Heavy Rain in Hawaii, February 1 to 5, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
345 PM HST SAT FEB 1 2014

.SYNOPSIS...
A SOMEWHAT UNSETTLED WEATHER PATTERN WILL PREVAIL FOR MOST OF THE
NEXT WEEK...ESPECIALLY OVER THE WESTERN END OF THE ISLAND CHAIN...AS
A COUPLE OF UPPER LEVEL DISTURBANCES TRAVERSE THE AREA. A WEAKENING
FRONT WILL MOVE OVER KAUAI TONIGHT...AND STALL NEAR OAHU AND MAUI
COUNTY SUNDAY...WITH CLOUDS AND SHOWERS FOCUSING ALONG THE FRONT.
LIGHT WINDS WILL PREVAIL ON SUNDAY...BUT AS TRADE WINDS RETURN ON
MONDAY AND TUESDAY...MOISTURE ASSOCIATED WITH THE STALLED FRONT IS
EXPECTED TO AFFECT KAUAI AND OAHU...AND BECOME ENHANCED BY A
DEVELOPING UPPER LEVEL DISTURBANCE. A SECOND UPPER LEVEL
DISTURBANCE MAY BRING MORE WIDESPREAD RAINFALL ON WEDNESDAY AND
THURSDAY. A WET TRADE WIND PATTERN IS EXPECTED FRIDAY AND SATURDAY.

&&

.DISCUSSION...
IN SUMMARY...A LONGWAVE TROUGH WILL PERSIST NW OF THE ISLANDS FOR
MOST OF THE UPCOMING WEEK...WITH SHORTWAVES ROTATING THROUGH THE
TROUGH BRINGING BOUTS OF UNSETTLED WEATHER...ESPECIALLY TO THE
WESTERN END OF THE ISLAND CHAIN.

CURRENTLY...CLOUDS AND SHOWERS ARE MOVING NE OVER THE ISLANDS FROM
OAHU TO MAUI...AHEAD OF A 125 MILE WIDE BAND OF CLOUDS AND SHOWERS
ASSOCIATED WITH A FRONT THAT IS CLOSING IN ON KAUAI FROM THE NW.
MEANWHILE...S WINDS OVER THE BIG ISLAND ARE MOSTLY DRY...BUT
AFTERNOON HEATING HAS LED TO INCREASED CLOUDINESS AND ISOLATED
SHOWERS OVER THE SLOPES. THE FRONT IS ASSOCIATED WITH A SLOW-MOVING
VERTICALLY STACKED LOW PRESSURE SYSTEM CENTERED ABOUT 900 MILES NW
OF KAUAI.

AS THE PARENT LOW ASSOCIATED WITH THE FRONT WILL BE SLOWLY LIFTING
OUT TO THE NE OVER THE NEXT 36 TO 48 HOURS...THE FRONT WILL LOSE ITS
FORWARD MOMENTUM...AND SOME OF ITS PUNCH...AS IT MOVES OVER THE
ISLAND CHAIN TONIGHT AND SUNDAY. THE FRONT WILL CONTINUE TO ACT AS A
FOCUS FOR CLOUDS AND SHOWERS AS IT CROSSES KAUAI AND OAHU THROUGH
TONIGHT...AND THEN STALLS NEAR MAUI COUNTY SUNDAY AND SUNDAY NIGHT.

AS THE LOW PULLS OUT FURTHER...THE ISLANDS WILL LIE BETWEEN HIGH
PRESSURE CENTERS FAR TO THE NW AND TO THE NE...WITH THE RESULT BEING
LIGHT WINDS ON SUNDAY. NE WINDS NEAR KAUAI AND E/SE WINDS NEAR THE
BIG ISLAND ON MONDAY AND TUESDAY WILL HELP TO SHARPEN A SURFACE
TROUGH NEAR KAUAI AND OAHU...WHICH WILL ACT TO FOCUS THE LINGERING
FRONTAL MOISTURE AS A NEW SHORTWAVE ALOFT APPROACHES. HENCE THE
MENTION OF THUNDERSTORMS AND/OR LOCALLY HEAVY RAIN FOR THE SMALLER
ISLANDS FROM MONDAY NIGHT THROUGH TUESDAY NIGHT.

ANOTHER SHORTWAVE ON WEDNESDAY AND THURSDAY COULD BRING WIDESPREAD
HEAVY RAINFALL TO ALL ISLANDS...AND A RETURN TO SOUTHERLY
WINDS...BUT CONFIDENCE IN THE TIMING AND PLACEMENT OF HEAVY RAIN
REMAINS LIMITED. HAVE HOWEVER ADDED LOCALLY HEAVY RAIN TO THE
FORECAST FOR WEDNESDAY AND WEDNESDAY NIGHT FOR THE SMALLER ISLANDS.
ANOTHER FRONT COULD POTENTIALLY STALL OVER THE ISLANDS BY THE END OF
THE WEEK AS HIGH PRESSURE BUILDS TO THE NW OF THE ISLANDS...WITH A
WET TRADE WIND FLOW EXPECTED AT THAT TIME. GIVEN THE UNCERTAINTY
SURROUNDING ISLAND WEATHER AROUND MID-WEEK...THE FORECAST FOR TIME
FRAMES BEYOND THAT CONTAINS AN EVEN HIGHER AMOUNT OF UNCERTAINTY.

