Small Craft Advisory 7, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST MON JAN 19 2015

.SYNOPSIS...
LIGHT WINDS AND DRY WEATHER WILL PREVAIL ACROSS THE STATE THROUGH
MID-WEEK...WITH MOST SHOWERS LIMITED TO SOUTH SLOPES OF THE BIG
ISLAND...AND NORTH SLOPES OF KAUAI. SOUTH TO SOUTHWEST WINDS WILL
INCREASE AHEAD OF A FRONT APPROACHING FROM THE NORTHWEST LATE IN THE
WEEK. THE FRONT WILL BRING INCREASED SHOWERS AND STRONGER NORTHERLY
WINDS TO KAUAI ON FRIDAY...AND TO THE REST OF THE STATE OVER THE
WEEKEND. TRADE WINDS WILL RETURN NEXT WEEK.

&&

.DISCUSSION...
ALTHOUGH SATELLITE IMAGES AND SCATTEROMETER DATA REPORTED LIGHT
EASTERLY TO SOUTHEASTERLY WINDS UPWIND...SURFACE OBSERVATIONS AROUND
THE MAIN HAWAIIAN ISLANDS RECORDED GENERALLY LIGHT AND VARIABLE
WINDS. SEA BREEZES WERE PRESENT...BUT FAR FROM DOMINANT. DEEP
RIDGING PREVAILED OVER THE STATE BOTH AT THE SURFACE AND ALOFT...BUT
THE INVERSION REMAINED NEAR ITS USUAL HEIGHT. A DISORGANIZED CLUMP
OF SHOWERS BENEFITED FROM THIS HEADROOM...ENVELOPING SOUTH SLOPES OF
THE BIG ISLAND...AND PRODUCING WHAT WAS LIKELY THE MOST WIDESPREAD
PRECIPITATION ACROSS THE STATE...THOUGH ACCUMULATION REMAINED ON THE
LIGHT SIDE. SATELLITE ESTIMATES OF PRECIPITABLE WATER ALSO SHOWED A
MOISTER AIR MASS OFFSHORE TO THE NORTH OF KAUAI COUNTY...BUT
GENERALLY DEFICIENT MOISTURE ELSEWHERE.

GUIDANCE PREDICTED GRADUAL...BUT SUBSTANTIAL CHANGES...THROUGH THE
WEEK. IN THE SHORT RUN...LIGHT WINDS AND DRY CONDITIONS WILL
PREVAIL...THOUGH THE SHOWERS ENCROACHING ON THE BIG ISLAND FROM THE
SOUTH...AND POSSIBLY MOVING ONTO KAUAI FROM THE NORTH...MAY BE MORE
PERSISTENT THAN THE CURRENT FORECAST SUPPOSES. PREVAILING WIND
DIRECTION WILL BECOME MORE SOUTHWESTERLY THOUGH...AS THE SURFACE
RIDGE RETREATS EAST AHEAD OF A FRONT APPROACHING FROM THE WEST
NORTHWEST.

BY WEDNESDAY...BROAD AND DEEP TROUGHING ALOFT WILL SHIFT SOUTH...
DENTING THE FLAT RIDGE OVER THE STATE. THIS SUPPORT WILL BE LIMITED
THOUGH...AND THE FRONT WILL WEAKEN SUBSTANTIALLY BEFORE STALLING
NORTHWEST OF KAUAI. A SECOND FRONT FROM THE NORTHWEST WILL MERGE
WITH THE FIRST BY THURSDAY MORNING...AND PRESS ONWARD TO KAUAI BY
FRIDAY MORNING. GUIDANCE GENERALLY PREDICTED THE COMPOSITE FRONT TO
SLOW DOWN AND WEAKEN OVER THE KAUAI CHANNEL...BUT TO PASS OVER THE
REST OF THE STATE IN A DIMINISHED FROM THROUGH THE WEEKEND.
PRE-FRONTAL SHOWERS WILL BE POSSIBLE BEFORE THE COMPOSITE FRONT
ARRIVES...BUT GUIDANCE LIMITED THIS ACTIVITY MAINLY TO THE BIG
ISLAND AND KAUAI AGAIN.

&&

.MARINE...
GENERALLY SMALL SWELLS WILL CONTINUE TO ARRIVE FROM THE NORTHWEST
THROUGH TUESDAY. A VERY LARGE WEST NORTHWEST SWELL IS EXPECTED TO
ARRIVE AT KAUAI BY LATE TUESDAY...AND THEN SPREAD GRADUALLY DOWN THE
ISLAND CHAIN TUESDAY NIGHT AND WEDNESDAY. THIS SWELL LIKELY WILL BE
THE LARGEST WE HAVE EXPERIENCED THIS WINTER SURF SEASON. THE MORE
WESTERLY COMPONENT OF THIS SWELL WILL CAUSE SOME SHADOWING IN
PLACES...WHILE OTHER AREAS WILL BE MORE EXPOSED THAN USUAL...SUCH AS
WEST-FACING SHORES OF THE BIG ISLAND. SOME SOUTH-FACING SHORELINES
ALSO MAY EXPERIENCE SOME SWELL WRAP. THIS SWELL IS EXPECTED TO PEAK
WEDNESDAY AND WEDNESDAY NIGHT...BEFORE DIMINISHING SLIGHTLY ON
THURSDAY. A SLIGHT REINFORCEMENT TO THE SWELL IS EXPECTED FRIDAY AND
SATURDAY...BUT THEN SURF WILL SUBSIDE GRADUALLY ON SUNDAY AND
MONDAY. TIDES WILL BE RUNNING ON THE HIGH SIDE DURING THIS TIME...SO
RUNUP MAY BE HIGHER THAN NORMAL.

WINDS WILL REMAIN BELOW THE SMALL CRAFT ADVISORY THRESHOLD THROUGH
THE FORECAST PERIOD...HOWEVER THE LARGE SWELL MENTIONED ABOVE WILL
BUILD SEAS TO ABOVE THE 10-FOOT ADVISORY THRESHOLD OVER WATERS
EXPOSED TO THIS SWELL.

&&

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

&&

RYSHKO