Small Craft Advisory 5, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
956 AM HST SAT JAN 23 2016

.SYNOPSIS...
WINDS WILL WEAKEN AND SHIFT OUT OF THE SOUTHEAST TODAY...BEFORE
BECOMING LIGHT AND VARIABLE TONIGHT AND SUNDAY AHEAD OF A COLD
FRONT APPROACHING FROM THE NORTHWEST. A BAND OF LOW CLOUDS AND
SHOWERS WILL ACCOMPANY THE WEAKENING FRONT AS IT PUSHES DOWN
ACROSS THE SMALLER HAWAIIAN ISLANDS FROM SUNDAY EVENING INTO
MONDAY. WEAK RIDGING DEVELOPING OVER THE ISLANDS BEHIND THE FRONT
WILL PRODUCE DRY CONDITIONS AND SOUTH TO SOUTHWEST WINDS FROM
TUESDAY THROUGH THURSDAY. EXTRA-LARGE WINTERTIME SWELLS WILL CAUSE
PERIODS OF HAZARDOUS SURF CONDITIONS ALONG MOST NORTH AND WEST
FACING SHORES OF THE STATE FROM MID-DAY SUNDAY THROUGH THE MIDDLE
OF NEXT WEEK.

&&

.DISCUSSION...
AN EAST-NORTHEAST TO WEST-SOUTHWEST ORIENTED SURFACE RIDGE IS
EVIDENT ABOUT 170 MILES NORTH OF KAUAI. THE PRESSURE GRADIENT
SOUTH OF THIS FEATURE IS MAINTAINING LIGHT TO LOCALLY MODERATE
EAST SOUTHEAST WINDS ACROSS MOST OF THE MAIN HAWAIIAN ISLAND
CHAIN THIS MORNING. VISIBLE SATELLITE IMAGERY SHOWS SOME LOW
CLOUDS...MOSTLY STRATOCUMULUS...OVER KAUAI AND OAHU...AND ALONG
WINDWARD SIDES OF MOLOKAI. THERE ARE ALSO SCATTERED TO LOCALLY
BROKEN CUMULUS CLOUDS AND ISOLATED SHOWERS STREAMING DOWN ACROSS
THE WINDWARD AND SOUTHEASTERN BIG ISLAND WATERS. THE CUMULUS CLOUDS
AND PRECIPITATION ELEMENTS LIKELY ORIGINATED FROM THE REMNANT
MOISTURE ASSOCIATED WITH A FORMER FRONT THAT DISSIPATED FAR EAST
OF THE STATE THURSDAY NIGHT.

A MID-LEVEL RIDGE OVER THE ISLANDS WILL MAINTAIN GENERALLY DRY
AND STABLE CONDITIONS THROUGH SUNDAY MORNING. THE FORECAST MODELS
CONTINUE TO INDICATE A COLD FRONT NOW LOCATED ABOUT 300 MILES
EAST OF MIDWAY ATOLL...OR 1000 MILES WEST NORTHWEST OF
KAUAI...WILL CONTINUE TO PROGRESS RAPIDLY EASTWARD THROUGH
TONIGHT. AS A RESULT...THE RIDGE IS EXPECTED TO WEAKEN AND SHIFT
SOUTH CLOSER TO THE ISLANDS THIS WEEKEND. THIS WILL CAUSE THE
PRESSURE GRADIENT TO BECOME SLACK AND RESULT IN LIGHT SOUTHEAST TO
SOUTH WINDS OVER MOST ISLANDS FROM LATER TODAY THROUGH SUNDAY.
THIS WILL ALLOW LOCAL AFTERNOON SEA BREEZES AND NIGHTTIME LAND
BREEZES TO DEVELOP FROM THIS AFTERNOON THROUGH SUNDAY. IN
ADDITION...HUMIDITY LEVELS WILL ALSO LIKELY INCREASE...PARTICULARLY
ON THE SMALLER ISLANDS...BY SUNDAY. AFTERNOON CLOUD BUILD UPS WITH
ISOLATED SHOWERS WILL ALSO BE POSSIBLE OVER THE ISLAND INTERIORS
LATER TODAY...AND AGAIN SUNDAY AFTERNOON...BUT RAINFALL TOTALS
WILL LIKELY BE LIGHT GIVEN THE RELATIVELY STABLE ATMOSPHERE.
MOSTLY CLEAR TO PARTLY CLOUDY CONDITIONS WILL PREVAIL TONIGHT
WITH THE LAND BREEZES. ALSO...THE LATEST OUTPUT FROM THE
UNIVERSITY OF HAWAII AT MANOA VOG MEASUREMENT AND PREDICTION
PROJECT /VMAP/ SHOWS THE LOW- LEVEL SOUTHEAST TO SOUTH WINDS WILL
CARRY VOLCANIC HAZE...OR VOG...UP OVER MOST OF THE LOWER
ELEVATIONS OF THE BIG ISLAND...AS WELL AS THE SMALLER ISLANDS...BY
LATER TODAY AND TONIGHT...AND CONTINUING INTO SUNDAY.

