FROM HILO SHOWS A STRONG CAPPING INVERSION AT THE LOW
HEIGHT OF 4200 FEET. THE LIHUE SOUNDING SHOWS A LESS PRONOUNCED
INVERSION AT ABOUT 5300 FEET. THE INCREASING STABILITY OF THE
ATMOSPHERE WILL LIKELY CONTINUE TO INHIBIT SHOWER DEVELOPMENT
THROUGH THE NIGHT...PARTICULARLY OVER THE EASTERN PORTION OF THE
STATE WHERE THE ATMOSPHERE IS DRIER.

A COLD FRONT...CURRENTLY ABOUT 160 MILES NORTHWEST OF WESTERN
KAUAI...WILL BRING NUMEROUS SHOWERS TO THE STATE AS IT MOVES DOWN
THE ISLAND CHAIN. IT IS EXPECTED TO ARRIVE OVER KAUAI BY MID-DAY
SUNDAY...MAKE IT TO OAHU AND MAUI COUNTY BY SUNDAY NIGHT...AND THEN
WEAKEN AS IT ARRIVES TO THE BIG ISLAND EARLY MONDAY. AN UPPER TROUGH
DIGGING DOWN OVER THE ISLANDS AS THE FRONT MOVES THROUGH WILL
DESTABILIZE THE ATMOSPHERE...SO ISOLATED THUNDERSTORMS ARE LIKELY
WITH THE FRONTAL PASSAGE.

A 1027 MB SURFACE HIGH ABOUT 1860 MILES NORTHEAST OF OAHU IS
BRINGING A GENTLE TO MODERATE EASTERLY FLOW TO THE STATE AT THE
MOMENT. WINDS WILL BECOME LIGHT AND VARIABLE AHEAD OF THE
APPROACHING COLD FRONT TOMORROW...AND THEN BECOME BRIEFLY STRONG AND
GUSTY FROM THE NORTHERLY DIRECTION WITH THE FRONTAL PASSAGE. WINDS
WILL DECREASE ONCE AGAIN AFTER THE FRONT EXITS THE STATE BEFORE
GENTLE TO MODERATE TRADES RETURN ON WEDNESDAY AS A HIGH BUILDS FAR
NORTHEAST OF THE REGION. TRADES WILL THEN BECOME MODERATE TO LOCALLY
FRESH THURSDAY THROUGH THE BEGINNING OF THE WEEKEND AS THE HIGH
REMAINS FAR NORTHEAST OF THE ISLANDS.

AFTER THE COLD FRONT EXITS THE STATE MONDAY AFTERNOON...DRY AIR
BEHIND THE FRONT WILL RESULT IN NOT MUCH IN THE WAY OF SHOWER
ACTIVITY MOST OF MONDAY THROUGH TUESDAY. HOWEVER...WEATHER MAY GET
INTERESTING LATER IN THE WEEK AS SOME MODELS ARE SHOWING A CUT-OFF
UPPER LOW DEVELOPING NEAR THE ISLANDS. ALTHOUGH THE PREVIOUS RUN OF
THE GFS STARTED TO AGREE WITH THE ECMWF AND NOGAPS IN SHOWING THE
LOW MOVING OVER THE STATE ON WEDNESDAY...THE 00Z RUN HAS BACKED OFF
AND IS NOW INDICATING THAT THE LOW WILL REMAIN NORTHEAST OF THE
ISLANDS AND WEAKEN. BOTH THE GFS AND ECMWF SHOW MOISTURE INCREASING
BY MID-WEEK...SO IF THE LOW DOES MOVE OVER THE STATE...THERE WILL BE
THE POTENTIAL FOR HEAVY SHOWERS AND THUNDERSTORMS. THERE IS LOW
CONFIDENCE IN THIS POSSIBILITY AT THE MOMENT DUE TO MODEL
INCONSISTENCY.

MODELS ALSO INDICATE THAT AN INVERTED SURFACE TROUGH WILL DEVELOP
FAR TO THE EAST OF THE BIG ISLAND LATE TUESDAY AND MOVE OVER THE
EASTERN PART OF THE STATE LATE THURSDAY AND INTO FRIDAY. THE TROUGH
WILL DRAW UP MOISTURE FROM THE ITCZ...AND WITH UPPER LEVEL HEIGHT
FALLS ACCOMPANYING THIS FEATURE...THERE WOULD BE SOME POTENTIAL FOR
ACTIVE WEATHER FOR MAUI COUNTY AND THE BIG ISLAND. WITH TRADE WINDS
PREVAILING DURING THIS TIME...SHOWERS WOULD FOCUS OVER WINDWARD AND
MOUNTAIN AREAS.