HOWEVER...CONFIDENCE IS INCREASING IN A PROLONGED WET PERIOD...
ESPECIALLY FOR KAUAI AND OAHU...FROM MONDAY NIGHT INTO THURSDAY...
AND POSSIBLY BEYOND.

&&

.MARINE...
WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY /SCA/
CRITERIA FOR AT LEAST THE NEXT SEVERAL DAYS...BUT A SIZEABLE
LONG-PERIOD NW SWELL ARRIVING TONIGHT AND BUILDING THROUGH SUNDAY
WILL PUSH COMBINED SEAS OVER SCA CRITERIA IN MANY ZONES THROUGH
MONDAY BEFORE DIMINISHING. ANOTHER NW SWELL ARRIVING AROUND TUESDAY
NIGHT WILL ALSO LIKELY RESULT IN MARGINAL SCA-LEVEL COMBINED SEAS.
HIGH SURF AND SMALL CRAFT ADVISORIES HAVE BEEN ISSUED WITH THIS
PACKAGE FOR INCREASING SURF AND SEAS ON SUNDAY. WHILE THE SCA WILL
INITIALLY
ONLY INCLUDE WATERS AROUND KAUAI AND OAHU...WINDWARD WATERS OF MAUI
AND THE BIG ISLAND WILL LIKELY NEED TO BE ADDED AS COMBINED SEAS IN
THOSE ZONES ARE EXPECTED TO EXCEED 10 FEET BY SUNDAY NIGHT. ALSO...
LEEWARD BIG ISLAND SHORES MAY SEE SURF BUILDING TO ADVISORY LEVELS
SUNDAY NIGHT AND MONDAY...AND W FACING SHORES OF THE BIG ISLAND MAY
NEED TO BE ADDED TO THE ADVISORY ON SUNDAY.

BOTH OF THE AFOREMENTIONED NW SWELLS ARE EXPECTED TO BRING ADVISORY
LEVEL SURF TO EXPOSED N AND W FACING SHORES OF THE ISLANDS...WITH
THE FIRST SWELL BEING THE LARGER OF THE TWO.

&&

.AVIATION...
AIRMET SIERRA FOR MTN OBSC FOR OAHU HAS BEEN CANCELLED...BUT WILL
LIKELY BE REISSUED LATER THIS EVENING AS THE FNT NEARS OAHU TOWARDS
08Z.

AIRMET SIERRA FOR MTN OBSCURATION WAS REISSUED FOR KAUAI DUE TO CLDS
AND SHRA ASSOCIATED WITH THE FNT AS IT MAKES LANDFALL. THE AIRMET
WL LIKELY BE LIFTED CLOSE TO 04Z OR SOONER. AIRMET SIERRA WILL
CONTINUE INTO THE OVERNIGHT HOURS FOR MAUI COUNTY...WITH THE FNT
EXPECTING TO STALL OVR MAUI COUNTY AFTER 08Z...AND LAST INTO SUNDAY.

THE SLY WINDS ARE EXPECTED TO DIMINISH DURING THE NEXT SEVERAL
HOURS. SO THERE IS THE POSSIBILITY THAT AIRMET TANGO FOR LO LVL TURB
WILL BE DROPPED FOR THE EVENING PACKAGE.

THE BIG ISLAND SHOULD PRETTY MUCH REMAIN PREVAILING VFR. THERE COULD
BE BRIEF MVFR CEILING AND VIS IN SHRA THIS EVENING AFFECTING
PRIMARILY THE HILO PUNA DISTRICTS. ALSO...WE WILL BE MONITORING THE
PREFRONTAL CLOUD MASS OVER MAUI COUNTY AS IT MAY AFFECT NORTHERN AND
WESTERN BIG ISLAND LATER THIS EVENING.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM 4 AM SUNDAY TO 4 PM HST MONDAY FOR NORTH AND
WEST FACING SHORES OF KAUAI NIIHAU OAHU MOLOKAI AND FOR NORTH FACING
SHORES OF MAUI.

SMALL CRAFT ADVISORY FROM 4 AM SUNDAY TO 4 PM HST MONDAY FOR
KAUAI NORTHWEST WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD
WATERS-KAUAI CHANNEL-OAHU WINDWARD WATERS.

&&

DISCUSSION/MARINE...BIRCHARD
AVIATION...LAU