THE FORECAST GUIDANCE SHOWS THE FRONT WILL REACH KAUAI SUNDAY
EVENING...AND THEN MOVE DOWN ACROSS THE SMALLER ISLANDS INTO
MONDAY BEFORE EVENTUALLY DISSIPATING OVER OAHU OR MAUI COUNTY. A
BAND OF LOW CLOUDS AND LIGHT TO BRIEFLY MODERATE SHOWERS WILL
ACCOMPANY THE PASSAGE OF THIS FRONT. MOST OF THE PRECIPITATION IS
EXPECTED TO FALL ALONG NORTH AND NORTHEAST FACING SLOPES OF THE
ISLANDS. IN ADDITION...THE NORTHERLY FLOW BEHIND THE FRONT WILL
NOT ONLY USHER IN DRIER CONDITIONS OVER THE SMALLER ISLANDS...IT
WILL PUSH MOST OF THE VOLCANIC HAZE EASTWARD AND SOUTHWARD.

MOST OF THE STRONGER UPPER LEVEL DYNAMICS THAT ARE ALLOWING THE
FRONT TO MAKE IT DOWN TO THE LATITUDE OF THE HAWAIIAN ISLANDS ARE
EXPECTED TO REMAIN WELL NORTH OF THE REGION. HOWEVER...THE
ARRIVAL OF THE SOUTHERN END OF THE UPPER LEVEL TROUGH MAY PRODUCE
LOCALLY STRONG WINDS OVER THE SUMMITS OF MAUNA KEA AND MAUNA LOA
ON SUNDAY AND MONDAY. IF SO...WE MAY NEED TO ISSUE A WIND ADVISORY
LATER THIS WEEKEND IF THE FORECAST MODELS CONTINUE TO DEPICT THESE
WINDY CONDITIONS DEVELOPING ON THE BIG ISLANDS SUMMITS.

A NEW SURFACE RIDGE IS EXPECTED TO BE IN THE VICINITY OF THE
ISLANDS STARTING TUESDAY. THE LATEST MODEL OUTPUT CONTINUES TO
SUGGEST THIS RIDGE WILL MOVE FAR ENOUGH SOUTH TO ALLOW SOUTHERLY
TO SOUTHWESTERLY WINDS TO DEVELOP...ESPECIALLY ACROSS THE NORTHERN
ISLANDS. DURING THIS TIME...THE MODELS ARE SHOWING A SERIES OF
FRONTS MOVING RAPIDLY EASTWARD FAR NORTH OF THE ALOHA STATE. THE
MOISTURE FROM THESE FRONTS WILL LIKELY REMAIN WELL AWAY FROM THE
ISLANDS...SO RELATIVELY DRY CONDITIONS AND LIGHT WINDS WILL OCCUR
FROM TUESDAY THROUGH MUCH OF THE NEW WORK WEEK.

&&

.AVIATION...
VFR CONDITIONS PREVAIL AT ALL TAF SITES AND THESE CONDITIONS ARE
EXPECTED TO CONTINUE THROUGH THE DAY AND ON INTO THE EVENING HOURS.
THERE MAY BE SOME BRIEF MVFR CONDITIONS OVER NE THROUGH SE FACING
SLOPES DUE TO LOW CLOUDS AND ISOLATED SHRA.

&&

.MARINE...
SURF ALONG ALL HAWAIIAN SHORES IS FORECAST TO REMAIN WELL BELOW
THE HIGH SURF ADVISORY CRITERIA THROUGH THIS EVENING. THE LATEST
GUIDANCE FROM THE WAVE WATCH III MODEL CONTINUES TO SHOW A LARGE
WEST-NORTHWEST SWELL SPREADING DOWN ACROSS THE HAWAIIAN WATERS
STARTING EARLY SUNDAY. THIS SWELL WILL LIKELY CAUSE SURF HEIGHTS
TO INCREASE TO THE HIGH SURF WARNING THRESHOLDS ALONG MOST NORTH
AND WEST FACING SHORES...INCLUDING THE LEEWARD BIG ISLAND...FROM
MID-DAY SUNDAY THROUGH MONDAY. THIS SWELL WILL DIMINISH SLIGHTLY
ON TUESDAY AND TUESDAY NIGHT BEFORE THE EXPECTED ARRIVAL OF A
POTENTIALLY MUCH LARGER NORTHWEST SWELL EARLY WEDNESDAY. THIS
SWELL WILL LIKELY CAUSE SURF TO AGAIN BUILD TO WARNING LEVELS
ALONG NORTH AND WEST FACING SHORES OF MOST ISLANDS FROM WEDNESDAY
AFTERNOON THROUGH THURSDAY. FOR ADDITIONAL DETAILS...SEE THE
LATEST COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
ISSUED AT 300 PM HST FRIDAY AFTERNOON.

WINDS ARE EXPECTED TO REMAIN WELL BELOW THE SMALL CRAFT ADVISORY
/SCA/ THRESHOLD OVER NEARLY ALL HAWAIIAN WATERS THROUGH MOST OF
NEXT WEEK. HOWEVER...THE LARGE INCOMING NORTHWEST SWELLS WILL
REQUIRE A SCA FOR ELEVATED SEAS FOR MOST HAWAIIAN WATERS FROM
MID-DAY SUNDAY THROUGH MOST OF NEXT WEEK. NOTE THAT SEAS MAY
BRIEFLY DIP BELOW THE SCA CRITERIA ON TUESDAY NIGHT BETWEEN SWELL
EVENTS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

DISCUSSION/MARINE...FOSTER
AVIATION...BURKE