&&

.MARINE...
THE VERY LARGE WEST NORTHWEST SWELL WILL CONTINUE TO BUILD
OVERNIGHT. SWELL/PERIODS SHOWED A SIGNIFICANT JUMP AT BUOY 51101
RIGHT AROUND MID-DAY...AND ARE CURRENTLY AROUND 23 FEET WITH PERIODS
AROUND 16-17 SECONDS. THE WESTERLY DIRECTION OF THIS GIANT SWELL IS
UNCOMMON...AND COASTAL FLOODING/DAMAGE IS POSSIBLE...PARTICULARLY
FOR THE KONA COAST OF THE BIG ISLAND. A HIGH SURF WARNING IS
CURRENTLY IN EFFECT FOR NORTH AND WEST FACING SHORES OF KAUAI COUNTY
AND OAHU UNTIL NOON MONDAY. A WARNING FOR THE WEST FACING SHORES OF
THE BIG ISLAND ALSO GOES INTO EFFECT STARTING 6 AM SUNDAY AND
LASTING THROUGH 6 PM MONDAY. HOWEVER...NORTH AND WEST FACING SHORES
OF MAUI COUNTY ARE ONLY UNDER A HIGH SURF ADVISORY THROUGH NOON
MONDAY BECAUSE THE WESTERN HAWAIIAN ISLANDS ARE EXPECTED TO BLOCK
SOME OF THE SWELLS ENERGY DUE TO THE WEST NORTHWEST DIRECTION OF THE
SWELL. PLEASE SEE THE HIGH SURF PRODUCT...CFWHFO...FOR MORE DETAILS
ON THE SWELL AND POTENTIAL IMPACTS FROM IT.

A SMALL CRAFT ADVISORY IS ALSO IN EFFECT DUE TO THE HIGH SEAS
CREATED BY THE CURRENT SWELL. CURRENTLY...JUST THE COASTAL WATERS
AROUND KAUAI AND OAHU ARE IN THE ADVISORY. THE REST OF THE COASTAL
WATERS...EXCLUDING MAALAEA BAY DUE TO THE SWELLS ENERGY GETTING
BLOCKED...WILL JOIN THE ADVISORY STARTING 6 AM SUNDAY. ALSO...THE
FRONT THAT WILL MOVE DOWN THE ISLAND CHAIN SUNDAY AFTERNOON THROUGH
EARLY MONDAY WILL BRING STRONG AND GUSTY WINDS WITH IT FOR A SHORT
PERIOD OF TIME...ADDING TO THE HAZARDOUS SEA CONDITIONS.

THE SWELL IS EXPECTED TO START LOWERING MONDAY NIGHT...ALTHOUGH SURF
WILL STILL REMAIN WELL ABOVE ADVISORY LEVELS FOR MOST NORTH AND WEST
SHORES.

A LOW PRESSURE SYSTEM IN THE NORTHWEST PACIFIC WILL STRENGTHEN
SIGNIFICANTLY STARTING SUNDAY AFTERNOON...CREATING ANOTHER VERY
LARGE WEST NORTHWEST SWELL THAT WILL ARRIVE LATE TUESDAY NIGHT. AS A
RESULT...SURF WILL ONCE AGAIN GO ABOVE WARNING LEVELS FOR MOST NORTH
AND WEST FACING SHORES WEDNESDAY AND THURSDAY. THE SWELL WILL ALSO
CREATE HAZARDOUS SEAS...SO ANOTHER SMALL CRAFT ADVISORY ISSUANCE
WILL BE NECESSARY AT THAT TIME FOR THE MAJORITY OF THE COASTAL
WATERS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF WARNING UNTIL 12 PM HST MONDAY FOR NORTH AND WEST FACING
SHORES OF NIIHAU...KAUAI AND OAHU.

HIGH SURF WARNING FROM 6 AM HST SUNDAY TO 6 PM HST MONDAY FOR WEST
FACING SHORES OF THE BIG ISLAND.

HIGH SURF ADVISORY UNTIL 12 PM HST MONDAY FOR NORTH AND WEST FACING
SHORES OF MOLOKAI...LANAI...MAUI AND KAHOOLAWE.

SMALL CRAFT ADVISORY UNTIL 6 PM HST MONDAY FOR KAUAI NORTHWEST
WATERS...KAUAI WINDWARD WATERS...KAUAI LEEWARD WATERS...KAUAI
CHANNEL...OAHU WINDWARD WATERS AND OAHU LEEWARD WATERS.

SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO 6 PM HST MONDAY FOR KAIWI
CHANNEL...MAUI COUNTY WINDWARD WATERS...MAUI COUNTY LEEWARD
WATERS...PAILOLO CHANNEL...ALENUIHAHA CHANNEL...BIG ISLAND WINDWARD
WATERS...BIG ISLAND LEEWARD WATERS AND BIG ISLAND SOUTHEAST WATERS.

&&

HARRISON